Space Warfare XIII: The Human Factor
Discussion of the recent post on Interstellar Empire led to a question that until now failed to get a post of its own: the role, in space warfare, of drones versus ships carrying human crews. Consider this deficiency now corrected.
A few provisos apply. Set aside for now the question of whether warfare, as we have known it and too much loved it since the Iliad, may be obsolescent as a viable mode of conflict among post-industrial communities.
Also set aside the Plausible Midfuture, a place where warfare in deep space is doubtful even if Earth orbital space is armed to the teeth. Set aside as well the general messiness of warfare on planets; my concern here is with space combat. We are dealing here with space armadas, a concept that is demi-operatic at least.
Will these armadas be made up primarily of warships with human crews - the familiar classical vision - or largely of robotic craft?
A lot of this comes down, I would argue, to good old money. The first 50 years of deep space exploration have been exclusively robotic because robotic spacecraft are cheaper. They are cheaper for several reasons: They can be much smaller; except for sample returns they don't need to come back; and in fact they don't even need to always get there.
So far as I can recall, every mission to the outer planets has (so far) been a success, but we only reached the point of batting .500 against Mars since I launched this blog. Such a loss rate was regarded as acceptable for human missions in the 16th century, but not in the 21st. (The more so because the enormous cost of human spaceflight, and resulting high profile, makes human spaceflight losses more controversial than, say, helicopter crashes.)
The situation in warfare is somewhat different, because soldiers are in some fundamental sense expendable - many of our military traditions are, in one way or another, built around that fact. But they are not lightly expended, if only because high quality crews are costly to train and difficult to replace. For post-industrial societies, where untimely death is no longer a sad commonplace, public resistance to casualties may be problematic even for authoritarian regimes.
Cost and risk of losses, taken together, are ample reason for the designers of combatant spacecraft to automate them so far as is practical. But how far is practical?
Kinetic weapons will have no human crews, for obvious reasons. There are almost equally strong reasons not to put crews aboard the buses that deliver them. Kinetics are most effective in a single wave that saturates defenses - the faster they are thrown the harder they will hit, and the less time the defense will have to stop them. This argues for a bus that uses its full delta v for maximum closing rate, rather than holding back propellant in order to recover the bus. For its basic mission it need not be very sophisticated, and you will not be re-using it anyway, at least not anytime soon.
So it is probably cheaper to make the bus expendable.
Lasers are a different matter, as are alternatives such as particle beams. (And for that matter kinetics, if these are slung on their way by coilguns. Flip side, bomb-pumped lasers are expendables, with military properties similar to kinetics.) A laser star is inherently reusable, and suited to missions, such as blockade or maintaining a 'presence,' in which repeated engagements may be required. A laser and its associated optics are also presumably sophisticated equipment. On all of these grounds putting a crew aboard a laser star seems much more plausible than putting one aboard a kinetic bus.
But what exactly would the crew be called upon to do? No gunners' mates are needed to shove photons into the breech, or even aim the laser. Actual precision aiming of the beam will be automated in any case, and assigning targets can be done from a few light seconds away.
The other traditional role of ships' crews is maintenance and repair. But drive engines and megawatt lasers do not, so far as I can see, provide much scope for onboard servicing, let alone damage control during battle. Repairs of either one pretty much need the services of a cageworks. Occasional replacement of smaller failed systems, or whacking balky parts with a wrench, can be done by service teams based elsewhere - at a space station, for defensive orbital forces, or aboard a tender for deep space constellations.
It is a peculiar fact that both many space emergencies - such as onboard fires or air leaks - and much of the corresponding scope for human emergency repair, relate specifically to life support habs. (Propellant tanks can also leak, but offer precious little chance of onboard repair.) I suspect, indeed, that life support maintenance will be a major role of space crews. But this sets up an odd circularity. Take away the hab and you eliminate many of the emergencies that a crew could respond to.
The final role for humans in space combat is command and control, especially rules of engagement decisions. We might not want to trust even high level AIs with these decisions - either because we are not quite sure of their motives, or because they have no motives at all, and so can free us of everything but the need to decide. But the scale and probable tempo of space combat are such that - as mentioned above concerning target designation - these functions generally don't need to be aboard the weapon platforms. Why not offload them to the 'tender' that provides teams for the occasional maintenance call?
Back in Part III of this series I gave the following description of a space combat constellation:
Taken as a whole you might call it a fleet. But it more nearly resembles a mobile, distributed, and networked fortification, deploying in action into a three-dimensional array of weapon emplacements, observation posts, and patrol details, all backed up by a command and logistics center.But even supposing that a main battle force is built along these lines, what about smaller independent mission packages - the equivalent of a cruiser, for example, for patrol missions?
Contrary to the (understandable!) assertion of a well known Evil Website, space is not an ocean. At sea, a single 10,000 ton ship has major advantages over four 2500 ton ships. It is more seaworthy, far more comfortable for its crew, harder to sink, provides a higher and dryer command for guns and sensors, and can maintain higher speed with less power and fuel consumption.
In space these considerations apply with far less force, if they apply at all. A single large hab pod is likely preferable to several smaller ones - but only the command ship / tender needs a hab pod at all. And the other force elements can be carried as riders, if desired, separating only to deploy for combat.
If your propulsion tech involves an electric drive powered by an external reactor, which also supplies the primary laser, you want to match the drive, reactor, and laser, which does argue for putting them together aboard the same spacecraft. And you might reasonably be less than comfortable about separating the crew hab from the main drive. But if your setting has fusion drive, or any self-contained drive, this is much less a consideration.
One other human-factor consideration to keep in mind was brought up in the linked discussion by commenter Tony: What happens to the morality of warfare - such as it is - when no soldiers put themselves at risk to fight it, because the fighting is all done by robots?
In the scenario I have outlined above this is not really the case. The constellation has a human crew, aboard the command ship / tender, even if it is 'behind the lines' relative to the weapon platforms. If the combat units of its constellation are defeated the crew must retreat, surrender, or face destruction - the choices that have always faced combatants who were disarmed in battle rather than killed outright.
Discuss.
Related Links:
Atomic Rockets, of course - especially, but not exclusively, the pages on space warfare.
And previously in the Space Warfare series on this blog:
I: The Gravity Well
II: Stealth Reconsidered
III: 'Warships' in Space
IV: Mobility
V: Laser Weapons
VI: Kinetics, Part 1
VII: Kinetics, Part 2 - The Killer Bus
VIII: Orbital Combat
IX: Could Everything We Know Be Wrong?
X: Moving Targets
XI: La Zona Fronteriza
XII: Surface Warfare
Also ...
Battle of the Spherical War Cows: Purple v Green
Further Battles of the Spherical War Cows
Plus
Space Fighters, Not
Space Fighters, Reconsidered?
And, indulging in heresy -
Give Peace a Chance
The image shows Achilles fighting Hector.
883 comments:
«Oldest ‹Older 401 – 600 of 883 Newer› Newest»Re: material anti-kinetics used as point defense
This is a bad, bad idea. All one does by breaking up a brillaint pebble with a countermissile is turn it into a swarm of high velocity debris you can't dodge. You've basically got to disable a kinetics ability to home at a long range, without breaking it up, then dogde the inert remnant (if necessary).
In fact, one pretty obvious kinetic tactic is to aim off of the predicted impact point, expecting a lot of your brilliant pebbles to be mobility killed, but creating severe constraints on defensive maneuvering by their continued existence. Only pebbles that survive to get within a certain envelope actually go to active homing.
Luke:
"Not necessarily (although some megastructures will also work). For example, proposed non-megastructure ideas that could cut down on space access cost include laser launch, high altitude scramjets, the Skylon/SABER concept, even some rotavator-style skyhook concepts (possibly combined with electrodynamic tether ideas). While you have stated that you have issues with some of these, laser-driven atmospheric lightcraft and free flying scramjets have been successfully tested - which is a lot more than you can say for any sort of controlled fusion."
Scramjets and hybrid jet/rockets are only going to make marginally viable SSTO reusables, at the very best. They may lift a few tons per mission. The same goes for laser launch. We know from experience that building stuff in space a few tons at a time is not likely to work out very well. So these technologies (and all of the megastructures too, BTW, except for maybe a space elevator) only make sense in launching small finished goods, not spacecraft parts.
"So you want the physically impossible (and thus impossible to build) magitech rather than the potentially physically possible but difficult to build megastructures (which, again, are not necessary)?"
No. I hope that what we today would label magitech somehow becomes possible in the future, even if we can't right now see how it could be physically possible. If that hope is not fulfilled, then all of these grandiose dreams will never come to pass, because they're simply not economically sound any other way.
It's not a matter of what I "want", Luke. It's a matter of recognizing what is economically impossible without a magitech solution, and living with it that reality.
Luke:
He3 was needed as McGuffinite as much as anything. The heroes were Lunar colonists. Even then, it still looks pretty good for spacecraft propulsion.
Tony:
The antiship missiles -- and more than one of them -- have to get through.
The same could be said of kinetics. It's a matter of sufficient overkill either way.
A laserstar cannot blast forever. It's power plant can carry only so much fuel.
You have to be able to do better then that. I can't see a laserstar running out of fuel as a likely scenario. Uranium doesn't mass that much. And I doubt expendable coolant will be required for power projection.
I agree that that has become the conventional wisdom. But all a laserstar can do is poke holes in things. It can't deliver high explosives or cluster munitions, or anything else that might be deemed desirable in an actual war with actual targets other than fleet units in deep space.
No, it just pokes those holes with very high precision and at the speed of light. Still, you favor kinetistars for this. I can work with that. More on that later.
And the biggest laser possible makes sense if -- and only if -- the laser cannot be economically overwhelmed by a ballistic or powered missile saturation attack. If it can be, then more, less powerfull lasers is the better choice.
That assumes that there won't be PD lasers. There will. I'm speaking of a laser as an offensive weapon only.
For offensive use, a single large laser will be more effective then an equal mass of smaller lasers.
There are basically three ways of deploying kinetics:
Lancers
Missiles
Projectors
1. Lancers are the tactic of pointing your spaceship at a target, dumping a bunch of stuff, and turning away. In the PMF, it's only useful at strategic level, and usually is hard to distinguish from a missile. It's mostly used because the engine in question is too expensive to use as a missile, and/or you're using it as a bus. If the lancer is reusable, then for a given payload this is the cheapest option, both in launcher and in projectiles.
2. Missiles are more expensive in terms of projectiles, but cheap in launchers. They suffer from serious performance issues. Either they are cheap, small, chemfuel, and low-velocity, or they're easy to confuse with a lancer. There's some overlap with the other two, as projectiles are self-steering. They are also the most practical way to deploy specialty weapons like nuclear warheads.
3. Projectors are anything that launches a projectile from a ship. Examples include railguns, coilguns, and chemical guns. They have cheap projectiles and expensive launchers. I consider them similar to lasers in terms of use, as both are rather expensive and not exactly expendable. The balance between the two will depend on specific technical details.
For tactical use, lancers are out. Changing orbit to launch a strike will take too long, and the remass requirements will be far too high. Missiles can work, but they are relatively heavy for mass-to-target, and rather expensive. Some might be useful, but mostly as peripheral payload launchers. Projectorstars are going to fall into the same strategic category as laserstars, so I'm not sure what we're arguing over.
As an aside, I'm not sure about the brilliant pebbles idea. If sensor suites for my individual laserstars are prohibitively massive and expensive, then what is the bill for those going to be? As for kinetic interception, the projectile will be pulverized, and you have a faceplate to protect yourself from the dust.
(SA Phil)
Tony,
Propellant and fuel are not the same thing. I only need propellant for thrusting, not Laser firing.
The Reactor is not going to run out of fuel during the mission. That isn't some debate topic, that is Basic nuclear reactor theory.
Naval Nuclear reactors last years/decades between refueling. I don't think suggesting months is implausible.
Cooling is only an issue if I don't have enough Radiator capacity. I don't need to fire it continuously for months. Just over and over again for months with a maximum duty cycle inside of the heat management limit.
If I have enough range Ill have hours/days to blow up oncoming missiles, I can afford to let the laser cool.
(SA Phil)
I think the kinetic point defense could work since it would imply a likely vector change after the explosion. You don't need to dodge the debris cloud you just need it to lack enough density that you will likely get hit.
Space is very big, If you have 100 projectiles in sphere 100 km apart your chances of getting hit are pretty tiny.
For that odd time you get unlucky - your Whipple shields will protect the most important things, redundancy the rest.
Nukes go years between refueling. But there's only so much energy in the rods. Running at full power would run through the supply sooner than running at half. Would this potentially put a hole in the energy reserve or would even a heavy engagement represent a fraction of the normal expenditure over the life of the rods?
It might come up sooner than we think. The railgun and lase ships are going to be sucking up power. Might finally make sense to make those ships nukes rather than fossil fuel. Has there been any discussion on that?
(SA Phil)
Nuclear power-stations try to run 100% as much as possible, its much easier to throttle coal and Natural Gas with demand.
Running full power and cutting decades down to years still gives you a pretty nice window though.
I think the Navy railgun destroyer concept is a Nuke design.
A long range laserstar woud be an effective part of a constellation if we look at it as an integrated whole (like Rick has said). If there is a terrestrial analogue it would be the CIWS turret on a modern warship, although the logic of space warfare inverts the desired opening ranges to as far as possible.
In terms of offensive ability, if (once again using the figures posted on earlier Rocketpunk threads) we once again have the ability to open engagements at ranges far beyond any effective kinetics; in this case the laserstar is the main battery in the fort; 15" railway cannon or naval monitor packing an 18' battleship turret.
I have never personally imagined a laserstar moving out on its own, and since my conceptualization is a fairly large assembly to begin with, there is no reason the laserstar can't also have KKV busses strapped to the truss for use when the range closes in (and readers of this blog have read these descriptions before). The Kinetic star I have never worked out in detail, but since it does not have the Liniac, cooling equipment or optical train of a laserstar it would be a much smaller vehicle.
WRT militarized space and the use of constellations, we already have a presumption in the background that there is a thriving space based economy, enough McGuffinite to be worth fighting for and fairly well developed orbital and deep space capability. If we remove these assumptions then we effectively invalidate space war using professional navies (or even issuing Letters of Marque). SOF commandos infiltrating space installations disguised as service personnel and some sort of orbital cutter to inspect questionable spacecraft and board them if required seem to be all that would be required in this case.
I like the term constellation. Laserstar works for discussion but is still an ugly and unevocative word. Can we think of anything better?
Also for drones, had a thought. Some ships in the constellation will be interplanetary with full drives. Others will have to be ferried but deployed while underway. For example, a ship will accelerate and once done deploy sensor drones or screening drones. They have weak thrusters and just move out a few thousand miles and then are recovered before the deceleration burn. Should there be different terms for these things?
What would be the deciding factor for the utility of carrying a weapon versus giving it the reactor, engine and reaction mass to keep up with the fleet. Am I mistaken in thinking there would be any savings? Would it remain cheap to have a 20 ton drone moving with the constellation because it's just as easy to equip it as such than bother with docking and recovery? Or would this severly depend on the tech involved?
In fact, one pretty obvious kinetic tactic is to aim off of the predicted impact point, expecting a lot of your brilliant pebbles to be mobility killed, but creating severe constraints on defensive maneuvering by their continued existence. Only pebbles that survive to get within a certain envelope actually go to active homing.
Funny, that's the theory behind the kinetic attacks in Attack Vector: Tactical!
=====
Just to really make someone's head hurt for a minute:
Based on the time/distance/shielding requirements for any nuclear reactor, the best candidate hull for a laserstar is going to be a heavily crewed ship, simply because of the long truss between the reactor and the crew hab!
A somewhat meta note on laserstars: They are not a hobby horse I was particularly eager to ride. For many years my conception of space combat was kinetics-dominant.
But discussion at SFConsim-l and later here left me reluctantly persuaded that even under pretty conservative assumptions, a laser (or bank of lasers, all firing through a single big telescope mirror) should be able to lay on destructive 'blowtorch' zaps out to ranges in the thousands of km, and 'scorch' damage that would fry enemy laser optics at several times that range.
These ranges are such that they pretty much spoil gyrating maneuvers, not just for 'realistic' propulsion but even for torch level drives.
This tends to put a great premium on weapon range, which in turn calls for the biggest main mirror it is practical to deploy, and the general concept of a laserstar follows from that.
Again, the meta point is that these are conclusions I embraced with great reluctance, after making the most conservative assumptions about laser performance that I could justify to myself as not being special pleading.
Make of that what you will.
The on advantage of kinetic missiles is that if your drive tech scales down and is cheap, they will always hit (within their mission profile, and assuming they aren't destroyed).
Light speed lag just isn't an inconvenience to them.
That being said, I tend to assume drives are expensive (which helps justify manned craft if your story desires it), so missiles are largely chemfuel affairs: high acceleration, but relatively low delta-v.
(SA Phil)
I dont see the nuclear reactor = high crew size connection.
The reactors we are talking about would not have the shielding and containment of a naval reactor, they would have just the reactor chamber and a shadow shield.
Tony:
This is a bad, bad idea. All one does by breaking up a brillaint pebble with a countermissile is turn it into a swarm of high velocity debris you can't dodge.
Once you hit it, you can dodge it, because it will no longer be homing. More to the point, usually, the debris spreads out rapidly and quickly becomes a minimal threat. Particularly if you have even minimal "Whipple shield" armor. Obviously, you need to disable the incoming kinetic far enough away that the resulting debris cloud is not a threat, but coming up with scenarios where using anti-kinetic rockets can only kill the missiles close enough to your spacecraft that the debris is a danger always seemed rather contrived - with modern rocket tech, even low delta-V gets you enough stand-off distance to significantly reduce the threat.
It occurs to me that space warfare with plausible midfuture(tm) drives might not even have "battles" per se. A fleet, constellation or what have you will approach at interplanetary velocities, make an attack run with lasers, KKV's, magic fairy dust or whatever weapons tech is in use at the time, and continue on in an extended solar orbit to be recovered (or not) later. This is interplanetary "bombing runs" rather than operatic space warfare.
The advantages are obvious; a spacecraft on a solar orbit trajectory does not need the huge amount of remass to decelerate or manouevre, this cuts the requirements by a factor of 4 if you don't plan to stop in planetary orbit or 8 if you don't have to stop, then accelerate back to Earth.
From a strategic perspective, it means you can get there much faster (using the example of a solar sail accelerating at 1mm/sec^2) we can get to Mars in about 180 days and coast back to Earth in another two years. Electric drives with similar capabilities will have similar flight times).
Tactically, you are closing at interplanetary velocity, which minimizes the time the enemy can take action and gives your KKV's the greatest kinetic energy on impact (although it also boosts the effectiveness of the defenders missiles).
Operationally, if the bombing run(s) are a success, you can then send your Imperial Procouncel and occupying forces (if any), while if they are not, then you keep those assets at home.
This sort of setup also favours drones, especially if they will swing by at high velocity, release of discharge weapons then are allowed to drift into interplanetary space.
Concerning warfare as bombing raids: now you get back to the question of what the ships are needed for. I think you're right that it'll just be drones if that's the case.
1. They're not regular bombers, you don't need people to fly dumb, iron bombs to the target before dropping.
2. They're not battleships, you don't need to sail the guns into range to fire at the enemy.
3. They're fitting with the ICBM with MIRV warheads model.
This sounds like we really are looking at late Cold War scenario rather than early Cold War. If we had WWIII in the 50's, it could have dragged on for years with bomber raids coming over the pole, fighters desperately trying to knock them down before they hit their targets. It would be prolonged attrition as cities are lost every few weeks and then there are lulls as each side tries building more bombs and bombers for the next raid. By the late Cold War, of course, both sides had enough weapons in place that the first strike would be overwhelmingly catastrophic with maybe a fitful second strike in the following week.
So then you come back to what the purpose of the war is. If we're talking one solar system, two civilized planets with a third one up for grabs, then a war goal might be to knock out the other planet's orbital assets so that the third planet is free for exploitation. There's no need for a landing and occupation on the opponent planet, just preventing them from getting assets up into orbit.
(SA Phil)
How much power Does a Laserstar need to "Blind" another Laserstar? IS it required to be on the "ship kill" level?
Could you have dozens of smaller laser drones designed to blind a Laserstar, then use a railgun/LGG kinetic ship to kill it?
Or even Laser drones teamed with kinetic missiles.
Another day, another list...
In no particular order:
1. Reactors and fuel. If you're supposing fusion, then there's obviously a fuel limit -- the amount of fusion feed products aboard. Depending on your fusion technology, these could be strictly limited by manufacturing expenses.
Even with fission, one has to realize that the mission isn't just months. It may be only a month or two out to Mars, and only a month or two back, but with milligee propulsion you're looking at transfers only around the synodic opposition. So even with a generous reaction mass reserve, you're "wintering over" at Mars for at least a year and a half.
And while terrestrial reactors can go for years on a single fueling, there are constraints to doing the same type of thing with spacecraft. The most obvious one is that you want to make the power plant as light as possible. Well, I hear you say, the difference between three years and ten years of fuel is only a few hundred pounds of fuel pellets. Yes -- and a few tons extra of reactor mass to encapsulate the large core. Maybe that will or maybe that won't be an issue. But I wouldn't rule it out as a limiting factor. Ifthere's anything spacecraft designers know, it's TANSTAAFL.
2. Laser coolants. The blithe assertion that lasers won't need expendable coolants is almost certainly wrong. Radiators represent a serious vulnerability in combat, and they are an impediment to maneuvering (because they are large and fragile and you can only impose very light moments and accelerations on them). It's hard to see how one would want to expose them under fire.
3. Lasers vs kinetics. Brilliant pebbles, which are the most likely type of kinetic projectile, don't need to be any larger than a desk and, until activated for terminal homing, don't need any more power than a BIOS battery. They would basically be dumped overboard or separated from a bus outside of laser range, and procede inert with nothing but a clock checking routine running and a programmed time of activation. Even the best passive surveilance sensors probably won't see them until they power up their sensor coolers. (Yes, I know there's no stealth in space, but there is such a thing as limits on sensor sensitivity.) This is a case where it may pay off to use active radar. Depending on how far out one expects to have to start shooting at kinetics, discriminating between real threats and random junk may be an issue.
4. Anti-kinetic kinetics. Yes, some debris will be put on trajectories away from the protected craft. Others might be put on a trajectory towards it. In any case you will get an expanding cloud of debris moving at something like the velocity of the intercepted projectile. With multiple expanding debris clouds coming more or less at you, dodging becomes problematical. And, oh yeah -- don't expect all of the debris objects to be small enough to be absorbed by a Whipple shield.
5. Tactical usefulness of kinetic attacks. I'm not sure why someone would think that kinetics wouldn't have tactical usefulness. It seems to me that with interplanetary spacecraft they would be the primary weapon used by a squadron attacking the orbitals from an interplanetary transfer orbit. If you're going to accelerate up to several tens of kilometers per second relative velocity to make a (relatively) fast interplanetary transfer, you might as well use the last 5 or 6 kps for kinetic bus velocity.
If you're already occupying an orbit around Mars or wherever, You just mount some or all of your kinetic busses on a solid rocket similar in power to an ICBM first stage. That should give you 4-5 kps relative velocity with your target, even one in essentially the same orbit.
6. Drones, laserstar or otherwise. Even if a carrier ship provides the interplanetary transfer delta-v, the drone (laserstar, whatever...) still has to have a first class, military grade propulsion system in order to maneuver effectively in combat. Same story with sensors -- a military grade suite, feeding high-end battle computers.
I want to reiterate that all of these systems are expensive, relatively rare, and maintenance intensive (because there's just never that much operational experience with them, if for no other reason). As attractive as drones might be to the tactical or operational planner, they will probably be economically impractical, except maybe for special missions worth the expenditure of valuable resources.
And after doing some thinking...
Using the laser optics for observation, even just refinementof the shooting solution, slows down your shooting...a lot. When you're observing, you're not shooting. That's obvious, but also, when you're switching over from observing to shooting and back, you're reconfiguring your optics. That's a mechanical operation that takes time, and is prone to error. Even if your laser emitter and targeting instrument are coaxial, at the same distance from the reflector, you either have to move them around, or move the reflector around, or adaptively change the reflector shape, and wait for vibrations to settle down, then adjust any errors caused by imprecise positioning (and the faster you try to accomplish a reflector focus shift or sensor/emitter position shift, the more imprecision you're going to introduce).
So you want to use your laser gun as it's own aiming scope. I wish you all the luck in the world, you're going to need it.
Tony,
1. Reactors and fuel. If you're supposing fusion, then there's obviously a fuel limit -- the amount of fusion feed products aboard. Depending on your fusion technology, these could be strictly limited by manufacturing expenses.
Even with fission, one has to realize that the mission isn't just months. It may be only a month or two out to Mars, and only a month or two back, but with milligee propulsion you're looking at transfers only around the synodic opposition. So even with a generous reaction mass reserve, you're "wintering over" at Mars for at least a year and a half.
===========
If I am "wintering" for a year and a half I can shut down the reactor, saving fuel if that were really a concern.
Reguardless,
Electric drives are very reaction mass efficient. They are designed to run at milligees for months on end. The whole reason they lack thrust is very little propellant is used.
Which was kind of the point.
The latest French Nuke sub is being designed to never be refueled, 30 years of fissile fuel built into the design.
It will be decomissioned around the time its reactor runs out.
-SA Phil
(SA Phil)
The original scenario was a deep space fight.
But people keep bringing up orbits, which imply much shorter engagement ranges.
Obviously there are different solutions for different parameters.
(Sa Phil)
As to radiators .. it really depnds on the encounter range. If no kinetic has a hope of closing on you whether your radiators are exposed or not is not worth worrying about.
Tony:
When you're observing, you're not shooting.
It depends on what you are observing. For example, take a near visible beam and beam pointer scope suitable for near visible light. You can build your light paths such that you can lase at your target while using the same optics to track the target and observe damage caused to the target (assuming you can resolve the target - if the resolution is smaller than the target you can just see it as a fuzzy blob but at the same time your beam will be wider than the target). Use frequency specific mirrors and filters to protect your optics from the beam radiation, or electro-optic switches with a pulsed beam, or some other method. Now the laser radiation follows one light path, while radiation not at the laser resonance frequency, or not at the time of the laser pulses, follows another beam path after bouncing off the primary and secondary mirrors.
SA Phil:
"If I am "wintering" for a year and a half I can shut down the reactor, saving fuel if that were really a concern."
The low power period during the stay at Mars or wherever is figured into the fuel allocation. So is the trip out and the trip back. Margin for combat maneuvering and weapon operation are also figured.
"Electric drives are very reaction mass efficient."
Fuel and reaction mass are not the same thing, except for chemical rockets and for certain types of (speculative) fusion and antimatter rockets. With the exception of chemical rockets, fuel is what provides power, generally sunlight or fissionables. Reaction mass is what you shoot out the ass end -- it can be water, hydrogen, methane, noble gasses, heavy metals...anything you can heat up or ionize.
"The latest French Nuke sub..."
...doesn't have the mass constraints that a spacecraft does.
"The original scenario was a deep space fight.
But people keep bringing up orbits, which imply much shorter engagement ranges.
Obviously there are different solutions for different parameters."
What there is is jumping back and forth between the plausible midfuture and semi-plausible future beyond that. There is also, I think, a disagreement between commenters about whether deep space combat is possible in either environment.
Certainly in the plausible midfuture there won't be combat outside planetary or asteroidal orbits, due to technical, logistic, and astrodynamic constraints. Fighting will probably be between prepositioned squadrons near to each planet/asteroid where humans live in numbers.
Past the plausible midfuture, there certainly might be the capability to fight in deep space, but I, at least, doubt the incentive. Even though you can see the enemy coming, you can't sit still at an interdictory point. Occupying a high orbit isn't going to help, because the enemy can time his approach (remember, we're talking about magitechnic amounts of delta-v past at this point in history). You might be able to drive out to meet him, put it would be a meeting engagement at high closing speeds, and you open up the planet/asteroid your trying to protect to any enemies that get past you. You may come out (or up, depending on how you choose to visualize things) to gain more maneuvering room and keep combat away from delicate facilities and/or populations. But you're not going to put the planet/asteroid outside of your weapons' effective range. Is that deep space? I guess it depends on your weapons' ranges, but in any event the planet/asteroid over which the battle is being fought still influences the action.
SA Phil:
The original scenario was a deep space fight.
But people keep bringing up orbits, which imply much shorter engagement ranges.
All scenarios I'm familiar with are in orbit around something. It might be a planetary orbit, it might be a solar orbit. I suppose if you are not gravitationally bound to a star the orbital nature of your motion around the galaxy is not important for your tactics. And if you are fighting in extragalactic space your path through space might not be any sort of periodic orbit at all. But usually I see people talking about fighting around planets or stars.
Sa Phil:
"As to radiators .. it really depnds on the encounter range. If no kinetic has a hope of closing on you whether your radiators are exposed or not is not worth worrying about."
Radiators are vulnerable to lasers too. Possibly moreso than any other part of your ship, because they are designed to operate at their thermal limits, and can't be armored. Add some laser light and you start melting them pretty fast. Also, though you can put armor along a radiator leading edge and point that edge at one enemy, other enemies are goint to be able to see and engage the radiator surface. And they wouldn't need or want to use narrow beams. They'd use wide enough beams to ensure hits, because they're not trying to burn through armor. They're just trying to thermally overload your radiators.
In an "eyeball frying" engagement, only a fool would actually try to, well, fry enemy eyeballs. Dueling enemy laserstars one on one is tactically stupid. You shoot at enemy radiators you can see, not enemy weapons. Presuming we're still talking about the spine mounted maximum laser, this pretty much guarantees that you're not staring down the bore of an enemy laser cannon.
Are we maybe seeing the point in expendable laser coolants now? But if Rick's right that it takes too much coolant for expendable coolants to be used on large lasers, then large lasers are ruled out, because at any range lasers fight, their cooling wings are going to be vulnerable and easily damaged.
OK deep space fight... Why is there a fight going on there?
If there is going to be a fight (other than some video game) there needs to be something there to fight over. If it is worth fighting over, there will be people there trying to get whatever is of interest.
There are only two things I can think of that would justify a fight in deep space.
1) You're trying to intercept a ship.
2) It is some sort of jump point for interstellar travel.
I'm only seeing case one in the form of a cycler, essentially a flying space station. Intercepting an inbound vessels in deep space involves too much of a change in velocity.
Re: Luke
No matter how you arrange your optics, you can have only one thing at the point of focus at one time. So you either:
Switch in and out a light diverter (prism or mirror) for your targeting sensor, or
Physically move the whole mirror to move its focus, or
Change the shape of the mirror as you switch back and forth between sensing and shooting.
All of these approaches introduces mechanical action, which introduces positioning imprecission and vibration. These have to be compensated for before continuing.
(SA Phil)
Yes I realize that fuel and reaction mass are not the same thing.
What I am postulating is that I know I can make a Nuclear Fission Reactor that can run for a great deal of time at full output. We don't know the fuel mass would be prohibitive at this point.
There is no reason to automatically assume it will be, since A)the length of the mission is undefined B)The mass limits of the vehicle is undefined C) the efficiency of the reactor is undefined.
If I can do that then I need long term heat dissipation, which can potentially be oversized enough to allow for Laser Cooling as well. The Laser On time will be limited by that cooling.
However in that system I just described it will not be limited by the Reactor Fuel.
The ReactoR fuel will be far more mass efficient than the ReactioN Mass (propellant), although its an apples to oarnges comparison.
The Reaction Mass/Propellant/Newton juice/liquified gas of an undefined origin will be efficiently used BECAUSE I have a high power electric drive system. That is how the system works.
With enough efficiency I can thrust nearly directly from point A to point B for the whole Mission. It may only be Milligees of thrust but it is milligees of thrust, which is actually a fair amount when applied for months.
AND If I choose to I postulate that I can run this ship with a computer control system. I feel this is very feasible because Control System design and electronics is something I have a lot of experience with.
That and 90+% of all spacecraft ever built have been electronically controlled with no humans pilots
The mass savings I get by leaving people off the ship could be used for both more Nuclear Fuel and Electric Drive propellant reaction mass.
-----------
The Deep Space and Armada are givens in the scenario described in the original posting. Which was restated by the original poster.
Tony:
Radiators are vulnerable to lasers too. Possibly moreso than any other part of your ship, because they are designed to operate at their thermal limits, and can't be armored. Add some laser light and you start melting them pretty fast. Also, though you can put armor along a radiator leading edge and point that edge at one enemy, other enemies are goint to be able to see and engage the radiator surface. And they wouldn't need or want to use narrow beams. They'd use wide enough beams to ensure hits, because they're not trying to burn through armor. They're just trying to thermally overload your radiators.
Thermally overloading is unlikely to work well. A reactor might be 20% to 25% efficient. Even if the laser is 100% efficient at turning electricity into laser light, the radiators already have to handle 3 to 4 times the laser's output of heat. If we take the efficiency of modern lasers of about 30%, the laser is only putting out about 1/10 of the heat load handled by the radiators. A radiator designed for fighting craft would probably be able to switch off coolant flow to areas that are close to the thermal limit. So while a fairly tightly focused laser (but not focused tightly enough to directly damage the radiator) might shut off certain sections of the radiator, the system as a whole could continue to operate at nearly full capacity.
No matter how you arrange your optics, you can have only one thing at the point of focus at one time.
Put your frequency specific mirror in the optics - now you have two focal points, one for light at the laser resonance frequency, one for everything else. Put your sensor at the focal point for everything else, and the laser's image at the other focal point (image because the beam is probably bounced off of several other mirrors).
SA Phil:
"However in that system I just described it will not be limited by the Reactor Fuel."
You can assert that, but you can't know that. It depends on how valuable reactor fuel is, how much people will allow to be flown on rockets that can blow up, and just how massive a reactor has to be as a function of fuel mass/cube. Any of those things could place hard limits on just how much fuel margin exists to generate weapon and sensor power.
"AND If I choose to I postulate that I can run this ship with a computer control system. I feel this is very feasible because Control System design and electronics is something I have a lot of experience with.
That and 90+% of all spacecraft ever built have been electronically controlled with no humans pilots
The mass savings I get by leaving people off the ship could be used for both more Nuclear Fuel and Electric Drive propellant reaction mass."
Once again, you can assert that. But that doesn't make it so. Military grade automation is no doubt likely to be expensive. If there's enough people and commerce someplace that it needs to be fought over, then people are almost certainly going to be cheaper than at least some grades of automation, even if it's a hassle to accomodate them.
"The Deep Space and Armada are givens in the scenario described in the original posting. Which was restated by the original poster."
Yes, Rick did state that we should concentrate on a deep space envrionment. But a deep space environment seems increasingly hard to justify. Battles are fought over real objectives, not empty space. Even past the plausible midfuture, empty space is not going to be all that easily accessible. People and their military forces are going to move from planet/asteroid to planet/asteroid.
Two forces going in the same direction at the same time are unlikely, because before a force is dispatched on an interplanetary transfer, it's either going to be unchallenged at it's point of origin, or a battle will have been won there, meaning it's going to be unchallenged at it's point of origin.
One can just barely imagine two forces dispatched almost simultaeously from the same planet/asteroid, either before fighting or while fighting is going on. In the first case they might just decide to settle things en route. In the other case they'd probably fight it out as soon after dispatch as possible, meaning they probably wouldn't be in deep space, really. Even if fighting it out in deep space, the combat would be much more like orbital combat than anything else (well, it actually would be orbital, technically, WRT the Sun). Both forces are going in the same direction, at roughly the same velocity, and probably don't have much maneuvering margin.
Finally, as I've already mentioned, the idea of planetary/asteroidal defense forces coming out/up to fight off an invader has certain attractions, until you remember that they can't leave the protected body undefended. So they're not coming out/up very far, very fast, because they have to keep their base orbitals within effective weapon range, in case any enemies get past them.
Luke:
"Thermally overloading is unlikely to work well..."
Remember, the radiators are going to be sized to cool the powwer plant and weapon(s) at maximum output and no more. They will be fully untilized in combat. 10% extra heat applied to the whole cooling system (and it would be) should cause it to overload. And that's with most pessimistic assumptions you could come up with. Suppose even more efficient lasers or power supplies...
"Put your frequency specific mirror in the optics - now you have two focal points, one for light at the laser resonance frequency, one for everything else. Put your sensor at the focal point for everything else, and the laser's image at the other focal point (image because the beam is probably bounced off of several other mirrors)."
Aside from the heat flux of shooting the laser through your sighting optics (nothing material is 100% transparent, and your laser, even defocused, is going to heat up some part of the sighting optics train), keeping two optics trains precisely aligned under combat conditions is not all that likely.
Re: fuel for reactors.
For civilian pressurized light water reactors, 5% enriched fuel might give you 60 GWD of energy per metric ton of uranium before the fuel needs reprocessing. The specific power of the fuel alone might be in the vicinity of tens of MW per ton. So if your one ton of fuel (neglecting the cladding and the oxygen in the U0_2) produces, for example, 60 MW, it can do so for 1000 days before it needs to be switched out for fresh fuel.
This is for commercial terrestrial PWR's, not space reactors. Still, it gives us a ballpark estimate of a few years of full power operation between refueling. For deep space operations, even electric plasma drives will probably spend a considerable portion of their time coasting and not doing much of anything. During this period, the reactor could be running at much lower power output. If you need full power for longer than a few years, bring replacement fuel.
Tony:
"Remember, the radiators are going to be sized to cool the powwer plant and weapon(s) at maximum output and no more. They will be fully untilized in combat. 10% extra heat applied to the whole cooling system (and it would be) should cause it to overload. And that's with most pessimistic assumptions you could come up with."
Absolutely not. Radiator designs are going to have at least 10% spare area to withstand attrition from micrometeorites during interplanetary travel.
On top of that, they're unlikely to be anywhere near their actual material thermal limits during normal operation. The radiator has to be at cold-side temperature for whatever heat cycle you're running - which, if you're using something like carbon-carbon heatpipes, will be a couple thousand degrees below the sublimation point of the material in question.
Re: Raymond
Whatever contingency margin you have, and whatever percentage of capacity you're running at, added heat over time is not going to be dissipated as fast as it is applied. It won't just be absorbed by the radiator, but everything in the laser spotlight: structure, tankage, armor, etc. And the hotter the radiator gets, the less efficient it becomes, both for thermodynamic and material reasons. That's why cars overheat on hot days, even when the ambient temperatur only goes up 20 or 30 degrees kelvin.
Tony:
Remember, the radiators are going to be sized to cool the powwer plant and weapon(s) at maximum output and no more.
Only if your engineers are incompetent. There is always an engineering safety margin, and if the radiators are expected to be exposed to an extra 10% increase in heat over that produced by the reactor, the engineers will allow for that.
Aside from the heat flux of shooting the laser through your sighting optics (nothing material is 100% transparent, and your laser, even defocused, is going to heat up some part of the sighting optics train)
Heating is not what I worry about - modern reflectivity is sufficiently high that thermal expansion can be corrected by active focusing and adaptive optics. Having laser light directly incident on my sensors is what I worry about. However, I glossed over these details because they are solvable. Optical bandgap materials (such as the commonly used dielectric layer mirrors) can give you frequency specific reflectivity on the order of 99.99% So ten of these in the optical path to the sensor will reduce the light on the laser resonance by forty orders of magnitude.
keeping two optics trains precisely aligned under combat conditions is not all that likely.
Sure, if you thwack the optics with a kinetic. But then, it's dead anyway.
Otherwise, not only are conditions on a spacecraft pretty much ideal for keeping things aligned, but you can actively control the alignment by tilting the mirror that joins the two optical paths.
Tony:
And the hotter the radiator gets, the less efficient it becomes, both for thermodynamic and material reasons.
???
I think you need to define efficiency here. Because the hotter a radiator gets, the more efficient it becomes at what it is designed to do - shed heat. The intensity of heat radiated, after all, goes up as the fourth power of the temperature.
Luke:
"I think you need to define efficiency here. Because the hotter a radiator gets, the more efficient it becomes at what it is designed to do - shed heat. The intensity of heat radiated, after all, goes up as the fourth power of the temperature."
Any material has varying emissivity, depending on the primary frequency being radiated. As you know, the hotter a material gets, the higher the primary emission frequency. If you take a radiator operating at it's optimum temperature for emissivity, then heat it up, you decrease it's radiative efficiency. That's why radiators can't keep on radiating at higher and higher temperatures without at some point melting.
Of course, what the radiator is more likely to do before it melts is have a seal failure or outright explode, due to overheating causing the working fluid to expand. And you can't solve this by lowering the fluid volume, because then it can't carry enough heat away from the machinery being cooled. You can also cause valve failures by introducing enough heat to deform the valve materials and cause them to sieze. Seal and valve failures, or just simple outgassing through safety valves, are actually probably the primary malfunctions you're aiming for by heating up the enemy's radiators.
Luke:
"Only if your engineers are incompetent."
Okay, to satisfy pedants, I should have said "not much more". Silly me, I presumed that people understood that safety margins were implied.
"Heating is not what I worry about"
It should be. Even with adaptive optics, the heating of optical parts, especially intermittantly heated and cooled ones, does not procede at all predictably. If you don't build settling time into the cycle, your adaptive optics controller will get into a vicious feedback circle. It would basically be the high end optics version of "chasing the bullseye".
"Sure, if you thwack the optics with a kinetic. But then, it's dead anyway.
Otherwise, not only are conditions on a spacecraft pretty much ideal for keeping things aligned, but you can actively control the alignment by tilting the mirror that joins the two optical paths."
At the levels of precision we're talking about, without the massive bases that terrestrial telescopes have for vibration dampening? The actuators on your adaptive optics might introduce unacceptable vibration.
Tony -
There is a simple way to reduce the load on my radiators: shut off the drive, and run my reactors at somewhat less than 100 percent, putting essentially all power into the laser. (Less only housekeeping power, an insignificant fraction.)
This makes me a sitting duck ... but to what? On the time scale of firing, maneuver is inconsequential, even with demi-operatic drives.
And if you are zapping any part of my spacecraft (such as the radiator fins), any zap I lay onto your main mirror will either be absorbed by it or else concentrated onto your secondary optics and laser (bank), with bad effects either way.
So far as I can tell, a laser weapon is highly vulnerable to end-on hostile laser fire - probably the most vulnerable thing aboard - but if you aren't zapping, the other guy's zaps are unimpeded.
On fighting in deep space, I am not anticipating fights in the middle of nowhere, but at the outer fringes of planetary space, lunar distance or greater. A defender can drift out on a long ellipse, and if the approaching attacker tries to 'go around,' the defender can block the move as easily as the attacker can attempt it. The time scale is way too long for a fake-out!
The resulting battle is effectively in deep space, taking place in 'flat' space far from the planet itself and any clutter of orbiting infrastructure.
See Part XI of this series, La Zona Fronteriza.
Well, at that range, teleoperations and maintenance aren't an issue. At that range, I wouldn't put it past continuous beam ground based laser systems.
Tony:
"You might be able to drive out to meet him, but it would be a meeting engagement at high closing speeds,"
That's why you turn around midway. You know where the enemy are and where they're going, so you can start matching speeds well in advance. You're not going to be caught by surprise not knowing what to do when the enemy comes barreling past.
Orbital mechanics are hard to work with, but here's a simple flat-space example of how you'd try to time things:
t=0: Invasion fleet detected, incoming from x=10 at v=-1.
t=0: Intercept fleet launched from x=0 at an initial v=+0 and a=+0.1.
t=3.75: Intercept fleet, now at x=0.703125 and v=+0.375, flips around and starts decelerating at a=-0.1.
t=5: Invasion fleet, now at x=5 and still at v=-1, begins decelerating at a=+0.1.
t=11.25: Both fleets pull up alongside at x=0.703125, v=-0.375, a=+0.1. Shootout begins.
t=15: Both fleets (or what's left of them) arrive at x=0, v=-0. What happens next depends on who won.
(Units arbitrary. Call it lightminutes and days if you must.)
Of course, this scenario has the invasion fleet performing less accelerations, but it should be remembered that unlike the intercept fleet, the invasion fleet must have already used propellant to set the course for the invaded planet, and have more propellant budgeted for stopping when they get there. They probably also need to budget propellant for getting back. So it's reasonable that the intercept fleet has a lot more delta-vee to work with. Assumed is that it's known to both sides that all ships at this techlevel have a maximum acceleration of 0.1.
Hmm. The fleets match speeds closer to the destination planet than I had been expecting. Still, the distance is non-negligible. Whether this maneuver is strategically useful and whether it still works in curved space are, for the moment, open questions.
(Also, if you wish, you can have the invasion fleet launch at t=-5, x=10, v=0, a=-0.1, instead of t=0, x=10, v=-1, a=0. It still behaves the same from t=5 onwards.)
"and you open up the planet/asteroid your trying to protect to any enemies that get past you."
No, because the intercept fleet's "matching speeds with the invader" maneuver is, per definition, the same one which puts it on a course back home. So there's no "getting past" you.
Luke:
"All scenarios I'm familiar with are in orbit around something. [...] But usually I see people talking about fighting around planets or stars."
For interplanetary space (orbiting a sun), orbital mechanics are important on a strategic scale (charting courses from planet to planet), but not on a tactical scale (fighting another fleet you met along the route). The tactical scale can be approximated as flat space unless your battles are taking incredibly long.
For orbital space (orbiting a planet), orbital mechanics are important even on a tactical scale.
Tony:
"Military grade automation is no doubt likely to be expensive."
Military grade people are also expensive. They need a lot of training and indoctrination, and then they go and die on you and you need to start all over again.
"Remember, the radiators are going to be sized to cool the powwer plant and weapon(s) at maximum output and no more. They will be fully untilized in combat."
Why? If, as Luke suggests, the maximum plausible laser power you might get hit with is only a fraction of the amount of power you're radiating anyway as waste heat, then it wouldn't be hard to design radiators just a little larger than you actually need, which will be enough to absorb any overload attempt from a similarly sized enemy ship.
If power supplies are highly efficient, to the point that you're outputting more power in laser beams than waste heat, then it becomes a different matter - now, bulking up your radiators to absorb laser hits will require a significant, maybe even unacceptable, increase in radiator mass. (No fission reactor based on anything resembling present-day designs will have efficiencies this high, but speculative technologies like fission-fragment reactors or aneutronic fusion reactors might.)
Also consider that lasers are probably going to use much less power than engines. Since you can probably afford to lower or shut off engine output during combat (combat is likely to take a small enough amount of time that shutting down your engine for the duration will have an insignificant effect compared to the duration of an interplanetary journey), this means that ships will in fact not even need to running at full power during combat, only when cruising. (I know this sounds backwards compared to what we're used to!) So if your radiators get overloaded, the worst it'll do is make you tone down your engine power and so reduce your jinking effectiveness.
"Okay, to satisfy pedants, I should have said "not much more". Silly me, I presumed that people understood that safety margins were implied."
But you don't need much more, since Luke's lasers don't add much more heat than your reactor is already producing.
Rick:
"On fighting in deep space, I am not anticipating fights in the middle of nowhere, but at the outer fringes of planetary space, lunar distance or greater."
Citizen Joe:
"Well, at that range, teleoperations and maintenance aren't an issue."
Not for the defender/"home team". For the attacker, though...
Rick, et al: If you are intercepting an incoming battle constellation with a closing velocity of 30 Kps, your BAL's have an effective range of 3000Km, and you launch your kinetics just outside this range, then your battle will only last a couple of hundred seconds. You probably will shut off your main drive and only use secondary RCS or even gyro controlled reorinitation of your ship(s) to keep face-on to the enemy. I don't see deep space intercepts lasting very long.
So, deep space interceptors would seem to have a place in space warfare.
Ferrell
Tony:
Also, though you can put armor along a radiator leading edge and point that edge at one enemy, other enemies are goint to be able to see and engage the radiator surface.
You can do better by a factor of two - you can always keep your radiators edge on to any two enemies, since a plane is defined by three points. If the other guy brings two of his friends to the fight, well ...
Any material has varying emissivity, depending on the primary frequency being radiated. As you know, the hotter a material gets, the higher the primary emission frequency.
Over the spectral ranges at which you have significant emission and temperatures that allow matter to exist as a solid (less than roughly 3500 K, for tungsten and graphite), you can have the emissivity curve both mostly flat and close enough to 1 to not make that much of a difference (in the 0.9 to 0.95 range).
If you take a radiator operating at it's optimum temperature for emissivity, then heat it up, you decrease it's radiative efficiency. That's why radiators can't keep on radiating at higher and higher temperatures without at some point melting.
If I increase the temperature of a radiator by 1%, the gray-body power radiated increases by 4%. That means you need a decrease in emissivity of more than 4% for a 1% increase in temperature to reduce the effectiveness of the radiator. You could design specific materials that did this at certain spectral ranges, but if you are trying to make the best radiator you can, why would you? Surface roughened carbon could have a near constant 0.95 emissivity over a wide spectral range and a very high operating temperature.
It also has nothing to do with why radiators can't keep operating at higher and higher temperatures - there are material limits and if the temperature gets too high the material melts or sublimates. But molten tungsten has about the same emissivity as solid tungsten, and sublimating graphite has about the same emissivity as graphite whose rate of sublimation is negligible.
Further, people who work with high power lasers for machining know that heating metals increases their emissivity - it is what allows lasers to efficiently cut what would otherwise be highly reflective metals.
It should be. Even with adaptive optics, the heating of optical parts, especially intermittantly heated and cooled ones, does not procede at all predictably. If you don't build settling time into the cycle, your adaptive optics controller will get into a vicious feedback circle. It would basically be the high end optics version of "chasing the bullseye".
I don't buy it. Adaptive optics can compensate for chaotic and unpredictable turbulence in the atmosphere in real time. The temperature changes in the optics should be similarly correctable.
You do get this result when you try to apply basic linear adaptive optics to thermal blooming in an atmosphere, but that's because as you focus the beam more to overcome the diverging lens effect, the more focused beam heats the air even more. You will not get this effect with mirrors (you might if you use lenses). Plus, since mirrors only reflect along their surface, they can be efficiently cooled (lenses are more difficult to cool).
continued ...
The actuators on your adaptive optics might introduce unacceptable vibration.
The whole point of active vibration damping is that the actuators themselves get rid of vibration. And it works quite well.
And that's with most pessimistic assumptions you could come up with. Suppose even more efficient lasers or power supplies...
I have no problem with more efficient lasers, there's nothing suggesting they can't increase significantly in efficiency.
The problem lies on the generator side. If you assume a perfect Carnot engine, you minimize the area of your radiators when the efficiency is 25%. Real generators will not be perfect Carnot engines - this will drive the optimal efficiency down a bit but not by too much for realistic generators. Since radiators need to be large to radiate the kinds of heat we are talking about, minimizing radiator area is likely to be a significant engineering driver, such that it will be worth it to have a larger power plant operating at lower efficiency if you can keep the temperature of the radiators up high enough to keep their area down. And if radiator area is not highly limiting and you expect radiation denial attacks, then you can build larger radiators to handle expected attacks.
This will be true for reactors that operate at all like those we are used to - heating a working fluid and using that fluid to move a generator. One possible "out" is if the reactor produces a hot plasma. Then it will be possible to tap the plasma using, for example, MHD generators with high efficiency - you are still limited by Carnot efficiency, but since the heat source temperature is so much higher than the heat sink temperature (or equivalently, since you have less entropy for a given amount of energy) you don't need to radiate as much heat so your radiators can be smaller (plus, no solid material could handle the radiator temperatures needed if you did go for Carnot 25% efficiency). The only theoretically possible reactors that could do this are D-3He fusion reactor (and even then you get about 30% of the energy in the form of neutral radiation, which adds to your heat load), plasma core fission (also gives a significant fraction of neutral radiation), and antimatter (which also gives you a lot of neutral radiation). With D-T fusion you pretty much have to tap the neutron-generated heat from within the lithium blanket using the working fluid method. More "efficient" forms of fusion seem to be unable to generate net energy according to our current understanding.
Rick:
"There is a simple way to reduce the load on my radiators: shut off the drive..."
I was under the impression that the power plant had been sized for shooting or propulsion, but not both. But even in the case you suggest, I have a suspicion that radiators are vulnerable to the enemy heating them with laser fire. I can't quantify it, but I'm sure the arguments given so far are too simplistic. The heating laser isn't just heating the radiator, it's heating up everything. My suspicion from experience with electronics and various forms of power machinery is that this is going to be a serious problem.
"This makes me a sitting duck ... but to what? On the time scale of firing, maneuver is inconsequential, even with demi-operatic drives."
Sitting still while somebody is spotlighting you with a gigawatt laser? Even if only 10% of that gigawatt is intercepted by your ship structure, you're going to heat up to unacceptable levels pretty quickly.
"And if you are zapping any part of my spacecraft (such as the radiator fins), any zap I lay onto your main mirror..."
You're thinking in terms of ship to ship duels. That's not how it's done. Each force has multiple ships, and each ship picks a target where it has the best angle to engage the radiators (and the rest of the structure). It's the space version of the land combat principle of engaging the enemy with flanking fire.
"On fighting in deep space, I am not anticipating fights in the middle of nowhere, but at the outer fringes of planetary space, lunar distance or greater. A defender can drift out on a long ellipse, and if the approaching attacker tries to 'go around,' the defender can block the move as easily as the attacker can attempt it. The time scale is way too long for a fake-out!
The resulting battle is effectively in deep space, taking place in 'flat' space far from the planet itself and any clutter of orbiting infrastructure."
I'm not thinking in terms of going around. I'm thinking in terms of blowing through on opposite or near opposite trajectories. It limits exposure for the attacker and puts the defending forces out of position WRT any and all surviving attackers. Milo's suggestion of matching trajectories with the attacker makes some sense, but the problem is that the attacker is going to start shooting before trajectories are matched, and in any case the defenders have to win outright or the surviving attackers will have free reign at the objective.
So, in all cases you probably want to keep a substantial reserve, and the critical battle is going to be in the orbitals, either against attacking survivors or the main force of the attacker, depending on the breaks. Or, if you don't keep a reserve in the orbitals, any surviving attackers win by default -- unless of course your intercepting force never got beyond effective weapons range of the orbitals.
Luke:
"You can do better by a factor of two - you can always keep your radiators edge on to any two enemies, since a plane is defined by three points."
So you have to armor not just the leading edge, but the longitudinal edge as well. Pretty free-wheeling with our mass budget, aren't you?
"Over the spectral ranges at which you have significant emission and temperatures that allow matter to exist as a solid (less than roughly 3500 K, for tungsten and graphite), you can have the emissivity curve both mostly flat and close enough to 1 to not make that much of a difference (in the 0.9 to 0.95 range)."
I've had considerable experience with materials changing their physical properties under thermal stress. I'm not so sure the curve is as flat as you assert.
"If I increase the temperature of a radiator by 1%, the gray-body power radiated increases by 4%. That means you need a decrease in emissivity of more than 4% for a 1% increase in temperature to reduce the effectiveness of the radiator. You could design specific materials that did this at certain spectral ranges, but if you are trying to make the best radiator you can, why would you?"
Because inefficieny at lower temperatures is not that big a deal. It's maximum efficiency at or near maximum capacity that you're aiming for.
"Surface roughened carbon could have a near constant 0.95 emissivity over a wide spectral range and a very high operating temperature."
Watch how rough you make that surface, champ. You don't want it so rough that microstructures are radiating into each other.
"It also has nothing to do with why radiators can't keep operating at higher and higher temperatures - there are material limits and if the temperature gets too high the material melts or sublimates. But molten tungsten has about the same emissivity as solid tungsten, and sublimating graphite has about the same emissivity as graphite whose rate of sublimation is negligible.
Further, people who work with high power lasers for machining know that heating metals increases their emissivity - it is what allows lasers to efficiently cut what would otherwise be highly reflective metals."
Tungsten is too heavy per unit volume to make radiators out of. Most forms of carbon aren't strong enough to hold the pressure of cooling fluids. Carbon fiber structures might be a candidate from the strength perspective, but the bonding resins would probably have problems with the operating temperatures.
I'm not sure what you're trying to get at with your comments about machining lasers. Unpolished steel and even aluminum are sufficiently non-reflective that they absorb enough heat to melt under assault of machining lasers.
"I don't buy it. Adaptive optics can compensate for chaotic and unpredictable turbulence in the atmosphere in real time. The temperature changes in the optics should be similarly correctable."
Atmospheric turbulence cahnges observing conditions at a low rate compared to the millisecond cycle times people are discussing here.
"The whole point of active vibration damping is that the actuators themselves get rid of vibration. And it works quite well."
Active vibration dampening requires a noise sink much more massive than the equipment being dampened. The mass of the planet Earth works very well for that. The hull of a spacecraft? not so much.
Anything you do that produces movement will generate waste heat in the form of sound vibrations. Even the most miniscule movement of an adaptive optics actuator will. Since there is no air in space, the sound will have to be entirely absorbed by the structure. But the structure of the spacecraft is not mounted on the Earth, wich is a very good sound absorber. So any movement in any structure on the vessel -- valeves opening and closing, power turbines rotating, switches opening and closing, coolant flowing through radiators, adaptive optic actuators actuating, radio and radar antennas pointing and training...any mechanical movement whatsoever, has to be absorbed by the vessel. In fact, it eventually comes out as a very slight increase in temperature of the whole structure. But while that's going on, it's shaking up everything inside, however slightly.
Maybe we accoustically isolate the laser system? Sure, we could do that. At the same time, any vibrations caused by any mechanisms inside the isolated section stay in there. Accoustic isolation works both ways, you know. I'm not sure what the benefit is -- adaptive optics and aiming mirrors have a lot of moving parts.
"And if radiator area is not highly limiting and you expect radiation denial attacks, then you can build larger radiators to handle expected attacks."
Radiator area could be limited by mass considerations. And in any case, whether the radiator is less dense and larger or more dense and smaller, it will be operated with as narrow a margin as possible, because mass is always an issue on spacecraft.
"This will be true for reactors that operate at all like those we are used to - heating a working fluid and using that fluid to move a generator. One possible 'out'..."
With any method of converting heat into work, there is waste heat coming out somewhere. There are not "out"s.
(SA Phil)
The Mass budget is really dependent on the mission requirements
If as is being postulated here - A laser platform can have a decidedly decisive range ..
To the extent that as long as you are willing to pay the mass penalty you will gain a massive advantage over other weapons systems ..
Then as long as you can still make the spacecraft work .. you would design around the mass penalty for all this heat management capacity.
If you cant make the Laser decisive in that way .. then you wouldn't.
------------
As to the radiators you could use tungsten piping and carbon fiber fins if you needed to combine the low mass of the carbon with the high strength for the fluid transport.
There are car radiators that use different materials for piping and fins, so it is possible.
It just wouldn't be as simple as using one material.
SA Phil:
"The Mass budget is really dependent on the mission requirements"
Only within economic and technological limits.
"If you cant make the Laser decisive in that way .. then you wouldn't."
Which I obviously don't think you can. What i see happening here is a lot of people convincing themselves of the dominance of lasers based on some very clever theoretical arguments. The problem is that reality places limits that theory doesn't recognize. Radiators are vulnerable. Mechnical systems -- even those designed to reduce noise -- introduce hard to damp noise on isolated platforms. The tactical assumption of the one-on-one duel is simplistic and wrong.
"As to the radiators..."
The point about radiators is that they are vulnerable to being heated past their working limits. You don't have to melt them. You don't have to even make them thermally inefficient (though I think you can). All you have to do is heat them enough to press them past their mechanical limits, probably most effectively by overheating the coolant and causing overpressure issues.
(SA Phil)
You come across though as Objecting to the Laserstar Idea, and then trying to shoot it down (pun intended) using any reason you can come up with.
I think that given the armada deep space war scenario, If such a incredibly effective Laser weapon system existed, they would make an effort to bring it into the action.
Pretty much what has been done with all "game changing" type weapons over the course of human history.
Wouldn't it be helpful if we could figure out how to get Nuclear missiles to work on something like a submarine?
Wouldn't it be useful to figure out how to drop big bombs from airplanes?
Wouldn't it be useful to figure out how make a canon that I can put on a ship?
Wouldn't it be be useful be able to take advantage of this sharp rock?
-------------
So its really the idea of the incredibly effective laser that is the core of the issue.
Not the more mundane engineering challenges. Engineering challenges can likely be dealt with.
No one has yet suggested doing anything that we could not do on Earth ... except for the Light-second range GW laser.
So I really don't see how it becomes truly impossible in space... except for possibly the Light-second range GW laser.
Tony:
"Radiator area could be limited by mass considerations. And in any case, whether the radiator is less dense and larger or more dense and smaller, it will be operated with as narrow a margin as possible, because mass is always an issue on spacecraft."
Hardly.
The current state-of-the-art in space radiators is the carbon-carbon heat pipe. A double-sided version is approximately 2 kg/m^2 mass per effective unit radiative area. With a sufficiently high temperature for the reactor thermal cycle's cold side (say, 1600 K), the radiator will emit approximately 250 kW/m^2 - equal to 125 kW/kg, more than two orders of magnitude lighter than the powerplant it would be mated to (given previous estimates of 1 kW/kg net powerplant specific power). Not to say the mass of redundant radiators would by insignificant - just that it's sufficiently low that a combat vehicle can easily afford a rather large safety margin, especially if attempted thermal overload is an expected enemy tactic.
I rather agree with Semianonymous Phil, in that you object to the entire idea of Large War Lasers IN SPAAACE and are trying to discredit it by any means necessary - and with all due respect, I think you're slipping towards the pedantry you so despise in doing so.
SA Phil):
"You come across though as Objecting to the Laserstar Idea, and then trying to shoot it down (pun intended) using any reason you can come up with."
I think the laserstar benefits enormously from being divorced from reality. When you start analyzing it in the context of reality, it starts looking fatally flawed, to me at least. WRT coming up with a new objection every day, well...I can't think of everything at once.
"I think that given the armada deep space war scenario, If such a incredibly effective Laser weapon system existed, they would make an effort to bring it into the action.
Pretty much what has been done with all "game changing" type weapons over the course of human history..."
A couple of things here:
1. If it's too impracticle to exist, then it won't.
2. With the exception of nukes, I have yet to hear of a game changing weapon that actually changed all that much. Every "revolutionary" weapon system you ever heard of, from metal swords to dreadnought battleships, has really only been an evolution of something that went before. There are a lot of reasons for this, but the primary one is that nothing is truly ever a surprise, and its limitations are at least aprtially known before it becomes operational.
"So its really the idea of the incredibly effective laser that is the core of the issue.
Not the more mundane engineering challenges. Engineering challenges can likely be dealt with.
No one has yet suggested doing anything that we could not do on Earth ... except for the Light-second range GW laser.
So I really don't see how it becomes truly impossible in space... except for possibly the Light-second range GW laser."
Well, in case anybody's missed it, my objections have a lot to do with the fact that doing it on Earth is not the same thing as doing it in space. Doing things in space introduces constraints that just don't exist on Earth.
In space you have to radiate heat. On Earth you can steam it off. (You can steam it off in space too, but only for a very limited amount of time.) Radiators are vulnerable to being overheated by enemy fire.
In space you have to absorb vibrations from mechanical operations within your spacecraft structure. On Earth you just sink it into the crust of the planet through your building foundation.
In space, your power plant, cooling system, and everything else have mass limits. On earth, not so much.
We're not talking about "mundane engineering challenges". We're talking about real constraints on operation. I can see the value of lasers for certain applications, but the laserstar is an unbalanced system, fragile in certain ways and mechanically limited in others.
(SA Phil)
By "mundane" I mean challenges that someone can already see potential solutions for .. Using current technologies.
Assuming you could get them into space.
----
In fact there are other, even simpler possibilities, once the laser exists.
A 100,000,000 ton icecube with a Nuclear reactor and one of these Lasers on it could fulfill the Laserstar objectives.
Melt Ice for Thrust
Melt Ice for heat dissipation
Etc.
Raymond:
"Hardly.
The current state-of-the-art in space radiators is the carbon-carbon heat pipe..."
My point was technology neutral. for any given density of material per unit of radiated heat, the spacecraft designer is not likely to include more margin than necessary. If he wants to build in margin for active hostile heating, he's going to have to skimp somehwere else.
"I rather agree with Semianonymous Phil, in that you object to the entire idea of Large War Lasers IN SPAAACE and are trying to discredit it by any means necessary - and with all due respect, I think you're slipping towards the pedantry you so despise in doing so."
Yes, I object to the idea. But I object for practical reasons: a laserstar is too specialized, it demands too many resources for what you get, has vulnerabilities that are too exploitable, and is not likely to have the effective range that is claimed.
While we argue over lasers, other are doing things with them:
http://nextbigfuture.com/2011/04/navy-moves-step-closer-to-lasers-for.html#more
Navy moves a step closer to lasers for ship self-defense with a field trial that disabled a small ship
The Office of Naval Research successfully disables a small target vessel using a solid-state, high-energy laser mounted onto the deck of the Navy's self-defense test ship, former USS Paul Foster (DD 964). Credit: US Navy photograph
Marking a milestone for the Navy, the Office of Naval Research and its industry partner on April 6 successfully tested a solid-state, high-energy laser (HEL) from a surface ship, which disabled a small target vessel.
The maritime laser from an older photo
The Navy and Northrop Grumman completed at-sea testing of the Maritime Laser Demonstrator (MLD), which validated the potential to provide advanced self-defense for surface ships and personnel by keeping small boat threats at a safe distance.
“The success of this high-energy laser test is a credit to the collaboration, cooperation and teaming of naval labs at Dahlgren, China Lake, Port Hueneme and Point Mugu, Calif.,” said Chief of Naval Research Rear Adm. Nevin Carr. “ONR coordinated each of their unique capabilities into one cohesive effort.”
The latest test occurred near San Nicholas Island, off the coast of Central California in the Pacific Ocean test range. The laser was mounted onto the deck of the Navy’s self-defense test ship, former USS Paul Foster (DD 964).
Carr also recognized the Office of the Secretary of Defense’s High Energy Joint Technology Office and the Army’s Joint High Powered Solid State Laser (JHPSSL) program for their work. MLD leverages the Army’s JHPSSL effort.
“This is the first time a HEL, at these power levels, has been put on a Navy ship, powered from that ship and used to defeat a target at-range in a maritime environment,” said Peter Morrison, program officer for ONR’s MLD.
In just slightly more than two-and-a-half years, the MLD has gone from contract award to demonstrating a Navy ship defensive capability, he said.
“We are learning a ton from this program—how to integrate and work with directed energy weapons,” Morrison said. “All test results are extremely valuable regardless of the outcome.”
Additionally, the Navy accomplished several other benchmarks, including integrating MLD with a ship’s radar and navigation system and firing an electric laser weapon from a moving platform at-sea in a humid environment. Other tests of solid state lasers for the Navy have been conducted from land-based positions.
Having access to a HEL weapon will one day provide warfighter with options when encountering a small-boat threat, Morrison said.
But while April’s MLD test proves the ability to use a scalable laser to thwart small vessels at range, the technology will not replace traditional weapon systems, Carr added.
“From a science and technology point of view, the marriage of directed energy and kinetic energy weapon systems opens up a new level of deterrence into scalable options for the commander. This test provides an important data point as we move toward putting directed energy on warships. There is still much work to do to make sure it’s done safely and efficiently,” the admiral said.
SA Phil:
"By "mundane" I mean challenges that someone can already see potential solutions for .. Using current technologies."
I could solve the overpopulation problem using current technology. Give everybody sequential serial numbers and shoot every odd numbered person. But I think there are reasons we don't do it that way.
The same goes for a lot of the proposed "solutions" for laserstar issues. There are reasons you either can't use them, or at least not effectively as claimed. Adaptive optics exist, but in a laserstar their actuators won't be pushing against a whole planet, but against a few thousand tons of spacecraft structure. Lightweight radiators can be made, but that doesn't mean they'll necessarily be built -- or even can be built -- with unassailable overload margins.
"In fact there are other, even simpler possibilities, once the laser exists.
A 100,000,000 ton icecube with a Nuclear reactor and one of these Lasers on it could fulfill the Laserstar objectives.
Melt Ice for Thrust
Melt Ice for heat dissipation
Etc."
I guess I'm really not supposed to ask this, but where does one hundred million tons of ice come from?
Tony:
"My point was technology neutral. for any given density of material per unit of radiated heat, the spacecraft designer is not likely to include more margin than necessary. If he wants to build in margin for active hostile heating, he's going to have to skimp somehwere else."
Very little of this discussion has been technology neutral (including your own objections), and radiator capabilities are no exception. Relative to the mass budget of the spacecraft as a whole, radiator mass is likely to be a marginal factor (not irrelevant, but small), and any designer of combat spacecraft worth his or her salt will account for active hostile heating. Besides which, safety margins well beyond civilian specifications would be a good idea in any case, giving generalized redundancy and resistance to battle damage.
(SA Phil)
Challenges with the Laser and its targeting I think I would lump into the "If the uber-laser exists" category
I was referring the the reactor/heat management/propulsion etc. Which would be extremely challenging, but not inconceivable.
----------
The giant ice cube? A comet .. or part of one.
It doesn't even have to be water, just some kind of Ice.
Raymond:
"Very little of this discussion has been technology neutral (including your own objections), and radiator capabilities are no exception."
But that point in fact was. Just because you can have more radiator per ton doesn't mean you install more of it. You install just as much as you need.
"Relative to the mass budget of the spacecraft as a whole, radiator mass is likely to be a marginal factor (not irrelevant, but small), and any designer of combat spacecraft worth his or her salt will account for active hostile heating. Besides which, safety margins well beyond civilian specifications would be a good idea in any case, giving generalized redundancy and resistance to battle damage."
Not really. You should read up on your naval history. You'd be surprised how many warships have been lost due to the failure of single fire mains. The lack of reserve buoyancy in most naval vessel types has actually been scandalous from time to time. Remember when they led convoys in the Persian Gulf with the tankers that were supposed to be under protection, because they were less vulnerable to mines than US Navy frigates? Or do you remember the USS Tripoli, an amphibious transport based on a merchant hull, that ran over an Iraqi mine in 1991 and stayed on station for a week before going into port for repairs? Battleships have been sunk by single mine strikes.
Frankly, I don't think laserstars would be built to begin with, because all of these things can be thought through before the first line was drawn in a CAD program.
SA Phil:
"Challenges with the Laser and its targeting I think I would lump into the "If the uber-laser exists" category"
But that's just the point. Who's going to build the uber-laser if there's no way to accurately target it, or maintain shot-to-shot precision?
"I was referring the the reactor/heat management/propulsion etc. Which would be extremely challenging, but not inconceivable."
But they would be impractical with current or reasonable foreseeable launch costs.
"The giant ice cube? A comet .. or part of one.
It doesn't even have to be water, just some kind of Ice."
Comets come in on hyperbolic orbits. How are you going to slow one down and move it to your shipyard?
Nukes go years between refueling. But there's only so much energy in the rods. Running at full power would run through the supply sooner than running at half. Would this potentially put a hole in the energy reserve or would even a heavy engagement represent a fraction of the normal expenditure over the life of the rods?
Running at high power does reduce reactor lifespan, but only close to the designed lifespan... something about decay products poisoning the reaction efficiency, IIRC.
"Military grade automation is no doubt likely to be expensive."
Military grade people are also expensive. They need a lot of training and indoctrination, and then they go and die on you and you need to start all over again.
Well, the autopilot on an aircraft is ~$2million. Training a pilot is also about $2 million, and the autopilot can't do combat maneuvers (yet). A combat-maneuvering capable 'FRED' (F'ing Ridiculous Electronic Device) would appear to cost a minimum of double the standard autopilot.
Carbon fiber structures might be a candidate from the strength perspective, but the bonding resins would probably have problems with the operating temperatures.
The stuff you're looking for is called reinforced carbon-carbon. It's used on the leading edges of the Space Shuttle, and you make it by heating the piece until the resins carbonize. How hot is re-entry plasma?
Active vibration dampening requires a noise sink much more massive than the equipment being dampened.
The AH101 uses active vibration damping of multiple-G flight loads, with actuators between the rotor mast and the airframe. I think a 1-ton mirror can be damped against even a hundred-ton spacecraft.
You are likely to end up using submarine minimal-vibration designs combined with 'sound mounts' (rubberized vibration dampers), but once you assume the mass costs for vibration damping into your big freaking laser, it all comes out in the wash.
Tony, I really don't get what your issue is with what is really a point-defense gun. The laser is big because the desired performance makes it so, but it's still the space equivalent of a Phalanx CIWS gun!
Note that as far as I'm concerned, the minimum laser energy delivery for combat utility is 25MJ per shot, based on the MIRACL tests back in the 1980s.
(SA Phil)
If there is no way to target it, then the uber-laser doesn't really exist.
If you can only target it at a much shorter range, it is decided less uber and then kinetics can much more easily kill the laser ship. At some point the laserstar becomes entirely impractical and the kinetics would wipe it out easily.
It is all a function of the effective range.
-----------------------
For lift capacity - we have to assume there is a marked improvement in this area or else Space Armadas don't exist. since Space Armadas are a given for the scenario .. some improvement in lift is implied.
-----------------------
As to the comet ...
Bring the parts to the comet (or fragment you hacked off) and build the ship there.
Since the comet solves all your reaction mass and heat problems, it is less problematic than it sounds.
Tony:
"Just because you can have more radiator per ton doesn't mean you install more of it. You install just as much as you need."
Conceptually and practically, I'd disagree. And the naval examples are illuminating, that's still a failure of design, not a flaw in the very concept, nor does it preclude more effective designs.
Considering that (for nuclear-electric craft especially, but also possibly the case with even aneutronic fusion) the heat rejection requirements of the powerplant will be far in excess of the laser, even if the craft isn't laser-armed at all, I'd budget a wide safety margin for radiators. It's simply a matter of survivability. If you destroy or disable enough of the radiator area, propulsion will be limited or disabled (most likely well before the laser is unable to fire) - and this applies to any source of battle damage, not just laser-based induced thermal overload.
Scott:
"The AH101 uses active vibration damping of multiple-G flight loads, with actuators between the rotor mast and the airframe. I think a 1-ton mirror can be damped against even a hundred-ton spacecraft."
All those do is smooth out the high-amplitude instantaneous loads. They don't remove the sound energy from the system. It's still rattling around in there, just with lower dynamic range.
"You are likely to end up using submarine minimal-vibration designs combined with 'sound mounts' (rubberized vibration dampers), but once you assume the mass costs for vibration damping into your big freaking laser, it all comes out in the wash."
As previously stated, you can accoustically isolate the weapon, but in doing so, and vibrations generated inside the isolation zone stay there. Remember all those adaptive optics actuators we seem to be so in love with?
"Tony, I really don't get what your issue is with what is really a point-defense gun."
I think it is an educated guess that something so seemingly dominant has to have practicality issues, because all uber-weapon concepts throughout history have. Even if I haven't accurately identified them, or have only been partially successful in doing so, I remain convinced that a real good reason or reasons why it can't work do exist. I've just got too much personal experience in practical military systems and their limitations, and have read to much military and technical history to be anything but skeptical.
Tony -
It seems to me that many of these same arguments could have been (and probably were) made about artillery being able to shoot with effect to multi-mile ranges.
After all, there were hundreds of years of experience showing that while cannons could lob a shot 2-3 miles, destructive effect required much closer ranges, usually no more than a couple of hundred yards. Navies were still assuming battle ranges of no more than ~3000 yards circa 1900.
In fact, it seems to me that the logic of the laserstar is not unlike that of the dreadnought battleship.
At the turn of the last century battleships carried a mixed armament of heavy but slow-firing guns capable of penetrating armor, quick-firing medium guns that could not penetrate armor but would wreak havoc topsides, and torpedoes to strike underwater below the armor.
In the dreadnought era only the heavy guns were retained as offensive armament. Smaller guns were retained purely for close-in defense, not for use against enemy battleships, while most battleships were not fitted for torpedo firing at all.
Yes, the ideal dreadnought carried eight big guns, not one, but that was due to particular technical considerations - salvo firing, weights distribution, and so forth. At a pretty mild level of abstraction, a dreadnought was a platform for a single offensive weapon system, its main battery.
Particular technical considerations could certainly modify my conception of a laserstar. If the optimum size and mass of the whole spacecraft turns out to be too big for the largest practical main mirror, you'll fit it with however many 'largest practical' mirrors it can readily carry.
Defense against kinetic attack will almost certainly be called for. One such defense, kinetics to take out the enemy bus, are probably better carried aboard a bus of your own, rather than directly aboard the laserstar - just as the first line of battleship defense against enemy light torpedo craft was the destroyer screen.
But for direct defense against incoming kinetics, so far as I can see the secondary armament of battleships is a misleading analogy - you want your biggest mirror(s) to engage a kinetic strike as well as enemy laserstars. (Simultaneous kinetic strikes along different vectors cause big problems, but making them simultaneous is very difficult.
Raymond:
"Conceptually and practically, I'd disagree. And the naval examples are illuminating, that's still a failure of design, not a flaw in the very concept, nor does it preclude more effective designs."
But that's the whole point -- naval vessels aren't vulnerable to seemingly survivable damamge because they are poorly designed. They're vulnerable because their design is the result of necessary compromises. Fast vessels like destroyers and frigates can't have merchant hulls, and they can't be too heavy. Battleships have to be bouyant enough to float their armor and weapons, but not too bulky, because they too have to be driven through the water at tactically useful speeds.
We all like to say that space is not the ocean, but there are very definite parallels. You don't just pile on mass because it would be useful for some purpose or the other. You've got performance issues to deal with, either delta-v, or acceleration, or both. You might want to put more radiator on the vessel, but you can't. More radiator might take up too much mass, and require too much extra remass (requiring more remass to bosst that remass, requiring more remass...). Or too much light radiator is too fragile under the accelerations and moments you're going to demand of yopur spacecraft.
"Considering that (for nuclear-electric craft especially, but also possibly the case with even aneutronic fusion) the heat rejection requirements of the powerplant will be far in excess of the laser..."
The heat rejection requirements of the powerplant include the power for the laser, and all necessary other draws, including propulsion and other things. The point of active heating of the enemy's cooling system is to drive him into choices he doesn't want to make:
Shoot less or maneuver less?
Shoot or maneuver, period?
Stop maneuvering and shoot less as well?
Stop shooting and maneuver less as well?
For these reasons, I think lasers just aren't going to be so big and powerful that they'd have such easily exploitable vulnerabilities. And if they're not that big and powerful, they're not going to be laserstars, or even primary weapons.
Tony:
"You might want to put more radiator on the vessel, but you can't."
And my point is exactly that there's no reason why you can't. This may be insufficiently technology-agnostic of me, but given the proposed options for plausible space powerplants and radiators, these are going to be minor compromises, rather than major ones.
Besides, what else would be creating this long-range thermal overload...except another laserstar?
Rick:
"It seems to me that many of these same arguments could have been (and probably were) made about artillery being able to shoot with effect to multi-mile ranges."
The problem, both on land and at sea, was effective fire control. I think you know my opinion of applying effective fire control to large, powerful lasers in space at more than a few thousand kilometers.
"In fact, it seems to me that the logic of the laserstar is not unlike that of the dreadnought battleship."
It is, for all the reasons you've outlined. But you have the fire control question still very (IMO) up in the air. Also, the vulnerability of radiators to hostile attempts at overheating exists, no matter how much some wish to deprecate it.
"Defense against kinetic attack..."
Is, I think, based on assumptions of detection and fire control effectiveness I'm not at all sure I buy. Incoming kinetics, until they power up their sensor coolers, are just going to be inert lumps, spinning for stability. You'll probably need active radar to detect them. As the attacker, I'd probably send in lightwieght decoys along with the active homing models. There are probably ways to discrimate the decoys from the active weapons, but the decoys are dangerous in themselves, so they have to be engaged.
And when you start shooting, we get back to the fire control issue of being able to actually hit small projectiles fast enough with all of the stuff going on inside your laserstar that can throw your shooting off. With all due respect Rick, your assumptions are based on unprecedented levels of detectability, reliability, and accuracy. You have your laserstar detecting the enemy attack at maximum theoretical effective range; hitting everything shot at at any range, with every shot; and doing enough damage to neutralize a threat that continues to exist until you blow it literally into space dust. I hope you can understand why I'm just not buying it.
Raymond:
"And my point is exactly that there's no reason why you can't. This may be insufficiently technology-agnostic of me, but given the proposed options for plausible space powerplants and radiators, these are going to be minor compromises, rather than major ones."
Many battleships, especially in WWII, wound up having their armor belts almost totally underwater because people kept adding indisputably necessary equipment topside, a couple of tons at a time. Many spacecraft have become less capable than desired, or required larger launch vehicles than initially planned, because engineers kept adding mass a few kilos at a time for this thing or that.
And that's the problem -- you're not making compromises, you're adding absolute amounts of extra mass to have bigger radiators for a given power output. More equipment mass means more remass. More remass means more remass. More remass...
"Besides, what else would be creating this long-range thermal overload...except another laserstar?"
My contention is that all this would be wargamed out and the engineers would say to themselves, "Let's take things in a different direction..." Even if one side did build laserstars, then we'd be back to the purple/green battle. Except the side that didn't build laserstars probably had a good reason (or a bad reason, it really doesn't matter) and would have developed an effective counter.
Tony:
So you have to armor not just the leading edge, but the longitudinal edge as well. Pretty free-wheeling with our mass budget, aren't you?
If what I am worried about is a diffuse beam with insufficient intensity to directly melt materials reducing my ability to shed heat, I don't need to armor anything. Just present near-zero cross section to the beam.
It's maximum efficiency at or near maximum capacity that you're aiming for.
For realistic radiator materials, efficiency (in terms of heat shed per unit area) always increases with increasing temperature. What limits you is material failure at high temperatures.
Watch how rough you make that surface, champ. You don't want it so rough that microstructures are radiating into each other.
Actually, yes you do. The microstructures radiating into each other is exactly what gives you high emissivity. It helps bring them into equilibrium with the radiation field and gives you a better approximation of a black body.
Atmospheric turbulence cahnges observing conditions at a low rate compared to the millisecond cycle times people are discussing here.
But at the same time you know when, where, and how much changes you will get.
Active vibration dampening requires a noise sink much more massive than the equipment being dampened. The mass of the planet Earth works very well for that. The hull of a spacecraft? not so much.
First, the hull of the spacecraft is much more massive than the mirrors.
Second, you can actively absorb the sound rather than moving it elsewhere. Better heat than vibration.
Radiator area could be limited by mass considerations.
If it is, then you are back to the case of a maximum of 25% efficiency, and radiation denial attacks are useless.
With any method of converting heat into work, there is waste heat coming out somewhere. There are not "out"s.
For the specific case I was discussing (getting around radiator limited designs), yes there is.
Tony, I know this will make you mad, but what the hell: after careful analysis, it seems to me that the basis of your argument against big lasers is that they can't be made perfect and so should not be built; nothing man builds is perfect, so your argument is deeply flawed. The argument should be under what circumstances and in conjunction with what other units should they be used? What mix of secondary armaments should it carry? All warships are vulnarable to some set of circumstances so they use tactics that minimize those vulnabilities. By your reasoning, the use of tanks should be discontinued because landmines, shoulder fired missiles, and cannon fire from other tanks can kill them. Do you see the circularity in your arguments? Maybe you should drop trying to kill off Laserstars and discribe your own concept for a spacewarship; if it is a superior concept, people will want to use it and drop the Laserstar concept on their own.
Ferrell
(SA Phil)
I think that relativistic kinetics could possibly give a Laserstar something to worry about.
Assuming you could get one with a decent chance to score a hit. Hard to do vector changes at relativistic speeds so it would need to be directed /mostly directed fire.
I just cant figure out how to get directed/semi-directed fire and relativistic speeds in the same place at the same time.
So I think the fractional light second Laser (if feasible) would be really hard to beat.
Except with some ungodly swarm of kinetic projectiles/missiles -- but that presents its own problems. (such as the intended victim rudely "sidestepping" the cloud of debris with a ten second solid rocket burn)
In the real world, the US navy now has this:
http://nextbigfuture.com/2011/04/navy-moves-step-closer-to-lasers-for.html
Navy moves a step closer to lasers for ship self-defense with a field trial that disabled a small ship
The Office of Naval Research successfully disables a small target vessel using a solid-state, high-energy laser mounted onto the deck of the Navy's self-defense test ship, former USS Paul Foster (DD 964). Credit: US Navy photograph
Marking a milestone for the Navy, the Office of Naval Research and its industry partner on April 6 successfully tested a solid-state, high-energy laser (HEL) from a surface ship, which disabled a small target vessel.
The Navy and Northrop Grumman completed at-sea testing of the Maritime Laser Demonstrator (MLD), which validated the potential to provide advanced self-defense for surface ships and personnel by keeping small boat threats at a safe distance.
“The success of this high-energy laser test is a credit to the collaboration, cooperation and teaming of naval labs at Dahlgren, China Lake, Port Hueneme and Point Mugu, Calif.,” said Chief of Naval Research Rear Adm. Nevin Carr. “ONR coordinated each of their unique capabilities into one cohesive effort.”
The latest test occurred near San Nicholas Island, off the coast of Central California in the Pacific Ocean test range. The laser was mounted onto the deck of the Navy’s self-defense test ship, former USS Paul Foster (DD 964).
Carr also recognized the Office of the Secretary of Defense’s High Energy Joint Technology Office and the Army’s Joint High Powered Solid State Laser (JHPSSL) program for their work. MLD leverages the Army’s JHPSSL effort.
“This is the first time a HEL, at these power levels, has been put on a Navy ship, powered from that ship and used to defeat a target at-range in a maritime environment,” said Peter Morrison, program officer for ONR’s MLD.
In just slightly more than two-and-a-half years, the MLD has gone from contract award to demonstrating a Navy ship defensive capability, he said.
“We are learning a ton from this program—how to integrate and work with directed energy weapons,” Morrison said. “All test results are extremely valuable regardless of the outcome.”
Additionally, the Navy accomplished several other benchmarks, including integrating MLD with a ship’s radar and navigation system and firing an electric laser weapon from a moving platform at-sea in a humid environment. Other tests of solid state lasers for the Navy have been conducted from land-based positions.
Having access to a HEL weapon will one day provide warfighter with options when encountering a small-boat threat, Morrison said.
But while April’s MLD test proves the ability to use a scalable laser to thwart small vessels at range, the technology will not replace traditional weapon systems, Carr added.
“From a science and technology point of view, the marriage of directed energy and kinetic energy weapon systems opens up a new level of deterrence into scalable options for the commander. This test provides an important data point as we move toward putting directed energy on warships. There is still much work to do to make sure it’s done safely and efficiently,” the admiral said.
Tony -
The problem, both on land and at sea, was effective fire control. I think you know my opinion of applying effective fire control to large, powerful lasers in space at more than a few thousand kilometers.
Yes. I believe I understand the general nature of your objections, and they are not really answerable with equations and such. There is a vast body of experience in warfare to show that weapons - even useful and successful ones - often have battlefield performance orders of magnitude below their bench test performance.
But let me explore another analogy. The infantry rifle is a classic example of the above situation. Match grade weapons can hit and kill at 1000 meters or more, but in the 'rock & roll' environment of firefights most of the shooting is at more like 50-100 meters. Indeed, my understanding is that modern assault rifles are less suited to precision shooting than the infantry issue rifles of 100 years ago.
All that said, snipers DO pick people off at very long ranges, approaching the bench range of the weapon. And in the peculiar conditions of space warfare there is a striking lack of underbrush, especially anywhere beyond a planet's inner orbital space.
So I've come to think that - by no means certainly, but more likely than not - there will be little or no rock & roll at least in the opening stages of a space battle, permitting lasers to achieve a fair approximation of their bench performance.
Returning to battleships for a moment, note that dreadnought era gun engagements were often fought at 10-20,000 yards, roughly half the nominal range of the guns, in spite of a lot of (literal!) rock & roll in naval battles, not to mention fog, mist, and other stage effects.
Tony:
"I was under the impression that the power plant had been sized for shooting or propulsion, but not both."
Power plants will be sized for whatever the most power-hungry component on your ship is. All less demanding components can then skim a little power off the top.
"What i see happening here is a lot of people convincing themselves of the dominance of lasers based on some very clever theoretical arguments. The problem is that reality places limits that theory doesn't recognize. Radiators are vulnerable."
Irrelevant. The biggest power-consumer is going to be your engine, so you're going to need radiators of about the same size whether you're using lasers or not. Lacking lasers on your ship won't make your radiators any less vulnerable. If lasers are really so good at overloading other people's radiators, as you suggest, then that's an excellent reason to build lasers immediately!
"The point about radiators is that they are vulnerable to being heated past their working limits. You don't have to melt them. You don't have to even make them thermally inefficient (though I think you can). All you have to do is heat them enough to press them past their mechanical limits, probably most effectively by overheating the coolant and causing overpressure issues."
You know, if I had a weapon that works by overheating its target, I'd aim it at any part of the enemy ship except the one specifically designed to handle high heat loads.
SA Phil:
"A 100,000,000 ton icecube with a Nuclear reactor and one of these Lasers on it could fulfill the Laserstar objectives."
Where are you getting a 100 megaton ice cube? Do you have any idea how big that is? The current largest vehicle in existance is only 0.65 megatons. The largest concrete structure is only 60 megatons.
And you also need to move around all that mass, so you're going to need a pretty big nuclear reactor to power those engines!
Also remember that due to the way the rocket equation works, if you're serious about using that 100 megaton ice cube as your reaction mass, you're going to need to find a new 100 megaton ice cube for every trip.
Tony:
"My point was technology neutral. for any given density of material per unit of radiated heat, the spacecraft designer is not likely to include more margin than necessary. If he wants to build in margin for active hostile heating, he's going to have to skimp somehwere else."
Yes. But he isn't going to need to skimp much, because we aren't talking about a large amount of additional heat.
There are a lot of optimizations you could make to any military vehicle if you could operate under the assumption that you will not get shot at. But nobody does, because that would be stupid.
"Just because you can have more radiator per ton doesn't mean you install more of it. You install just as much as you need."
Correct. But in this case "need" means for all combat purposes, including defense. If you expect to get shot at with any given type of weapon, then you will try to design your ship with whatever features it needs to be resistant to this weapon.
Tanks could surely move a lot faster if they ditched their armor. Ever wonder why they don't?
The added mass in radiators that we're proposing adding to these spaceships is, proportionally, far less than the amount of mass that tanks spend on armor.
"The point of active heating of the enemy's cooling system is to drive him into choices he doesn't want to make:"
The point is that those choices will only cause him minor inconvenience. They won't be mission-threatening.
SA Phil:
"I think that relativistic kinetics could possibly give a Laserstar something to worry about."
Where did you get relativistic kinetics? Were they a complimentary gift when you bought your 100 megaton ice cube?
Any macroscopic relativistic objects are well beyond the plausible midfuture technologywise.
Milo,
Where did you get relativistic kinetics? Were they a complimentary gift when you bought your 100 megaton ice cube?
Any macroscopic relativistic objects are well beyond the plausible midfuture technologywise.
=========
I think perhaps you should have read a bit closer.
I also said I could not figure out how it to do it.
Thus I didn't get them.
Reinforcing how valuable a laser with a long range really is.
Milo,
"A 100,000,000 ton icecube with a Nuclear reactor and one of these Lasers on it could fulfill the Laserstar objectives."
Where are you getting a 100 megaton ice cube? Do you have any idea how big that is? The current largest vehicle in existance is only 0.65 megatons. The largest concrete structure is only 60 megatons.
And you also need to move around all that mass, so you're going to need a pretty big nuclear reactor to power those engines!
Also remember that due to the way the rocket equation works, if you're serious about using that 100 megaton ice cube as your reaction mass, you're going to need to find a new 100 megaton ice cube for every trip.
=================
Yes I imagines a fragment of a comet or a small comet. The 100,000,000 ton is actually not necessary it was just a placeholder value for "really big ice cube" a 100,000 ton ice cube might work instead, Depending on the actual mission requirements.
So either find a comet blow one up into pieces with nuclear weapons ..
And then use it as part of the space craft.
Since you can have massive mass flows in the form of steam, you should be able get a very respectable thrust number in order to get milligees of acceleration. (horribly inefficient of course)
And yes, you are correct you would need a new ice cube every time. That is the downside to the design.
(SA Phil)
Sorry, the previous two posts were by me.
Basically -
I cant figure out C fractional mass drivers either.
And
Yes giant Ice cubes comet/chunk spacecraft are weird. However I am hardly the first person to suggest the idea.
Anyway, back to what the original subject was...I think...
The use of high delta-V combat drones at less than one light second from the 'mothership' is a concept I can agree with; automated robodestroyers in space just seems like a really bad idea militarily that would appeal to some types of politicians, and leave it at that. The whole Laserstar vs. Kineticstar argument seems false to me because any decent designer would have a mix of weapons on a single ship. If you expect to get heated by your opponent, then design in heatsinks; the average length of any space battle will probably only last about 200 seconds, so for X amount of total heat you radiate during that time, make your heatsinks' capacity 2X for 200 seconds. Problem solved.
Ferrell
Re: Ferrell
I'm not deprecating laserstars because they're imperfect. (And I'm not even angry that you think I am.) I simply think they are overspecializations with little chance, as described by Rick, of being tactically effective or economically practical.
And I've already described multiple times what I think a space warship would look like -- a balanced (in terms of weapons, propulsion, and protection), manned unit. There would possibly be class-specific, mission- oriented optimizations in larger navies, analogous to the surface warfare vs antisubmarine optimizations in escorts in modern navies. I suspect that this vision doesn't catch on with a lot of people because it's too obvious, non-specific, and mundane to excite the imaginations of people looking to make space warfare different and somehow sexier than just more of the same thing people have been doing for the last 5000 yrs.
The above pretty much goes for every other recent counterargument. The laserstar is a neat tactical theoretician's toy, but it's simply not likely to be practical in application, for all the reasons I've already outlined multiple times.
I suspect that this vision doesn't catch on with a lot of people
On the contrary, while details vary, I think the next following discussion thread suggests that your vision is much closer to what the community as a whole wants and expects than what I've proposed in these posts is.
(After all, a major function of this blog, as it has developed, is to challenge familiar space/SF tropes.)
(SA Phil)
Actually for the longest period of Naval warfare in history, Warships were highly specialized and only had one weapons system.
Any other weapons on ships were far less effective.
The oared Ramship dominated for over a thousand years.
------------
I think the chaotic maneuver highly kinetic weapon scenario is more interesting as well.
But if you extrapolate a Light Second Effective Laser - The numbers sure seem to be in its corner.
As a galley geek I'll have to quibble - the ram was only occasionally the primary weapon, and never the exclusive one. Even Athenian triremes carried a few javelin troops, and boarding was the primary tactic through most of the galley era.
Regarding lasers, even ranges much less than a light second provide an awful lot of dominance. In my exploration of laserstar characteristics I was actually looking mainly at ranges on order of 3000-30,000 km, thus 0.01-0.1 ls.
(SA Phil)
Hmm, I was given a different impression about how the ramming worked.
Basically the a favored tactic when the sides were even was to try to "ram" through one of the oar sides, so the attacking ship remained mobile and unentangled.
And then direct ramming (which could include boarding) when the odds seemed good.
But I could be wrong. Since I was not there, my knowledge is only as good the sources I have seen.
You mean shearing off oars? Yes, that was a common tactic. But the primary weapon was boarding.
There's a marked bias, at least in the anglosphere, to regard boarding as somehow unseamanlike, 'a land battle fought at sea.' That was not really the case; superior seamanship conveyed major advantages. For example, think of the advantage of a well ordered line over a ragged one.
Bigger galleys meant bigger boarding parties, which explains tetrēreis (i.e., "fours", sing. tetrērēs) and pentēreis (i.e., "fives", sing. pentērēs).
In the age of sail, bigger ships meant more cannons and much larger ones, hence monster first rates like the Nuestra Señora de la SantÃsima Trinidad which ended its life with 140 guns.
In the age of steam, Dreadnaught battleships eventually reached a climax with the Yamato with an 18" main gun battery (although US battleships were far better and balanced designs).
We see the same thing with aircraft carriers (US Navy carriers have air wings bigger than some nation's air forces), and it is a fair assumption that any space warcraft will expand to carry the largest practical weapons battery. FEL lasers of up to a megawatt have been proposed for 747 carrier aircraft, the limiting factor in this case being there are no larger aircraft in common service. If a 747 sized laser can scale to a megawatt, then a 747 sized spacecraft might be the minimum size for a space warship, and things can only get bigger from there.
Tony, I actualy do agree with you on balanced weapons mix on space warships; I just wanted to try to get the discussion back on track :) I also believe there should be a mix of ship types in any space fleet to be effective over a wide range of circumstances. We all have a tendency to 'beat a dead horse' and I'm just as guilty of it as anyone else!
Ferrell
(SA Phil)
Doesn't a Laserstar constellation give quite an opportunity for mixed ship types?
The Laserstar could be escorted by both offensive and defensive ships with a mix of kinetics and shorter range directed energy.
And to change vectors back on topic those ships could easily be drones.
Rick:
"There's a marked bias, at least in the anglosphere, to regard boarding as somehow unseamanlike, 'a land battle fought at sea'."
Which may be a good thing if your heroes are landlubbers who just happen to travel by ship once, and you want their skills to still be useful when that ship gets attacked!
Not to mention the fact that the villain doesn't have to worry about how to convey his diabolical monologue through semaphore.
Actually, boarding actions in space do in fact make sense to a degree. No matter what it's carrying, any interplanetary or interstellar-capable spaceship is almost guaranteed to be more valuable than its payload (in fact, even if you were after the cargo it would make more sense to take the ship anyway since you'll need to move it in the first place). Even if it's only for the parts and remass, a spaceship represents a significant investment in resources, logistics and personnel, and as such is going to be worth a lot of money in its own right.
Tony:
Can you please stop being contradictory. If we can afford lots of humans (5 tons a piece) how are we shaving grams on radiators? If lots of crew is practical, then by definition, things like armor are. At 125 kW/kg, if I can shave a crewmember, then I can add 625 MW of waste heat disposal. You can't have it both ways.
On a larger level, I have gotten the feeling over the course of this discussion that your opposition has taken on a life of it's own.
"Laserstars must be impossible. So what that you have shot down all of my previous arguments? Here's some new ones, and I'll change reference frames to keep the battle going."
I am not claiming that they are ultimate weapons. But things like tanks are built around one weapons system. And nobody is really advocating having absolutely only one mirror, just one offensive one.
Mangaka2170:
Nobody's been advocating boarding. It came up while discussing galleys.
Thinking even further, if there is a trend to build larger and and more capable ships, there is also a counter trend that the most useful ships are much smaller fleet units.
The Roman Navy made great use of the liburna rather than larger tetrēreis and pentēreis, while later on small galliots did most of the grunt work for the Ottoman Empire and the Serenìsima Repùblica Vèneta even if larger galleys like "Lanterns" or "Capitanas" were considered the core of the fleet.
In the age of sail, frigates did a lot of the work suppressing pirates and the other day to day activities of navies, and Dreadnaughts and Aircraft Carriers may show the flag, but Frigates and Destroyers once again carry a large part of the load.
For operatic space navies, we may have constellations of Kinetic and Laser stars, but the day to day activities will be carried out by "LEM warrior" type cutters and patrol ships in orbit.
Boarding came up in the context of galleys, but the patrol task of boarding suspicious spacecraft could be where much of the action turns out to be.
Which relates to Thucydides' point. It is notable that very little fiction in the 'wooden ships and iron men' genre takes place aboard 3-deckers, or involves great fleet actions. It would not be surprising if the same applied to space.
Regarding laserstars, there is a reason why a couple of earlier posts in the discussion were called 'battles of the spherical war cows.' We need to know the general characteristics and possibilities of space weapons before we can really explore their use in service.
I have not yet engaged - pun intended - with the implications of combined arms action involving both lasers and kinetics, weapons that I tend to see as complimentary rather than alternatives.
Over the years, as I say in the following post, I've been more a kinetics guy, which is one reason I'm particularly interested in exploring the maximum potential of lasers within an overall tech framework.
I think that most of us have come to the conclusion that a mix of ship types, weapons systems, and manned and unmanned ships are the best for space forces...the details are what we're uh...disgussing... :)
Ferrell
(SA Phil)
I don't see how you could realistically board another spacecraft - unless it was disabled
Even if both ships were unarmed, as long as they can both move under their own power - the boarding cant really take place.
If one is disabled, or one unarmed - then I can see it, although the habs will probably be as small as feasible.
And it might be simpler just to punch a bunch of holes in the hab and wait a few hours/days for their space suit air to run out.
Byron:
"Can you please stop being contradictory. If we can afford lots of humans (5 tons a piece) how are we shaving grams on radiators? If lots of crew is practical, then by definition, things like armor are. At 125 kW/kg, if I can shave a crewmember, then I can add 625 MW of waste heat disposal. You can't have it both ways."
Except that I'm not trying to have it both ways. The laserstar, as described by Rick, is an independent, unmanned, self-propelled gun mount. If there's any application that demands mass consciousness, that would be it.
"On a larger level, I have gotten the feeling over the course of this discussion that your opposition has taken on a life of it's own. 'Laserstars must be impossible. So what that you have shot down all of my previous arguments? Here's some new ones, and I'll change reference frames to keep the battle going.'"
Ummm...not quite. I'm skeptical of dominant single weapon system, both from personal experience and lengthy study. It would pretty much be unprecedented. Even in the age of big gun battleships, their actions were pretty much limited to fighting each other in broad daylight. At night, and/or when there were torpedo launching craft around -- from submarines to destroyers, and eveything in between -- their operations were severely constrained. Even with radar fire control, as at Surigao Straight, torpedoes tended to do the real battleship killing. So I look for the holes in any system that somebody claims overwhelming dominance for.
But I don't think about this stuff 24 hours a day. So if it takes me more than one post to think of all the angles, please excuse me. I'm just one guy. But I do think it should be interpretted as cautionary that different angles do keep suggesting themselves as time goes by. It should make one seriously wonder, IMHO, if the laserstar is really all that.
"I am not claiming that they are ultimate weapons. But things like tanks are built around one weapons system."
Things like tanks have very limited utility, all things considered. I've seen tanks withdrawn in combat when infantry stood their ground, because they were concerned about air strikes -- friendly air strikes.
"And nobody is really advocating having absolutely only one mirror, just one offensive one."
Then what are they advocating? Because we keep hearing that the primary justification for laserstars is that if you're going to have a laser, you have to have the biggest one possible. That implies a single, maximal laser per spacecraft.
Yes. And we have submarine threats in space all the time. And there's water to run torpedoes through. I'm not claiming that it's the ultimate weapon, just that it will dominate the tactical picture just as the battleship did. Think about it. Why did torpedo boats come into existence? To kill battleships. Why were destroyers made? To protect battleships. Carriers? Scouts. I do understand that you only have so much time, but you seem to switch arguments with great regularity.
The one big laser does work the best, but Luke has pointed out that a single generator can have multiple beam paths, for various uses. At close enough range, it's better to zap two brilliant pebbles then it is to zap one at four times the intensity.
(Incidentally, the size on those keeps changing. Earlier in this thread, you said desk-size, but on SWXIV, you said 10 kg. Can you really fit all the stuff in that sort of thing?)
Early Roman warships used a "Corvus" to grapple enemy ships and provide a gangway for Marines to storm the enemy ship. Think of a gangplank with a set of claws or spikes on the bottom.
A Rocketpunk patrol/boarding craft for orbital use might have a similar device that combines a cutting head, airlock and a pressurized tunnel to allow customs officers/police/Marines to move from the cutter to the hostile ship. A set of extendable arms with grapples or claws to pull the ships together also seems to be in order here.
I can see a ship shaped something like a deep pie plate, with a ring of thrusters around the edge to provide a high degree of mobility, several of the grapple/landing legs (for docking on a cooperative target you just gently grab the docking collar's handles and pull in) around the face and the "Corvus" in the center. A complimentary airlock would be in the back face of the cutter (bottom of the pie plate).
A weapons mount would be co-located with the Corvus, and the internal arrangement would probably be an open drum with cargo nets to hold everything and everyone in place. I don't see this sort of patrol cutter spending more than a few days at a time on patrol, nor carrying large numbers of customs officers/police/Marines. Maybe an all up crew of 4+8 would be sufficient and nothing more powerful than a 25mm Chain Gun as the weapon (with an option to mount a missile launcher if needed).
A quick and dirty sort of military/paramilitary vessel
Byron:
"Yes. And we have submarine threats in space all the time. And there's water to run torpedoes through."
Don't be facile, Byron.
"I'm not claiming that it's the ultimate weapon, just that it will dominate the tactical picture just as the battleship did. Think about it. Why did torpedo boats come into existence? To kill battleships. Why were destroyers made? To protect battleships. Carriers? Scouts."
In the end, the battleship only dominated the tactical picture vis-a-vis battleships. They couldn't come close inshore because they ran on mines or got torpedoed by, well anything carrying torpedoes. Some battleships were torpedoed in anchorage, by both submarines and aircraft. And battleships without air cover pretty regularly got sank by both land and carrier aircraft.
And neither torpedo boats nor submarines nor aicraft were designed as direct counters to battleships. Torpedo boats of all types -- including submarines, which are just a highly specialized type of torpedo boat -- were originally designed to give smaller navies an alternative to the battleship for certain missions, freeing up what battleships they had for encounters on the high seas.
"I do understand that you only have so much time, but you seem to switch arguments with great regularity."
Actually, I add arguments as they occur to me. Case in point:
"The one big laser does work the best, but Luke has pointed out that a single generator can have multiple beam paths, for various uses. At close enough range, it's better to zap two brilliant pebbles then it is to zap one at four times the intensity."
Which brings me back to my initial argument, the one I started out with, have not abandoned, and have not changed -- it only works if your firing platform is stable enough. I don't believe it can be kept stable for targetting ship sized objects at significant fractions of a light second. I don't believe that that they could be kept stable enough to attack small homing kinetics at more than a few thousand kilometers at best.
"(Incidentally, the size on those keeps changing. Earlier in this thread, you said desk-size, but on SWXIV, you said 10 kg. Can you really fit all the stuff in that sort of thing?)"
Imprecision on my part, but not malicious or deceptive. The desk sized projectile would be something from the operatic or demi-operatic environment. It would be more properly called, in SDI terminology, a "smart rock".
The 10 kg "brilliant pebble" is actually based on SDI research, and is intended to be typical of the more nearterm space combat environment. It is essentially an IR sensor, a microcomputer, and four cold gas thrusters (for x and z axis translation). You can get that down to one thruster if the bus can spin the projectile at 10 rpm or better.
I used the term "brilliant pebble" for both because I thought it would be more recognizable to the interested layman. That's because it's still being kicked around today in ABM discussions.
"Yes. And we have submarine threats in space all the time. And there's water to run torpedoes through."
Don't be facile, Byron.
You started the comparison, not me. When I saw reference to stealth threats, my sarcasm kicked in.
In the end, the battleship only dominated the tactical picture vis-a-vis battleships.
Not really. Most of the tactical development before WWII was centered around battleships. If you missed it, all of those developments were somehow to support or undermine them.
And neither torpedo boats nor submarines nor aicraft were designed as direct counters to battleships. Torpedo boats of all types -- including submarines, which are just a highly specialized type of torpedo boat -- were originally designed to give smaller navies an alternative to the battleship for certain missions, freeing up what battleships they had for encounters on the high seas.
That's not how I'd describe it. A torpedo boat was the predecessor to the modern missile FAC, and it was there mostly to sink battleships. Yes, you are correct in that that is something battleships otherwise would be doing, but they were useless for other missions.
And I never claimed that aircraft were designed to counter battleships. I claimed that carrier aviation started off as scouting for battleships, which is true.
I question if the Brilliant Pebble can have the sensors needed to engage a ship at long range. It'd be pretty easy to jam with an IR laser at low power, and probably not too tough to decoy. And you would know where it's coming from, as you saw the missile that launched it.
Oh, and I will admit that coastal work has a good parallel-low orbit. The solution is simple in both cases. Don’t go there. There are other ships for that.
I dont see the nuclear reactor = high crew size connection.
The reactors we are talking about would not have the shielding and containment of a naval reactor, they would have just the reactor chamber and a shadow shield.
Reactors and the containment system are not flight-serviceable. It's the massive number of systems that flat-out will require maintenance to remain functional for 90+ days and still be affordable in quantity. Current civilian ships the size of a military vessel have a crew of a dozen, maybe two dozen if they still have a deck department. A military ship has dozens of systems that the civilian ship does not have, each one of which requires people skilled in it's use and repair so that it's failure doesn't result in the failure of the mission and or loss of the ship. Those systems include ship's crew to manhandle cargo in unimproved ports in the case of supply ships.
"The AH101 uses active vibration damping of multiple-G flight loads, with actuators between the rotor mast and the airframe. I think a 1-ton mirror can be damped against even a hundred-ton spacecraft."
All those do is smooth out the high-amplitude instantaneous loads. They don't remove the sound energy from the system. It's still rattling around in there, just with lower dynamic range.
No, they are active noise attenuation actuators, flexing the hull to create an out-of-phase vibration that (nearly) completely cancels the vibrations caused by the flight loads. Antinoise like those fancy Bose headsets, not passive damping like 'mickey mouse ears'. Those units are actually far more effective than passive sound mounts. I'm pretty sure that several submarines use such, and radiate maybe 100w acoustic into the water. Or less, and you're talking about tens to hundreds of megawatts of generated energy inside that hull.
Expensive? Yes. Mass-intensive? Probably, but if you need it for the laser to be effective, it will be in the budget.
=====
My assumed combat ship design is like the Sulaco: 100MW+ Laser(s) with multiple large (~2.4m) combat mirrors, dumb kinetics, smart kinetics, and possibly particle beams.
Sensors are a large number of 1m telescopes (both IR and visible light), arrayed into an effective aperture of about 50m; radar and LIDAR for active search; a 'fuzzbuster' ESM suite; and some others to be added later.
Yeah, the optical-search is probably overkill. Gotta be able to look in all directions at once, though!
This is a big ship. A good 300m long, with a 40m hab centrifuge for the ~85 crew needed. This gives me a nice ~200m liniac to feed the laser(s) in the truss between the reactor and the hab section. That's not xrays, but that's up in the extreme UV range, IIRC.
However, this is about the *minimum* size I would consider to be combat capable.
Scott:
Personally, I prefer toroidal accelerators for free-electron lasers. They're a little more massive per unit length, but if you're working with hard UV or soft X-ray wavelengths, you'll have to use grazing mirrors, which limits your ability to redirect the beam path. Using a toroid instead allows you to mount two mirror assemblies, one on each side, one pointing fore and one aft, which gives you better coverage in general and especially when decelerating into a combat zone. It also allows you to have auxiliary wiggler/mirror assemblies for visible-wavelength lasers using the same accelerator, and still gives plenty of space in the middle for radiators, habs, whatever. (Bonus: it gives you the basic layout for the ships from the Independence War game, which I rather adored.)
I don't think particle beams would be bothered with much, though - lasers will get you almost if not as much power, with less spread for a given range.
"As previously stated, you can accoustically isolate the weapon, but in doing so, and vibrations generated inside the isolation zone stay there"
What could be done is to transit the acoustic and vibration energy to a fluid-containg sink (ie propellant tank). The vibrations would be smoothened out by liquid flow, allowing better aiming. Or you coudl have a mechanical pendulum which only bounces back the vibrations at a well-known rate. You shoot between the swings, when all the vibration energy is contained in the swinging mass (you spin it dimwits, I'm not proposing a grandfather clock with gravity tech).
"My assumed combat ship design is like the Sulaco: 100MW+ Laser(s) with multiple large (~2.4m) combat mirrors, dumb kinetics, smart kinetics, and possibly particle beams"
Dumb kinetics are useless at the PMF laser ranges here (yes even at 1000km, they have to have 18km/s from the start against milligee ships).
Particle beams are when the FEL is run without the wigglers, and uncapped. Electrons shoot into space. Otherwise it is a huge mass penalty (on the order of coilgun masses).
Better have the laser, missile pods, and explosive shotgun/grenade launchers attached to the hull.
"Personally, I prefer toroidal accelerators for free-electron lasers."
The best design, but right now I'm thinking of trying to make the linear accelerator coil inside a cylinder, making a spring-like shape.
One possibility this forum hasn't yet considered:
The PMF space history is probably going to be preceded by lots of technological breakthroughs in the civil and Earth-based applications domain, with unmanned probes the sole to claim space as their initial application.
This therefore predicts biotech and electrical interfaces to be much more probable in 100 years than fusion torches or even wimpy laserstars.
Habs? Riders? CC ships? Hell no. Brain in vat crew with large expert-system support linked into the ship for minimal cost and mass. You can afford them for every ship, get zero human-to-drone lag and negligible performance penalties (100kg in 2m^3 attached to a ship with a kiloton dry mass).
My take on laserstars: Neat idea, wrong application.
If laserstars accelerate in milligees and can be killed with a much cheaper kinetics wave, they won't be mobile.
You'd keep 4 laserstars (full orbital coverage) in low orbit with only maneouvering thrsters.
They can be resupplied within the hour, maintenance is a shuttle mission away, ranges cover several tens of thousands of km.
Anything further away is interplanetary missile territory, or fleet-killer kinetics waves.
Need to upgrade? Don't give the damn thing engines and armor. Give it longer range. And even longer range. And then...
It's always cheaper to add a second section to your laser than to add a nuclear-electric thruster, always easier to increase range than to move the laserstar (laserstation here) closer.
This assumes that:
a)Earth is a major player
b)We can make 100nm lasers but...
c)the atmosphere is too much of a hinderance so we keep the BAL in orbit
d)We have chemical thrusters, nuc-electric stuff but not fusion magitech. They're enough for IPMs and anti-Fleet KKV waves, and are PMF.
Then what are they advocating? Because we keep hearing that the primary justification for laserstars is that if you're going to have a laser, you have to have the biggest one possible. That implies a single, maximal laser per spacecraft.
Or there's design constraints. We never saw Paris guns on ships because it just wasn't practical. You could only make a gun so big and still fit inside an armored turret.
Now lasers aren't going to be exactly like battleship gun mounts with photons so the question is whether an ideal laserstar would be equipped with one big, honking laser or whether there's call for several. Earlier discussions said that one laser, several emitters would be possible so maybe there's dorsal and ventral emitters on raised towers so that there's a cone of fire slightly greater than 180 degrees so there's no blind spots.
Having to engage multiple prime targets simultaneously and on all sides is probably more Star Wars than realistic. I think multiple incoming kinetic impactors would be the closest we'd get to that. And then there's the question of whether the big emitter will be agile enough for that kind of work. I have no idea. Maybe there's call for point defense emitters that are smaller, handle smaller energy loads but are perfect for targets to small and too fast to target with the big emitter.
(Caveat on this that I have no idea which way the physics would argue it; I'm completely willing to be convinced either way.)
Scott:
What would those systems be, and why can't they be made more reliable? Sensors are the only things military vessels will use in cruising that civilian ships don't have. They're solid-state electronics. Not a lot of maintenance required. Ask ElAntonius if you don't believe me.
Lasers or whatever won't be in constant use. They might have to be checked occasionally, but I don't see the constant work required on modern naval vessels.
I don't think we'll agree here, either.
KraKon:
Carriers can be killed with a wave of much cheaper anti-ship missiles. They're still around. I see laserstars assuming the center of space warfare tactics, how the battleship was in the first part of the century, or the carrier in the second. Other stuff will be used, but around it. After all, things like interplanetary kinetics need a target, and they work a lot better as defensive weapons.
jollyreaper:
Agility doesn't really enter into it. Any kinetics will be CBDR, so you just have to point at them and they'll stay there.
Byron:
"You started the comparison, not me. When I saw reference to stealth threats, my sarcasm kicked in."
Well, keep it under tighter control, B. The point was that there are counters and alternatives to everything, not that there could be stealth in space.
"Not really. Most of the tactical development before WWII was centered around battleships. If you missed it, all of those developments were somehow to support or undermine them.
Mostly to undermine them. And that's my point -- battleships never even dominated battles against other battleships. In all of those engagements, the actual use or fear of torpedoes had significant tactical effects. Beatty broke off the engagement at Dogger Bank due to a (spurious) periscope sighting. Jellicoe broke off at Jutland due to an actual torpedo attack. The Japanese actually built a whole navy based on using light forces to attrit the USN coming across the Pacific. In the actual event battleships were lost to torpedoes, air attack, light force gunfire -- just about everything except battleship gunfire, with the notable exception of the Kirishima. And that ship only got in an engagement against US battleships as a consequence of desperation on both sides -- neither navy really wanted to risk it's battleships within the envelope of enemy air cover, but they were down to nothing but battleships.
That's the same situation I find laserstars in. They are really good at engaging other laserstars, but otherwise they're pretty much a tactical and operational handicap.
"That's not how I'd describe it. A torpedo boat was the predecessor to the modern missile FAC, and it was there mostly to sink battleships. Yes, you are correct in that that is something battleships otherwise would be doing, but they were useless for other missions."
The whole point of torpedo craft (and mines) was to make approaching the enemy shore too risky and expensive, meaning that close blockades could not be established. This wound up creating the distant blockade, where torpedo craft (in the form of submarines) were used in attempts to counter. So, a craft deisgned as a deterrent to close approach wound up being an oceangoing instrument for imposing a blockade of its own. The actual engagement and destruction of battleships was almost an afterthought by 1917.
"And I never claimed that aircraft were designed to counter battleships. I claimed that carrier aviation started off as scouting for battleships, which is true."
I didn't mean to imply that you did. I just included aircraft for the purpose of completeness. And carrier aviation, whatever the battleship admirals thought, was from the very beginning trying to figure out how to sink battleships. They just played the scout game to keep the money flowing.
"I question if the Brilliant Pebble can have the sensors needed to engage a ship at long range. It'd be pretty easy to jam with an IR laser at low power, and probably not too tough to decoy. And you would know where it's coming from, as you saw the missile that launched it."
Unless your IR laser was powerful enough to burn out the IR sensor.
(At which point you might as well be shooting a real laser weapon at it.) All it would do is provide a real nice target to home in on, like anti-radiation missiles home in on actively emitting radars.
Decoys have already been successfully discriminated by current BMD brilliant pebbles. It's just real hard to make a flare or a balloon look like an RV. It would be even harder to make one look like a substantial spacecraft.
WRT to knowing where it's coming from, that's certainly a valid argument. But these things are very small and running at very low power until the terminal phase of the attack, so you probably have to identify them with active radar. Now radar does have trouble discriminating decoys from similarly sized and shaped warheads. That may or may not be significant, but it is another complication to the combat environment.
Scott:
"No, they are active noise attenuation actuators..."
The problem is that there's nothing outside a spaceship to dump sound into. It has to be radiated away as heat. And while you may be able to effectively attenuate sound by active dampening, all you can do is even out the thumps so that the ship has a case of low amplitude jitters. If you want to add mass to absorb those jitters, you could certainly do that, but then that mass has to be moved around to wherever the ship goes. And using tanked reaction mass works less and less well the more reaction mass gets used up. You have to have a dedicated dampening mass.
A Rocketpunk patrol/boarding craft for orbital use might have a similar device that combines a cutting head, airlock and a pressurized tunnel to allow customs
I forget who it was but a writer from the golden age of SF was convinced boarding actions would be incredibly common in space combat. His argument was as follows: you thrust at the enemy and he thrusts at you and you make your pass, firing at the closest point, jousting with spaceships. You then counterthrust and have another go at it. If the weapons aren't powerful enough to cripple ships with a single hit, the combat continues. Each pass is closer and closer as there's less velocity to build and kill during the fight. Eventually the ships are damaged and close to each other and one of the captains decides to ram the other and directly board.
I was never entirely convinced by that argument. My assumption is that in the normal course of combat, weapons will be utterly devastating; the enemy either misses or your ship is obliterated. But that's just an assumption. Let's assume that boarding actions can be fought. Would the defenders really allow their ship to be captured? I could see fighting in the hope of fending off the enemy but if you are about to lose, do you have a standard scifi reactor core that can be overloaded? Your enemy's just latched onto a fireship.
Ok, so let's look at history. Ships of the line did not have atomic scuttling charges or explody reactors. They did have powder magazines. And we know those ships were capable of blowing up real good. I'm pretty sure I've read a few accounts of ships that were deliberately sabotaged with powder magazines but the saboteurs were not on a suicide mission, they were trying to get our with their skins intact. But has there ever been a case of a boarding action that ended with a suicidal act of defiance, blowing up the magazine? If not, there's an argument to be made that crews won't blow up their ships if they think there's a chance of becoming POW's and getting traded back in a year or two. Could an enemy be too horrific to surrender to? Russians and Germans surrendered to each other in WWII and conditions in the camps were supposed to be worse than on the front. Perhaps that's a testament to the power of positive thinking, that anything has to be better than the hell we're living in now.
But let's say we're in a scenario where the warship has to chase down a courier vessel and retrieve stolen data tapes containing the plans for an imperial superweapon. They can't just destroy the target, they must positively capture the tape, interrogate the senator and see if copies have been made. We'll ignore the question of why the tapes weren't just transmitted in the first place or duplicated a hundred times and sent via multiple ships.
Talk has been made of laserstars performing laser surgery on target ships. Let's assume that the laserstar's own defenses are capable of withstanding attack by the target, that there's no risk of losing the laserstar to return fire. In that sort of situation, I think successful capture would be far less likely. So, the first thing that would make sense is to immobilize the target. Is the ship a truss-and-doodad design where all the parts and pieces are clearly visible or is it a more traditional scifi design where everything is tucked within an armored shell?
If the engines are on a truss, it should be possible to cleanly sever the truss without harming the hab section. Maybe low-power shots against the engines could simply disable them, melting them to the point where the safety cutoffs activate.
Now the ship can't get anywhere. I like the suggestion about radiators. Low-power shots against the radiators will keep the heat rising inside the ship -- the laser is used as a heat lamp at this point, not actually doing damage to the radiators (yet). The attacker can hail them and demand surrender.
If they remain stubborn, shuttles can be sent over as boarding craft. The laserstar itself would not board the ship. Could you imagine what would have happened to the Star Destroyer if Leia's ship self-destructed inside? I think SOP would be to treat any captured vessel as a giant bomb until EOD clears it.
So the shuttles fly over. If the ship self-destructs, the most you lose are the shuttles and boarding crew. (and given the quality of remotes, there might not even need to be a boarding crew.) The boarders would first try to ascertain the location of all the people onboard. Knockout gas is supposed to be an impossibility, too hard to gauge the dosage -- you might put some people to sleep and others could OD and die. So the next best thing would be cutting a hole in the hab and bleeding off air until the pressure drops past the point where people will maintain consciousness. Ship's life support will keep dumping more air in from reserves until exhausted. The boarders will likely be filling their own cylinders with the bled-off air and can add it back in as required. All that's left would be defenders with their own air supplies. As to how you take them out, that depends on whether you're a strong believer in drones and automatics or whether you think you need spacemen with guns. I'm a fan of the idea of a tackler drone. It's either snake-like or octopus-like with very strong, padded tentacles. It will tackle a target and wrestle them to immobility. What if it gets shot? It's only a non-thinking machine so it can take risks; the next bot will get the shooter or the bot after that. Tacklers will work against people with independent air supplies, who don't have any exposed skin for a wasp drone to sting and deliver sedatives.
Simultaneous to this, there needs to be attention paid to the main computer, make sure there's no dead man's switch or any other devious programming that will make the whole place go boom. Once the ship is rendered safe, the prisoners are brought back to the boarding craft and returned to the warship. If there's inherent value to the captured ship, salvage crews could attempt to take over control and render it spaceworthy.
As a general rule, any tech will tell you that a box that's been rooted by a hacker can no longer be trusted, even if you think you caught everything he did. Nuke the OS and reinstall -- it's the only way to be sure. I would think that when taking over a captured ship, none of the software can truly be trusted. But it's a lot more complicated than reinstalling an OS on a laptop. There's all of the embedded systems with their own firmware, any one of which could have a nasty payload. We've already seen this in the real world with the alleged printer installed in Iraq before the first Gulf War that screwed their air defense network, the pipeline controllers that deliberately caused a major oil catastrophe in the USSR at the end of the Cold War... It may be the cost of making a ship truly safe after capture might be prohibitively expensive. Security experts have already said that even with complete access to the source code and libraries for modern software, there's no guarantee you'll catch every dirty trick if they're in there. This is why client nations are increasingly worried about the equipment they're buying from patron states. Sure, you've got this lovely fancy jet fighter but what happens if the US decides to invade you and your F-16's are coming in and the attackers emit a modulated broadcast right on the same frequency the radar uses? Oh, wow, the whole radar just shutdown. Didn't know that backdoor was in there, did you? The plane's still in the air but it can't fight worth a damn. Even if the US gave you the source code as a precondition for the sale and even if you had crackerjack programmers looking it over, there's no guarantee you're safe. Even if you find a backdoor, that might just be the one you were meant to find so you'll stop looking; the real one's still in there.
I'm using radar as an example because I think cylon superhackers is a silly trope, just networking two computers together shouldn't make you vulnerable. But if someone has root access to your system or if they were the ones who sold it to you, there's considerable room for worry. You won't be running wifi on a military system but radar represents exactly the kind of input you would be vulnerable to.
The usual request for everyone to lighten up on each other a bit. (This is a drill. This is only a drill. No one is actually under attack ...)
Whether wisely or otherwise, I'm thinking of a new post, concentrating on laserstars, to clarify this discussion. There are not only several issues, but several types of issues.
But I'll make one quick quibble here: I don't see why a laserstar (or anything with a powerful laser armament) would bother with active radar, which it is already so well equipped for active lidar. It takes far, far less energy to light things up brightly than to zap them!
Rick:
"But I'll make one quick quibble here: I don't see why a laserstar (or anything with a powerful laser armament) would bother with active radar, which it is already so well equipped for active lidar. It takes far, far less energy to light things up brightly than to zap them!"
You have to be able to use your search sensors independent of your fire control sensors independent of your actual weapons. Lidar might have a significant role in target acquisition and battle damage assessment, because it has significantly better discrimination capabilites than radar, but radar puts out broader beams and scans faster, making it a better search sensor. TANSTAAFL.
Tony, Rick:
I think I'm with Rick on lidar. Passive infrared will pick up any engine flares bright as day, which immediately gives you the search area and probable trajectory. Active lidar can then be used to get a firing solution. If the incoming kinetics use active lidar pings as prompts to modify their trajectory, a) that can also be seen with passive infrared, and b) might be worth doing at long range anyways, just to use up propellant (which final-stage missiles will be relatively short on). Also remember that at most engagement angles outside Earth's shadow, the sun will provide visible-spectrum highlighting (or heat the projectile up so it shows up better on passive infrared), and the lidar can be used in passive mode instead.
Raymond:
"I think I'm with Rick on lidar..."
As already stated, lidar makes a good discriminating sensor. It doesn't make a good search sensor. If you want to do your fire control and battle damage assessment with lidar, be my guest. You're probably on the right track. If you want to find small kinetics in time to engage them, you better have radar.
Tony:
Incoming kinetics have to be launched, and unless we're dogfighting around a planet's low orbit, I'll see the launch and get a good idea of the trajectory. If the incoming are in the sun at all, they'll either reflect visible light or emit infrared (or both), and either way I can get a fix on them with greater accuracy from further away. The further out they are when I spot them, the faster I can light them up with active lidar and get firing solutions. On top of that, we've got far more methods of stealth for radar wavelengths than visible or infrared (as in, we have some for radar, and none for visible or IR that work in space).
Not to say radar won't be part of the arsenal - X-band radio is quite useful in space anyways, and using it for radar isn't that hard, and millimetric radar would be good for spotting small debris which could do significant damage. I just suspect that for tracking spacecraft and missiles, the combo of active lidar and passive infrared gives you better coverage and longer range.
Well, keep it under tighter control, B. The point was that there are counters and alternatives to everything, not that there could be stealth in space.
Yes, but you're still missing the point. Asymmetrical warfare must have something symmetrical to fight against. Your kinetics work well as asymmetrical weapons, but the laserstar is the symmetrical one. You're claiming that because there are alternatives to laserstars, laserstars are useless. I'm not sure what logic you're using there.
Mostly to undermine them. And that's my point -- battleships never even dominated battles against other battleships. In all of those engagements, the actual use or fear of torpedoes had significant tactical effects.
But development was still around battleships. Let's look at Beatty's mind at the end of the war:
"I have my BBs. They are good. A few years ago, people came up with torpedo boats to kill the BBs, but then the destroyer was created to protect the BBs. The torpedo boat became the submarine, but the destroyer altered to protect against them, too. The light cruiser is there to scout for the BBs, while the other cruisers are there to replace the BB in missions where BBs are too expensive or overkill. Now I have carriers to help me find the enemy BBs and stop the enemy from finding my BBs."
Everything comes back to the battleship. The same will be true of laserstars.
didn't mean to imply that you did. I just included aircraft for the purpose of completeness. And carrier aviation, whatever the battleship admirals thought, was from the very beginning trying to figure out how to sink battleships. They just played the scout game to keep the money flowing.
Yes. That's exactly what I meant. Initially, the navy bought them to support the battleships. The fact that they surpassed them is not relevant to the current discussion.
Unless your IR laser was powerful enough to burn out the IR sensor.
(At which point you might as well be shooting a real laser weapon at it.)
Yes. But how much power does it take to kill a CCD? As much as it takes to burn away a projectile? Really?
WRT to knowing where it's coming from, that's certainly a valid argument. But these things are very small and running at very low power until the terminal phase of the attack, so you probably have to identify them with active radar. Now radar does have trouble discriminating decoys from similarly sized and shaped warheads. That may or may not be significant, but it is another complication to the combat environment.
Yes. But I know where to point my lidar, because I tracked your projectiles after the missile burned out. As to discrimination, I just maneuver. The decoys either won't follow, will look different when they do, or aren't decoys at all.
Maybe the solution to all this is to supplement your laserstars with a dedicated kinetic defense platform. It has the big radar, and a bunch of IR lasers to knock out kinetic sensors. That might be a problem with home-on-jam, unless they were targeting the defensestar to being with.
Ok...several things;
1)Dumb kinetics= mine sweeping, ASAT, surface bombardment, maybe point defence.
2)heat management systems have various fluids moving through pipes and valves; there are pumps, fixtures, mechanical asymblies, joints, and who-knows-what-else in a space bourn system; whether you have a hab attached to the ship or not, it will still need maintanance at some point; people onboard would make it a little easier, in my opinion.
3)boarding spacecraft: As far as I can tell, mostly SWAT/Coast Guard type operations, but not a regular thing for military operations.
4) Brilliant Pebbles are/were/will be launched in groups; you're gonna need a lot of IR emmetters to spoof them all and if you miss one...
5) Me, I'd make it as hard for the enemy to jam my sensors as possible; the more, the more types, both passive and active, that I could realisticly mount on my spacecraft, the better. A blind enemy is called 'prey'. ;)
Ferrell
What would those systems be[?]
Remass pumps, since any failure could render the ship mission-killed. All the sensors. Fire Controls. Whatever point-defense systems you have. Combat is not the time to discover that your PD guns aren't working. Whatever offensive systems you mount. Your reaction-control systems.
and why can't they be made more reliable?
Cost. The Hubble Space Telescope cost almost $2.5 billion (more than a complete submarine!). Even if it had maintained budget, the original cost was still $400 million. I'm talking about militarily needing to mount multiple telescopes of this size. Modern military vessels have 'government-provided equipment' (ie, sensors and weapons) costs of about 1/10 their total construction costs. $400m times 5 telescopes is $2b, so now the estimate of your spaceship is $20 billion dollars... do I need to keep going down this road?
Sensors are the only things military vessels will use in cruising that civilian ships don't have. They're solid-state electronics. Not a lot of maintenance required. Ask ElAntonius if you don't believe me.
Sure, if you are willing to accept the degraded performance when you get to your mission area. Scientists will cry a little, and then write the specs so that the degraded performance is enough to accomplish what they want.
When 'degraded' sensors equal mission failure (or the conversion of your ship into a rapidly-expanding cloud of plasma), not maintaining the systems is not an option. Even the Air Force would not accept that chance, and the Navy absolutely would not accept it.
(SA Phil)
Part of Hubble's cost is related to its uniqueness though.
If you have an industry churning out spacecraft components, individual component prices will fall.
When we made the first few early prototypes of a car under development they easily cost over $500,000, even with the majority of the parts being off the shelf.
SA Phil:
"Part of Hubble's cost is related to its uniqueness though.
If you have an industry churning out spacecraft components, individual component prices will fall.
When we made the first few early prototypes of a car under development they easily cost over $500,000, even with the majority of the parts being off the shelf."
Weapon systems and military grade sensors aren't exactly made up of SAE standard components. Even when common components are used, many systems installed in ships are unique to a ship or to a small selection of ships. Each of those systems have to be individually designed, built, and tested.
And all of these semi-unique systems run counter to the primary rule of successful automation -- extensive operational experience.
(SA Phil)
Tony, It was an annecdottal example. I was not suggesting it was a 100% spot on comparison.
A purpose built one of a kind engineering system, first and only of its kind -- is going to be far more expensive than a common component used in 1000 systems.
For many reasons, if only for the fact that you tied up both engineering and construction costs in the same one off.
More typically economies of scale come in to play. If you build 1000 of something the per unit is less than 1. If you build a million of something .. it is far far less.
It doesn't matter if its a military system or not. Its a basic technical reality. A One Off is the worst case cost scanrio for an Engineering project.
Re: SA Phil
Naval systems are often one-off or very short run. The same is going to be true of military space systems. There may be hundreds or thousands of common components in them. But there are also going to be hundreds or thousands of two/four/eight of a kind parts, and the system overall may only be installed in exactly the same way in one ship or a few ships. Automotive (or any high unit volume) production analogies simply don't apply.
Tony:
Half the ship will be civilian. There's no need for naval-grade engines or reactors. Yes, you might take a mass hit, but you make it up on cost. I don't see it as insurmountable.
(SA Phil)
Even building 10 of something is cheaper than building 1 of something if you didnt know how to build it first.
How hand built it is or how crazy hard to build doesnt change that.
--------
I have a very good understanding of the relative Engineering realities. You are not the only one with relevant experience here.
Since I personally have 17 years R&D experience.
While my father helped design those ships you like to refer to ..
Byron,
I think this is actually going to be far more prevalant than it is today. Since even civilian craft are going to need "military" levels of performance from most of their systems.
Or to be more accurate, the requirements of many of the civilian and military systems are likely to be the same.
-(SA Phil)
Byron:
"Half the ship will be civilian. There's no need for naval-grade engines or reactors. Yes, you might take a mass hit, but you make it up on cost. I don't see it as insurmountable."
It's not insurmountable. But it's not going to lead to automotive or even aviation levels of cost and maintainability either. Going off of present day, real world examples, in 1990, when the USS Cleveland's extraordinarily mundane steam plant had a forced-draft blower failure, it took six weeks to find and install a replacement that was nominally only a warehouse pick and a 12 hour flight away. IIRC, they had to find a similar blower in size and performance with the original item, then build an interface for existing boiler. "Common" stuff just ain't so common when you talk about large, complex, relatively rare technological artifacts.
SA Phil:
"Even building 10 of something is cheaper than building 1 of something if you didnt know how to build it first."
I'm talking about integrated systems Phil, made up of hundreds or thousands of component systems, not individual end user items.
"I have a very good understanding of the relative Engineering realities. You are not the only one with relevant experience here.
Since I personally have 17 years R&D experience."
It's not experience relevant to naval sea systems. We're not talking about building prototypes for eventual production runs of thousands or tens of thousands. We're talking about systems where prototypes prove principles but have no relation to the final design, or where the prototype is actually installed in a service hull and worked out on the job. (The Navy does a lot of that.)
"While my father helped design those ships you like to refer to .."
Perhaps you should ask him just how many four-drum Terrier missile magazine installations were designed and built. Or how many mods of the more common three-drum ones were eventually installed, on how many ships apiece. Or why they never bothered to automate fin mounting in any of those installations.
Tony,
Spoken like a true end-user.
-(SA Phil)
SA Phil:
"Spoken like a true end-user."
Now I'm truly curious. How do you figure?
(SA Phil)
Because only someone unfamilar with the process would construct such an intricate Strawman pulled entirely from wherever you got that one.
You made about a dozens assumptions about how automotive development works - most incorrect.
And then taking your incorrect assumptions and complete lack of knowledge about my body of work assume I have never done anything like your military examples- which is also incorrect.
And then you top it off by naming some systems you worked with in the past and say "See here's proof you dont know!"
But if you would rather assume that the types insane costs run up on the Hubble program would plague Rick's Space Armada - thats cool.
I simply disagree.
SA Phil:
"Because only someone unfamilar with the process would construct such an intricate Strawman pulled entirely from wherever you got that one.
You made about a dozens assumptions about how automotive development works - most incorrect.
And then taking your incorrect assumptions and complete lack of knowledge about my body of work assume I have never done anything like your military examples- which is also incorrect."
Okay, this should be easy enough. Name integrated systems you worked on that didn't go into full or limited production of at least a few hundred examples. A reminder here -- integrated systems, not parts or subsystems.
Of those, how many were sold to a customer? In what quantity?
Of those, how expensive were they in comparison to production systems of comparable performance (or complexity, if performance was unique)?
"And then you top it off by naming some systems you worked with in the past and say 'See here's proof you dont know!'"
Not system I worked with, but systems I'm aware from observation or technical documentation. Systems I've worked with have all been software -- very expensive, bespoke software that ran on one or a few computers at most. But despite the ease of software reproduction, when the development expense can only be spread over a few installations, and the product, as a system is a unique product, you wind up with a high per unit cost, and high extended maintenance cost, for reasons closely analogous to limited installation mechanical systems.
"But if you would rather assume that the types insane costs run up on the Hubble program would plague Rick's Space Armada - thats cool.
I simply disagree."
Disagree away.
Tony,
Okay, this should be easy enough. Name integrated systems you worked on that didn't go into full or limited production of at least a few hundred examples. A reminder here -- integrated systems, not parts or subsystems.
====================
90% of every thing I worked on never went into "production"
"Systems" was a joke in the Dev Community. Everyone had a business card that said they did "Systems".
No Protoype Vehicle or Test Fleet at the advanced level bears more than a superficial resemblance to the Production Prototype Builds let alone the actual Production Vehicles.
You kept track of them by how much content was actually production intent, not how much wasn't. It was less paperwork that way.
Every Advanced build is an exercise in trying to get something that was never designed to work in that vehicle to actually work well enough to figure out if the next version of that something that they were already working on was even going to work at all.
The earlier the build, the fewer examples of each. You don't get mature designs until much later in the process. In fact the process drives the designs (hopefully). That doesnt even begin to describe the custom electronic tools and test cell setups you need to build.
The most hillarious example would have been V106 - since that one was new engine, new engine control system, new control system tool set, new injector system, new injector control system, new transmission control system, New emissions system .. all put into vehicles one generation earlier than the ones they were supposedly designed for.
They never actually officially ever built One of those, although we had about 30 prototypes of 6-7 different configurations "working".
They are still suing people over that program.
-(SA Phil)
Re: SA Phil
Okay -- almost exactly what I thought. You're talking about subsystems and individual parts when you speak of production economies of scale. With all-up military integrated systems, you basically have a collection of not-quite-prototype/not-quite-service systems put into service. Your description of "30 prototypes of 6-7 different configurations" pretty closely parallels the Terrier missile installations I was talking about. Except those installations were actually sold to the customer as service systems and installed in the fleet. Thats one of the reasons naval systems need so much TLC -- they're not completed products, as the average person thinks of completed products. Everything is: well, it works enough of the time that it won't be absolute suicide to rely on it in combat...let's put it out to the Fleet and learn the rest by doing.
(SA Phil)
No Not really,
It still costs far more to do the first version of anything than even the cobbled together later versions.
The first version you dont even know how to do it. The later version you do know. So you dont incur the original cost, even in the instances that you make things the same way.
Once you know something will work and you have built a few, its easier to build a few dozen more.
The costs drop even on hand built cobbled together stuff.
You are asserting the Military Equipment you are refering to always lives in the state we called "Advanced Program"
So would always be far more expensive than any civilian technology.
But that level isnt what the Hubble was. The Hubble was an engineering debacle of Biblical Proportions. I worked with one of the Engineers on that project. He had nothing nice to say about it, nor Nasa's Dev Community for that matter. He said their documentation was so bad - that if they wanted to redo Apollo, they would have to start over from Scratch since no one knew where everything was anymore.
By comparison a Military engineering debacles are rather tame. Like the Long Beach, which was originally supposed to be only 5000 tons.
(SA Phil)
As to the "systems" assertion-
There was a reason that "Systems" was a joke.
Everything is a system. Unless its on the bench.
SA Phil:
"You are asserting the Military Equipment you are refering to always lives in the state we called "Advanced Program"
So would always be far more expensive than any civilian technology."
I wouldn't go that far, and don't think I have. But if you want to color me as saying that military systems are, by their nature, relatively rare, just past developmental stage, constantly being upgraded, and much more expensive than civilian systems, I think that's fair.
As to the "systems" assertion-
There was a reason that "Systems" was a joke.
Everything is a system. Unless its on the bench."
Which is why I used the modifier "integrated" after I realized you weren't tracking what I was trying to get at.
(SA Phil)
I am wondering if the mid-future Space Military technology will resemble our current Naval/military.
For the next 50 - 100 years I can see it.
But if Space Travel were "commonplace" I think it might be a lot different.
Because a lot of the requirements will be the same.
For example propulsion -
It wont be the difference between a Nuclear Cruiser and a Diesel Freighter
It will be the difference between a Diesel Truck and a Diesel Truck. Both the civilian and the military will have the same demands - get there as fast as possible with the least reaction Mass as possible.
Both Civilian and Military reactors will need to have as much power for as little mass as possible.
I expect spacecraft will have open architecture/modular designs.
Everyone is going to need this Laser/Mirror/Telescope tracking ability -- since it will be the best way to communicate with other ships and space stations/moon colonies/w-e.
In addition - we will not see what we do at present - where Our Military and even our Civilian Tech is constantly pushing the technology envelope. Nearly every technology in our daily life is less than 100 years old, many less than 50.
That will not be the case 200 or 300 years from now.
(SA Phil)
Yeah "Integrated System" sounds pretty fancy.
I worked for a group called Special Systems - which sounds even more special.
I am hoping you do not just mean Hardware and Software development "integrated" together -- because that would be really annoying.
Since that is exactly what Powertrain Electronics Development does.
Not quite the same demands for military and civilian hardware. Some you can call dual-use. The air force and navy will fly executive jets, have military sedans that Are just repainted Detroit models. But a destroyer is built differently from a container ship. Container ships operate as efficiently as possible, you go from point A to point B for the least possible fuel. Military ships need power and performance. You could compare a navy clipper and a yankee clipper for the ice runs of the 19th century but can't compare a destroyer with that container ship. Container ships have provisions for being watertight but aren't designed to handle battle damage. It's complicated to make a ship fit navy standards for damage control. There have been attempts to build military ships in civilian yards with civilian equipment but they have always been cpromised designs suffering from economizing measures.
Consider how supersonic airliners failed in the market because subsonic was good enough. The air force atill lusted after supersonic bombers for a very long time. They want hypersonic bombers now and we will see them long before hypersonic or suborbital liners, even though you think there would be a market demand for it. Not yet. $1500 for a 12 hr flight versus $30k for 45 minutes? Market's just not there. Make it $2500 and maybe we can talk.
(SA Phil)
but what happens when the realities of propulsion are such that the military can't really move faster than anyone else?
There's a fair amount to suggest that that may be the case in the midfuture.
I still think "cargo" will be much different in a plausible midfuture(tm) setting.
People and warships need to get from point A to B as fast as possible, which implies the smallest ships carrying the largest power plants as practical. Cargo needs to go by the cheapest, most energy efficient route, which means a ballistic orbit.
While passenger and military ships are blasting off at milli G accelerations, cargo is being packed in an ISO container and shot out a mass driver or tether to coast to Earth or wherever. No crew, minimal computer or thruster system and designed to drift for years or decades if needed. Logistics will become a "pipeline" to be filled with containers.
This kills the "tramp freighter" trope, but gives EarthForce a rational to exist (examine ISO containers to ensure there is no contraband and protect against containers going into intercept orbits with Earth). It also places severe limits to what the colonies can do, even mongo mass drivers or ravening beams of death powering laser thermal propulsion are mostly suitable for local defense.
Space war will be very human in this setting; EarthForce will need spies, sabouter's and Marines to occupy colonies, and power and fortunes can accrue through manipulation of the futures markets
(including messing with shipments en route or the home launchers). Economic power can be used to increase political power, which can also be harnessed to increase political power and aspirations.
SA Phil:
"Yeah "Integrated System" sounds pretty fancy.
I worked for a group called Special Systems - which sounds even more special.
I am hoping you do not just mean Hardware and Software development "integrated" together -- because that would be really annoying.
Since that is exactly what Powertrain Electronics Development does.
Integrated systems are layered systems of systems, interfaced together to accomplish a specific mission. An automobile is actually a pretty good commonplace example of an integrated system. Some of the subsystems are: powertrain, suspension, body, etc. The powertrain has its own subsystems: engine, transmission, power distribution, etc. Within the engine are further subsystems: aspiration, fuel distribution, cooling, etc.
The point I was making about all of this -- and I think you would confirm it -- is that it costs one whole heck of a lot of cabbage to develop an integrated system to the point where it works. The individual parts may be common and relatively cheap to manufacture, but building up the layers of subsystems into a totally integrated system that works is serious, expensive work. The first departure between the average military system and the average automobile is that the automobile is a complete product, designed to be salable to a naive or nearly naive end user, with minimal expert support in the form of a wrench turner with some diagnostics training. The military system is just past prototype stage and is designed to be operated and maintained by a team of comprehensively trained technicians, often supported by even more expert factory representatives in the field. The second departure is that automobiles are made up as much as possible of standard parts, and manufactured as inexpensively as possible in long runs, with relatively little aftermarket modification contemplated. Military systems are designed to be built in very small runs (which has well known costs), and are designed to be modified and updated (adding the cost of modularity and easily severable interfaces). In fact, even the most ubiquitous military systems, like aircraft, AFVs, and common naval weapon mounts, are really more in the nature of low volume, high-end cars like Lamborghinis or Rolls Royce. And we all know how much those cost over the Mustang or Cadillac.
(SA Phil)
Tony,
Okay by your definition I worked on Integrated Systems.
Since most of my particular efforts were engine/transmission electronics and the required electronic/computer tools.
But we still had to know all the other systems to get them to work as a whole in something that was never designed to mesh.
Ill back off a little on saying that Naval ships will be much cheaper than one offs -- assuming of course they are bleeding edge. If they are using a whole lot of module off the shelf "systems" I think you could get a lot of savings.
The modern US military isnt really designed around cost savings. That wasn't always the case though.
(SA Phil)
Yeah a lot of cabbage is true - a typical new model costs 500 Million to develop.
SA Phil:
"But we still had to know all the other systems to get them to work as a whole in something that was never designed to mesh."
That's an ongoing conflict in software development. Should systems be designed by software "architects", and implemented by programmers who only know what their piece needs to do? Or should everyone have at least a conceptual view of where they fit in? Or should knowledge of the internal workings of all subsystems be available to all people who work on the project? You would probably get as many different answers as people you talk to. Also, the proliferation of Web services and Web data feeds creates an environment where developers often only know an interface specification for accessing their content, without really knowing it's validitiy.
"Ill back off a little on saying that Naval ships will be much cheaper than one offs -- assuming of course they are bleeding edge. If they are using a whole lot of module off the shelf "systems" I think you could get a lot of savings.
The modern US military isnt really designed around cost savings. That wasn't always the case though."
Naval systems tend to be bleeding edge or, if not, so specialized that there really isn't an outside equivalent. Who but the Navy and Air Force really have a use for S band phased array radar?
WRT USN frugality, it usually works itself out as a limitation on the number of units, not skimping on installed technology. This combines to create small numbers of very expensive systems.
SA Phil:
"Yeah a lot of cabbage is true - a typical new model costs 500 Million to develop."
Now imagine spreading out that development cost (or more, sometimes ranging into the billions of dollars) over only ten or twelve or twenty or even a few hundred units, rather than tens or hundreds of thousands.
but what happens when the realities of propulsion are such that the military can't really move faster than anyone else?
There's a fair amount to suggest that that may be the case in the midfuture.
Broadening this point a bit, suppose that at some future date most military equipment is a mature tech? In the 16th century, English naval shipbuilding tended to be highly experimental, not unlike the modern era. In the 18th century the tech of full rigged ships was mature, and RN tech progress was gradual and incremental.
This is not a situation we are familiar with, though in some ways CVs must approximate it - the airgroups have changed a lot more in the last 40 years than the ships themselves have.
Rick:
"Broadening this point a bit, suppose that at some future date most military equipment is a mature tech? In the 16th century, English naval shipbuilding tended to be highly experimental, not unlike the modern era. In the 18th century the tech of full rigged ships was mature, and RN tech progress was gradual and incremental.
This is not a situation we are familiar with, though in some ways CVs must approximate it - the airgroups have changed a lot more in the last 40 years than the ships themselves have."
A couple of things worthy of note:
1. Even at the height of technological stagnation, military practice was not entirely the same as merchant practice. Naval vessels could expect to get good service out of impressed merchant crewmen, especially in the purely nautical trades (sailor, carpenter, boatswain, etc.). But nval vessels had entirely different construction requirements, mostly because they had to mount large numbers of cannon and accomodate hundreds of crewmen to service them in combat. Being built more sturdy to resist gunfire was also an issue.
And even though technological progress had slowed down, there was still innovation. The large USN frigates, particularly the Constitution were notable for thick, dense hull sides and sturdy framework.
2. Even when basic technologies mature, as with CVNs, the weapons and sensors continue to advance, and cost more and more. The constant dollar value of the carrier air wing and its weapons, even with fewer and larger aircraft embarked, has not exactly gone down over the past fifty years.
Tony,
Now imagine spreading out that development cost (or more, sometimes ranging into the billions of dollars) over only ten or twelve or twenty or even a few hundred units, rather than tens or hundreds of thousands.
===============
That was actualy something I was trying to get it with my earlier point -
The Hubble was a one-off, so the development was for one Hubble, not 10.
If it had been 10 at least you got 10 units for that same chunk of development money.
Usually an additional side effect is that One Off doesnt get the same level of refinement as something designed to be mass produced.
(SA Phil)
That was actualy something I was trying to get it with my earlier point -
The Hubble was a one-off, so the development was for one Hubble, not 10.
If it had been 10 at least you got 10 units for that same chunk of development money.
I never understood why they didn't run off a couple of them for these big projects. Would it cost all that much more to build two or three hubbles? Sure, it costs to launch them but once they're up in orbit, how much more will it cost per year to run two or three instead of just one? Setting aside the nightmare of shuttle servicing missions.
It seemed to me the way to go would be to treat the telescopes as disposable. You're aiming to build two at a time, then revise for new technology, build two more, revise and build two more... Launch the scope, will operate for as long as it can. You might end up with maybe six at a time operating before the earlier ones become unusable. Sure, the launch is going to be bloody expensive but what's the alternative? What would we have done if the shuttle carrying Hubble blew up, scratch the whole project?
SA Phil:
"That was actualy something I was trying to get it with my earlier point -
The Hubble was a one-off, so the development was for one Hubble, not 10.
If it had been 10 at least you got 10 units for that same chunk of development money.
Of course, but spreading costs over ten or twenty or two hundred units is significantly more expensive, per unit, than spreading costs over ten or twenty or two hundred thousand units. Automotive industry conceptions of economy of scale simply don't apply. Even exclusive limited editions are built to a certain point of completion on the production line before they go to the custom shop.
"Usually an additional side effect is that One Off doesnt get the same level of refinement as something designed to be mass produced."
But one-offs or short runs are not intended to be refined. There's no profit in refining something that's intended to be used by industry insiders or other highly sophisticated customers. Fancy trim and packaging don't affect whether something works or not, and the customer knows it. Some military systems I've seen have actually been kind of kludgy to the point that one might wonder whether the designers and builders took a perverse pride in a lack of refinement. But that's not always true, some systems I've seen had a very high degree of fit, finish, and design-for-use that you wondered why somebody spent so much time and effort on something that was purchased to be used by people who had no choice in their tools.
jollyreaper:
I never understood why they didn't run off a couple of them for these big projects.
For interplanetary exploration they often do, and then send them both. Pioneers 10 and 11, Vikings 1 and 2, Voyagers 1 and 2, and Mars Exploration Rovers Spirit and Opportunity are all examples of this approach. There are also generally non-flying test articles that are built. Fully functional spares are kept on the ground so that problems can be investigated by experimenting on hardware identical to flight articles.
On top of all this there are manufacturing prototypes of almost every significant component, so that the builders can make sure they got everything right before building the flight parts. I was once at a JPL open house where they had a manufacturing prototype of the Mars Pathfinder lander on display in the spacecraft fab machine shop. It was a test article made out of soft aluminium, created to test the programming of the milling machine before cutting aircraft aluminum for the real part.
Now, I told you all of that to tell you this -- None of that really applied to the Hubble because it was built to be launched and serviced by the Space Shuttle, even to the point of possibly being brought back down to the ground for a service call (though they never actually did that, because flying Shuttles was just too expensive). There was no point in making more than one, in the minds of the project team. They weren't sending it away forever, and they could always get it back (they thought, originally, in the 1970s) that they could get a service mission, or a return and relaunch mission, manifested on a few months notice.
Rick:
"Broadening this point a bit, suppose that at some future date most military equipment is a mature tech?"
All too often, mature tech is obsolete tech. The military can't afford to just "use something that works", it needs to use the thing that works best, so that it'll be able to defeat the enemy's thing.
"In the 18th century the tech of full rigged ships was mature, and RN tech progress was gradual and incremental."
Right up until those full rigged ships got sunk by ironclad steamships, right?
The 1911 .45 remains a very excellent pistol and there's no need to upgrade. The b52 and c130 have had avionics upgrades but the airframes are the same -- new 130s are still coming off the lines.
Some tech peaks early, some tech matures and becomes obsolete. Some tech matures and you know will eventually become obsolescent but you're still waiting for it to happen!
Tony,
But one-offs or short runs are not intended to be refined. There's no profit in refining something that's intended to be used by industry insiders or other highly sophisticated customers. Fancy trim and packaging don't affect whether something works or not, and the customer knows it. Some military systems I've seen have actually been kind of kludgy to the point that one might wonder whether the designers and builders took a perverse pride in a lack of refinement. But that's not always true, some systems I've seen had a very high degree of fit, finish, and design-for-use that you wondered why somebody spent so much time and effort on something that was purchased to be used by people who had no choice in their tools.
------------------
I wasn't really referring to fit and finish when I mentioned refinement. I was referring to things like ease of use, smoothness of operation, and functional reliability.
Which goes back to much earlier in this thread. If new vehicles had the sorts of reliability problems you were attributing to military systems -- the Car companies would all go out of business.
The Idea of a Mechanic riding shotgun for every trip died over 100 years ago.
If you are going to have low crew and no crew spacecraft you are going to need reliability.
A bleeding edge propulsion system that is 10% better is useless if your ship needs to mass 30% more because of the extra size of the crew to maintain the systems.
I suggest even most military vessels will largely take advantage of Mass Produced, Modular systems whenever possible.
Spacecraft will look like they are lego sets or something similar
With a central beam to which are attached standard-type reactors, radiators, Propellant Tanks, communications packages, Habitats, etc.
Many Military vessels might only differ from their civilian counterparts in terms of weapons and extra Whipple shields / Radiators.
(SA Phil)
It seems the idea that "quantity has a quality all of its own" hasn't got as many fans as it used to.
The Lanchester equations suggest we have taken the wrong road somewhere along the line, "it takes an N-squared-fold increase in quality to make up for an N-fold increase in quantity."
How to break the cycle is hard to define, unless you suggest taking some arbitrary metric (say system performance in 1990) and applying it using the least expensive "today" systems. This also suggests warfare could once again move to an artillery contest of sorts; the side with the most KKV's can overwhelm lasers and enemy kinetics.
Working laser weapons actually also validate the equation, if we take the ability of the beam to rapidly engage multiple long range targets as the "quantity" rather than the laser itself. Once again, the potential advantages of this technology means everyone will be making heroic efforts to make working laser weapons.
SA Phil:
"I wasn't really referring to fit and finish when I mentioned refinement. I was referring to things like ease of use, smoothness of operation, and functional reliability.
Which goes back to much earlier in this thread. If new vehicles had the sorts of reliability problems you were attributing to military systems -- the Car companies would all go out of business.
The Idea of a Mechanic riding shotgun for every trip died over 100 years ago."
Your comments are absolutely correct for the automotive industry. But the levels of performance and reliability are set by customer expectations. The Naval customer realizes that the machines are going to need a lot of handholding in operation and a lot of maintenance.
"If you are going to have low crew and no crew spacecraft you are going to need reliability.
A bleeding edge propulsion system that is 10% better is useless if your ship needs to mass 30% more because of the extra size of the crew to maintain the systems."
This goes back to the acceptance of realistic assumptions about context. For a war to happen in the first place, you have to have enough people and enough property in or around the objective to make fighting worthwhile. That means people are simply not going to be to expensive to use as military assets.
The Naval customer realizes that the machines are going to need a lot of handholding in operation and a lot of maintenance.
That's not how I'd put it. I'd say that the naval customer expects that their machines will take handholding. You seem to view this as a fundamental requirement. Commercial gear requires a lot less maintenance. Why? Because a warship has a large crew for DC reasons, so there's no reason to spend money on automation. It's not a law of nature.
This goes back to the acceptance of realistic assumptions about context. For a war to happen in the first place, you have to have enough people and enough property in or around the objective to make fighting worthwhile. That means people are simply not going to be to expensive to use as military assets.
What is that supposed to mean? He's right. This isn't about launch costs of people, it's about the fact that the extra 30% crew is going to take up 30% more of everything. Even if people aren't as expensive as today in space, I don't think they'll be as cheap as today on Earth. And you are also confusing the cost to get a human to a location with the inherent cost of the human. Humans could be cheap to place, but expensive to have.
Thucydides:
"The Lanchester equations suggest we have taken the wrong road somewhere along the line, 'it takes an N-squared-fold increase in quality to make up for an N-fold increase in quantity.'"
The problem is adequately defining "quality". The only quantitative means is to define it as the number of Red units killed per Blue unit killed. The math generally works out, but the inputs aren't simple. The inherrent quality of direct fire forces (training, experience, equipment) are modified by the tactical posture, terrain, fortification, artillery support, air support, etc. For example, a company of average troops, plus a fortified outpost, plus artillery support, plus a couple of well timed and directed air strikes, can easily defeat a battlion of equally proficient enemies.
Byron:
"That's not how I'd put it. I'd say that the naval customer expects that their machines will take handholding. You seem to view this as a fundamental requirement. Commercial gear requires a lot less maintenance. Why? Because a warship has a large crew for DC reasons, so there's no reason to spend money on automation. It's not a law of nature."
That's simply not factual. Warships are not manned by reason of how many bodies could or should be available for DC tasks. They're manned on the basis of how many people are needed for normal operations and maintenance. That's generally significantly more than those needed to operate all mission-essential systems in combat.
WRT the differences between commercial gear and naval equipment, commercial gear is designed and built to be operated at minimum cost, while naval equipment is designed and built to be deployed to the fleet as quickly as possible. Reliability and maintainability refinements take a very distant back seat to availability.
Also, reliability and maintainability have a cost. With commercial gear, that can be spread across many units, sold the world over. With naval equipment the cost of improved reliability and maintainability are spread over a few dozen or a few hundred units that can be sold to only a few customers (Generally your own government and few trusted allies). Navies simply don't have the money to spend on refinements or the time to wait for them to be perfected.
"What is that supposed to mean? He's right. This isn't about launch costs of people, it's about the fact that the extra 30% crew is going to take up 30% more of everything. Even if people aren't as expensive as today in space, I don't think they'll be as cheap as today on Earth. And you are also confusing the cost to get a human to a location with the inherent cost of the human. Humans could be cheap to place, but expensive to have."
To put it as kindly as possible, horsefeathers. I'm a computer programmer. I have a college education and fifteen years of job experience, five of which are on a specific proprietary platform. Fifty years ago, finding my replacement would have taken weeks, perhaps months. Nowdays I can be replaced tomorrow, or at most by next week. There is absolutely no reason to think space technologies, as they are further refined and commoditized, to be any different.
So, it really is a question of the cost of putting someone on the deckplates at some place in the solar system. And to have an environment where war is possible, we're going to have to have a technological base and an economy capable of moving lots of people and their goods around at reasonable prices. In that kind of environment, people are, well, cheap.
To put it as kindly as possible, horsefeathers
That puts me in mind of coining a new expression: "dinosaurfeathers." Something that may indeed be true but is aesthetically ruinous. T-rex actually looks like a giant, angry turkey? Dinosaurfeathers! Space fighters don't make any kind of rational sense? Dinosaurfathers! I know it's true and I have a problem with that.
Tony:
Yes. Here on earth you could be replaced tomorrow. But what about on a colony where they need each technical-minded person? In space, people who are technically inclined will be far more required then those who aren't compared to today. There may not be anyone available to replace you, as they're all doing other stuff. However, those are the sort of people you need to run your ships, too. It makes sense to minimize the number required.
Shorten it to dinofeathers!
"In that kind of environment, people are, well, cheap."
Humans are expensive, deacdes long investment, sometimes unreliable, expensive to transport (compared to dumb cargo), don't always go according to plan, and we only use them because automation with sufficient reliablity is EVEN MORE expensive. And that's today. On an extrateerrestrial colony, or worse, a space hab, they'd be much more expnsive as you have to pay the air they breath and the water they drink.
(SA Phil)
The problem is the mass to support larger crews can directly reduce your ship's performance.
Its easily possible a bleeding edge military propulsion can't overcome the Mass penalty of all the extra crew.
Thus it could be that the warship designer who uses commercial parts can make a warship with higher overall performance.
Its just basic Newtonian physics.
You dont see this in the modern Navy becuase this tradeoff does not exist with Ocean-going ships. High Crew Mass does not equal reduced warship performance.
I sugest that even warship desgners will design their ships for the best overall performance.
It gets even worse if there is no measurable performance difference between military and commercial ship components.
At that point the Military would be having large crews just to be conservative.
Byron:
"Yes. Here on earth you could be replaced tomorrow. But what about on a colony where they need each technical-minded person? In space, people who are technically inclined will be far more required then those who aren't compared to today..."
And you accuse me of being inflexible...
By the time there are enough people distributed throughout the solare system to make interplanetary war possible, there will be enough surplus of skills to make people less than precious. That was the whole point I was making -- when there were few college educated computer programmers, replacing them was difficult. When there are more of them, not so much.
SA Phil:
"You dont see this in the modern Navy becuase this tradeoff does not exist with Ocean-going ships. High Crew Mass does not equal reduced warship performance."
I don't know where you get this idea. A corvette can cary as many guns and missiles as a destroyer, and motor around just as fast. What it can't do is go overseas for six months or spend weeks on end away from port. Some of these capabilities have to do with fuel storage and hull size (for making headway in rough seas). But they have as much or more to do with supplying accomodation for large crews of watchstanders and maintainers, and storage space for all of their supplies.
(SA Phil)
Tony,
The answers to your objection are all actually contained in the text of your objection.
Tony:
"So, it really is a question of the cost of putting someone on the deckplates at some place in the solar system."
Which is a question of mass more than anything. More crew -> more mass -> more propellant -> bigger powerplant. The tradeoff is the increased cost of reliability versus the additional costs of moving more mass (in the form of crew) to compensate. Yes, spacewar implies marginal mass increases are less expensive by far than they are now. It still gives an incentive to use the same components as civilian craft whenever possible, to get back some (not all, but some) of the small-production-run costs, since the marginal performance gains of many just-past-prototype systems will be insufficient to offset the mass cost. (Remember, we're talking PMF, and one- or two-kiloton craft max, where crew size (in the form of accommodations, provisions, and shielding) is a non-trivial mass penalty. Recall your previous example of merchant hulls vs destroyer hulls - many of those differences may not be the same scale when speaking of interplanetary spacecraft.
Also note that civilian craft will have many of the long-endurance requirements of military versions, including long periods between depot maintenance (see your own arguments in the space station thread) and fairly continuous operation.
SA Phil:
"The answers to your objection are all actually contained in the text of your objection."
Please elaborate.
Re: Raymond
Going back to the 18th Century analogy, please note that both civilian and naval vessels had essentially the same propulsion systems, similar endurance requirements, and similar construction methods. They were still significantly different in design, construction, and cost, for reasons that should be obvious.
Also, (and this appliesto Phil too), if you apply the same logic to interplanetary spacecraft, then the major dichotomy would be that commercial vessels would carry cargo and pax, while naval vessels would carry weapons and crews. That's actualy true today as well, for similar sized vessels, though naval vessels do devote more internal volume and tonnage to propulsion systems. There's no reason to suspect that anything would be different in space, particularly if you insist on standardizing on the same propulsion systems.
Right up until those full rigged ships got sunk by ironclad steamships, right?
That was (ahem!) a major tech revolution. If there is a future 'decelerando' - and on some time scale there almost certainly will be - you could easily have the situation where new units typically enbody modest tweaks of 50 year old overall designs.
When another tech revolutions comes along, that will no longer apply.
There are some important differences between seacraft and spacecraft - notably, for two ships of the same top speed, double the displacement requires a lot less than double the propulsion power. Which makes adding crew accommodation relatively cheaper.
Rick:
"There are some important differences between seacraft and spacecraft - notably, for two ships of the same top speed, double the displacement requires a lot less than double the propulsion power. Which makes adding crew accommodation relatively cheaper."
It depends on your technical assumptions in a couple of ways:
1. Once you start getting into the Isps above 3,000 or so, you start looking at mass ratios lessthan 2.0. This means that you're not multiplying the whole ship mass by some outrageous factor to add delta-v, and
2. There's no reason to think that warships would necessarily have to have more mass than commercial ships. As previously stated, they dynamic might be that merchant ships carry cargo and pax, while military ships carry weapons and crew.
Byron:
"Humans could be cheap to place, but expensive to have."
Actually, automation is most supported by the opposite assumption - if humans are cheap to maintain on a planetary surface (even a non-Earth one), but expensive to move around through space.
Jollyreaper:
"T-rex actually looks like a giant, angry turkey?"
Once again, nope. Other closely related dinosaurs did, but not the king.
"The problem is the mass to support larger crews can directly reduce your ship's performance.
Its easily possible a bleeding edge military propulsion can't overcome the Mass penalty of all the extra crew.
Thus it could be that the warship designer who uses commercial parts can make a warship with higher overall performance."
True...until you look at the larger picture.
Sure a human hab might increase the dry mass by 30% (I'm highly doubtful of needing a crew of 12 when 2 trained persons and a lot of computers can handle the job just fine-battles might last several days, but the pew pew is several minutes at most. And it's all computer-controlled pew-pew), and with the nuclear-electric exhaust velocity of 20km/s and a dV of 50km/s, the mass ratio will go up from 12 to 15, performance will only go down by 20%...if we're using chemical rockets or nuclear thermal-the only warships we'll see are killsats and IPMs.
Now, this 20% decrease in performance means the ship takes 20% longer to get up to interplanetary velocity; with a milligee ship trying to reach 20km/s, this will take 7 months (yikes), but a human-hab equipped ship will take 9.6 months.
During pew-pew, the ship won't be accelerating at all, so the ship's performance won't be hit by having humans onboard or not.
The time-scales involved are therefore multi-year missions anyways. My conclusion is that either a)the mission is too long for humans-you ditch them because of the timescales or b)the humans stay on the ship, but the timescales are so long anyways that a 20% reduction in performance will have little impacts on the tactical or strategic level.
Also, the PMF future is friendly to humans in this aspect. In a Terra-Mars setting, with Mars rebelling or something, you'll have Terrans on Earth, but also on Mars, and probably already acting as a Police force in mars orbit. What you do is send the robotic ships to the trouble spots, and the orbiting (and overwhelmed of course) terrans move out, then come back in with the cavalry. They'd have in-situ control over the drone ships without having to ride them shotgun the whole way from earth.
If we move a bit farther out, say Earth vs the Jovian Moon colonies, and we're not expecting any allies to remain standing/loyal to Earth before you can come back in with force, you'd have 2 ships.
The fast, chemical rocket, human-dedicated ship and the slower, nuc-electric laserstar. The drones are sent out first. Then the human command ships get an Oberth boost and catch up with the drone ships.
During combat, the command ship can stay close to the drones, but can also move out or into the battle much faster than the opponent's laserstars. The will render tactics concentrating on taking out the command ship impractical, as your weapons can't catch up, and allows the command ship to escape the battle if it feels it is losing. The only problem is that while the chemical-fuelled command ship can escape the battle, it can't come back home. It can surrender, but if that's not an option, it better have a friendly base around. But if you didn't have that, what's the point of trying to hold onto the colony?
"It gets even worse if there is no measurable performance difference between military and commercial ship components."
If the commercial ships use the same drive as you do, and the military ship uses the same modules or frame as the commercial ship, it will still perform better.
Commercial ships, all other factors put aside, seek profit. Military ships can afford uneconomical actions as otherwise they'd be destroyed.
This translates into military ships pushing their craft to the maximum. Instead of using their nuclear reactor at a safe, long-life 300MW, they'd push it to 500MW, it'll last only a single mission but they can afford to replace it later.
A commercial craft has to balance fuel and remass consumption against the cost of delaying the transport. The military craft will burn through propellant trying to achieve minimal transit times during a given Hohmann window....
"By the time there are enough people distributed throughout the solare system to make interplanetary war possible, there will be enough surplus of skills to make people less than precious."
In space, it is all too easy to seperate the source of abundance from its point of application. Technicians might become cheaper and cheaper as the colonies grow, but a few AU away, you're limited to how many you can bring along with you. Lose one and the rest become proportionally more valuable. So while replacing a technician might be cheap back home, in the middle of a laser pew-pew, they're going to be worth their weight in gold!
Minor quibble...
"The answers to your objection are all actually contained in the text of your objection. "
Maybe he meant that for a large increase in crew size and accomodation, the reduction in performance can be compensated for by a very modest increase in powerplant power and fuel capacity? Wasn't explicit though, but that's what I understood.
"Yes, spacewar implies marginal mass increases are less expensive by far than they are now. It still gives an incentive to use the same components as civilian craft whenever possible, to get back some (not all, but some) of the small-production-run costs, since the marginal performance gains of many just-past-prototype systems will be insufficient to offset the mass cost. (Remember, we're talking PMF, and one- or two-kiloton craft max, where crew size (in the form of accommodations, provisions, and shielding) is a non-trivial mass penalty."
Depends.
For example, using the cherished nuclear-electric milligee drive laserstar as a model, if the nuclear reactor has a very high power density, then a 30% increase in dry mass can be compensated by a 5-10% increase in powerplant mass. Same performance, same relative propellant consumption, but a larger ship that consumes more propellant as an absolute value.
"When another tech revolutions comes along, that will no longer apply."
I think the major tech revolution here is the nuclear pulse propulsion tech that will leave nuc-electric craft eat its dust (I think that was just a blatant hint for upcoming writing, but its up to Rick...)
"Once you start getting into the Isps above 3,000 or so, you start looking at mass ratios lessthan 2.0."
What exhaust velocities does this thread assume for nuclear-electric craft?
"2. There's no reason to think that warships would necessarily have to have more mass than commercial ships. As previously stated, they dynamic might be that merchant ships carry cargo and pax, while military ships carry weapons and crew."
On the contrary, I see commercial spacecraft in PMF being MUCH larger than military ships. Interplanetary barges don't have to shrug off weapon fire, nor do they have to achieve minimal transit times, so they can afford to use open hull/maximal isp designs; the one I use in my future history is a bunch of processed ores, shaped into hundrend ton cubes, attached by a net. In the front of the net is a very large solar array and a small electric drive. The barge is accelerated from its origin by nuclear-thermal tugs; nearing the inner solar system (destination), it uses its electric drive to decelerate. For the opposite trajectory, the whole thing is done in reverse (with a tug-push on both ends). For a given increase in payload mass, structural mass increases very little, and propellant mass insignificant as supplied at origin and destination.
Ok, here's a good comparison for civilian vs. military costs.
One of the items they were working on at the Pentagon that might have escaped the axe was the box missile. It's shipped in storage containers. The whole thing is integrated -- communications, power supply, etc. You can put this on the back of a flatbed truck. Voila, instant mobile missile launcher. You can preposition it in a field -- instant firebase. Mount it on the deck of a ship -- instant missile boat.
Now the targeting info all gets handed off to it. You put one of these out in the field and any authorized grunt within range of it can designate a target for it to shoot at. Current man-portable antitank weapons need to be moved directly into position and the crew with launcher need a line of sight on the target before engaging. There's no provision for indirect fire. Apache choppers were moving towards modifying the Hellfires for indirect fire. The old TOW's were optically guided using wires to control the missiles, early Hellfires used a laser designator, the newer ones use radar. So wait, does the bird firing the weapon need to be lasing the target? Not anymore. Could one bird spot a target and call down weapons from another? That's the idea -- don't know if they actually went into production with this yet.
So the box missile was going to run with that. If I recall the design correctly, it uses the same laser designator idea from the canceled super-rifle the Army wanted. You have a GPS receiver and a laser pointer. You shoot the target, position is triangulated, sent back to the launcher. Launcher fires the missile out to the exact GPS coordinate and then uses the onboard seeker to locate and engage the target.
So, you can turn any flatbed into a missile truck, any ship into a missile boat. Now consider the advantages of ubiquitous trucks and ships to modify and consider the disadvantages versus proper military vehicles.
I think the same mix of good and bad will be found with military starships vs. the civilian variety.
Krakon:
"For example, using the cherished nuclear-electric milligee drive laserstar as a model, if the nuclear reactor has a very high power density, then a 30% increase in dry mass can be compensated by a 5-10% increase in powerplant mass. Same performance, same relative propellant consumption, but a larger ship that consumes more propellant as an absolute value."
Not exactly. You also have to account for the additional mass of engines, generators, shielding and radiators, which scale more linearly than reactor cores and take up a greater portion of the overall powerplant mass.
"What exhaust velocities does this thread assume for nuclear-electric craft?"
I usually go with the published VASIMR specs as a baseline: variable exhaust velocity between 30 km/s to 300 km/s. The top end of this range isn't terribly useful, though, as craft in the 1 kW/kg specific power range aren't powerful enough to make it efficient for interplanetary travel, so the practical limit is 150 km/s unless you're only doing station-keeping.
"Not exactly. You also have to account for the additional mass of engines, generators, shielding and radiators, which scale more linearly than reactor cores and take up a greater portion of the overall powerplant mass."
Shielding probably won't have to be increased by much (if at all) is you're just running the powerplant hotter. And since we can easily reduce the shielding by moving the whole reactor 5 meters further back, the mass penalty can be made minimal.
Radiators will be a problem, as you're dumping out more heat. They don't weigh much (low mass penalty) but area will be increased. Or you make sure radiator overloading tactics are inefficient, and just push them closer to their material limits (run them hotter, they'll be more efficient but the radiator will be just that much closer to melting).
As for the engine and the generators: I assumed they'd be highly proportional, as in you pump in more energy and it'll just work harder. I'm pretty sure that these types of equipment will have material limits much higher than the power levls they're supposed to work with. After all, how do you do an emergency thrust? (Okay, bad example with ion drives, but you get the idea. There's limits we can afford to be narrower).
"I usually go with the published VASIMR specs as a baseline: variable exhaust velocity between 30 km/s to 300 km/s. The top end of this range isn't terribly useful, though, as craft in the 1 kW/kg specific power range aren't powerful enough to make it efficient for interplanetary travel, so the practical limit is 150 km/s unless you're only doing station-keeping."
In that case, we're already at the levels where performance degradation by increasing dry mass will reach their asymptotic limit in performance decrease.
At 20km/s, an increase in 30% dry mass leads to a performance decrease of 20%. At 150km/s, an increase in 30% dry mass leads to a performance decrease of 23.76%. At 300km/s, an increase in 30% dry mass leads to a performance decrease of 23%.
Has anyone noticed how this thread, on the human aspect, has turned more technical, while the thread on the nature of warfare methods has turned...into a philosophical thought experiment?
jollyreaper:
Ok, here's a good comparison for civilian vs. military costs.
One of the items they were working on at the Pentagon that might have escaped the axe was the box missile. It's shipped in storage containers. The whole thing is integrated -- communications, power supply, etc. You can put this on the back of a flatbed truck. Voila, instant mobile missile launcher. You can preposition it in a field -- instant firebase. Mount it on the deck of a ship -- instant missile boat.
It's not that simple. For land applications you would generally want a large quantity of small missiles that fly maximum range ballistic profiles. For sea applications you would want a relatively small number of larger missiles that can fly out to a decent range using non-ballistic flight profiles. Also, naval versions would need to be capable of withstanding the marine environment, and you would still have to construct secure mountings on the ships in in question.
In space, the parallel concerns would lead to a variety of missiles for a variety of missions, combined with a variety of warheads for different missiles.
Maybe it could be addressed as an inventory management issue, mostly, but there would no doubt need to be flexible interfaces built into the ship to accept the entire range of possible weapons that could be mounted. Note that this requires quite a bit of dedicated, specialized gear in a modern fighter-bomber, which is probably the closest paralle to a space warship we have in service today. That kind of interface and communications hardwar is not installed on commercial aircraft.
jollyreaper:
"Now the targeting info all gets handed off to it. You put one of these out in the field and any authorized grunt within range of it can designate a target for it to shoot at. Current man-portable antitank weapons need to be moved directly into position and the crew with launcher need a line of sight on the target before engaging. There's no provision for indirect fire. Apache choppers were moving towards modifying the Hellfires for indirect fire. The old TOW's were optically guided using wires to control the missiles, early Hellfires used a laser designator, the newer ones use radar. So wait, does the bird firing the weapon need to be lasing the target? Not anymore. Could one bird spot a target and call down weapons from another? That's the idea -- don't know if they actually went into production with this yet."
Indirect fire vs AFVs just doesn't have a very high rate of return, because you basically have to catch them sitting still without overhead concealment. There are also fire support coordination issues that make it hard to get a timely indirect fire mission.
Apaches could always fire indirect with other Apaches or even ground troops illuminating. But again there are coordination issues. These issues are less when one Apache is designating for another in the same unit, but it still takes some planning and practice. Most of the time Apache crews like designating for themselves.
jollyreaper:
"So the box missile was going to run with that. If I recall the design correctly, it uses the same laser designator idea from the canceled super-rifle the Army wanted. You have a GPS receiver and a laser pointer. You shoot the target, position is triangulated, sent back to the launcher. Launcher fires the missile out to the exact GPS coordinate and then uses the onboard seeker to locate and engage the target."
Who can communicate with which launchers? What means of communication will they use? What authority will they need to initiate a strike? How will that authority be confirmed by the launcher's control computer? How will launchers be distributed in the first place? How will they be repositioned in case of advance or withdrawal? Who has authority over distribution, emplacement, and repositioning?
These aren't just "engineering issues" that can be worked out. There are issues of tactical doctrine, logistics management, and command responsibility. I have a sneaking suspicion that one of the things that killed the concept was an inability to work out, even in theory, acceptable answers that would allow such systems to be practical and effective.
"So, you can turn any flatbed into a missile truck, any ship into a missile boat. Now consider the advantages of ubiquitous trucks and ships to modify and consider the disadvantages versus proper military vehicles."
See above. Nothing is ever that simple, even with seemingly self-contained systems.
KraKon:
I'm not sure where you're getting this from.
Sure a human hab might increase the dry mass by 30% (I'm highly doubtful of needing a crew of 12 when 2 trained persons and a lot of computers can handle the job just fine-battles might last several days, but the pew pew is several minutes at most. And it's all computer-controlled pew-pew), and with the nuclear-electric exhaust velocity of 20km/s and a dV of 50km/s, the mass ratio will go up from 12 to 15, performance will only go down by 20%...if we're using chemical rockets or nuclear thermal-the only warships we'll see are killsats and IPMs.
First, that's not how it works. I should have been more clear earlier, but a manned ship will not be a drone with a hab bolted on. An equivilant manned ship will have the same delta-V and acceleration as the drone, but the entire thing will be 30% bigger, and 30% more expensive. Why don't we bolt on a hab? Simple. The ship has to do the same mission either way.
As to crew, I've covered this before. I doubt two guys can do maintainence if there's a lot of it. If there isn't, then why are they aboard? Not to mention the fact that you still need a control ship around.
but the timescales are so long anyways that a 20% reduction in performance will have little impacts on the tactical or strategic level.
I'm curious where this came from. On a tactical level, yes. On a strategic level, that's about as wrong as it can be. 20% will be highly significant, particularly if it's also more expensive.
This translates into military ships pushing their craft to the maximum. Instead of using their nuclear reactor at a safe, long-life 300MW, they'd push it to 500MW, it'll last only a single mission but they can afford to replace it later.
And how do they do that? People in space will run the reactors as hot as possible and safe. Period. There is no way I know of to run a reactor that hot safely. I'm not an expert, but it seems that the military won't be that much ahead of civilians.
And I'm really not sure about how that barge will work. Nuke-thermal? Why not nuke-electric. Here's an example of something I did for Spherical War Cows, as a recoverable kinetic bus. It'd also work as a tug:
If I assume the same tech as given here (30 km/s exhaust velocity), and wish to throw the projectiles at 10 km/s, the ship might break down as follows:
50% kenetics
10.8% recoverable ship
28.4% launch fuel
10.8% return fuel
The actual delta-v is 30 km/s for the recoverable part, while still being able to launch 50% of the launch mass in kenetics.
For that matter, why not give it a nuke-electric drive for use on both ends?
See above. Nothing is ever that simple, even with seemingly self-contained systems.
Concerning all the objections you raised, I'm not advocating for the system, just describing what was on the drawing boards and what had actually reached the prototype stage.
I just checked: it is dead.
http://en.wikipedia.org/wiki/XM501_Non-Line-of-Sight_Launch_System
The Non-Line of Sight Launch System (NLOS-LS) is a self-contained missile launcher under development by NETFIRES LLC, a partnership between Lockheed Martin and Raytheon for the United States Navy's Littoral Combat Ship and previously the United States Army's Future Combat Systems before it was canceled. Each Container Launch Unit (CLU) holds 15 missiles, and a communications system. CLUs can be linked for coordinated launching. The missiles are fired and controlled remotely. The weapon is roughly 2 meters tall, and can be transported on just about anything larger than a pickup truck.
Israel Aerospace Industries JUMPER System is the same concept, but with 8 missiles instead of 15 and without the IR seeker.[1]
You can argue back and forth about how useful it would be but the indisputable facts are A) the military believed in the idea and funded it and B) it's dead now so there's no way to know whether or not it would have performed as advertised.
As a personal bias, I remain completely skeptical of all performance claims until unbiased field tests are performed.
jollyreaper:
"Concerning all the objections you raised, I'm not advocating for the system, just describing what was on the drawing boards and what had actually reached the prototype stage."
And i'm just filling in stuff that's left unsaid in brochures or Wikipedia articles, which are written by marketing copywriters and technowank fanboys respectively.
Tony -
It depends on your technical assumptions in a couple of ways:
1. Once you start getting into the Isps above 3,000 or so, you start looking at mass ratios lessthan 2.0. This means that you're not multiplying the whole ship mass by some outrageous factor to add delta-v, and
2. There's no reason to think that warships would necessarily have to have more mass than commercial ships. As previously stated, they dynamic might be that merchant ships carry cargo and pax, while military ships carry weapons and crew.
For this particular purpose I'm not addressing differing performance levels, or civilian ships. Only the fact that for sea ships of a given performance, increasing displacement (mass) by x percent increases power plant requirement by something less than x percent - for fast ships, which naval ships generally are, a lot less than x percent.
For spacecraft of a given performance, that relationship is linear - same acceleration, double the mass: double the thrust and power. Secondary factors may improve on this, such as moving into a more optimal engine size regime, but it is not something you can generally count on, the way you can count on larger ships being more power efficient.
But bear in mind that I'm not primarily expecting laserstars to operate without human servicing through a while months-long mission, only suggesting that maintenance personnel may be housed aboard another ship in the constellation, and not aboard the laserstar when it goes into action.
KraKon -
Has anyone noticed how this thread, on the human aspect, has turned more technical, while the thread on the nature of warfare methods has turned...into a philosophical thought experiment?
Life is funny that way!
Re: Rick
Another way of looking at it is that smaller naval vessels are significantly inefficient. If naval architects were unconstrained by military realities and requirements, they would have built nothing but battleships and supercarriers. I think all this proves is that one will build the most efficient ship possible for a given mission, all factors being taken into consideration.
I think all this proves is that one will build the most efficient ship possible for a given mission, all factors being taken into consideration.
No dispute there. Except, somewhat, to the term 'ship,' which I think does tend to bias our thinking about spacecraft. Which are rather like ships in some respects (prolonged missions), but very unlike ships in other respects (such as the way they move).
Reading over the comments, I've come to the conclusion that (for military purposes), the PMF will be devided into before the first space war and after. Before, the only spacecraft even remotely like a combat spaceship will be orbital customs inspectors and gunships, and a very few asteroid interceptor/deflectors; after, combat spacecraft will be purpose-built with the proformance standards published even before the first CAD file is opened. Durning the first space war, combat ships will be civilian ships modified for combat. By the end of the conflict, if it lasts long enough, you might see ships designed for combat; these ships would essentually be like the modified-to-combat civilian ships, but be purpose-built. They would be the optimal version of those first jerry-rigged civilian ships. Most civilian spaceships of this era would be logistics vessels; they would normally carry passengers and cargo from one planet to another and back again, in a reasonable timeframe. If outposts need supplies more often than they need crews rotated out, then there will be robot freighters; if they don't need supplies more often than crew swaps, then there might not be any. So, if you don't have any warships, it doesn't matter if the other guys' warships are crap; they still win...until you can build your own combat spacecraft.
Ferrell
Nearly any rocket can be rigged as a crude missile. Therefore, the absolute minimum capability a warship needs in order to be effective is the ability to disable and dodge a civilian ship that's on a collision course with it.
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