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 201 – 400 of 883 Newer› Newest»WRT jinking:
When you can pull off accelerations of 1g or more for extended periods of time (even intermittently), we are talking demi-torch drives or better. If you're relying on chemfuel or nuke-thermal, you'll run out of reaction mass so quickly it'd be worth the laser time just to run you dry of propellant. If you're using nuke-electric or fusion, you're not getting anywhere close to a full g. Sorry, not buying it.
Also note that most plausible midfuture lasers aren't going to be used at a million km. We're talking more the class of weapons with effective carbon armor scorch ranges somewhere between 1000-100,000 km. And at that close of ranges, jinking is even less effective.
WRT powerplants:
Scott said: "And while nuclear reactors are not field-maintainable, the generator systems are."
This may be a small quibble, but I don't think space reactors are going to follow the example of terrestrial vehicular pressurized water reactors. Almost all the designs I've seen proposed or examined have been high-temperature gas reactors, with turbine or magnetohydrodynamic generators, lacking the heavy shielding which would allow human crew within a hundred meters. Generally speaking, these generators would be located sufficiently close to the reactor to preclude human maintenance (even with the shadow shield). And in the case of MHD generators using EM pumps, there would be very few moving parts in the whole system to maintain, even if the reactor were approachable.
Speculative fusion designs also have few actual mechanical parts, be they compact spheroidal tokomaks or antimatter-catalyzed microfusion engines.
WRT sensors:
We are talking about (primarily infrared) telescopes with nothing resembling the kind of sensor clutter found in terrestrial environments in any spectrum. We are talking about engine signatures visible across the solar system for any useful power level. We are talking about room-temperature objects being visible at astronomical unit ranges. We are talking about a computing environment better than ours, and we can already achieve full-sky searches in a matter of hours.
You do not require perfect anything to get accurate trajectory data on enemy hardware lit up like a christmas tree, and quickly to boot.
WRT maintenance in general:
Scott's six-sigma example is useful - current space tech sits somewhere between the extremes. From the 1 mil -> 99% starting point, while we may not be going for 99.99996% at 10 bil, but we do seem to go for five nines at 100 mil. I don't really see that changing much.
Scott:
"The cost increases by an order of magnitude every decimal point of reliability increase. If 99% reliable is a million dollars, 99.99996% reliable will be about 10 Billion."
If you rely on redundancy, then each doubling up on your equipment will double your number of nines. (If both the main and the spare have a 99% chance of working, then there's a 99.99% chance that at least one will work.) Of course, you're also doubling the amount of mass you have to carry.
(SA Phil)
One thing to keep in mind - automation and computer/embedded controllers are most certainly going to Improve in the near/mid future.
Thus the ability to automate spacecraft will definitely be far and away more effective than in a current generation Naval ship.
Most Naval vessels being 10+ years old technology anyway - and not designed particularily for automated function.
(SA Phil)
One interesting thing regarding the ai drone/remote drone/no-drone debate is that it will play itself out LONG before there is any Space warfare.
In the next 50 years probably we will see how the mix of robot/human combatants will shake out.
The Mid-future Space scenario will be based on that mix, not the one we have now at the infancy of automated warfare.
Look at how much more common robots and controllers are in a factory setting than they were 30 years ago.
Time is up. I'm surprised no one got the answer:
10 m/s2.
This is going to require 4 separate engines capable of 1 metric G (my term for 10 m/s2). Total mass will likely be in the same region as modern chemical engines on a booster. Delta-V is going to be correspondingly limited, unless you happen to have at least a demi-torch.
The above scenario seems to rule out dodging at any sort of plausible midfuture range. However, there are several of elements in the problem that haven't been considered. Some will decrease the efficiacy of dodging, while others will increase it.
1. Beam diameter:
The beam will have nonzero diameter, so in the above scenario, the ship accelerating at 10 m/s2 would still have been hit by about half the beam. This would increase the delta-V required to avoid a hit.
2. Perfect dodging:
I have assumed that the ship began dodging at the instant the enemy would have opened fire (relative to light lag), and was able to hold a course the entire time. This would cause problems if this was not true. Dodging would require that (if the enemy was aiming at the center of the ship) that no part of the ship was in the same line as the center was 1 second previously, and was not accelerating in a straight line. This would tremendously complicate dodging.
3. Beam inaccuracy:
This can either help or hinder dodging. If the diameter of the inaccuracy circle was 10 meters, and the hit probablity for each area was constant, dodging as described would reduce hit probability to about .333 instead of 1. However, if the circle had a diameter of 20 meters, then dodging at 10 m/s2 would be useless.
On a slightly more theoretical level, I've figured out several rules related to dodging. First, the required delta-V will scale inversely with distance, while the acceleration will scale with the square of distance. Second, if you are able to accelerate faster, you can cut the required delta-V. The theoretical minimum is the circle radius/time. If you use constant acceleration, then that is doubled.
Burnside's Law
Seems obvious on the face of it, but after all I was sad when Mycroft died in Moon is a Harsh Mistress, I thought the bombs were some of the more interesting (and saner) characters in Dark Star, I even recall a Berserker short story in which the "heroes" were AIs based on WWI fighter pilots.
And then there are the Bolo stories.
Right now, we can explore the solar system with fairly dumb probes right now because in space you can rely on Newton to keep things simple while we think about it, and on Mars because the 'bot can sit there for a week while we have committee meetings to decide where it will go for the next meters. That's not good enough for weapons. The smart weapons we have at the moment may be using AI techniques, but they are a long way from understanding what they are doing and revising what they do depending on understanding the circumstances.
Any AI smart enough to be trusted to make decisions about killing people (including other AIs) more than a couple of light-seconds from a controller is probably smart enough to have an interesting personality. It is interesting that some ground-combat SF writers have risen to the challenge, but space-combat authors beg off.
Thus the ability to automate spacecraft will definitely be far and away more effective than in a current generation Naval ship.
Most Naval vessels being 10+ years old technology anyway - and not designed particularily for automated function.
And while it's been mentioned before, a good thing to bring up -- the cost of additional manpower on a modern navy ship is not in the same ballpark as the cost of manpower for any reasonably theorized spaceship. Here on Earth right now, we don't automate things a human can do more cheaply. When we're talking about each human adding millions and millions of dollars to the operational cost of the ship, automation really starts paying off.
While I don't want to overestimate the abilities of automated systems, I do wonder just how many people would truly be required for standing watch. I think a lot of that will depend on the mission profile of the ship. If the ship needs to be at 100% for weeks on end, you have to rotate watches but even with big crews that gets wearing. Combat accounts from WWII talk about the deterioration of crew performance and morale when operating for days at a time at full alert.
The Navy's been making noises about seriously implementing more automation in the fleet so it'll be interesting to see what comes of it in the future.
Seems obvious on the face of it, but after all I was sad when Mycroft died in Moon is a Harsh Mistress, I thought the bombs were some of the more interesting (and saner) characters in Dark Star, I even recall a Berserker short story in which the "heroes" were AIs based on WWI fighter pilots.
And then there are the Bolo stories.
Them's just people by a different name. And if someone did write a story about a non-sentient probe like the Mars rovers, they'd be doing their level best to personify the little lump of metal and plastic.
Byron:
"Maintenance has degenerated into purple vs. green. I don't think we'll agree on that."
Sorry, but that's incorrect. It's an argument between those who know what they're talking about from personal experience and those who wish to hand wave that experience away as irrelevant, because (they claim) somehow technolioal principles will be different in space.
"As to laser accuracy, Luke knows a lot more about it than either of us, and he seems to think it will work."
Luke knows a lot about theory. I would never take that away from him. Practical application? Not so much. That's where my expertise lies. Lab and field capabilities are worlds apart, and there's nothing that anyone can come up with that is going to change that.
"And particularly if your theories on lasers are correct, is anyone going to bother shooting at 3 light-seconds? That makes no sense given your assumptions."
Yet Luke calims that targets have to be light hours, or at least light minutes, away to be safe.
"Also, you make 1 G sound like a little bit. It isn't. That engine will take a considerable amount of your dry mass, and it won't be terribly effective closer in."
I'm making the simple -- and reasonable -- assumption that the power levels available for weapons are also available for propulsion.
"As to my math problem, are you going to solve it, or not?"
Are you sure you want me to? Okay...
An infintesimally narrow beam will have to miss by the spacecraft's radius, if it is aimed at the center. So:
r = 10 / 2 = 5
The equation for distance traveled under acceleration is:
d = a * t^2 / 2
where:
d is distance traveled
a is acceleration in some dimensional unit per second
t is time equal to duration of acceleration
Using the given numbers:
5 = a * 1^2 / 2
5 = a * .5
a = 5 / .5
a = 10 m/sec^2
Which seems pretty stiff, until you remember that you're figuring on compressing the power to shoot an effective laser pulse 150000 km into a sphere 10 m in diameter. Given that constraint -- or, more accurately, lack thereof -- it doesn't seem unreasonable that the spherical-cow-star would be able to manifest the necessary maneuvering power.
Also, a point I missed in my jinking example: any kind of jinking is going to complicate the laser engagement problem by rendering dwell on target practically impossible to achieve. This would drive the laser designers to higher power, shorter duration pulses. But power plants are limited in size as are cooling systems. So the trade off is probably not going to be in favor of engagements at very long ranges -- certainly not light hours or minutes, probably not even light seconds.
As for sensors, I think we can disregard previous discussions about eyeball frying, either of sensor suites or weapon optics. WRT weapons, pulsing means you don't have to have your weapon optics unhooded all of the time, and you can gauge when the enemy can and can't lase you. (Unless he's concentrating the fire of several weapons on you, but in that case you're not likely to be standing and fighting.) Also, if you're jinking at all effectively, the enemy isn't going to be dwelling on any part of your ship very long at all. And the jinking is guaranteeing the pulsing to begin with. Or if the enemy is lasing at his maximum continuous level, you might simply not unshutter your weapon while you're threat sensors show an external light flux that is too high.
Speaking of which, targetting sensors don't have to be as sophisticated as assumed by the eyeball frying scenario. What is more likely is that the ship will be equipped with gangs of relatively robust threat sensors that can stand up to eyeball frying energy fluxes. While any individual sensor might not be too accurate, the sum total of threat sensor data should give enough information to accurately target something that is pointing a virtual searchlight right at you. Also, if you need more paralax with less sensitive sensor arrays, place them on masts extending a sufficient distance away from the ship. They can be relatively flimsy, because you're not going to be doing any serious maneuvering in an eyeball frying contest anyway.
Of course, competent system engineers are going to think this whole process all the way through and probably decide to forego attempts at eyeball frying to begin with.
Re: Raymond
The above is meant to answer your comments as well.
Tony:
Say 7 seconds. A jink that moves the target spacecraft 100m in that time only takes an impulse of 15m/sec (1.5 g) for one second.
A spacecraft accelerating at 1.5 g in anything like the plausible near future will need a chemfuel rocket (or ORION, but I'm not going to get in to that). 1.5 g is low enough that we can use H_2/LOX, with an exhaust velocity of around 4.5 km/s. If our target's mass is 63.2% propellant, it can put on a delta-V of 4.5 km/s.
So, our target is at 3 light seconds out. Let's suppose it wants to close to within 2 light seconds. That means crossing 300,000 km. If, despite having chemfuel rockets, it is moving at a relative speed of 30 km/s, this means 10,000 seconds in which it has to evade the laser. I will ignore for the moment that as it gets closer, the time between jinks decreases and the cost to jink increases. So, it needs to spend 15 m/s of delta-V every seven seconds. That's over 20 km/s of delta-V. In fact, after 300 seconds the target will be out of propellant, after having closed to only 2.97 light seconds.
That's a lot of power, but we're notionally talking about spacecraft that can fire a combat effective laser pulse 1 million kilometers.
You do not need raw power to get combat-effective lasers out to 1 million km (although raw power will suffice if you have it). If we limit ourselves to 1 MW, a 1 meter spot size will drill armor steel at a rate of 0.2 mm per minute (admittedly not very impressive) and a 10 cm spot size at nearly 1 cm/s. For 1 micron near IR you would need a very impressive 1,000 meter wide primary aperture to focus to a 10 cm spot at this distance - impressive, but perhaps building a 1,000 meter segmented mirror in space (where you don't need to worry so much about structural issues) is cheaper than sending up manned war craft. And as you get shorter wavelengths the easier it becomes to focus. We currently have x-ray lasers that can emit powerful diffraction-limited beams tunable between 10 nm and 0.1 nm (see the LCLS at SLAC, for example). Scientists can be somewhat annoyed because the high brightness of these beams means they only get one shot to take a measurement, because the x-ray pulse vaporizes their experimental set-up. Of course, as a weapon that is exactly what we want. So if we have a 1 MW beam of 1 nm x-rays and we want to focus it down to a 10 cm spot at 1,000,000 km, you only need a 1 meter wide x-ray zone plate. (You do need to get a fairly large linac into orbit, but with today's technology we could make the linac considerably more compact than SLAC, and I expect the linac would be considerably cheaper than a manned combat space craft.)
continued ...
continued, to Tony:
And this level of accuracy is only achievable with high-precision, low-vibration pointing gyros, and, I failed to mention earlier, after an amount of time has been allowed for induced vibrations and changed haeting profiles to settle down.
That's what adaptive optics with actively deformable mirrors, and active vibration control, allow you to overcome. We have the technology. I have seen it in action (although, admittedly, not applied to high powered laser systems). It is pretty impressive.
there has been an ongoing assumption of perfect sensor alignment, perfect translation of the raw data into actionable information, and perfect boresighting of the weapon.
If you use the same physical mechanism for sensing as you do for projecting your damaging beam, the first and third of these are automatic. This has been known and implemented since 1884 (and perfected in the 1960's), with the development of the single lens reflex camera - the viewfinder is automatically perfectly aligned and "bore-sighted" with the film (or digital sensor, nowadays). A near visible laser would use a very similar system, although I would be tempted to use a frequency specific window/mirror, rather than a flipping mirror, to switch between the laser lightpath and the sensor lightpath (among other things, this means you will not be dazzled by the glare from the laser incident on the target).
For VUV, EUV, and x-ray lasers you might use a different system, perhaps using the beam as x-lidar for both targeting and attacking.
Them's just people by a different name.
Yup. Which suggests that the insistence on human piloted fighters in SF stories instead of the sort of "people" liable to pilot a "space fighter" has more to do with lazyness on the part of writers than any real demand on the part of readers.
Re: Luke
I'm sorry, but you obviously don't understand what boresighting is. It is the practice of aligning your sensors and weapons so that point of aim coincides with point of impact at a given range. It's a purely mechanical process of alignment. To take your SLR camera example, the viewfinder center and the line of sight of the lens train are not preflectly aligned, even in the best cameras. They're very close, but the unavoidable imprecissions in lens and prism alignments means that there will always be a difference. It's not critical in photography, but it would be critical in weaponeering. Using the weapon as a light collector would in no way alleviate the need to accurately align the sensors and for boresighting purposes.
WRT your economic arguments, if you want to invest everything in one (or a few) large laser weapons, while I can invest in several hundred or several thousand or tens of thousands of brilliant pebbles with which to attack it (them), I'd feel pretty confident in the result.
As for the rest, please read my other comments to Byron and Raymond.
I wanted to point out something regarding jinking to avoid lasers. While jinking once may not use up too much resources, you don't know WHEN to jink. That means that in order to take advantage of the jinking method, you need to be jinking for the entire duration of the encounter. Also, due to the nature of lasers, you don't know when you've been targeted (unless someone is using a broad scanning radar for firing). So, that 3 light second range laser could work very well as an opening shot. So could a light minute range laser.
Barring reactionless thrusters, jinking isn't going to be a valid defense against lasers.
Re: automation
What people seem to forget is that weapon systems have been automated for over half a century. Technology has greatly improved over time. In the beginning it was all cams, gears, and selsyns, with scores of humans aligning sensors, monitoring computers. Nowdays everything is digitized and can be controlled from the CIC by a reltively few people, with automated loading and firing likewise requiring few live bodies. But guess what? You still need a lot of humans to maintain all of that automation. Complex machinery and even solid state electronics takes a lot of TLC to keep working. Talk of further automating the ships is just that: talk.
(SA Phil)
On repair/maint.:
If you are willing to live with the possibility of your mission failing due to the lack of a crew for repair and/or maintenence ...
You are accepting the crew won't be there. So you design around it.
Its not as if the drone decides to fail because there is no human crew present.
Re: Citizen Joe
When you can jink, and how much jinking you can do is a tradeoff. Jinking would be most effecitve at the start of the engagement, and at long range. (It's the same with AFV jinking, BTW -- but it's still done, because it works to a certain degree.) And it may not even be effective for a large vessel. It should be quite effective for a brilliant pebble, which only needs to move a meter at most during the light-time-round-trip-plus-computing interval.
SA Phil:
"On repair/maint.:
If you are willing to live with the possibility of your mission failing due to the lack of a crew for repair and/or maintenence"
Stop right there. Why would any commander or even policy maker be willing for that to happen?
Yup. Which suggests that the insistence on human piloted fighters in SF stories instead of the sort of "people" liable to pilot a "space fighter" has more to do with lazyness on the part of writers than any real demand on the part of readers.
Well, I don't think proper drone fighters would come across like "people." If you think about it, military training focuses on removing the sense of self and individuality. You're part of a team, there's an objective, you're not paid to think, you're not paid to question orders. Hoorah. All the little quirky bits we like when we think of "people" would be the kind of thing military theorists would love to strike from the design spec of the common grunt if they had the means. Certainly if we're talking military AI, they're going to want sober, serious, no-nonsense bots. They don't need a drone fighter woolgathering, writing poetry, or questioning the war.
Now as of right now, you can't get humans without all those other little bits and you can't fight a war without humans. But you don't need human-level intelligence everywhere and so that's where the question of the drones comes in. And from there the question is at what point do expert systems cross over into being AI's and is there a point at which a designed intelligence has to have those extra bits, can't have one without the other?
For example, emotions are important in human decision-making. People with brain damage that removes the ability to feel emotion will dither over even tiny decisions. So it may prove that an expert system works up to a point when making decisions that can be systemized into rules but for fuzzier situations, the kinds of questions that we say calls for a human, for an AI to take on that kind of responsibility it will need emotions. And with all of that you might get the additional baggage of individuality, concept of self, and the potential for disagreeing with orders. Why run with an AI instead of a human? Might be cheaper -- AI's a 50lb brain in a box that just needs 4000 watts of power that's always on and cooling while a human needs tons of life support mass and you need several of them working in shifts...
(SA Phil)
Price/resources/other varaibles.
Plenty of reasons.
What If you have 5 ships and a 20% ship failure rate. You only need 2 ships to destroy the final target.
The chances are good one ship will fail in its mission. But chances are pretty good the overall mission will suceed anyway.
(SA Phil)
Probably even better mass benefits that jolyreaper suggests
The embedded controller in your car weighs about 2 pounds and requires less than 50 watts to do what it does.
A human couldnt even control an engine for a dynamic range. Too many decisions to make in too short a time.
Meenwhile a $9 chip can take over for the main processor even if you take a drill and run it through the CPU.
And all you notice is a check engine light and a (intentional) warble.
Complex machinery and even solid state electronics takes a lot of TLC to keep working. Talk of further automating the ships is just that: talk.
But they think they can do it. And we're going to have the paperless office any day now. I'm curious to see what develops.
Crazy thing, was reading about the cost of operation of current hardware. A 12-hr strike flight for a B1 bomber, inclusive of fuel and the ridiculous amount of maintenance that puppy requires, is a quarter million bucks. $750k. That's not including the cost of the smart munitions. Damn.
Re: SA Phil
Sorry, but a 100% chance that one of five ships will fail from unspecified random factors implies a significant chance that all will fail.
If you are willing to live with the possibility of your mission failing due to the lack of a crew for repair and/or maintenence"
Stop right there. Why would any commander or even policy maker be willing for that to happen?
Nobody would ever go out and say that any more than the designers of Fukushima said "We're setting out to build a powerplant and accept a non-zero probability of catastrophic meltdown." But you read between the lines looking at the compromises made and determine that this is what they're saying.
So no general says "I'm willing to accept that cutting corners will possibly jeopardize our success" and no politician will run on that but you look at the decisions that get made and you'll see that's what they're really saying. Likewise, nobody said "We're setting out to build showers that will electrocute our soldiers" and nobody later said "We don't care that our soldiers are getting electrocuted by crappy showers built by crappy contractors" and yet here we have dead soldiers killed because of crappy showers, showers the military knew about for years and did nothing to fix.
As of 2008: "At least 12 U.S. troops have been electrocuted in Iraq since the start of the war in 2003, according to military and government officials. In fact, the Army issued a bulletin in 2004 warning that electrocution was 'growing at an alarming rate.' It said five soldiers died that year by electrocution, with improper grounding the likely culprit in each case."
(SA Phil)
Tony,
Lets call it 1% then.
The actual number was not important. It was just an example.
-------
The reason you dont have a 100% automated Naval Ship is not the technology -- it is the cost.
A cost that has gone down significantly in the 40 or so years it has become possible.
200 years from now? Do you really think electronics in general will need the kind of "TLC" it does now?
Do current systems need the "TLC" the ones did 40 years ago?
jollyreaper:
"But they think they can do it. And we're going to have the paperless office any day now. I'm curious to see what develops."
Ummm...not quite -- some claim it can be done. Judging by my experience with the reliability of even the newest common engineering artifacts, I would strongly advise against holding your breath.
"Crazy thing, was reading about the cost of operation of current hardware. A 12-hr strike flight for a B1 bomber, inclusive of fuel and the ridiculous amount of maintenance that puppy requires, is a quarter million bucks. $750k. That's not including the cost of the smart munitions. Damn."
Which is a function of all of the man hours that go into keeping the things in combat condition. It also helps to illustrate why CG(X) was canceled and DD(X) scaled back -- they just got too expensive for what they had to offer. Also, significantly, the supposed crew reductions due to automation was down to 140, similar to a ballistic missile submarine of similar size. Ask Scott how dependent on the shore industrial establishment submarines can be.
(SA Phil)
Jollyreaper is correct
These decisions are made every day. It is part an parcel of any kind of development.
Risk vs Cost is the way it is done.
They knew the Pinto would blow up, they decided it would be cheaper to let it.
A warship is no different. Its just a large series of engineering/economic compromises.
Tony:
"I'm making the simple -- and reasonable -- assumption that the power levels available for weapons are also available for propulsion."
Neither simple nor reasonable, actually. For starters, laser ranges are governed by absolute power and mirror size, whereas propulsion is governed by specific power (power per unit mass, just to clarify and avoid another mess of assumptions). You can easily have a laser in the tens or hundreds of megawatts, powered continuously by a reactor even more powerful, and still only get somewhere between 0.1-10 kW/kg effective propulsive power (depending on where along the nuclear spectrum your techlevel sits). A fully-fueled Shuttle with 2 SRBs and the SLWT gets well over 100 kW/kg. You'll need even better if you don't want to run out of propellant within minutes.
TL;DR - if you think craft will be jinking within a light second or so, you're waving your hands so hard they're blurry.
Welcome to a couple of new commenters!
It's an argument between those who know what they're talking about from personal experience
So far as I know, everyone in this discussion has the same level of personal experience in space operations (including ground support), namely zero.
Arthur Clarke assumed that comm relay in space required a space station with a maintenance crew - specifically to replace vacuum tubes ('valves' to some of you), but broadly to perform the many maintenance functions that our terrestrial experience generally shows that complex gadgetry requires.
But so far, at least, space experience seems to be that it costs more to human-rate a spacecraft than is saved by having human maintenance techs on board. This may or may not be the case with the much bigger and more capable spacecraft of a demi-operatic future.
pulsing means you don't have to have your weapon optics unhooded all of the time
Bear in mind that pulsing, in this context, is in the kHz range. Making shutters for big primary optics that open and close at that rate will be ... challenging.
WRT your economic arguments, if you want to invest everything in one (or a few) large laser weapons, while I can invest in several hundred or several thousand or tens of thousands of brilliant pebbles with which to attack it (them), I'd feel pretty confident in the result.
See my discussion of just this scenario in 'Further Battles of the Spherical War Cows.' I reached much the same conclusion, that under an assumption that spacecraft cost is roughly proportional to mass, a killer bus capable of saturating and overwhelming a laserstar with its payload of small target seekers would cost a good deal less than the laserstar itself.
But even if those assumptions are true, they don't banish laserstars to irrelevance, because kinetics are expended by firing them, while a laserstar can zap weaker opponents at pretty much no cost to itself.
In my view this makes killer buses and laserstars complimentary weapons, suited to different missions. Depending on your objectives and threat picture, you might well want to procure both, and perhaps even incorporate both in the same constellation.
Tony (addendum):
"Sorry, but a 100% chance that one of five ships will fail from unspecified random factors implies a significant chance that all will fail."
Wrong probabilities. Given five craft and a 20% failure rate, at least one will fail only 67.2% of the time. All five will fail a mere 0.032% of the time.
"[Jinking]should be quite effective for a brilliant pebble, which only needs to move a meter at most during the light-time-round-trip-plus-computing interval."
Define brilliant pebble here, so we're on the same page. Also, please explain how said pebble is supposed to have an effective range of a light-second, plus how fast said pebble must be moving relative to the target to penetrate even thin armor.
"Speaking of which, targetting sensors don't have to be as sophisticated as assumed by the eyeball frying scenario."
The eyeball-frying scenario is about rendering laser mirrors ineffective, so as to eliminate or reduce point-defense fire and facilitate subsequent kinetic strikes for a hard kill. Nothing to do with blinding sensors.
Tony:
I'm sorry, but you obviously don't understand what boresighting is. It is the practice of aligning your sensors and weapons so that point of aim coincides with point of impact at a given range. It's a purely mechanical process of alignment.
For a near visible laser, the mechanical alignment process is not the limiting factor on precision. You can be reasonably sloppy here (obviously not too sloppy) because a slight mis-alignment of your optics affects the laser and the sensor in the same way, so the two exactly compensate for each other.
The closest I can think of to what you use bore sighting for on modern firearms is a single calibration to determine which pixels on your sensor correspond to where the beam will go. This is fairly simple - just shine the beam on something and see which pixels light up. There is no additional mechanical fiddling necessary. In a maintenance-heavy model of spacecraft combat, you might want to re-calibrate every so often by throwing out your calibration board and shining the laser on it again.
You will need to align and calibrate with the wide field sensors, but the final targeting is greatly simplified and made more reliable and rugged by using the same light path for both beam and sensors.
The economic arguments are starting to wander away from the topic - if long range lasers are not economical then they will not be used and we are back to the no light lag case. If it is economical to get laser ranges out to several light seconds or even a light minute, then we need to consider if evasion is possible and if so, under what conditions. The main reason I had for bringing up costs was to avoid derisive dismissal of the technology when we are already assuming manned space combat vehicles.
For maint./repair I think you have to assume you have Drones that have a reasonable lifespan with minimal breakdowns
Think: Furnace / Washing Machine / Television Set
Not:
Jet Aircraft
If you are at the hours of maint. for each hour of flight stage / you wont have drones.
So far Spacecraft have been more like the former than the later.
------
Even the most famous of all Space Repair of a robot spacecraft - The Hubble -- was not necessary.
In a conversation I had with an Engineer on the project, they wanted to spend a few hunderd K and weeks to test the optics before launch, but it was deemed unneccesary by people up the food chain.
For maint./repair I think you have to assume you have Drones that have a reasonable lifespan with minimal breakdowns
Think: Furnace / Washing Machine / Television Set
Not:
Jet Aircraft
If you are at the hours of maint. for each hour of flight stage / you wont have drones.
So far Spacecraft have been more like the former than the later.
------
Even the most famous of all Space Repair of a robot spacecraft - The Hubble -- was not necessary.
In a conversation I had with an Engineer on the project, they wanted to spend a few hunderd K and weeks to test the optics before launch, but it was deemed unneccesary by people up the food chain.
Tony:
Wow. You can do math!
Sorry, but that's incorrect. It's an argument between those who know what they're talking about from personal experience and those who wish to hand wave that experience away as irrelevant, because (they claim) somehow technolioal principles will be different in space.
Yes. Because you obviously have experience on the types of vessels we're discussing. If I want to know about Long Beach, I'll ask you. If I want to know about submarines, I'll ask Scott. But unless you're using a Dean Drive (and if you are, I'm never speaking to you again) that experience isn't completely relevant.
Luke knows a lot about theory. I would never take that away from him. Practical application? Not so much. That's where my expertise lies. Lab and field capabilities are worlds apart, and there's nothing that anyone can come up with that is going to change that.
And if you were a laser engineer, that argument would have merit. But you aren't. You're applying your experience in a completely different field. While we won't have diffraction-limited lasers, we have formulas for that.
As to automation, I will continue to maintain that it will be a balancing act between cost and capability. If I can cut a really expensive human for a cheap part, I will. Modern warships aren't automated to the maximum simply because the crew will be there anyway, so why not have them do the job? The example of satellites is a good one.
Which seems pretty stiff, until you remember that you're figuring on compressing the power to shoot an effective laser pulse 150000 km into a sphere 10 m in diameter. Given that constraint -- or, more accurately, lack thereof -- it doesn't seem unreasonable that the spherical-cow-star would be able to manifest the necessary maneuvering power.
And just where did I say that it was a sphere? I was thinking of a cylinder with a 10 meter diameter. And plausible midfuture means not being able to pull a demi-torch out of nowhere whenever it's convenient.
Jinking works for AFVs because the cost of a course change is negligible. If they are moving in any direction, the cost is the same. Constant position is free. To look at spacecraft, take the derivative. Velocity is free, acceleration costs stuff.
And you could try accepting that other people could be right. I freely admit that maintenance could go either way. You seem completely certain that you're correct, to the point of contradicting yourself to make your points.
SA Phil:
"Jollyreaper is correct
These decisions are made every day. It is part an parcel of any kind of development.
Risk vs Cost is the way it is done.
They knew the Pinto would blow up, they decided it would be cheaper to let it.
A warship is no different. Its just a large series of engineering/economic compromises."
The fact that risk management tradeoffs have to be made and the level of acceptable risk are orthogonal. We got sidetracked on what a level of acceptable risk was for individual units, but what I was reacting to was your assertion that mission failure would be an acceptable tradeoff for a lack of maintenance. You have to understand that someone who has training and experience in the use of a vocabulary will interpret statements using that vocabulary in a certain way. When you say mission failure, that means to me that the entire mission fails, not that a single unit does. There is no way that a military commander or his political superiors would accept that a mission failed for lack of simple maintenance and upkeep. Not even a 1% chance, unless it was prohibitively expensive to institute that level of reliability. Whatever that translates to in individual unit reliability is perhaps an interesting question, but not relevant to the principle under discussion. Whatever that percentage is, it had better be maintained, in order to ensure that the mission doesn't fail because the force wasn't materially ready.
(SA Phil)
For a spacecraft hower a "Mission" is also that spacecraft's planned journey.
"But they think they can do it. And we're going to have the paperless office any day now. I'm curious to see what develops."
Ummm...not quite -- some claim it can be done. Judging by my experience with the reliability of even the newest common engineering artifacts, I would strongly advise against holding your breath.
The "paperless office" comment was meant to show I'm well aware of how deliveries can fall short of promises. Since they're going to make the attempt regardless of our opinion on the matter, all we can do is sit back and watch.
So far as I know, everyone in this discussion has the same level of personal experience in space operations (including ground support), namely zero.
Ha! Earthlings are so easily fooled. And my Illudium Q-36 Explosive Space Modulator is nearly in place. MUHAHA!! *cackle* *gloat*
Lentulus:
"It is interesting that some ground-combat SF writers have risen to the challenge, but space-combat authors beg off."
Many space operas feature spaceships which have their own AI personality while also being staffed by a full human crew. It often isn't explained how these complement each other to justify needing both.
Except, of course, that the spaceship's avatar gives the captain a cute robot girl to flirt with.
Re: Raymond and Luke
Actually, required laser power at the target is governed by your ability to collimate the beam and how much spot dwell time you can get on the target. (And the spot dwell time is the figur of merit. It doesn't matter if you can bore through the ship's skin in a second if the beam is only on any given piece of the skin for a miniscule fraction of that. even the effects of flash heating over an area of skin won't add that much damage.) The less collimated the beam and/or the less dwell time, the more power you need in a given amount of time. With the likely millisecond range dwell times, the available power will have to be magitechnically enormous for continuous beam, or even for the multi-hertz pulse frequencies you claim. Also, the heat generated by the system at full power is going to be a big problem in space. At the 100000 km ranges you claim, I would think several hundred megawatts would be necessary per millisecond of laser pulse to get any effect on target.
And even a little jinking will cause very spot dwell times to go down. A 10 cm beam (if it could be held perfectly still, which it can't) moving across a surface at a meter a second only has an effect over any one spot for 100 milliseconds. You better get a lot of energy into that beam per second -- certainly more than a megawatt, or even a few hundred megawatts.
But if you have that much energy to put into beam weapons, you're getting into torch drive energy generation efficiencies.
(SA Phil)
I think even a paperless office is possible --- if it weren't for the humans involved in said office.
The same goes for automation. A lot of the risk leading to the need for repair is caused by humans who built the thing in the first place.
It could all be designed out, given sufficient motivation and resources.
Lots of catching up to do here!
Space ICBM's don't have to level a planet (and won't in a plausible midfuture(tm) scenario), but moving sufficiently fast can cause unacceptable levels of damage. A design for an ORION asteroid busting interceptor (which I have referenced several times) can accelerate at 100G, cover millions of kilometers in hours and hit with about a gigaton of kinetic energy. This would demolish any incoming spacecraft, Island Three, or turn Cheyenne Mountain into Cheyenne lake.
I think one of the big issues about maintaining space hardware involves how it is used. We know submarines and fighter aircraft need lots of maintaining, but they are also subject to lots of stress during routine operations. Spacecraft mostly coast to their destination, and are under minimum stress for most of their lives except during launch from Earth.
By analogy, a V8 engine in a top fuel dragster needs to be stripped and totally rebuilt after a single run totaling a few seconds. A V8 engine in a Formula One race car can run for several hours before rebuild, while the one in your car (assuming there are still V8 cars out there) can run for the lifetime of the car without rebuild. Similar engines subjected to differing levels of stress have far different lifetimes.
A military spacecraft will be coasting for most of its service life, and only have to run its systems at high power for a short time during combat. Having the ship coming in for depot level maintainance after a mission does not seem to be too unreasonable of an assumption.
Re: Luke and boresighting
You're still missing the point. Using the weapon as a light collector has no bearing on the precision with which sensors can be aligned to use that light. At the levels of precision we're talking about, even the slightest microscopic jiggle will cause the image to wander across the collection area.
If you're looking strictly at long range laser defense, one option might be a "Swiss Cheese Ship". Let's say you're ship is actually an open truss with 90% void. When closing with a laserstar, you "simply" continuously reconfigure your ship so that your critical components are never in a predictable flight path. Since you're not actually changing your collective flight path, just the relative location of the components, you don't use up precious remass to move the whole ship. Also, you don't need a massive drive because you can use mechanical leverage to move the components around very quickly.
Note that this sort of design is of major concern for asteroid hunters. We aren't sure if asteroids are one solid mass or if they are rubble piles. If the latter, an attack on a rubble pile will just disrupt it for a little while until its microgravity pulls it back together.
Re: relevance of current experience to future technology.
IMO this is a straw man. Machines are machines. Machine reliability is a function of resources expended on reliability. It has been suggested that because we can achieve such high levels of reliability in space today, we should expect as much or more in the future. What is missing in this discussion is the expense of reliability in current spacecraft. Hundreds of millions -- even billions -- of dolars have to be expended on designing for and testing reliability and durability on relatively simple systems. The level of reliability and durability that some people are assuming to be industrial grade in the future would lead to trillion dollar (in constant dollar) warships, even leaving the cost of boosting the ship into orbit out of the equation. Affordable levels of reliability and durability will be much lower.
Also, military systems are low rate production items. In some respects even relatively ubiquitous systems, like attack helicopters, are almost hand made. There is also relatively little operational experience with them, compared to common items like cars or toasters. That means that they are constantly failing in unpredictable ways, and have to be given a lot of care by maintainers.
Finally, there is this constant thread of humans are expensive, automation is cheap. It simply isn't so. If we first assume that there's enough human activity in space to motivate interplanetary war, then we have to accept an interplanetary economy that can shuttle around a lot of humans and a lot of goods. So the resources exist to put humans wherever they need to be in any potential war. That makes humans cheaper than automation, by the same logic that makes automation preferable today -- humans are expensive where humans are expensive, but if they're ubiquitous (e.g. an interplanetary economy capable of motivating and supporting a war) they're cheap.
Tony:
That makes total sense. Because technology never leads to reliability increases in a given field. Which is why we have space stations for communications relays, with people up there to change the circuit boards when the burn out.
even leaving the cost of boosting the ship into orbit out of the equation
This is something you keep forgetting. Stuff in space is expensive, particularly humans. Which is why we try to automate.
Which is cheaper? Ten $10 widgets and a $1 million human to swap them out or two $1000 widgets?
Byron:
"Wow. You can do math!"
Wow. You invite me to work a problem, then attempt to rhetorically minimize my results when they turn out correct. One can only presume that you hoped I did not know the math, and you were searching to discredit me on that basis. Cheap and shabby, B.
"Yes. Because you obviously have experience on the types of vessels we're discussing...
See above -- this is a straw man argument. The kind of experience I'm talking about informs a general knowledge of machines suitable for a given purpose, under realistic conditions. If we wish to presume unlimited funds for reliability and durability design and testing, you would have a valid argument. But since we're talking about military systems that can actually be built for reasonable amounts of money, hand waving about some imagined disconnect between future technology and that currently available is meaningless posturing.
"And if you were a laser engineer, that argument would have merit. But you aren't. You're applying your experience in a completely different field. While we won't have diffraction-limited lasers, we have formulas for that."
More hand waving. I'm not talking about technological specifics, but engineering principles and practical experience with practical equipment. That translates to any age.
"As to automation, I will continue to maintain that it will be a balancing act between cost and capability. If I can cut a really expensive human for a cheap part, I will. Modern warships aren't automated to the maximum simply because the crew will be there anyway, so why not have them do the job? The example of satellites is a good one."
I've already addressed this, but to reiterate: humans will not be expensive in an environment where interplanetary war is possible, because there have to enough humans to go around to make the war possible in the first place.
"And just where did I say that it was a sphere?"
"You are in a 10-meter diameter laserstar...I'm doing a spherical cow."
"I was thinking of a cylinder with a 10 meter diameter.
Which would naturally be perfectly oriented WRT the target? You're not only shifting the goalposts, but invoking unstated assumptions.
"And plausible midfuture means not being able to pull a demi-torch out of nowhere whenever it's convenient."
I would agree. But it also means not assuming magitechnically powerful laser weapons with magitechnically perfect aim and absolutely no instinct for self-preservation on the part of potential targets.
"Jinking works for AFVs..."
It also works for laser targets if you don't impose unreasonable conditions. I was originally thinking in terms of completely avoiding hits, as AFV jinking is intended to do. But it is probably enough to jink just sufficiently to reduce laser spot dwell times to a manageable level.
"And you could try accepting that other people could be right. I freely admit that maintenance could go either way. You seem completely certain that you're correct, to the point of contradicting yourself to make your points."
I see...
I think you're going to have to accept that not all people were taught or accept the artificial rules of high school forensics competitions. I assess my personal experience to be relevant where I think it's relevant, and rely on it in those situations. I don't accept purely theoretical arguments on anything, at any time, simply because somebody worked out the math or the formal logic correctly. Theory and practice are not and never have been the same thing. I try to exercise decorum in debate as much as I can, but I think what I think and I will say what I think.
Byron:
"That makes total sense. Because technology never leads to reliability increases in a given field. Which is why we have space stations for communications relays, with people up there to change the circuit boards when the burn out.
This is something you keep forgetting. Stuff in space is expensive, particularly humans. Which is why we try to automate.
Which is cheaper? Ten $10 widgets and a $1 million human to swap them out or two $1000 widgets?"
I've already said this a couple of times, but since I wouldn't want you to feel like I was ignoring you...
The grounding assumption in all of this is that we have enough people in space and enough trade between those people to motivate interplanetary war. That means space access is relatively inexpensive and people are therefore relatively cheap.
Here's where I will play in your ballpark for a moment -- yes, absolutely, we don't know what technology would look like in such an environment. But I'm willing to bet that it would not be heavily geared towards automation, with enough people around to take care of it, and needing something to do to earn money to enable a trade economy that can motivate and support a war.
Tony:
At the 100000 km ranges you claim, I would think several hundred megawatts would be necessary per millisecond of laser pulse to get any effect on target.
I estimate that 100 MW focused into a 10 cm spot over 1 millisecond will evaporate approximately 1 mm of armor steel. The depth of material removed is approximately linear up through 1 GW. The effect will, of course, depend on where the beam is incident - sensors will be more vulnerable than hull material, for example.
If you focus the beam tighter you can do better - for example, use a 10 meter zone plate rather than a 1 meter zone plate with the x-ray laser. The latter example will drill through about 7 cm of armor steel in 1 millisecond with 100 MW.
But if you have that much energy to put into beam weapons, you're getting into torch drive energy generation efficiencies.
If I can make space reactors at 1 kW/kg, and I need 1000 MW of electricity for my beam weapon to be effective, then I need a 1000 ton reactor.
If I use the same 1000 MW, 1000 ton reactor to drive an electric plasma thruster with a 100 km/s exhaust velocity (typical of modern ion drives), I get 10 kN of thrust. This will accelerate the 1000 ton reactor at 0.01 m/s^2, assuming I have no other equipment to accelerate other than the reactor (reduce this as necessary for propellant, crew habitats, sensors, armor, weapons, and so on). It will consume 200 g of propellant per second, so with 1720 tons of propellant (for a 100 km/s delta-V with nothing other than propellant and a reactor) I can accelerate for 99 days before exhausting my propellant stores.
Now I don't know about you, but 0.01 m/s^2 for 99 days does not strike me as torch levels of performance.
We can also see what our reactor would do if used as a thermal rather than electric thruster. If our reactor is 25% efficient, we can pull 4000 MW of heat out of it and use it to power a hydrogen rocket. A nuke thermal rocket can get around 8 km/s of exhaust velocity, so we get a thrust of 500 kN. This will accelerate the reactor alone at 0.5 m/s^2 and consume 125 kg of propellant per second. With 1720 tons of propellant (for 8 km/s of delta-V with nothing other than propellant and a reactor) you get about 4 hours of acceleration.
Again, this does not seem like much of a torch to me.
Note that scaling up your power source to get a more powerful beam does not change your acceleration or endurance (for the same fuel fraction).
Using the weapon as a light collector has no bearing on the precision with which sensors can be aligned to use that light. At the levels of precision we're talking about, even the slightest microscopic jiggle will cause the image to wander across the collection area.
This is a solved problem for multi-tens-of-meter scopes operating at near visible wavelengths. We are not talking about putting this scope on a jeep bouncing along a rutted dirt road, or on a naval vessel buffeted by wind and waves, but rather on a stable platform in the vacuum of space, where the optics can be isolated from the vibrations of any machinery in addition to active vibrational suppression on the optics. Over multi-light second ranges the rate of slew to keep the target at the focal point is small and can mostly be handled by the mirror's micro-actuators rather than moving the scope as a whole.
(SA Phil)
Being in the electronic field myself I am a bit perplexed.
A $50 circuit board today is probably 10x as reliable as a $5000 circuit board that did roughly the same task 20 years ago.
We dont even repair most circuit boards anymore. They fail so much less often and they are so cheap its easier to replace them.
20 years ago, repair was common, laborous and uncertain.
---
Machines may be machines, but technology marches on.
It will be possible to design reliable spacecraft in the future for less real dollars than it costs today, and it will not require the levels of maint. and repair that modern military equipment does during operation.
Whether they leverage that ability to make drone warships is not as certain, but ignoring the history of technology doesnt seem to be the place to start.
------------
Many early cars broke down once per day. How does that compare to now?
Re: Luke
If you have to put a 1000 ton reactor in space to get sufficient beam power, you aren't going to use beam weapons, unless lifting 1000 tons is a relatively inexpensive proposition. That of course implies something a little bit more powerful than NERVA type NTR and more efficient than Hall thrusters. Simply put, you can't suppose a thing -- even an unspoken implication -- then turn around and unsuppose it a step or two later.
Re: SA Phil
It turns out that even with all of the improvements in electronics over the last several decades, it has only changed the typeand volume of things we do with electronics, not the necessary human involvement in their use. Yeah, the glass-enclosed temple of Big Iron has gone, but we still have system administrators and programmers galore. They don't switch out circuit boards anymore, or write thousand line batch processes. They switch out blades (or bad drives in RAID arrays), and write several thousand lines of code to support an interactive web page. I see the trend continuing: increased computer reliability and durability will change what people can do, and at what points in the process, but it won't change the necessity for people to be involved.
Tony:
That of course implies something a little bit more powerful than NERVA type NTR and more efficient than Hall thrusters. Simply put, you can't suppose a thing -- even an unspoken implication -- then turn around and unsuppose it a step or two later.
I never unsupposed it. If you have 1000 MW, you can use it for propulsion. In the mid future, this involves nuke or plasma, and I considered both of these possibilities and made a ballpark estimate of their performance. In neither case will you get torch levels of performance, as you claimed.
The issue here is not total power but specific power. At 1 kW/kg you can't get torches - you always have too much mass for the available power. But if you need lots of power you have the option of building a big massive reactor to give you that power.
(SA Phil)
Tony,
But thats kind of the thing.
The Spacecraft isnt going to do all sorts of things; its only going to do a few narrowly defined things.
Basically it will --
*generate electricity at a constant rate.
*accelerate at a constant rate or not at all.
*change facing
*charge capacitors
*choose a target
*track a target
*fire a laser
*manage heat
Sure there will need to be lots of humans around to deal with the new implications of technology -
They just wont have to be on that warship to make it function.
In many ways a combat spacecraft will be far less complicated than a modern naval warship or even a modern automobile.
Re: Luke
You totally missed the point. You supposed a 1000 ton reactor in space. You're not going to put a 1000 ton reactor in space without propulsion technology that we would today call "magitech" (e.g. large masses of fusion-heated remass expelled at tens of thousands of degrees out of a non-material (perhaps electromagnetic) nozzle). But if you have the magitech to put the reactor in space you:
1. Won't need to put that big a reactor in space, and
2. Will have the specific power available to do quite a lot of otherwise inconceivable maneuvering, including the jinking of spacecraft under laser threat.
Tony:
"If you have to put a 1000 ton reactor in space to get sufficient beam power, you aren't going to use beam weapons, unless lifting 1000 tons is a relatively inexpensive proposition."
I don't think you're listening. That thousand-ton reactor isn't for the laser, it's for the engine. It's a prerequisite for interplanetary travel at reasonable speeds with reasonable payloads. The reactor's up there anyways (and you'll likely have to lift it in pieces), is already a requirement for propulsion, and will almost certainly provide more than enough power to run said laser on the side. Such a reactor, however, won't provide anything close to what you'd need to successfully jink against incoming laser fire at light-second ranges.
Perhaps you've got some other assumptions, like the mass of the spacecraft involved being in the hundred-ton range or something. Perhaps you're just being contrary to play devil's advocate. You claim you're not relying on specific technical details, only principles, but attempt to discredit laser weaponry as a class with very specific objections. I understand what you're getting at on the whole: real-world combat conditions aren't ever as neat and orderly as theoretical ones. Fine. Granted. Given. But a lot of your objections are, as Luke's already pointed out, solved problems, operating in a very different environment compared to current military experience.
Hell, that's the point of all of these space warfare threads - how the known conditions of space are different (and frankly occasionally counterintuitive) compared to terrestrial ones, and how many of our assumptions about what constitute "combat conditions" on Earth have to be revised for space.
(SA Phil)
If you built the 1000 ton reactor on the moon you could lift it with chemical rockets.
It is not insurmountable at all.
Once its in orbit it is definitely managable.
Any space warship is going to be built in space. There will be no landing/launching capability- It would be too much of a mass penalty.
Tony:
You totally missed the point. You supposed a 1000 ton reactor in space. You're not going to put a 1000 ton reactor in space without propulsion technology that we would today call "magitech" (e.g. large masses of fusion-heated remass expelled at tens of thousands of degrees out of a non-material (perhaps electromagnetic) nozzle).
I disagree. The ISS is 400 tons. The space shuttle orbiter is 100 tons. This is within an order of magnitude of 1000 tons, and we can loft them into orbit without magitech. In the mid future, some increase in our ability to make big things in orbit is plausible. For a significant manned presence in space in the mid-future, the ability to make structures and machines of hundreds to thousands of tons is not only plausible, it is necessary. Just how much do you expect these spacecraft with a crew of a dozen to mass?
Thucydides:
"an ORION asteroid busting interceptor [...] can [...] cover millions of kilometers in hours"
Millions of kilometers in hours calculates to about 300 km/s. No way is an ORION going to have that much delta-vee. Even fusion rockets have to squeeze to get that much.
And even at 300 km/s, and with a huge missile massing five kilotons (which is a ship size), you will still "only" do damage comparable to the Tsar Bomba. So, now you've used a whole bunch of nuclear explosions to accelerate a ship to the point where its kinetic energy can do damage comparable to a single nuclear explosion. Congratulations.
Anyway, this is a "city-killer" type weapon, which means it needs a guidance system sufficiently good to reliably hit a city (on a rotating planet, don't forget).
And such a weapon is decidedly lacking in finesse.
Citzen Joe:
"If you're looking strictly at long range laser defense, one option might be a "Swiss Cheese Ship". Let's say you're ship is actually an open truss with 90% void. When closing with a laserstar, you "simply" continuously reconfigure your ship so that your critical components are never in a predictable flight path."
A simpler way to achieve the same effect with far less moving parts is to simply have your ship rotating. If the ship has a hole in the middle (like a donut), then there's no part of it that isn't moving. As a bonus, rotation provides artificial gravity too.
If you want you can also arrange important stuff on spokes radiating out from the center of rotation, with vacuum between them, rather than using a single donut shape. This would probably mean needing more structural materials, but it would prevent people from targeting your ship with the idea of "I'm not sure what I'll hit but I'm bound to hit something". You can also have the reaction wheels make continuous minor adjustments to rotation speed so your motion isn't too predictable (and so you can try your hand at juggling eggs in variable gravity).
Luke:
"We are not talking about putting this scope on a jeep bouncing along a rutted dirt road, or on a naval vessel buffeted by wind and waves, but rather on a stable platform in the vacuum of space, where the optics can be isolated from the vibrations of any machinery in addition to active vibrational suppression on the optics."
Can they be isolated from your ship being shaken by hits from enemy weapons?
(SA Phil)
Actually its a bit unfortunate that Lasers are so effective
Otherwise you could use much smaller warships to do your fighting.
A couple of megwatts of electric power...
A Light Gas Gun for hypervelocity kinetics..
Combine your reactor and electric drive so it could either work as a NTR for thrust or a plasma drive long legs.
The scale makes it much simpler.
But the Lightsecond range of the Laserstar wipes those ships out.
Re: SA Phil
"*generate electricity at a constant rate."
Really? What about varying power levels for varying types of targets and firing cycles? And what do you do with all of the power generated when not firing?
"*accelerate at a constant rate or not at all."
It has been found advantageous to throttle launch vehicle engines, even when the flight profile can be planned out years in advance. I don't see any likelihood in a single level of acceleration being found satisfactory for a warcraft.
"*change facing"
That's a suspiciously war-gamey sounding term...
In general, a maneuverable spacecraft needs twelve degrees of freedom:
+ roll
- roll
+ pitch
- pitch
+ yaw
- yaw
+ x translate
- x translate
+ y translate
- y translate
+ z translate
- Z translate
Some of these can be combined if operational conditions allow, but for maximum flexibility, each of these maneuvers should be independently invocable. the Apollo CSM managed this with four thruster clusters, each containing four thrusters, for a total of sixteen. For a large craft without the balance and symmetry of the Apollo CSM? Who knows how complicated the maneuvering system could get.
"*charge capacitors"
And discharge them. And manage all kinds of non-full charge modes.
*choose a target"
Who knows how complex the sensor suite and battle management system is going to be.
"*track a target"
Precisely. How complex and tempermental is this system likely to get? It won't be simple.
"*fire a laser"
Invoking the previously mentioned capacitor discharge and recharge, which puts stress on the power generation and distribution.
"*manage heat"
Passive heat management is reliable but inefficient. Active heat management is a lot less than reliable, and gets more complicated the more effective you try to make it.
Tony:
First, My comment about you and math was inappropriate and I'd like to apologize.
You do have a point about military weapons being rare, but I don't see them being substantially different from civilian spacecraft.
More hand waving. I'm not talking about technological specifics, but engineering principles and practical experience with practical equipment. That translates to any age.
This is the problem I have with your approach. You would claim that your expertise (What I know of is Navy service) would make you better qualified than a satellite designer to comment on reliability in spacecraft. I know we don't have one, but you've done the same with Luke. There is no engineering principle that demands human maintainence. A car engine is quite complex, and it goes with very little. I know that not all the factors are being considered, but it's still a relevant data point.
Your argument amounts to 'It won't work at an ideal level, so it will only work to my position' None of us had said it would be ideal, but it might be closer to ideal then you're willing to admit.
Which would naturally be perfectly oriented WRT the target? You're not only shifting the goalposts, but invoking unstated assumptions.
Actually, these are on your end. A Spherical Cow is a rough calculation, and cylinders do have diameter, too. The orientation is assumed, as you want to use the laser, and I was doing a best-case scenario. The point is that acceleration to dodge is going to be significant, which drops Ve available. As for dwell times, that's what pulsing is for.
Tony:
I think you're going to have to accept that not all people were taught or accept the artificial rules of high school forensics competitions. I assess my personal experience to be relevant where I think it's relevant, and rely on it in those situations. I don't accept purely theoretical arguments on anything, at any time, simply because somebody worked out the math or the formal logic correctly. Theory and practice are not and never have been the same thing. I try to exercise decorum in debate as much as I can, but I think what I think and I will say what I think.
Thus, you refuse to accept math, claiming that it's theory, and that your experience leads you to distrust theory. This is all well and good, but we're debating a theoretical subject. Theory is all we have.
The grounding assumption in all of this is that we have enough people in space and enough trade between those people to motivate interplanetary war. That means space access is relatively inexpensive and people are therefore relatively cheap.
That does not mean that people are as cheap as they are on modern naval vessels. Plus, there is the performance aspect that I've brought up and you haven't addressed. And maybe for one side (the colony), people are inherently more expensive then they are on Earth (the supply of technical people is limited) so they automate.
Tony:
Your 100 MW reactor is sort of overkill. You could use a smaller pulsed system or something. Luke's numbers are for CW lasers. And the low damage might be useful for story purposes.
For a large craft without the balance and symmetry of the Apollo CSM?
Do you understand how strange that sounds? Any spacecraft will have a mass-symmetrical axis, and the engine will point through it.
Luke:
"I disagree. The ISS is 400 tons. The space shuttle orbiter is 100 tons. This is within an order of magnitude of 1000 tons, and we can loft them into orbit without magitech. In the mid future, some increase in our ability to make big things in orbit is plausible. For a significant manned presence in space in the mid-future, the ability to make structures and machines of hundreds to thousands of tons is not only plausible, it is necessary. Just how much do you expect these spacecraft with a crew of a dozen to mass?"
I make no presumptions about launch vehicle technology except that we are never likely to put more than 150 tons in orbit at a time using chemical rocketry. That implies a six or seven piece nuclear plant that has to be assembled in orbit. Even with modular construction, that's a job whose complexity and expense completely invalidates anything we may think we know about space structures. And we haven't even started talking about the mass, bulk, and complexity of the laser generator.
Figuring chemical rocket launch costs can someday be brought down to an absolute floor of $2000/kg, the mass of the reactor alone would cost $2B to put into orbit. Then you have to add the cost of putting up the laser shooter and all of its sensors and other support equipment. Then you add the cost of development and construction of all of this stuff. How many tens of billions of dollars? For a single weapon system?
In short, I don't think it would ever be economically practical with anything like the power and propulsion systems available today or in the foreseeable future. It would take magitech systems currently only seen in science fiction. So, though I don't want to hurt your feelings, I'm constrained to place your analysis in the "unreasonable, impractical, and illogical" bin.
SA Phil:
Actually its a bit unfortunate that Lasers are so effective
I think it is more accurate to say that effective lasers are not implausible. By the same token, less effective lasers are also not implausible. I expect the first space-based laser directed energy weapons to be fielded to have effective ranges of maybe around 3,000 km - much less than what the enthusiastic discussion has been about. Whether they get much better than this will depend on your tech assumptions. Relatively short laser ranges probably make for a more interesting story and exciting combat
Tony:
One final thought. How much have you studied spacecraft design? Have you at least read through Atomic Rockets? I'm honestly wondering this. If you want my credentials, I've read Atomic Rockets several times, and done this.
(Sa Phil)
If I can only accelerate in the milligees I dont need to vary thrust.
Steady State is much better for reliability than dynamic, much much simpler too.
This goes for everything. Ill just discharge extra electricity I dont need into a dummy load made of tungsten or superalloy, I already have massive heat disipation built into the system.
Sure you will have active cooling -- which is controlled by the computer. With nice fat wide ranges so it doesnt have to change much.
But really the more steady state you can make your craft, the better. The only exception would be for coasting on batteries with everything shut down. But that is on or off.
Changing facing is just a simple way of saying "manage all those other thrusters you need to make your ship point in different directions"
You aren't going to be making "combat manuevers" you are going to point the laser at target you decide needs to die first kill it, and then change facing and go on to the next one. Maybe an "emergency vector change" if someone sent a cloud of debris at the ship. But that would be a on/off too.
The range is way too far for anything else. This is a light second range capable laser, it isnt going to be swooping and doing space ocean stuff.
Its more like a Giant Turret than a Fighter Plane.
Tony:
And we couldn't launch 10 10MW reactors and hook them together?
Again, I (and I think most of us) view plausible midfuture as technological in nature. The economics can be handwaved far more easily.
Tony:
The grounding assumption in all of this is that we have enough people in space and enough trade between those people to motivate interplanetary war. That means space access is relatively inexpensive and people are therefore relatively cheap.
and
Even with modular construction, that's a job whose complexity and expense completely invalidates anything we may think we know about space structures.
snip
Figuring chemical rocket launch costs can someday be brought down to an absolute floor of $2000/kg, the mass of the reactor alone would cost $2B to put into orbit.
You can't have it both ways. If you can send enough people in to space to have trade and war, you have the expertise to assemble large structures and can afford to do so.
Rick: to answer your question about ISS maintanance requirements; it takes 3 crewmembers full time to do the required maintanance; so, with a crew of 6 that means that 50% of a standard crew is dedicated to maintanance. As far as I know, that was pretty close to what was needed by Mir as well.
NASA had, a few years ago, this "smaller, quicker, cheaper" design philosophy that resulted in a 50% failure rate of deep space probes. The Casini Saturn Probe (CSP)could have been built and launched for a couple of hundred million dollars, but it cost a billion due to its reliability. If we needed 100's of CSP's for some reason, then they wouldn't cost so much; nor would they be anywhere near as reliable. Trying to determin the cost of construction, upkeep, and operating military spacecraft of even half a century from now is like discussing the cost of creating a fleet of steam driven big-gun battleships and arguing about the proper tactics they should use in modern-day navel warfare.
Ferrell
(SA Phil)
Luke,
Thanks - Yeah 3000km lasers are a lot easier to defeat with some sort of kinetic attack. (which could mean the simple lower power spacecraft could be viable)
Byron,
I was thinking of a car engine as well. Since that is what I have the most electronic controls experience with.
Car engines are extremely difficult to control you have a lot of dynamic variables. Yet somehow they are also extremely reliable. AT least by the time the public gets them. More than reliable enough to be one of many in a drone squadron (assuming said reliability carried over).
Raymond:
"I don't think you're listening. That thousand-ton reactor isn't for the laser, it's for the engine..."
I was responding to this:
"If I can make space reactors at 1 kW/kg, and I need 1000 MW of electricity for my beam weapon to be effective, then I need a 1000 ton reactor.
If you need a 1000 ton reactor to make your beam weapon effective, you're not going to have beam weapons using any current or reasonably foreseeable technologies to put them in space. If you do have the propulsion power in dense and efficient enough form to economically put such large power systems in space, you're not going to need such large power systems in the first place, because whatever powers the propulsion is likely to make child's play out of powering laser weapons -- and also maneuvering to avoid them.
"Perhaps you're just being contrary to play devil's advocate. You claim you're not relying on specific technical details, only principles, but attempt to discredit laser weaponry as a class with very specific objections. I understand what you're getting at on the whole: real-world combat conditions aren't ever as neat and orderly as theoretical ones. Fine. Granted. Given. But a lot of your objections are, as Luke's already pointed out, solved problems, operating in a very different environment compared to current military experience.
Hell, that's the point of all of these space warfare threads - how the known conditions of space are different (and frankly occasionally counterintuitive) compared to terrestrial ones, and how many of our assumptions about what constitute "combat conditions" on Earth have to be revised for space."
I'm going to make what is going to sound like an arrogant and patronising assertion, but stick with me for a few. If you still think it's arrogant and patronizing when you've heard my reasoning, please feel free to say so. Ready? Here we go...
The idea that the space combat environment is going to be fundamentally different from any of the historical terrestrial ones is pure, unadulterated tripe.
Humans have been engaging in organized, state-based, technological warfare in a wide variety of environments for five thousand years. In all of that time, the basic logics of strategy, economics, and technology have never changed. The details have, as have the relative values of various factors. But the underlying principles have always been there.
There is absolutely no reason to believe that any of this will change in space. War will only be possible where there enough humans and human interaction to give a reason for it. It will only be fought when there are enough humans to make its objectives worthwhile, with weapons that are relatively economical to use and which can interact efficiently with the human objectives at stake. Relatively economical systems, capable of interacting efficiently with human objectives tend not to be overly complex or overly automated, in toto. Certain systems designed to fight other systems may over time become more automated, but they still require human involvement to remain economical and useful within the human social system we call "war".
The idea that the space combat environment is going to be fundamentally different from any of the historical terrestrial ones is pure, unadulterated tripe.
You're completely correct, so long as you consider air, naval, and land combat to be fundamentally the same. I suppose that's why I keep reading about air battleships and land cruisers. Not to mention cloud sieges.
Luke:
"You can't have it both ways. If you can send enough people in to space to have trade and war, you have the expertise to assemble large structures and can afford to do so."
Certainly, but not with chemical or nuclear thermal rockets, unless your idea of warfare is relatively small guided missiles and small arms for boarding parties.
I'm not trying to have it both ways. I'm just pointing out incompatible technological assumptions.
(SA Phil)
Tony,
I think what they are getting at is Physics support the GW laser
They dont support a torch ship.
You cant get acceleration by just dumping power into space, you need to use a reaction engine.
And this reaction is not going to be muscular enough to change your velocity that quickly.
Look over the propulsion page at atomic rockets, you'll eventually come to the same conclusion. It has all of the disapointing details.
The real problem is scale, space is just too big.
Byron:
"You're completely correct, so long as you consider air, naval, and land combat to be fundamentally the same."
They are the same, for the levels of granularity I'm considering. See, I'm not talking about tactics and technical specifications in isolation. I'm talking about more or less efficient application of basic engineering principles, more or less efficient logistics, more or less skillfull application of strategic logic...all those things that actually decide wars, but which the technorati of SF fandom never seem to want to talk much about. (Mostly because they don't know much about those kinds of disciplines.)
"I suppose that's why I keep reading about air battleships and land cruisers. Not to mention cloud sieges."
We have had Flying Fortresses and Cruiser tanks, which were conceived with resistance to attack and freedom of operational maneuver respectively in mind. Destroyers have been called "greyhounds of the sea", metaphorically describing their nautical function by reference to a certain type of land animal used in pursuit of game.
More practically, an air raid can be likened to an old timey cavalry raid, in both purpose and effect. Screening an aircraft carrier with destroyers and cruisers, and securing an artillery fire base with infantry have the same tactical purpose. Satellite and aerial reconnaissance are trying to accomplish the same thing.
Tony:
Certainly, but not with chemical or nuclear thermal rockets, unless your idea of warfare is relatively small guided missiles and small arms for boarding parties.
Again, I do not entirely agree. Torch level thrusters are unlikely to be usable for launch from a planetary surface (at least not one with an atmosphere). Thus, torch drives are uncoupled from launch price. However, there are many semi-plausible proposals for methods of launch other than chemical rockets. I will neglect space elevators for now as being a bit too implausible for the more hard-nosed realists among us, and point out rotovators with electrodynamic tethers, laser launch, and high altitude scramjets as technologies that could plausibly be around by the mid future.
SA Phil:
Tony,
I think what they are getting at is Physics support the GW laser
They dont support a torch ship.
Physics don't support lasers that outrange missiles either, not without power technologies that translate into much more effective propulsion thant we have today.
"You cant get acceleration by just dumping power into space, you need to use a reaction engine.
And this reaction is not going to be muscular enough to change your velocity that quickly.
Look over the propulsion page at atomic rockets, you'll eventually come to the same conclusion. It has all of the disapointing details.
The real problem is scale, space is just too big."
Assuming we'ren ot missing something absolutely basic, the levels of power density required to make ultra long range lasers in space possible is going to easily translate into very powerful propulsion systems. Such systems will have to be relatively light, reliable, and fusion-based, meaning the handling of thousands or millions of degree reaction mass plasmas, in high thrust quantities is going to be, as one person likes to put it, a "solved problem".
Tony:
"If you need a 1000 ton reactor to make your beam weapon effective, you're not going to have beam weapons using any current or reasonably foreseeable technologies to put them in space. If you do have the propulsion power in dense and efficient enough form to economically put such large power systems in space, you're not going to need such large power systems in the first place, because whatever powers the propulsion is likely to make child's play out of powering laser weapons -- and also maneuvering to avoid them."
It's entirely the other way around. That scale of reactor assembly is going to be a prerequisite for reasonable-timescale manned interplanetary travel in the first place. For there to be enough infrastructure out there not only worth fighting over, but worth creating dedicated military hardware to do so, that scale of powerplant will be the norm, not the exception. Nowhere along that line of speculation is it required to be able to lift everything from the surface of Earth in a single launch. What would be implied by such a scale, however, is that somewhere along the way the economics of spaceflight have changed. Whether it's cheaper, mass-produced rockets, reusable first stages, metastable metallic hydrogen, launch loops, space elevators, laser launch or surface-to-orbit wormholes, we're assuming it's cheaper to get to orbit in the first place, and that it's already feasible to launch and assemble fairly complicated, massive machinery. (Personally, I'd lean towards laser launch in a scenario wherein laser weapons with light-second effective ranges are a substantial factor.)
In terms of the economics, I'd list a laserstar massing a kiloton or two as valuable (and costly) as a battleship or carrier, in which case that $2 billion launch price isn't unreasonable. A laser platform of such power would be multi-mission-capable, and a useful support weapon for a variety of engagements - orbit-to-surface bombardment, launch denial, maybe even unmanned cargo propulsion during peacetime. It would also be as central to military planning on both sides as carriers are to modern naval forces. None of this sounds unreasonable to my ears.
Luke:
"Again, I do not entirely agree. Torch level thrusters are unlikely to be usable for launch from a planetary surface (at least not one with an atmosphere). Thus, torch drives are uncoupled from launch price. However, there are many semi-plausible proposals for methods of launch other than chemical rockets. I will neglect space elevators for now as being a bit too implausible for the more hard-nosed realists among us, and point out rotovators with electrodynamic tethers, laser launch, and high altitude scramjets as technologies that could plausibly be around by the mid future."
Sorry Luke, but scramjets appear to me to be a pig in a poke, and all of the megastructure solutions implicitly require the kind of mass and energy manipulation that puts portable fusion power plants (and resulting rockets) in the toolbox to begin with. Also, all of these supposed solutions launch at most a few tons at a time, so you're faced with the callenge of building a nuclear reactor in space out of several score to several hundred parts. Rotsa Ruck, GI.
Another thing. Using a fusion heated rocket in a planetary atmosphere doesn't have to be environmentally destructive. You just lean out the plasma/remass mixture so that your exhaust is only a few tens of thousands of degrees at the nozzle. You still get excellent Isp, if not the kind of outstanding Isp you get in vacuum.
Re: Raymond
You are of course entitled to disagree, but to me anything remotely resembling an interplanetary civilization that needs war to solve problems in the first place is going to be based on power systems we can only imagine the bare outline of right now. When they start shooting lasers at light second ranges, i guarantee you they will be shooting them at ships capable of effectively jinking, that fire missiles capable of 100+ g accelerations for several minutes.
As for laserstar economic efficiency? They're totally not worth the investment, because they (and any other type of weapon systems that has to sit still in combat) can be effectively overwhelmed with a much cheaper kinetic attack, launched from beyond laser range.
Tony:
Such systems will have to be relatively light, reliable, and fusion-based, meaning the handling of thousands or millions of degree reaction mass plasmas, in high thrust quantities is going to be, as one person likes to put it, a "solved problem".
If you want light, you will not be looking at fusion. Not in the plausible mid-future. Much as I want them to, plausible fusion reactors do not scale down well.
Also, plausible fusion reactors will not give you high thrust from their plasma. Plausible fusion reactors give you 80% of their energy in the form of high energy neutrons. These cannot be confined nor directed by magnetic fields, and at high enough power levels that the plasma can give you significant thrust the neutrons will melt your reactor. You could use the neutron's heat for a thermal rocket, similar to fission nuke thermal, or you could use it to drive a heat engine to generate electricity, but in either case you are limited by the same engineering considerations that limit fission reactors - handling the heat and handling the radiation (except that the radiation environment around a fusion reactor is much harsher than that around a fission reactor).
Tony:
"The idea that the space combat environment is going to be fundamentally different from any of the historical terrestrial ones is pure, unadulterated tripe."
No, that's not stupendously arrogant to say.
It's also not aimed at what I was saying, either.
There are always going to be parallels between various sorts of military endeavours. This is a given. But take air warfare as an example: as various technologies entered into the picture (radar, guided missiles, jet engines, ECM, stealth, and in a related way, satellites), many of the details changed substantially. Engagement ranges increased. Possible targets shifted and expanded. Costs and logistics changed (mostly upwards). And yes, we still teach Immelmanns to pilots, and we still put guns on fighters. That doesn't mean that air warfare still follows the assumptions it began with.
As for the engine power stuff, well, we do have numbers. Lots of them. Some speculative, some very much empirical. Those numbers all suggest fast interplanetary drives being a) powerful, and b) not as powerful as would be required to use them for launch. A Shuttle plus SRBs puts out roughly 33 GW of power. If you want a plasma drive to get to orbit, bring a reactor at least that powerful, within the dry mass envelope. You don't need that for fast interplanetary, though, not even close. However, the powerplant will still have to be powerful enough to make running a laser incidental.
Funny enough, the lasers proposed (and prototyped) for fitment on modern fighters have the same relation of available power to required power. Jet turbines put out easily over a hundred megawatts, and the lasers planned for retrofitting onto the F-35 are in the 100-150 kW range - capable of using merely parasitic power. (Before you complain - the lasers in question are solid-state, provided in 15kW modules and attached in series. I forget the company's name, but they've already got a prototype for that specific application.)
Tony:
Another thing. Using a fusion heated rocket in a planetary atmosphere doesn't have to be environmentally destructive. You just lean out the plasma/remass mixture so that your exhaust is only a few tens of thousands of degrees at the nozzle. You still get excellent Isp, if not the kind of outstanding Isp you get in vacuum.
Torch level performance cannot be contained inside of a spacecraft. The heat loads are simply far too high. The only way you can make it work is to initiate the reaction outside the spacecraft and let most of the neutral radiation escape into space. The small fraction of neutral radiation that you do intercept will still impose severe heat loads.
For this reason, torch level rockets cannot work in an atmosphere. The air interferes with whatever it is you are using to light your fusion - laser beams, heavy ion beams, antiproton beams, whatever (with the possible exception of Z-pinch, but I don't see Z-pinch giving you high enough repetition rate for overall high average thrust - you would need to take down the blasted remains of the old electrical connections and re-install a new set of electrical connections each time). Further, the air screws up the propagation of the plasma. Finally, the open structure you need for your magnetic nozzle that lets most of the radiation escape will not be at all streamlined and will have difficulties at the supersonic airspeeds you will need for launch.
Sorry, but I find fusion launch vehicles less plausible than even space elevators. The physics is simply against them. (Unless you are using a land based fusion reactor to generate electricity for, say, a laser launch station - in which case you might technically claim to have fusion launch.)
Tony:
"You are of course entitled to disagree, but to me anything remotely resembling an interplanetary civilization that needs war to solve problems in the first place is going to be based on power systems we can only imagine the bare outline of right now. When they start shooting lasers at light second ranges, i guarantee you they will be shooting them at ships capable of effectively jinking, that fire missiles capable of 100+ g accelerations for several minutes."
Then we'll have to disagree.
I can see how you'd build a nuke-electric craft, a large war laser, and laser launch facility to put them in orbit - and do it all without a whiff of magitech, using only the physics we know. I'm not sure how to pay for all of it, nor do I claim there aren't any engineering problems yet to be solved. But that's sorta the definition of "plausible", innit?
As for laserstar economic efficiency? They're totally not worth the investment, because they (and any other type of weapon systems that has to sit still in combat) can be effectively overwhelmed with a much cheaper kinetic attack, launched from beyond laser range.
And I'll see it coming from a solar system away. Not that I won't have my own missiles on their way, mind you.
This was the whole point of the spherical war cow threads. Missiles vs lasers. Closing velocities vs mirror diameters. Mass and cost of each alternative. Despite what you seem to think, I'm with Rick in favoring a combined-arms approach. Lasers for lesser targets, mirror kills and defense against kinetics; missiles for hard kills and first strikes. And as far as this thread goes, I'm actually leaning towards drones mostly being useful for missile buses and lightweight recon - mostly because I suspect any big war laser will be kinda finicky and maintenance-heavy.
(SA Phil)
Why are Launch thrust capable fusion torches, 100G space missiles, etc in the same realm of plausibility as a big Laser, a Big Lens and a Big Fission reactor with a Lorentz Force type drive?
Those aren't the same at all.
The former require massive leaps in far-future technology
The later require some near/mid-future Engineering solutions and a solvable heavy launch system with orbital industry.
(SA Phil)
So the 1000 ton Fission reactor-
Lets use a Helium cooled Pebble Bed perhaps -- since that's easy to do in stages
Stage 1- A Tank made of thickwalled Tungsten
Which is used to Hold propellant for the launch. (this is a lot of the mass and becomes the chamber for the reactor core.)
Stage 2-the fuel- Can go up in lots of launches so the mass is manageable.
Stage 3 - The machinery for the hot gas turbines etc, also can be multiple launches.
Stage 4 - The Helium and the Helium Storage - Presumably we have SOME kind of space program already. Maybe ship this from the moon.
I really don't see it as implausible at all.
An acceleration of 30 m/s (a good liftoff thrust) with an exhaust velocity of 5 km/s (similar to current chemical rockets - and really that's stretching it, you'd rather have more if you can to avoid excessive mass ratios) requires an engine power of 75 MW/ton ship.
By constrast, I once calculated that an ion thruster capable of reaching Saturn in reasonable times (100 days) would need some 15 MW/ton ship. I would be very happy with a fusion rocket of ths performance, which is significantly better than peak fission technology.
The thing is that while chemical engines carry a lot of power, they carry little energy.
Do current systems need the "TLC" the ones did 40 years ago?
No, they don't need the same amount of TLC that the old systems did.
They need *more*, because there are more interactions that happen. I own an AK-design rifle (design circa 1946, with the stamped parts). It has 7 moving parts in operation. I oil it every so often, and clean it once a year whether it needs it or not. In fact, it is not 100% reliable if it is immaculately clean! My buddy's AR has 15 moving parts, and it must be kept immaculately clean or it is 0% reliable.
Another friend has a 1963 Chevy pickup truck. It needs an oil change and a tune-up every 3 months, that I can do with a screwdriver and a calibrated ear. My 1996 Subaru needs a computer specialist just to tell me what's wrong with it, and then you need to spend the man-hours to fix what the computer has identified.
More systems interactions = more chances for stuff to go wrong!
Ask Scott how dependent on the shore industrial establishment submarines can be.
Having the ship coming in for depot level maintenance after a mission does not seem to be too unreasonable of an assumption.
And that's the answer for boomers. One MONTH of maintenance from 600+ people 16 hours per day. Attack subs actually have maintenance requirements more like the Long Beach, since they don't have the obscene operational tempo that boomers do. However, note that the surface fleet has been experimenting with boomer-style multiple-crewing, and has been appalled at the increased maintenance due to use. Boomer-level optempo results in boomer-level maintenance requirements.
Also, the Shuttle gets depot-level maintenance after every mission, so I think that is a reasonable assumption for other spacecraft.
Hey, guys, I can lift that 1000-ton reactor with a couple months' notice, because I need ~10 Shuttle SRBs all at one time. That's 1960s tech. Given the usual multi-year lead time on nuclear reactors, I could have the launch mechanism built and tested and waiting for GE or Westinghouse to finish construction. Then you launch the reactor and a shuttle-equivalent to park it in the ship assembly orbit a couple days later.
It will be possible to design reliable spacecraft in the future for less real dollars than it costs today,
Ok, I'll buy that, especially if we can get economies of scale going again. Only building 5 orbiters drove the shuttle costs through the roof, just like how cutting the production runs of the F22 and F35 is driving up their per-unit costs.
... it will not require the levels of maint. and repair that modern military equipment does during operation.
Now, here's where we have a problem. Military equipment appears slightly less reliable than than civilian-grade stuff until you give military-grade stuff to a civilian. Then you discover that the military uses stuff a lot more. Hummvee in military use lasts ~5 years. Military-spec Hummvee in civilian use lasts 10 or more.
(SA Phil)
The attack ship doesn't get used hard for 10 years though. It goes on one mission. Then it gets full repair.
The debate is whether it needs on- board repair or not during the mission.
I'm not sure what it says about this blog and community that a discussion of crews aboard laserstars has gotten closer to the flame line than discussions of queerness and abortion did.
As usual in these cases I ask everyone to stay mindful that they're dealing with explosive stuff, and handle it accordingly.
Raymond -
Hell, that's the point of all of these space warfare threads - how the known conditions of space are different (and frankly occasionally counterintuitive) compared to terrestrial ones, and how many of our assumptions about what constitute "combat conditions" on Earth have to be revised for space.
+25
That is very much the point of these threads. Space is a radically different environment, at least as different from planetary combat environments as the sea is from land. This doesn't negate the general laws of war, but it changes a lot of other assumptions about how things would unfold in combat.
(Since no space wars have been fought, this is all of course speculation.)
But I do think that our familiar analogies, perhaps especially naval ones, can lead us astray. For example, a laserstar, as I've conceptualized it over this series of posts, is NOT a 'space battleship.'
(No one here has said that it was, but the space-battleship trope is so powerful, and so 'natural' when dealing with a big spacecraft fitted with a powerful weapon, and intended to play a key role in space battles, that I have to sort of continually remind myself that it isn't a space battleship.
In some ways I think a railroad gun would be a closer analogy - deployed on a vast plain with no brush, go gullies, no dust, and no night. And even this analogy doesn't fully capture the situation.
But getting back to the meta point, my goal in these posts is mainly to challenge familiar assumptions, including my own, and explore the possibilities of the space environment.
Modern cars aren't designed for maintainability. I thought the difference in approach between Russia and the west designing military hardware was interesting. You have to build ease of maintenance into the spec or else you get crap.
If the right pressure was applied, I think we would see brilliantly maintainable cars. But the dealers want you coming back to them. Look at how stupid expensive scan tools are to shut out independent shops. Your damn laptop should be able to interface with every car out there and the scan programs should be free. Nope. Soak ya.
Ok, lemme back up a second.
A ballistic missile submarine gets used with a high operational tempo, but it's powerplant is generally running at some small percentage of rated power. All the rest of the stuff (all the maintenance hogs, in other words) is used 24/7. The only time the plant goes to full power is when you need to maneuver in a hurry (say, for combat scenarios).
Sounds like our nuke-electric spaceship, coasting along just generating the 'ships service' load, doesn't it.
Granted, you probably wouldn't have all the maintenance involved in keeping the hull rust-free, but you'd still have maintenance involved in checking the hull armor for micrometeorite hits. Thing is, that's depot-level work on a sub.
It's 300+ man-hours per day doing all the preventative stuff that allows you to go do that 90-day patrol and come home.
As it is, we're talking about ship costs comparable to a Nimitz-class carrier for each one of our spaceships. Let's *assume* (for large values of making an ass out of myself) that due to series production the per-unit costs are comparable to a submarine, $2 billion. More technically, 0.02% of your GDP in a single item that will take you 5 years to replace.
Now, can you afford to have it not come back if putting humans on it would have allowed that? Even if it increased the cost of the ship to 0.1% (cost of an aircraft carrier), I don't think you could.
Look at what happened with Operation Eagle Claw. How much egg on face because the mission failed? Lots. Why did the mission fail? Because *critical spare parts were not available*.
Tony:
Seriously? A B-17 is nowhere near a battleship. I was actually referring to the idea of a Victorian 'aerial dreadnought', and the type of vehicle like the german ratte. The point is that not all warfare is equal.
Scott:
I think the question was more about submarine gear. However, I have another example. Take ENIAC and the phone I'm typing this on. I'll leave it at that.
Rick:
What it says is that we're a bunch of geeks.
Tony:
Seriously? A B-17 is nowhere near a battleship. I was actually referring to the idea of a Victorian 'aerial dreadnought', and the type of vehicle like the german ratte. The point is that not all warfare is equal.
Scott:
I think the question was more about submarine gear. However, I have another example. Take ENIAC and the phone I'm typing this on. I'll leave it at that.
Rick:
What it says is that we're a bunch of geeks.
(SA Phil)
Byron/Scott
The original question quoted was actually about electronics equipement. It was quoted partly out of context I suppose to allow for those annecdottes.
I still maintain that in electronics there is no comparison between 1970 technology and today's for reliability. Even if you ignore the capability portion.
I dont have a specific annecdote because I have repaired thusands of circuit boards in my lifetime.
When you add in capability the example Byron gives is a pretty good one. When is the last time your computer failed because there was a Moth corpse bridging a logic circuit?
---------
As to car repair - I do not think the annecdote between a 1963 Ford and a 1996 Suburu is very apt. 1960's US cars in general had a fairly high breakdown rate, 1990's Suburu's did not, modern cars have even less. (A 1996 is not a modern car)
Since the subject was reliability without repair - whether something is easy to repair is beside the point, The point is how likely it is to fail to the point it cant function.
The bean counters would be with me on this one - cars fail less often now.
At Ford, they even added a warble to make some "check engine" conditions seem worse than they are to get people to take their cars in.
...than a satellite designer to comment on reliability in spacecraft. I know we don't have one...
There's no such thing as a "Satellite Designer", but I can sort of raise my hand here.
Without too much detail, I am an engineer involved in custom ASICs that go in unmanned and manned spacecraft.
WRT reliability: the biggest problem of reliability in space is usually radiation hardening...that's actually one of the biggest challenges preventing the use of cutting edge computers in satellites. As process technology improves and chips get higher logic density, their radiation hardness goes down correspondingly. So the biggest challenge with strong AI in space will be getting computers powerful enough and sufficiently rad-hard enough.
Typically the vast majority of effort on current spacecraft doesn't go into preventing problems...it goes into the mitigation of the effects of errors (IE, your computers can identify when something goes wrong and clear to a protected clean state).
I cannot go into any specifics of any current or past programs, but based on how we treat space missions in general I don't think maintenance is a significant factor.
Spacecraft tend to be largely disposable after one mission anyway, while naval concepts require a lot more station keeping.
(SA Phil)
So if you have a much higher mass spacecraft could you more thoroughly shield the control system to compensate?
For critical systems shielding is acceptable, but it's not common. Rad-hardened chips are possible now (and in use every day), and there's various techniques to mitigate glitches due to radiation.
But generally speaking, spacecraft are assumed to fail sooner or later.
Since I didn't work on it, a great example is the Mars Rovers: the general populace was surprised when they lasted much longer than the projected mission time.
Anyone in the space business wouldn't be: because the mission required X time, they had to be designed to have an MBTF much, much higher than that, in order to put the chances of a failure within X out to miniscule.
The key is that failure is assumed, and mitigated, not prevented.
That's actually why I don't believe we'll ever see true drone weapons in space without a human (probably lots of humans) giving the "go fire" command in the loop. I just don't think the human in the loop will have to be in the spacecraft or anywhere near it, and when talking about potential WMDs, you don't want an AI that is potentially glitchy making that final decision.
(SA Phil)
To a lesser extent that is how a Car control system works also.
It interogates the sensors, if any are out of range, it uses a chunk of code that infers the value instead.
Basically 90% of all the sensors in your car can fail and it will still function. It might lose mileage or "performance" but it will work.
Even if the main processor fails it will recover from that and run on a backup.
And that system uses parts that are the cheapest we can possibly find.
I should point out that it's because radiation shielding is expensive in terms of mass, while redundant ICs and checker systems are not.
(SA Phil)
yeah - I was imagining that I could swing a few extra kilos of shielding in my 5000 metric ton Laserstar.
Blogger is killing me! I have to post from a totally different computer with a different IP address. Tony is right after all ;)
I will make two observations about reliability and cost:
1. It is increasingly possible to repurpose civilian grade equipment for military purposes. Insurgents do that with everything from usiong cell phones and the Internet for communications (often with the unintended side effect of catching a 2000lb bomb after hanging up) and things like garage door remotes to trigger IED's. On the home team's side, soldiers make mini ISP's out in the FOBs (although they are not for military purposes, the ability to access Google Maps, SKYPE, the Weather network and email all add a lot of flexibility). I believe the USAF bundled several hundred PS2's to make a supercomputer on a budget, and how many Soldiers or Marines supplement their kit with commercial GPS, GMRS radios etc? This stuff functions well enough that soldiers feel it is worth the cost and mass penalties to get.
2. Looking farther afield, solid state devices based on quantum wells seem capable of doing lots of things we need devices for today. I was astonished to discover that heat can be transmitted via quantum wells (for example). Metamaterials have also been proposed to transfer heat, somewhat in the manner properly tailored materials can act as waveguides for microwaves. How this will scale is unclear to me, certainly for microchips and small electronics, perhaps for something with the heat output of a car engine? Wil McCarthy has written a good non fiction primer (Hacking Matter) on the subject. While solid state objects and tailored or unusual properties of matter won't solve all problems, it seems that in the plausible midfuture(tm) time frame we may be able to sidestep many issues.
For critical systems, definitely. When you're weaponizing a ravening beam of death you definitely don't want a flipped bit to tell that sucker to fire.
So the control systems on any given weaponized spacecraft will be heavily shielded, with heavy redundancy, and all the latest rad-hard techniques.
However, the problem with shielding electronics is that eventually they have to talk to something, and if that's unshielded it becomes your failure point (never mind that shielding isn't 100% anyway).
So unless your spacecraft is a lead box, you still have to pay the radiation piper.
It's not really that bad of a problem: there's tons of critical space missions today that deal with space radiation daily. My whole point is that the model in use for spacecraft today is:
-It WILL fail. Design for fail-safe.
-Manned programs are hugely expensive partially because they need to have much higher failure tolerance. Failure of an unmanned mission is embarrassing, failure of a manned mission is catastrophic.
-Space-based computers are never trusted computers.
Furthermore, I'd posit to look at manned space programs:
The only manned space mission in history where the crew were able to execute repairs and bring themselves home is Apollo 13. Furthermore, the crew were unable to rescue the mission...they were unable to repair what they had; they could only jerry rig survival solutions.
Sure, you could argue that crew members aboard can replace faulty circuit boards. That's not what happens now. Faulty circuit boards are simply shut down and their redundant partners continue their duties, with reduced guarantee of reliability.
(SA Phil)
Makes you wonder if a more far future AI system will be something like the Geth in Mass Effect 2
Dozens of parrallel AI systems all working in concert to solve problems. If one fails, oh well - there are more where he came from.
If one wanted to Hal out and sabotague the ship the other AIs would vote that AI down and it would be disconnected.
ElAntonius:
OK, so I misspoke.
As to the Mars Rovers, I personally think that JPL's 90-day missions are a funding gimmick. They reduce the operations budget to get the mission approved, and when the thing keeps working, congress isn't going to shut it down. (I'm only about 50% serious here. And I'm not saying that the Rovers were expected to last this long.)
Scott:
Now, can you afford to have it not come back if putting humans on it would have allowed that? Even if it increased the cost of the ship to 0.1% (cost of an aircraft carrier), I don't think you could.
This only works if the chance of loss of the drone is 6 times what the crewed vessel would be. (I know the cost says five, but to quote ElAntonius "Failure of an unmanned mission is embarrassing, failure of a manned mission is catastrophic")
I doubt that even a totally remote drone for a given mission will have that sort of reliability disadvantage. (By totally remote, I mean without a tender. If the tender is there, that should take care of 90% of the manned advantage.)
It depends on how much investment there is in creating an AI: if it has to be taught like a human, and requires years of effort and cutting edge hardware, then your AI core is effectively a human for determining what the reliability requirements of a mission are.
If you can stamp out fully functional AIs on the cheap, sure. But even then, why not leave the thinking at home and make the drone remote?
My thing is this: your brains are either in an "at risk" position in the mission, or they're effectively at home. If they're at home, drones are ultimately disposable and are more likely to be little more than KKVs.
Any mission where the spacecraft has to come home is far closer to being "manned". Life support and mass penalties are a huge deal today, but they're not what is stopping us from putting men on Mars and they won't be what's stopping us from putting men on the trigger of a laserstar. Mission success is a binary state, and you can design a spacecraft for pretty much any mission.
I think it was Rick that said that laserstars are not battleships, and that couldn't be more true. A combat mission in space is going to be much more customized, I think...for example:
"We need to destroy the orbital shipyards around the Earth; what spacecraft do we need to accomplish this?"
At that point, I think an unmanned KKV swarm.
Re: Raymond and Luke
Thanks for helping me make my point -- there's no plausible midfuture technology that's going to support the kind of interplanetary economy that would make laserstars part of the plausibility profile.
Oh, BTW, Raymond -- I never rejected a combined arms approach. I just don't see a valid mission for such highly specialized types as laser and kinetic stars. I think that space warships, to the degree that they exist as a specialized type, will each have a variety of weapons and, as fleets get bigger, they may divide into several classes, each being optimized for their missions, but none of them ever being totally one thing, or totally another.
(SA Phil)
Maybe we need a definition of Mid-future?
The Laserstar idea that is being tossed around here masses less than a modern attack submarine.
Byron: Think of it this way; if you need 99.99999999% reliability for 90 days, you implicitly get 99% reliability for 900 days (no math there, just thought experiment). It's not like we but bombs on missions on a 90 day timer.
Laserstars are a really curious beast. If you need them to come back, you start introducing a lot of the same costs of a manned mission: you can't expend all your propellant on getting there and fighting, for one. On the other hand, I don't think there's a real need for humans in the real-time loop, outside of a "weapons free" command that would have to be issued to a manned mission anyway.
I think any sort of interplanetary military offense is going to be assumed to be unrecoverable: on mission success, we just leave it there (just like the mars rovers, or portions of the lunar landers). That to me implies that laserstars require lasing tech to be "nothing special" in terms of costs, or for there to be suitable resupply facilities at the target destination.
Another thing to think about are reactor and rocket costs: whether it's cheaper to beef up a laserdrone with habs than it is to launch a separate hab craft with laserdrone support comes down to whether the life support or the reactor/rocket combo is the prohibitively expensive combo.
Raymond:
"There are always going to be parallels between various sorts of military endeavours. This is a given. But take air warfare as an example: as various technologies entered into the picture (radar, guided missiles, jet engines, ECM, stealth, and in a related way, satellites), many of the details changed substantially. Engagement ranges increased. Possible targets shifted and expanded. Costs and logistics changed (mostly upwards). And yes, we still teach Immelmanns to pilots, and we still put guns on fighters. That doesn't mean that air warfare still follows the assumptions it began with."
To me, the parallels are always more important than the differences. To begin with, technological change does not have the effect that a lot of people think it does. Early modern battle arrays were consciously and effectively modelled on Roman ones, even though modern man was equipped with firearms and pikes, not swords and javelins. The line ahead was just as effective a naval formation with steam and rifled cannon as it was with sail and smoothbores. With all of the technical advances, the three main missions of airpower haven't changed sinc WWII: close air support, interdiction, and strategic bombardment.
But that's only a minor piece of what I'm getting at. What I'm addressing is much more in the realm of metaconcepts. Overspecialization (I'm looking right at you, laserstar) is just as much a dead end as trying to put too many capabilities on a single platform. Humans will always be available for and involved in warfare at every level, because war is a human endeavor, seeking to achieve human objectives. For big wars, with big warships, you need big economies, which require lots of energy.
Rick:
"But I do think that our familiar analogies, perhaps especially naval ones, can lead us astray. For example, a laserstar, as I've conceptualized it over this series of posts, is NOT a 'space battleship.'"
Actually, there is a familiar naval analogy for a laserstar, and not a very reassuring one: WWII submarine. Like a WWII submarine, it's a one trick pony -- all it can really do is kill ships. Also like a WWII submarine (before snorkels) it has to be out in the open to do it's job. It's vulnerable to more balanced warships (especially ones designed to hunt and kill laserstars), other laserstars, and anything else out there that has ordnance that can exploit its vulnerabilities.
A submarine being able to dive to temporarily evade attack hardly breaks down the anaology. It's got to come up for air at some point, when it will again be vulnerable. The parallel would be the laserstar not emitting or maneuvering, and running it's powerplant as cooly as possible.
But, if we accept this analogy, then we have to face the fact that the laserstar is only effective when the enemy isn't prepared for it. If the enemy is prepared for it, it, like the submarine, is just going to be evaded or killed, without much chance of doing any damage in return.
(SA Phil)
Or Maybe .. not so much.
Define a typical Nuclear Electric Cargo ship....
*EM Plasma Drive, large Electrical demand propulsion.
*Big Nuclear Reactor, to provide said electricity.
*Heat Management system, to accomidate Nuclear Reactor.
*Facing Adjustment, the only way to "steer".
*Electronic Control System, to run the ship.
So all the Laserstar does is put a Laser on the front.
----
If you were to take a modern ocean frieghter and stick a Machinegun on it- is it some how completely different?
Byron:
"One final thought. How much have you studied spacecraft design? Have you at least read through Atomic Rockets? I'm honestly wondering this. If you want my credentials, I've read Atomic Rockets several times, and done this."
I've read Atomic Rockets several times too. And I've studied spacecraft design not just through the highly speculative avenue of AR, but also through reading about real rockets and spacecraft, both online and in a wide variety of technical histories in book form.
I process what I read through a filter of hard experience and careful study of a wider variety of things. I don't want to be harsh about this, but I find that the SF technorati work their sums in isolation and come to conclusions without asking themselves if the answers make economic or (where applicalbe) military sense. I always try to conceive of the econmic and (where applicalbe) military sense of things. If it means I come to different conclusions using the same data, that's the way it's going to be.
This is only a suggestion, but perhaps you should as yourself whether Winch Chung and the people who contribute to him know everything? AR is a great site, but it's not a bible.
Byron:
"And we couldn't launch 10 10MW reactors and hook them together?"
Do you meant 10 x 100 Mw reactors? You could, but with chemical rockets the cost is prohibitive. I keep trying to make this point, but people seem to keep missing it: the laserstar future require radically cheaper access to space, which implies radically improved power systems. It's simply not plausible midfuture as I understand it.
"Again, I (and I think most of us) view plausible midfuture as technological in nature. The economics can be handwaved far more easily."
Technology is all about economics. If your technology is chemical launch vehicle and milligee plasma interplanetary drives, then you can't economically embark on the laserstar future. If your technology supports the laserstar future, it ain't going to make use of chemical boosters and very low thrust electric rockets. It will have better and much more powerful ways of producing and manipulating energy.
Addendum, for Byron and anybody else:
The word "plausible" in plausible midfuture means plausible in all respects, not just plausible in the sense that a physics professor will be satisfied by your math. The economics, history, culture, and non-rocket technologies all have to make sense.
SA Phil: I think it's more analogous to putting a battleship cannon or a cruise missile launcher on a cargo ship.
However, I disagree that it's that simple. Military craft have entirely different use profiles than civil craft, and their reliability and stress requirements are totally different.
At the minimum, the laserstar requires beefed up cooling for the laser, potentially higher remass stores, beefed up communications equipment, and a reinforced structure to handle all the extra mass.
It's more like trying to put a battleship gun on a sailboat.
(SA Phil)
Okay so what is your definition for plausible as far as Lift capacity?
Orbital Industry?
Lunar Industry?
Spacecraft propulsion?
You are ruling out two of the technologies we have TODAY. Nuclear Reactors and Electric Thrusters.
Because you claim we will lack the ability to get reactors into orbit.
And continue to lack it for what? 100 years? 1000? 10000?
Is "mid-future" Mid century? Or sometime later than that?
In his short story "Superiority", Arthur C. Clarke predicted your approach is doomed to failure.
(SA Phil)
ElAntonius,
Its only different in terms of improving the Laserstar. All of the basic components are the same. Nuclear reactors, Electric Drive, etc.
If you can build one it becomes far more plausible you can build the other.
SA Phil:
"Okay so what is your definition for plausible as far as Lift capacity?"
Using chemical rocket technology:
Maximum per lift = 150 tons
Minimum $ per kg = 2000
"Orbital Industry?"
Implausible. Industry will stay on the Earth throughout the chemical booster era.
"Lunar Industry?"
Implausible. During the chemical booster era there will be nothing on the moon worth spending the money to do anything with it.
"Spacecraft propulsion?"
Nuclear or solar electric, depending on the breaks.
"You are ruling out two of the technologies we have TODAY. Nuclear Reactors and Electric Thrusters.
Because you claim we will lack the ability to get reactors into orbit. "
I'm not ruling anything out. What I'm saying is that with chemical boosters and milligee thrust electric rockets the laserstar future is implausible. Give me fusion-heated boosters and torch drives, and we'll discuss it.
"And continue to lack it for what? 100 years? 1000? 10000?
Is "mid-future" Mid century? Or sometime later than that?"
At the moment, plausible is the chemical booster and milligee electric rocket era. How long that lasts depends on how long it takes to find something significantly more powerful and (hopefully) a lot cheaper.
papa said...
In his short story "Superiority", Arthur C. Clarke predicted your approach is doomed to failure.
------------
(SA Phil)
But the thing is, its not whether or not the Laserstar is the best version of interplanetary warship
Its being argued that its not even plausible to build a Nuclear Electric Spacecraft with a Big Laser on it.
SA Phil:
"Its being argued that its not even plausible to build a Nuclear Electric Spacecraft with a Big Laser on it."
Because it's not. It's not economically realistic. Aside from the fact that it would be prohibitively expensive to put the power supply and everything else into space with plausible launch vehicel technology, why would you build one in the first place? To shoot down the Chinese Squadron, which has all of three small ships armed with a few missiles and a defensive laser apiece?
(SA Phil)
Tony,
Ahh I get it. You define "plausible" differently than the other posters.
You say some problematic technology is prerequisite to change all the other variables.
Other posters are suggesting that with some refinements to currently understood technology something could be done.
So for you space warfare is entirely implausible until there is such a thing as a fusion lift device or its equivilent.
Its too bad fusion drives woudln't actually work like that. A Fusion reactor/drive would not be a vairiable Thrust/ISP knob that shoots whatever the requisite amount of fused helium plasma at various speeds out the back of a spacecraft.
Byron:
"Seriously? A B-17 is nowhere near a battleship. I was actually referring to the idea of a Victorian 'aerial dreadnought', and the type of vehicle like the german ratte. The point is that not all warfare is equal."
Let's take it for granted in the future that I can recognize when you're being sarcastic, k?
And yes, seriously. All warfare is aimed at achieving some objective. Battleship fleets ultimately existed to protect a state's sea trade and attack the enemy's. (Yes, it's a long and tortured connection, but that was the fundamental point of their existence.) Strategic air forces existed to attack a nation's domestic economy, while tactical air forces existed (in part) to protect against such a thing happening in return. The means were different, but the objectives were the same: wreck the enemy's economy while avoiding the enemy wrecking your own.
"Take ENIAC and the phone I'm typing this on. I'll leave it at that."
Take the telegraph and the ENIAC. Technologies generally become more powerful and reliable over time. But if you're talking about bleeding edge technology -- which a lot of military technology is and always will be -- power is usually harvested at the expense of reliability.
ElAntonius:
I think any sort of interplanetary military offense is going to be assumed to be unrecoverable: on mission success, we just leave it there
This is where we disagree. If we have regular shipping, it will almost by definition be recoverable. The lasers will be in the same boat.
As to humans, any manned mission will suffer a significant performance penalty. I'd estimate it at the 30% range for a medium laserstar, and I'm willing to send you my spreadsheet I used to get the numbers. That's going to be a significant cost factor.
It would be possible to install a hab on only one laserstar, but see my comments about either performance or decapping, depending on how you choose to do it. I don't see that as practical.
Tony:
Yes. But now you're ignoring paralells. For example, they don't use Roman formations anymore. The reason the same formations worked was becuase in both cases firepower was insufficent to stop a formation unless you were in a formation. That has changed, and nobody uses them now.
The same applies to naval tactics. And while the basic form of a given form of warfare may stay the same, that doesn't mean that differnt forms of warfare are the same.
On economics, I see them as something that should be dealt with, but fundamentally we're dealing with stories here. Economics is much softer then science, and easier to handwave. Which would you prefer? A story with hard science and soft economics, or vice versa? I know my answer.
And I know AR isn't the bible. I've done a lot of research on my own as well.
The word "plausible" in plausible midfuture means plausible in all respects, not just plausible in the sense that a physics professor will be satisfied by your math. The economics, history, culture, and non-rocket technologies all have to make sense.
Yes. Becuase you are the ultimate arbiter of definitions.
As to cheaper launch costs, look up "launch loop".
Technology is not the ultimate arbiter of economics. We have the technology for doing things at a few dollars per kilogram. But it requires using nuclear weapons. Again, would a near-future story with a permanant moon colony be unrealistic if all the science is right? There is no technological barrier to order of magnitude lower launch costs then we have today.
I'm going to partially depart from Plausible Midfuture for a moment. Let's say we detect incoming aliens and can somehow determin that they are hostile and can be fought. Don't ask how. The tech level is plausible midfuture. Might the economics change? I'd think they would, and fast.
For that matter, did Apollo make economic sense?
SA Phil:
"Ahh I get it. You define 'plausible' differently than the other posters."
What I'm doing is insisting on consistency in the plausibility profile. If you want chemical rocket launch vehicles and milligee electric rockets, don't expect weapons to be highly energetic or very long ranged.
"You say some problematic technology is prerequisite to change all the other variables."
Uhhh...no. I'm saying that if you suppose weapons of a certain energy level, then you also suppose other high energy technologies, because (and maybe I haven't made this point clear) weapons represent only a small fraction of the power usage on any platform in which they are installed. Propulsion is a much bigger user of power. I see no reason for that to change in space.
"Other posters are suggesting that with some refinements to currently understood technology something could be done."
Sure -- soemthing could theoretically be done. But it would be so expensive and uncalled for that it would not be practical, for any value of "practical".
"So for you space warfare is entirely implausible until there is such a thing as a fusion lift device or its equivilent."
Incorrect. Space warfare with laserstars and whatever else goes along with them is implausible. Space warfare with missiles and killsats? that's already almost here.
"Its too bad fusion drives woudln't actually work like that. A Fusion reactor/drive would not be a vairiable Thrust/ISP knob that shoots whatever the requisite amount of fused helium plasma at various speeds out the back of a spacecraft."
That's why I've been talking about fusion-heated reaction mass. The plasma would be a very small component of the exhaust. You inject plasma into some volume of reaction mass to get gas temperatures in the tens or hundreds of thousands of degrees and enough pressure to get high thrust. How you would contain and direct such hot gasses is of course an interesting question, but it will have to solvable for high thrust fusion-heated rockets to work.
IOW, it's an invention of the "if you could solve this set of engineering problems, you get these engineering results" type. Which is why I put it beyond the plausible midfuture.
Phil:
Its too bad fusion drives woudln't actually work like that. A Fusion reactor/drive would not be a vairiable Thrust/ISP knob that shoots whatever the requisite amount of fused helium plasma at various speeds out the back of a spacecraft.
Actually, it would. Shoot other remass (whatever you want) into the plasma as it leaves. You get higher thrust.
Tony:
This is still nonsense. The fact that the highest-level strategic objectives of war are the same does not mean that the methods of fighting are the same. The fact that the ultimate purpose of air and naval forces is to wreck the enemy's economy doesn't mean they were fought the same. Airpower can't blockade something by staying on station, for example, and naval power doesn't directly attack the enemy's homland.
You're taking broad strategic paralells and generalizing them to the tactical and operational levels. I wouldn't put a general from the American Civil War in command of a modern land force any more than I'd give it to a modern admiral. That's in the same enviroment.
Take the telegraph and the ENIAC.
Where did that come from? They didn't even do the same thing.
For a given technology and a given number of parts, reliablity will increase with time.
Tony:
If you want chemical rocket launch vehicles and milligee electric rockets, don't expect weapons to be highly energetic or very long ranged.
Where have we done so? I used half a light-second becuase it was the farthest out I think is even remotely plausible, and I was demonstrating the futility of dodging even in a best-case scenario. You've claimed that PMF laserstars are impossible. They are impossible if you insist that they have the sort of range tha makes dodging even remotely plausible. We were being generous in our examples.
(SA Phil)
Byron about fusion drives,
Sure that makes sense but, that higher thrust process isnt near the effciency of a Fusion Drive anymore.
Making the torch concept infeasible.
Fusion lift vehicles would also irradiate everything downstream of them, that they didnt simply melt, which would be a disavantage.
Phil:
He3 fusion (what I've studied) has capabilites of up to 10e6 seconds. The problem with that is that it's far higher then is needed for most missions. It's amazing how fast you can get around at .1 G, constant. Then you boost if you need to go faster for launch or tactical reasons.
He3 fusion is pretty clean, and I wouldn't use it for launch, anyway. My universe uses launch loops.
Byron: Yes, I agree that humans are a significant penalty...hell, while performance might be 30%, engineering costs of making the damn thing man rated are probably 10 times that (currently).
I'll jump back a bit and reiterate that I generally take a dim view of deep space warfare, because I just don't see it as plausible. There's precious little to fight over up there, and the costs are enormous.
If we grant that there IS something to fight over, then it still has all sorts of strategic considerations...namely, the "then what". I'll grant that interplanetary trade is one possible justification, but that is in itself rather flimsy...it's hard to imagine space travel as being cheaper than any sort of terrestrial alternative.
If we do fight in space, it'll be proxy fights in and around colonies, not epic Earth v. Whatever battles, but that's a whole 'nother topic.
I would be interested in hearing your thoughts on this: if the hab ship is by definition the worst performing space craft (and I agree that it is), then any missions involving a constellation including a hab ship of any type will be limited by the performance of said hab ship, correct? So if you're sending a hab ship with your fleet, you have to pay the performance penalty. In my mind, any constellation that includes humans amongst it is by definition a manned mission, even if it is largely drones. (I'm not trying to justify crewed vs. drones, as we're done to death on it. I just tend to assume that in space, performance is either sufficient or not.)
I just fail to see a scenario for fleet v. fleet engagements in space that doesn't require some sort of magitech or oscillating hands.
SA Phil: I'm not arguing against Laser Star existence, I'm just taking issue with your saying it's like strapping a machine gun on a cargo ship.
The problem is much bigger than that, but I agree once you have the tech for one you can make a military craft out of it (at the minimum, you can make a missile out of it).
Crew sizing:
This has been brewing in my head for a while. We've largely drifted past it, but I'll spit it out anyway in the hopes that it helps someone.
We've discussed adding crews to laserstars, often for backup C2. This often is a suggestion for a few people, even as low as 1, for the entire mission. I feel that this is impractical for several reasons.
First, if I am going to crew a laserstar, I am going to make sure that it is capable of independent operation. A crew of only a few guys does not satisfy this. There are not enough people to keep watch continually. While I have said that it only takes 1 person to fight a laserstar, this is only if the crewmember is supported by a command ship. The controller is supported by sensor operators, admirals, cooks, and mechanics. All he has to do is fight his drone. For independent operations, higher command is needed, along with all the other specialties. This puts a minimum crew of somewhere around 16, versus at most 5 or so per extra drone for a tender.
There are also significant economies of scale from consolidating crew. While Rick's 5 tons/man is a good baseline, it's just that. Take a treadmill, which crewmembers are required to use 30 minutes a day for health reasons. One treadmill can support up to 48 people, but I need the same treadmill for 4 or 48. You could not ship it with the 4-man crew, but then you comprimise living standards.
The same applies to may items of equipment. Things like galley and laundry facilites have a minimum size, which probably equates to crews in the low dozens. Even without independent capability, it will be inefficient to split crew among multiple ships.
(SA Phil)
Byron,
HE3 -> HE3 requires a lot more energy to make work, doesnt it? Its something like 10 times the temperature of DT or DT-H3.
(SA Phil)
ElAntonius,
I only mean in terms of relative feasibility.
If I already have a spacecraft in space with a nuclear electric drive and all the supporting systems, putting an off the shelf laser on it seems feasible.
If I have a frieghter in a harbor, putting a machinegun on it seems feasible.
ElAntonius:
I'm not sure what you mean by manned missions being lower performance by definition. What I meant was that, for a given specification, a manned ship is going to mass about 30% more. The performance hit is the one you take from the extra cost of supporting all that. Performace was probably not the best word. A control ship could easily be the same hull as a laserstar, with a hab instead of a laser.
As to deep space warfare being plausible, this is the Earth problem. If we get rid of Earth, then it becomes more plausible. See AV:T and Rocketverse.
Phil:
Yes, it is harder. It also is better for space applications, because you don't need anywhere near as much shielding.
Byron:
"Yes. But now you're ignoring paralells. For example, they don't use Roman formations anymore. The reason the same formations worked was becuase in both cases firepower was insufficent to stop a formation unless you were in a formation. That has changed, and nobody uses them now."
But they do use formations and tactics at the small unit level that were developed fifty or more years ago, right around the time the military service rifle technologically matured. And it turns out that the frontal warfare of the world wars was a passing phase, while the counterinsurgency of "indian" war and (on a larger scale) operational maneuver have returned with a vengeance.
Still, an Austrian musketeer fighting to keep the Turks from taking the Ravelin in 1683, were he miracled into a Soviet trench at Stalingrad in 1942, might have been impressed by the range and effectiveness of the weaponry being used, but he would have implicitly recognized what was going on. You want to keep this up? I can.
"The same applies to naval tactics. And while the basic form of a given form of warfare may stay the same, that doesn't mean that differnt forms of warfare are the same."
Sorry, but that's a specious argument. All warfare partakes of the logic of strategy, the possibilities of logistics, and the constraints of economics. Technology and tactics are just mediating phenomena.
"On economics, I see them as something that should be dealt with, but fundamentally we're dealing with stories here. Economics is much softer then science, and easier to handwave. Which would you prefer? A story with hard science and soft economics, or vice versa? I know my answer."
I toss aside books where the economics don't appear to match the technologies. Is that a clear enough answer for you?
"And I know AR isn't the bible. I've done a lot of research on my own as well."
Then let's leave off invoking AR as if it were the big joker in a game of Spades, hmmm?
"Yes. Becuase you are the ultimate arbiter of definitions."
Because I am a practical man, and practicality outweighs "gee whiz" in my book by a factor of at least 100 to 1.
"As to cheaper launch costs, look up "launch loop"."
It's a conceptual design for a megastructure. So is a space elevator. So is a Dyson shpere for that matter. Let's keep things down to Earth, why don't we?
"Technology is not the ultimate arbiter of economics. We have the technology for doing things at a few dollars per kilogram. But it requires using nuclear weapons."
You just gave a pretty good example of why economics is the ultimate arbiter of technology. We could do something highly energetic with nuclear explosives, but we would not, because economics tells us we can't get away with it.
"Again, would a near-future story with a permanant moon colony be unrealistic if all the science is right?"
If there's no valid economic reason for a lunar colony, it would be totally unrealistic and, for a lot of people, not just myself, totally unreadable.
I don't know why this is so hard to get through to people -- theory is fine, but practical application is what's really real.
"There is no technological barrier to order of magnitude lower launch costs then we have today."
But there are all kinds of economic barriers, the biggest one being no demand, even at that cost reduction.
Byron: Well, when I say performance what I mean is that the added mass increases cost, complexity, and all else being equal reduces the mission profile. For example, a drone that can (say) make it to Mars, slingshot around, and come back to Earth might not be able to complete that same mission with 30% more mass on account of being manned.
To my mind, a totally unarmed hab/CIC ship wouldn't be as simple as a drone ship with the laser replaced by habs, since it has to accommodate an additional scenario: the mission abort.
Most unmanned missions don't build much in the way of mission aborts, because they are considerably more expendable than manned missions. And if we're being cynics, and accept that our soldiers either come back as victors or in bags, then we can ignore the abort as well.
However, if we do want our hab ship to have the ability to turn tail and run, it will need substantially more remass per ton than the drones, which can be considered lost causes in event of a mission failure.
That and the fact that I suspect that habs will mass quite a bit more than a laser, but that's gut feeling and I don't have math on it.
My whole point is that a constellation's mission profile is limited to what the worst performer in the group can do.
Byron:
"I'm going to partially depart from Plausible Midfuture for a moment. Let's say we detect incoming aliens and can somehow determin that they are hostile and can be fought. Don't ask how. The tech level is plausible midfuture. Might the economics change? I'd think they would, and fast."
Only because the benefit justifies the cost. Once again, the Chinese Space Squadron with three little vessels, each armed with a few missiles and a short-ranged laser, just doesn't justify anything like a laserstar level of expenditure.
"For that matter, did Apollo make economic sense?"
As a Cold War weenie waving exercise it made perfect economic sense. It stopped making economic sense the second the Apollo 11 crew splashed down, having completed all the stated strategic objectives. It only continued for another three years on inertia and public good will, both of which turned out to be finite, for perfeclty good economic reasons.
(SA Phil)
The reason for the Lunar colony could be to solve the launch problem.
Build a colony on the moon which has a Spacecraft Industry.
All of a sudden you have a massively larger lift capability with regards to completed components.
Tony:
But they do use formations and tactics at the small unit level that were developed fifty or more years ago, right around the time the military service rifle technologically matured.
That would be...exactly what I've been saying. Tactics and operations are based on technology balance, not raw technology. The reason for the similarity in naval tactics you mentioned earlier is that the balance hadn't changed. On the ground, it's been roughly the same since WWII.
Replace your musketeer with a regiment, give them modern rifles, let them shoot a bit, and see what happens when they try their normal tactics.
This arguement is fundamentally stupid. Wars are not fought the same, regardless of technology. I'm done here.
Did you notice the part about the launch loop being feasible with current technology?
So Apollo was economically feasible, but what about the shuttle? What about the decisons around Constellation's cancellation? People do all sorts of things that are really stupid from an economic perspective. Look at ethanol.
ElAntonius:
I look at my drones as unmanned ships. They would have aborts, because I see laserstars as expensive, and not expendable. So my hab is a laserstar with a hab instead of a laser.
I agree with you on performance, which is why I don't like the rider.
Welcome to a new commenter!
Regarding Clarke's Superiority, it seems orthogonal to this discussion. The story is not about the characteristics of any particular space warfare tech, but a cautionary note about the possible hazards of trying to dramatically upgrade your techlevel during wartime.
Regarding the overall debate here, I am to blame for not being clear enough, but most of you are also to blame for not reading the original post carefully:
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.
A setting with interplanetary armadas (let alone interstellar ones) is pretty well beyond the Plausible Midfuture [TM] techlevel.
That said, a) getting into Earth orbit is a quite different problem from deep space travel, and b) travel performance in deep space goes up as the cube root of drive engine power density - even torch drives are likely to be blazing along at 50 milligees.
We're talking demi-operatic tech, but in the context of the whole discussion on this blog, I'm implicitly imagining a tech that lies on the far side of the plausible midfuture, not an entirely different tech path.
On a different tangent, laserstars as I've conceived them in this series of posts are not only not 'space battleships,' they aren't really 'warships.' Again quoting the original post, itself quoting an earlier one:
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.
In this context the laserstar is essentially a mobile weapon mount.
In a setting that called for something like 'space cruiser' missions - a 'survey ship,' in the parlance of my old future history - I tend to picture a craft that does carry a significant onboard crew, and a mixed armament.
But such a ship has absolutely no business mixing it up with a constellation that includes a laserstar.
Byron: At risk of getting green/purple, we cut to the heart of a critical assumption. I tend to see the mission as being manned or not, regardless of how many ships are in the mission.
If we assume that the laserstars have to support abort as well, I'm fine with what, although I'd struggle to see how a ship already engaged would be able to turn tail and run.
Although I suppose that the abort scenario becomes really important once you see what the defenders put up to intercept you, so any aborts probably happen long before any battle is joined.
(We're launching an offense! Oh crap, they launched 2x as many interceptors as we thought they had. Abort! We're launching a 3x offense! Oh, budget cuts meant they don't have any more drones than they used to, we win! Hey, they've surrendered!)
I also agree that cutting Earth out makes for better stories, though I tend to favor non-unified planets and limited battles in orbit, with the Earth eliminated in that her influence can't possibly reach the scenario in a timely manner. That comes from my inherent love of Fighter/Gunship tropes, though, and justifying it there is easier, especially if no one uses Laserstars.
ElAntonius:
That's pretty much what I had in mind. Plus, the laserstars are going to be built for more then one mission. I don't see the current model of spacecraft being continued in the long run, though I do understand that you may feel differently.
Tony:
"I never rejected a combined arms approach. I just don't see a valid mission for such highly specialized types as laser and kinetic stars. I think that space warships, to the degree that they exist as a specialized type, will each have a variety of weapons and, as fleets get bigger, they may divide into several classes, each being optimized for their missions, but none of them ever being totally one thing, or totally another."
I think you and I are a bit closer than you'd think on this. "Laserstar" is a term with different shades of meaning here. I've always taken it to mean a multi-mission, multi-armament craft whose primary weapon is a large laser, and whose role in all-out combat is more about supporting fire than closing with the enemy (intercepting incoming kinetics, disabling enemy mirrors attempting to do the same, attacking lesser targets as part of mop-up operations). Comparative laser effectiveness scales in a fashion more comparable to tank guns than naval ones, and one big laser is better than multiple smaller ones of equal total power. I imagine larger craft would have large lasers, and smaller craft may even forgo them altogether.
As far as the laser power problem, I think you're still missing the point. The required power for a milligee nuke-electric drive for a reasonably-sized spacecraft is easily more power than required for a large laser of half- to full-light-second range (given suitable mirror size and laser wavelength). Since nobody's going to bother jinking with milligee drives (and even if they did, it'd be nearly useless), your previous arguments about required pulse power are, frankly, invalid. The power systems you decry as "impractical" and "overly expensive" to place into orbit are already required. Using them to power a laser is, frankly, relatively trivial. And such a laser platform would range through a large volume of cislunar space - hardly useless.
Byron:
"This is still nonsense. The fact that the highest-level strategic objectives of war are the same does not mean that the methods of fighting are the same."
Already stated in another reply, but to encapsulate, technology and tactics are just mediating phenomena, not defining factors.
"The fact that the ultimate purpose of air and naval forces is to wreck the enemy's economy doesn't mean they were fought the same. Airpower can't blockade something by staying on station, for example, and naval power doesn't directly attack the enemy's homland."
Blockading on station went out with the wooden screw steamer. Steel battleships imposed distant blockades from strategically positioned anchorages. And air power, when used against transporation targets, imposed trade disrupting blockages within enemy economies. More directly, aircraft have been used on patrols supporting blockades (British vs Germany, WWI) and counterblockade (Allies vs Germany WWI and WWII) operations. Even more directly than that on more than one occasion, sewing mines in enemy waters (WWI Japan and Haiphong Harbor in North Vietnam).
As for naval power vs enemy homelands, perhaps you should ask the Japanese, Afghans, and Iraqis who were bombed and/or cruise missiled by naval forces what they think about that. Or, going back further, what the Barbary pirates thought about US Navy raids or the US Marine operation against Derna.
"You're taking broad strategic paralells and generalizing them to the tactical and operational levels. I wouldn't put a general from the American Civil War in command of a modern land force any more than I'd give it to a modern admiral. That's in the same enviroment."
I wouldn't take a contemporary rifleman and put him in a contemporary tank without significant amounts of retraining. But i would expect the rifleman, once he had been trained in AFV technology, and specific AFV tactics, to understand how to employ those to achieve an objective. Once again, don't confuse differences in technology with differences in fundamental approach.
"Take the telegraph and the ENIAC.
Where did that come from? They didn't even do the same thing."
The telegraph is a direct ancestor of computing technology. Digital logic gates were first investigated with switching technology directly derived from telegraph and early telephone technologies. Vacuum tubes and transistors were only succeeding refinements. Also, Morse code was one of the first binary data communications codes (though the variable word length is a bit of an anacronism).
"For a given technology and a given number of parts, reliablity will increase with time."
Certainly. The problem with military vehicle and anti-vehicle technology (which is what we're essentially talking about here) is that it's never very mature.
"Where have we done so? I used half a light-second becuase it was the farthest out I think is even remotely plausible, and I was demonstrating the futility of dodging even in a best-case scenario. You've claimed that PMF laserstars are impossible. They are impossible if you insist that they have the sort of range tha makes dodging even remotely plausible. We were being generous in our examples."
Once again, a laserstar is only plausible in an environment where the power sources and propulsion technology are essentialy magitechnic. And even then they have serious military utility problems. If you want to stick to current or reasonably foreseeable technologies, lasers are going to have ranges of only a few thousand kilometers at best, and missiles will probably be a mauch more viable offensive option.
Tony:
Apparently you didn't get my message. I'm done with the "all war is the same" debate. I've done it once before, and I'm not stupid enough to do it again. You're stubborn enough that I can't win, and I'm too stuborn to lose.
I'll leave laserstar plausibility to others right now.
Byron: Long run, definitely not. It's not economically feasible. However, for the plausible midfuture I don't see naval tropes as being feasible; for as long as mass fraction has to be carefully tailored to the mission at hand I believe missions are going to be largely one shot in nature, even if the craft are designed to come back.
What I mean by this is that I don't think we'll see a Laser Star in orbit around Mars being launched towards the Asteroid Belt in response to an uprising any time soon...Belt missions will have tailored space craft.
All that changes as soon as we can get to the point that arbitrary course changes are possible, or if we have sufficient infrastructure throughout the solar system to arbitrarily resupply and reconfigure our constellations.
(SA Phil)
You have to admit it was a great line in the Fallout series
"War .. war never changes"
Of course the physics of war has changed by many orders of maginitude.
And in this plausible midfuture space war they would change again.
But what's the reason for needing the reduced launch costs?
We built railroads to get resources more cheaply. We did not build railroads to support the railcar industry.
Raymond:
"As far as the laser power problem, I think you're still missing the point. The required power for a milligee nuke-electric drive for a reasonably-sized spacecraft is easily more power than required for a large laser of half- to full-light-second range (given suitable mirror size and laser wavelength). Since nobody's going to bother jinking with milligee drives (and even if they did, it'd be nearly useless), your previous arguments about required pulse power are, frankly, invalid. The power systems you decry as "impractical" and "overly expensive" to place into orbit are already required. Using them to power a laser is, frankly, relatively trivial. And such a laser platform would range through a large volume of cislunar space - hardly useless."
That's a single weapon, taking up a whole interplanetary spacecraft chasis. Technically doable, but economically insupportible.
(SA Phil)
Why is it economically unsuportable? --- you have an armada to fend off.
I would like to reemphasize my previous math. Even top-level current predictions for fusion performance would not produce enough power to allow it to be used for liftoff. Fusion is at its core still an ion thruster and its advantage lies in missions that need high exhaust velocities. (And using fusion-thermal doesn't solve that. Unlike present fission-electric reactors, which only capture a small percentage of the power generated by the reaction meaning that a fission-thermal rocket can be used instead to make use of a larger proportion of that power, aneutronic fusion reactors are postulated to have fairly high efficiencies of electricity or ion-based thrust generation. Thus, even if there is some engineering motive for making fusion-thermal rockets, the first-order math will look identical to fusion-electric.)
Scott:
"A ballistic missile submarine gets used with a high operational tempo, but it's powerplant is generally running at some small percentage of rated power. Sounds like our nuke-electric spaceship, coasting along just generating the 'ships service' load, doesn't it."
A nuclear-electric spaceship would be thrusting throughout the majority of its trip, and would have its power plant and engines running at full power continuously. It would only power down its main engines when it needs to free power for lasers, or when it's parked in orbit or needs to do fine maneuvers like docking.
ElAntonius:
"WRT reliability: the biggest problem of reliability in space is usually radiation hardening...that's actually one of the biggest challenges preventing the use of cutting edge computers in satellites."
Radiation and the shielding against it is a good example of a simple process with no moving parts, and radiation damages all equipment equally, including uninstalled spares.
Ionizing radiation is also microscopic damage of the sort that cannot be fixed with a screwdriver.
So this seems like the kind of thing that can only be remedied by building a better gadget to begin with, not by performing maintainance.
"Typically the vast majority of effort on current spacecraft doesn't go into preventing problems...it goes into the mitigation of the effects of errors (IE, your computers can identify when something goes wrong and clear to a protected clean state)."
This is perfectly reasonable for an AI. People slip up all the time.
"But generally speaking, spacecraft are assumed to fail sooner or later."
Isn't that true for all equipment ever?
Even if the "later" is "three centuries later", it still fails eventually. And I challenge you to find me a nautical battleship that remained in service for three centuries.
"That's actually why I don't believe we'll ever see true drone weapons in space without a human (probably lots of humans) giving the "go fire" command in the loop. I just don't think the human in the loop will have to be in the spacecraft or anywhere near it, and when talking about potential WMDs, you don't want an AI that is potentially glitchy making that final decision."
Well yeah, although I would add that a strong AI could qualify for such decisions. Just not an expert system.
"Failure of an unmanned mission is embarrassing, failure of a manned mission is catastrophic."
This is true for civilian exploration and for peacetime military patrols. In wartimes, militaries will readily order soldiers into risky activities if there's a strategic justification for it.
"It depends on how much investment there is in creating an AI: if it has to be taught like a human, and requires years of effort and cutting edge hardware, then your AI core is effectively a human for determining what the reliability requirements of a mission are."
If an AI has to be taught like a human but the educated AI can then be "copied" into multiple bodies cheaply as long as you keep at least one copy in a safe location rather than sending it to die, then that would present a major advantage over human crews.
"If you can stamp out fully functional AIs on the cheap, sure. But even then, why not leave the thinking at home and make the drone remote?"
That depends on the mass and power costs of the AI. If it's lightweight, then you could just as well put it on the ship, even if it only gives a minor boost in effectiveness. (Most importantly, it lets the ship keep working if communications are disrupted, for example due to the ship and the homebase being at opposition relative to the sun.)
"Any mission where the spacecraft has to come home is far closer to being "manned"."
How much we care about bringing back ships with only AIs on board is going to be an interesting philosophical question.
Particularly if AIs can cheat death anyway using backup copies, or even transmitting their mental state back from the front lines without physically returning.
Byron:
"Which would you prefer? A story with hard science and soft economics, or vice versa?"
That depends. In a fantasy story, I would take a complete lack of real science to be perfectly in line, but I would still expect the economics to make sense. If your magic sword costs less than a horseshoe, I'm going to complain.
"Let's say we detect incoming aliens and can somehow determine that they are hostile and can be fought. Don't ask how. The tech level is plausible midfuture."
If we previously had no significant space presence, I am not even going to try building space battleships. Instead I am going to build lots and lots of missiles and hope they can do the job. If I need lasers, I'll build 'em on the ground.
Tony:
"weapons represent only a small fraction of the power usage on any platform in which they are installed. Propulsion is a much bigger user of power."
Which means that your laser's performance is going to depend entirely on the quality of your laser technology and not at all on the quality of your power generating technology, since however much or little your reactor puts out, it'll still be enough for your laser.
There is no obvious way to predict at what rates laser technology and reactor technology will develop relative to each other.
SA Phil:
"Fusion lift vehicles would also irradiate everything downstream of them, that they didnt simply melt, which would be a disavantage."
Wrong. Most fusion reactions produce nonradioactive exhausts, such as helium-4. There is the issue of neutrons released from the reaction itself, which could cause neutron activation in the surroundings, but this can be mitigated by using an aneutronic fusion reaction or by adding sufficient shielding.
ElAntonius:
That's what modular tanks are for.
Milo:
I was speaking of SF, not fantasy. And that's not what I meant by soft economics. I was speaking of the background. How good is the justification for being in space? Is it OK to fudge a little on that?
As to the invasion, I'm just speculating. Maybe you need space-based defenses for whatever reason.
Rick:
"In this context the laserstar is essentially a mobile weapon mount."
I pretty much thought that was where you were coming from. But even leaving the plausible midfuture aside, I have a serious economic plausibility issue with the laserstar as conceived. An economy -- any economy, in any age -- can only produce so much high end, military grade equipment. Devoting complete sets of propulsion and sensor equipment to what amounts to single gun mounts just doesn't seem economically likely to me. And it's not as if you can draw parallels between laserstars and hellfire-armed predators. The laserstar can't be given the equivalent of a low power IC engine and a cheap, disposable sensor suite. It has to be given the equivalent of a high performance jet engine and a complete combat-capable sensor set and weapon management system. Whatever those consist of in the future, they're not likely to be cheap to the point of even semi-ubiquity.
In fact, I would have to revise my naval analogy away from the submarine, which, after all, did have good usefulness, under the right circumstances. The laserstar would be in effect a destroyer armed with a single 16" battleship gun (if we ignore the mechanical stresses firing even one 16" round would impose on a destroyer). To get the equivalent of one battleship's firepower, you have to have nine ships, plus a command ship, each of those ships equipped with a complete battleship fire control system, from sensors to computers to pointing and training hardware. And, using the Iowa and Fletcher classes as contemproray baselines, you would wind up with 600k hp of installed steam plants on destroyers replaceing 212k hp on the battleship.
Now, no analogy is 100% accurate, but I think this one is illustrative of the principle: dividing a capability into many smaller platforms seems somehow logical, but in reality the overhead kills you before you get out of the starting gate.
SA Phil
"Why is it economically unsuportable? --- you have an armada to fend off."
No you don't. You have the relatively lightly armed People's Liberation Army Space Force, equipped with three rlatively lightly armed doddlebugs.
(SA Phil)
But if the Laserstar is the most effective weapons system you can mount on said chassis than it makes perfect sense.
They were contemplating Lasers with a range of 150,000KM.
In a milligees acceleration scenario, 150,000KM makes the Laser thousands of times more effective than the Kinetic weapon, because the Kinetic weapon will most likely take hours to traverse the distance.
But the Laser takes half a second.
They would use whatever weapon system is the most effective, unless they simply cant afford to.
Tony:
See my previous comments about my view of laserstars - namely, the primary weapon, but not the only one; most likely the centerpiece of a constellation, not peripheral; best constructed and employed in smaller numbers and greater size; and frankly a better candidate for requiring crew than pure missile boats.
(SA Phil)
an Armada is a given for the Scenario.
http://www.rocketpunk-manifesto.com/2011/03/space-warfare-xiii-human-factor.html
Tony:
That's an intersting analogy, but it ignores a lot of important aspects. First off, the thing about power is an artifact of the enviroment the ships had to operate in. The same won't apply in space. Secondly, for a given mass of laser stuff, the fewer pieces it's in, the better. Third, tanks fit the model we're using quite well. Could you make a tank with a bunch of smaller turrets? Yes, but it wouldn't be as effective as a single big turret of the same mass. Likewise, you could make a giant multi-turret tank, but those have other issues.
The problem with laserstars is that you want the biggest laser possible, which means that unless the biggest laser possible is tiny compared to the normal ship, it makes sense to mount them one to a ship. Plus, ships have redundancy in a way that spacecraft largely don't. One kinetic hit, and your laserstar is dead. Splitting up your weapons makes sense.
Byron:
"That would be...exactly what I've been saying. Tactics and operations are based on technology balance, not raw technology. The reason for the similarity in naval tactics you mentioned earlier is that the balance hadn't changed. On the ground, it's been roughly the same since WWII.
Replace your musketeer with a regiment, give them modern rifles, let them shoot a bit, and see what happens when they try their normal tactics.
This arguement is fundamentally stupid. Wars are not fought the same, regardless of technology. I'm done here."
Then for the last time, technology and tactics are simply mediating phenomena. They're not what war, or even fighting, is about.
"Did you notice the part about the launch loop being feasible with current technology?"
Maybe technically doable, but in no way that I can see economically feasible.
"So Apollo was economically feasible, but what about the shuttle?"
Apollo had a strategic mission that justified the expenditure. Shuttle didn't. Gregg Easterbrook exposed this way back in 1980, before the Shuttle ever flew. (I don't agree with Easterbrook on his categorical objections to human spaceflight, but I do agree with a lot of what he has to say about NASA priorities.) About the only practical use the Shuttle ever had was as a high tech jobs program, which is the basis on which many politicians supoorted it (no matter what they publicly said) throughout its lifespan.
"What about the decisons around Constellation's cancellation?"
I think the Constellation program was a boondoggle from day one. The fact that the Obama Administration (which I generally can't support on any matter of policy), actually invoked and applied the recommendations of the Augustine commission is evidence that not all of Washington is drunk and/or high all of the time.
"People do all sorts of things that are really stupid from an economic perspective. Look at ethanol."
So, you advocate doing stupid things simply because others do?
Maybe it's time we stop using this "plausible midfuture" term and define some more concrete eras of the hypothetical future.
"Plausible midfuture" is vague, and so I take it to refer to a fairly broad span of time. I also note that it's midfuture, not near future, so it shouldn't be "the same kind of space presence we have now only slightly more".
Perhaps the most important milestone is whether any celestial body other than Earth has infrastructure advanced enough to build its own spaceships.
Technologies that I consider definitely beyond the midfuture include interstellar and/or relativistic-speed travel
Byron:
"As to the invasion, I'm just speculating. Maybe you need space-based defenses for whatever reason."
We signed a treaty with the aliens stipulating that it is considered a war crime to fend off a space invasion without having space-based defenses?
Okay, in that case I launch a single dinky satellite with a 5 W laser pointer and a flag painted on its side. Tben I swat the enemy fleet out of the sky with missiles.
There is one caveat. If the aliens build a base on Dione and start mining and manufacturing operations, then we may want to attack their infrastructure rather than just defend against their invasion. Attacking is considerable more difficult since we now need to project force beyond the limits of Earth's Hill sphere. I'm not sure if missiles would still be up to the task.
Tony:
"Then for the last time, technology and tactics are simply mediating phenomena. They're not what war, or even fighting, is about."
Unfortunately, the topic of this thread is what technology and tactics people would use, not what the war is about in a political context.
Knowing the big picture is useful, but you also need to polish the details.
Byron:
That's what modular tanks are for.
I'd be interested to hear how you expand this. To my mind, the current greatest challenge to deep space "fleet" tropes is the fact that current space missions have to be planned years in advance, with strict launch windows and technology near fully tailored to the specific mission at hand.
No hostility here, just curiosity.
Tony:
No, I don't. I'm saying that people do stupid things, and that they can be used as justification. As to Constellation, I was talking about cancelling everything except Ares I/Orion, which is the only part the private sector is close to duplicating.
Milo:
That might work as justification. I like that idea a lot, actually.
ElAntonius:
It's simple. The basic ship is either entirely modular (strap on as many tanks as you need) or has a core tank, with the delta-V for the minimum planned mission, and strap-on tanks for missions which require more.
No offense, but I think that working in spaceflight is slightly blinding. That is, you assume that people won't tolerate inefficience in spaceflight in the future because they don't today. They don't today because they can't. It's a perfectly understandable perspective, but I'm not sure it's right.
And no offense taken.
ElAntonius:
Another thought. Military missions will almost by definition not be planned years in advance (I do know about contingency planning, but those are if x then y, not at time t do z) simply because the military enviroment doesn't lend itself to that sort of planning. Your enemy will probably pick the worst possible time from an orbital perspective to make trouble, and you'll have to have the capability to deal with it, or be willing to wait.
Byron:
"That's an intersting analogy, but it ignores a lot of important aspects. First off, the thing about power is an artifact of the enviroment the ships had to operate in. The same won't apply in space."
It will apply anywhere. Each vessel has an irreducible mass overhead in monolithic, indivisible systems: fire control, propulsion (because engine mass doesn't scale directly with power output -- an RD-180 rocket engine, for example, is precisely half of an RD-170, but the respective thrust to weight ratios are 78.44 and 82.00), auxiliary machinery (a docking adapter masses the same whether you mount it on a battleship or a kiddie cart), etc. The exact ratios would of course be different, but the principle is invariant.
"Secondly, for a given mass of laser stuff, the fewer pieces it's in, the better."
???
"Third, tanks fit the model we're using quite well. Could you make a tank with a bunch of smaller turrets? Yes, but it wouldn't be as effective as a single big turret of the same mass. Likewise, you could make a giant multi-turret tank, but those have other issues."
Tanks are optimized for a much more complex combat environment than space. If the ground were absolutely flat and all you had to fight were other armored vehicles, the same logic would apply to tanks that apply to ships.
"The problem with laserstars is that you want the biggest laser possible"
This has been asserted, but I have my doubts as to laser range and effectiveness in a practical context.
"Plus, ships have redundancy in a way that spacecraft largely don't. One kinetic hit, and your laserstar is dead. Splitting up your weapons makes sense."
Now this is (finally!) an interesting point of discussion. Because if your ships are as vulnerable as, say, fighter aircraft, then any one can be destroyed by a single shot. But we still arm fighters with multiple weapons, not just one mondo cannon. And armed drones (except for suiciders like cruise missiles) carry multiple, relatively short ranged weapons as well.
I think the laserstar is a neat idea in isolation. But once all of the economic and military factors are taken into account, it just doesn't look very effective.
SA Phil:
"But if the Laserstar is the most effective weapons system you can mount on said chassis than it makes perfect sense."
Theoretically effective and practically effective are two entirely different things.
"They were contemplating Lasers with a range of 150,000KM."
Which I frankly don't believe in, if one of the requirements is they actually hit the target with military effect at that range.
"In a milligees acceleration scenario, 150,000KM makes the Laser thousands of times more effective than the Kinetic weapon, because the Kinetic weapon will most likely take hours to traverse the distance.
But the Laser takes half a second."
If the laser can't obtain a hit at that range, then the kinetics win by default, as long as one of them survives to hit the laserstar.
"They would use whatever weapon system is the most effective, unless they simply cant afford to."
And the laserstar is not affordable, by any conceptual design revealed here.
Byron: No offense taken.
I agree that military hardware will need to be significantly rapid response, though it strikes me that your scenario aligns with my "infrastructure" alternative.
Reconfigurable ships depend on spread out infrastructure capable of refueling/reconfiguring the ship at various destinations in the Solar System...otherwise, we're stuck with one off missions that depend on returning to home base every time before a new mission can be launched.
I'd define that a constellation's "sphere of influence" is defined pretty much by its capability to reach an area...if there exists no capacity for reconfiguration within its sphere of influence, then it's stuck with the current mission until a resupply ship arrives.
To that end, in the modular ship scenario I think a space power's ability to respond to situations is defined solely by the location of reconfiguration/resupply stations it has.
How rapid is the response? Are we talking orders of days, weeks, months?
Tony:
You have a point. But will the economies of scale really be that big? I'm not certain they will be, but I think there's a good chance. But there's also production economies of scale to consider. It might be cheaper to buy a dozen single laserstars than three quads of equal performance.
As to irreducable minimums, I don't think reactors will scale quite that much, particularly if they have to be launched in pieces.
As for lasers, I think Luke has addressed this. A big laser is better then two smaller ones half it's size.
If lasers aren't terribly effective, then that's even more incentive to make one big one. I don't share your doubts on this, and that's probably a lot of the issue.
But we still arm fighters with multiple weapons, not just one mondo cannon.
I'm with Raymond on laserstar armament. They have one primary offensive laser and several smaller defensive lasers. But this is a false comparison. The multiple weapons are required to be effective across a variety of ranges. A laser can refocus to deal with that, and it isn't going to dogfight.
And the laserstar is not affordable, by any conceptual design revealed here.
But an even larger ship is?
ElAntonius:
That scenario makes sense, but I see those more as refueling stations. I don't expect completly modular warships, and even if that were true, reconfigureability implies a lot of stockpiled gear. Say, enough to build the whole ship.
Refuling depends on what you're using for remass, and how tolerant your engine is. Thermal engines have a significant advantage there.
Byron:
"No, I don't. I'm saying that people do stupid things, and that they can be used as justification."
You mean literary justification? Okay, here's your plot: The US wasted all of its money building two laserstars in GEO, which were taken out by Chinese and Pakistani kinetics, launched in waves over several weeks, until one per laserstar finally got through.
"As to Constellation, I was talking about cancelling everything except Ares I/Orion, which is the only part the private sector is close to duplicating."
Well, they really only cancelled Ares I. The Ares V work to date and workforce are going to be flowed into the Space Launch System, which will be a general duty super heavy launch vehicle in the 70 to 100 ton class.
Tony:
No, they're studying heavy launch vehicles. They've just delayed the program a while, and they are going to come back to the same solution. But Orion is still in development, despite Obama's proclamation that SpaceX will do the same job for NASA.
ElAntonius:
Response time is heavily dependent on techlevel. If you have almost-torches then orbital position matters a lot less, and response times will be shorter. With modern tech, we have to use optimum windows, and slow orbits. I can't say for sure without knowing the tech level.
Milo:
Nobody ever won a war with defense. If the aliens are out there, I'd ready a fleet to stop them from trying a second attack.
Byron:
Actually, I was thinking more along the lines of laserstars carrying missiles as well, not just additional (smaller) mirrors for the main laser. My takeaway from the laser vs kinetics threads was thus:
- Lasers can disable other lasers at greater range than they can inflict a hard kill.
- Lasers are really the only good defense against incoming kinetics.
- To ensure a hard kill, it's probably best to inflict a mirror kill, then follow up with kinetics.
- At sufficient power levels, mirror sizes and wavelengths, lasers can be powerful enough (and long-enough ranged) to be able to counter almost anything short of an all-out missile bombardment.
- Such a laser would be an important and useful strategic weapon within orbital space.
Raymond:
OK, that makes sense. I was mostly trying to point out that the laserstar wasn't exclusively a single big laser, which is what Tony seemed to think we were proposing.
Tony:
By your logic, aircraft carriers are obsolete today. You may think that, but the US Navy apparently doesn't.
The problem with declaring them obsolete is that a laserstar or carrier has uses other than all-out war, but an anti-ship cruise missile or kinetic doesn't.
Another issue is that a kinetic lacks presence. It can't loiter at a trouble spot the way a laserstar can. I'm not arguing that lasers are all-powerful, but they do have their uses.
Byron:
"You have a point. But will the economies of scale really be that big? I'm not certain they will be, but I think there's a good chance. But there's also production economies of scale to consider. It might be cheaper to buy a dozen single laserstars than three quads of equal performance."
There is no possible way that 12 of any vessel can be less expensive than 3 with similar propulsive and sensor performance.
"As to irreducable minimums, I don't think reactors will scale quite that much, particularly if they have to be launched in pieces."
If they have to be launched in pieces, they might only have 1Mw/t performance, while a monolithic reactor might have 1.5 Mw/t. But the cost to develop an ultra heavy launch vehicle for just two or three laserstar reactors might make launching 20 or 30. small modular reactors attractive. Except that 20 or 30 super heavy launch vehicle missions would break the bank, so you're not going to do that either.
"As for lasers, I think Luke has addressed this. A big laser is better then two smaller ones half it's size."
As a matter of physics principles, yes. That has nothing to do with economic practicality.
"If lasers aren't terribly effective, then that's even more incentive to make one big one. I don't share your doubts on this, and that's probably a lot of the issue."
If lasers aren't effective, big or small, they're a waste of time and money.
"I'm with Raymond on laserstar armament. They have one primary offensive laser and several smaller defensive lasers. But this is a false comparison. The multiple weapons are required to be effective across a variety of ranges. A laser can refocus to deal with that, and it isn't going to dogfight."
It's going to be doing effectively the same thing as dogfighting, when a hundred brillian pebbles that it can't even target, until they get within few tens of thousands of kilometers, are shot at it.
"But an even larger ship is?"
No. Remember, we're straddling two regimes here: the plausible midfuture, in which a laserstar is probably not economically practical, even if it is theoretically possible; and the magitech future, in which laserstars are economically possible, but probably not a good economic choice.
Tony:
Um, no. That's not what I meant. I was speaking of 12 laserstars each with one laser and 3 each with 4 lasers. All the lasers are the same, and equal performance means same acceleration and delta-V.
I'm going to leave you alone in your little bubble of economic unhappiness now. This discussion on economic plausibility isn't going to be resolved.
Byron:
"No, they're studying heavy launch vehicles. They've just delayed the program a while, and they are going to come back to the same solution."
I doubt that seriously. The Ares V, as originally designed, just too big. It only made sense in the context of landing on the moon with the super-sized LEM they had envisioned. For general super heavy lift, a 70 to 100 ton class launch vehicle makes more sense.
"But Orion is still in development, despite Obama's proclamation that SpaceX will do the same job for NASA."
The Orion crew vehicle is still being worked on, but not the Ares I launch vehicle. Orion still has potential use for NEO exploration, among other things. But for those kinds of missions, it would go up on whatever super heavy LV they finally settle on. For trips to the ISS, Falcon 9/Dragon are more than sufficient.
Byron:
"Um, no. That's not what I meant. I was speaking of 12 laserstars each with one laser and 3 each with 4 lasers. All the lasers are the same, and equal performance means same acceleration and delta-V."
I know what you meant. It's just a fact of economic life that 12 vessels cost more than 3, because the 12 vessels need 12 (less efficient, even if similar performance) propulsion systems, 12 sensor suites, 12 chassis, etc.
"I'm going to leave you alone in your little bubble of economic unhappiness now. This discussion on economic plausibility isn't going to be resolved."
I'm a happy person. You, on the other hand, seem to be getting increasingly unhappy. I think I know why, but it's not really for me to say...
Tony:
No, that's not true. If we ignore things like development costs and economies of scale, yes. But in that case, why did we build 4 Iowas? Why not one ship with 12 turrets? Why do we bother with multiple vessels at all? Just build one big ship every couple years.
Byron:
"By your logic, aircraft carriers are obsolete today. You may think that, but the US Navy apparently doesn't."
How does that follow? Because they're large and expensive? They're also very flexible and they don't eat up our entire defense budget on a single, inflexible capability.
"Another issue is that a kinetic lacks presence. It can't loiter at a trouble spot the way a laserstar can. I'm not arguing that lasers are all-powerful, but they do have their uses."
What in the world are you talking about? A kinetic weapon is a single shot, just like a single pulse from a laserstar. It's carried on a bus or a manned spacecraft, which can loiter pretty much anywhere it's owners want to insert it into orbit.
Byron:
"Nobody ever won a war with defense. If the aliens are out there, I'd ready a fleet to stop them from trying a second attack."
Can't. Your "aliens appear from nowhere" scenario suggested an interstellar invasion, and we don't have the technology to strike back across those distances, even with a massive funding project. Furthermore, if they travelled that distance STL then that it'll be years at least before they even learn their invasion failed, nevermind sending a new wave. Knocking out the fleet that's here now is quite sufficient to buy us safety until we can develop better technology.
Unless they actually have some infrastructure that's within plausible reach for us to attack, the only thing we plausibly can strike at is their military platforms. And those are better engaged defensively.
If they do try to build infrastructure in our solar system, it would probably be easier to harry them and keep them from completing construction than to destroy the infrastructure once it's done.
If the aliens have old, mature bases in our solar system that we just failed to notice before for some weird reason, then that falls outside the parameters of your scenario as I initially understood it.
Tony:
How does that follow? Because they're large and expensive? They're also very flexible and they don't eat up our entire defense budget on a single, inflexible capability.
Because it costs less in anti-ship missiles to sink them then they cost to build. Who says a laserstar isn't flexible? It's far more so than a bunch of kinetics.
As to presence, the bus will need time to get up to speed, and it can't park in their orbit. But the fact that it's single shot is part of the point. A laserstar can blast forever (provided it can get rid of the heat, but this is for gunboat diplomacy). A kinetistar can't.
As to happiness, I'm happier when I can drewam of laserstars without you shouting "it's not economically viable."
Milo:
Knocking out the fleet that's here now is quite sufficient to buy us safety until we can develop better technology.
What if they have a base in the outer system like you proposed. I know it's not a perfect scenario, but if I could think of a better one, I'd turn it into a book.
Byron:
"No, that's not true. If we ignore things like development costs and economies of scale, yes. But in that case, why did we build 4 Iowas? Why not one ship with 12 turrets? Why do we bother with multiple vessels at all? Just build one big ship every couple years."
We built four Iowas because that was the economically reasonable size of 16" gun ship. Between the wars, when playing around with maximal BB designs, some Spring Styles were actually worked out that had as many as 24 x 16" guns (IIRC -- have to check with my Friedman when I get home). They could have built them, but they would have wound up with too few units.
At the other end of the spectrum, we know for a fact that one of the primary motivations behind the all-big-gun ship was that you could get more guns at sea for the same ship cost. In actual practice, it worked out that two dreadnoughts, with a combined broadside of 16 big guns, cost about the same as three pre-dreadnoughts, with a combined broadside of 12 big guns.
So, all of the economic and military factors are traded off, but it never works out that the maximal or minimal design is fielded. What leaves the factory or the yard is something that provides an acceptable balance between cost and capability.
Tony:
Exactly. It turns out that the most economical size of a battleship is around 9 guns. But a tank is best at 1 gun. Why do you assume that spacecraft will follow battleships instead of tanks, particularly when the physics seem to favor the biggest laser possible?
Byron:
He3 fusion (what I've studied) has capabilites of up to 10e6 seconds. The problem with that is that it's far higher then is needed for most missions.
I am getting away from the basic thrust of Rick's post (manned vs. unmanned), but the more I look at the exotic types of fusion, the more cold water gets thrown on my idealistic and hopeful expectations of them. In brief, here is a summary of what my current understanding of the field is:
D-T - this is by far the easiest fusion reaction to get going. Nonetheless, it is still fiendishly difficult. D-T fusion puts out 80% of its energy in the form of extremely energetic neutrons, which makes the reactor an extreme radiation environment that is very difficult on materials and which will activate the structural materials to produce significant long-term levels of radiation for weeks to months after the reactor is turned off. In practice, T would be regenerated by 6Li and 7Li, so your fuel would be D and Li.
D-D - significantly more difficult to ignite than D-T, with only small benefits. The neutrons are lower energy, and from the primary reaction only about 40% of your energy is in the form of neutrons 9and lower energy neutrons than the D-T reaction, which are easier to deal with). However, the non-neutron producing branch results in T as a by-product, which immediately fuses to produce the high energy neutrons. In addition, more energy is lost to the form of bremsstrahlung (basically you can think of this as x-rays) so the usable energy left in the plasma is not all that much better than D-T.
D-3He - about as hard to ignite as D-D. It has the advantage that the desired reaction produces no neutrons. Unfortunately, you also get D-D side reactions, which do produce neutrons. The neutron energy and neutron energy fraction are roughly the same as for fission, so a D-3He reactor would be about equivalent to a fission reactor as far as the prompt radiation environment. Without long-lived fission products and neutron-activated actinides, it is much more friendly as far as long term radio-contamination. D-3He also loses a substantial fraction of its energy to bremsstrahlung, but of all the fusion methods it leaves the most energy remaining in the plasma (about 75% or so, if I recall correctly). While the lower radiation environment makes it look promising with respect to D-T, the increased difficulty of getting it to ignite means your performance (specific power) will be lower by a significant amount.
p-11B, 3He-3He - the various truly aneutronic reactions that have been proposed have a significant drawback - if you do not have tons of simultaneously fusing plasma (perhaps down to kg quantities with high compression), you always lose more energy to bremsstrahlung than you gain by fusion. While various hopeful methods have been proposed to get around this limit, the best analyses I've seen indicate that none of them work. Barring some completely new idea for suppressing the bremsstrahlung (which, ultimately, means keeping the electrons cold and the ions hot, and not letting the two meet) no truly aneutronic fusion method can work. Further, the increased recalcitrance of these isotopes to actually undergo fusion means that any reactor that used an aneutronic reaction would have a lower specific power than a D-T or D-3He reactor by many orders of magnitude.
(SA Phil)
Tony,
Whether a Laser is more effective in an actual combat situation vs theoretical than a kinetic is a bit academic. You would have to have experience with the non-existant weapons platforms in the untested settings.
Assuming they had the experience and the Laser was still the most effective then that is the one they would use.
Likewise we have no idea how much more a laser costs than kinetics. If you want to make an assumption, ok, but that doesn't make it a definite truth.
We also do not know what the economy will support, because the economy is undefined. Declaring that the economy can't support it is a bit pointless.
Because of the limits of the propulsion technology; if the kinetic ship masses the same as the Laserstar it will have many of the same cost requirements -- since the propulsion requires the big powerplant. Its fairly likely the two ships will have comprable Mass requirements since Kinetics have Mass. But they might differ.
The effectiveness of a kinetic ship will be inversely proportional to the Laser's range. The longer the range the lower chance the kinetic will win in a duel between them. At some point you get two extremes. If the Laser has a very short range the kinetic will always be better. If the Laser has a very long range, the Laser will always be better.
If battles are fought at 1 light second and Lasers are effective, kinetics will only be useful at relativistic speeds which we dont get with milligee drives. Or in Implausibly large swarms, Mass again.
Because at Hypervelocity all the Laser needs to do is make a missile unable to move under its own power then sidestep the wreckage. And with long hours to shoot down the Kinetic storm it will easily be able to do so.
If battles are fought at 1 km the the laser is pointless, a Machinegun would be more effective.
Tony, re: economy of launch and torch drives.
You seem to miss the logical chain. Torch drives do not give you cheap launch. Cheap launch technologies do not give you torch drives. The two are uncoupled. Further, you do not need torch drive performance to open up the solar system to a manned presence. Thus, plausible cheap launch technologies could yield futures (although not necessarily mid-futures) in which you have an extensive manned space presence and space infrastructure. In particular, the cost to get large modular reactors and lasers into space does not result in torch drive levels of performance.
Byron:
"Because it costs less in anti-ship missiles to sink them then they cost to build."
The antiship missiles -- and more than one of them -- have to get through. That's not an easy task with an escort screen for local defense and aircraft to attack the potential missile shooters before they can get off a shot. And unless the missiles start uncontrolable fires, the carrier can't be sunk, it can usually only be forced to go back to port for repairs.
"Who says a laserstar isn't flexible? It's far more so than a bunch of kinetics."
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.
"As to presence, the bus will need time to get up to speed, and it can't park in their orbit. But the fact that it's single shot is part of the point. A laserstar can blast forever (provided it can get rid of the heat, but this is for gunboat diplomacy). A kinetistar can't."
A laserstar cannot blast forever. It's power plant can carry only so much fuel. A kinetic bus has multiple shots as well -- as many brilliant pebbles as can be mounted. It can deliver them all at once, providing a saturation effect against a single target, or spread them out over time and space, to attack multiple targets. It can, as already mentiond, also deliver chemical or nuclear explosives. It can be placed in any orbit from which it can be effective.
Oh, and one further thought on fusion - external pulsed propulsion (the only variety that is plausible for torch levels of performance) require driver beams with a pulse energy of between 10% and 1% of the fusion yield. Consequently, if you have, say, a 1 TW torch you also have at least 10 GW directed energy weapons. Using antimatter as a "fast ignition" ignitor might reduce this somewhat, but you still need significant beam-produced compression.
Byron:
"Exactly. It turns out that the most economical size of a battleship is around 9 guns. But a tank is best at 1 gun. Why do you assume that spacecraft will follow battleships instead of tanks, particularly when the physics seem to favor the biggest laser possible?"
As already explained, tanks are designed for a much more complex combat environment. If battleships were expected to fight only in river deltas, they would have single, small guns too.
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.
Luke:
"Tony, re: economy of launch and torch drives.
You seem to miss the logical chain. Torch drives do not give you cheap launch. Cheap launch technologies do not give you torch drives. The two are uncoupled. Further, you do not need torch drive performance to open up the solar system to a manned presence. Thus, plausible cheap launch technologies could yield futures (although not necessarily mid-futures) in which you have an extensive manned space presence and space infrastructure. In particular, the cost to get large modular reactors and lasers into space does not result in torch drive levels of performance."
Sorry, but I don't accept the assumptions that underly the above. Inexpensive launch with non-torch drive performance presumes huge investments in megastructures and equally large cargo throughputs. This is in the class of you can't get there from here ideas. You don't need cheap space launch until you have a large interplanetary economy, but you can't get a large interplanetary economy without cheap space launch. Torch drives (as in Heinleinian torches, not just .01 gee fusion plasma drives) notionally give you cheap space access, and obviate the need for megastructures.
IOW, cheap space access may not be theoretically coupled with torch level propulsion performance, but it seems to me to be coupled tightly in a practicality sense.
And Yes, I know I'm invoking magitech when I presume portable (in the sense of small and light enough to put on a launch vehicle), high thrust torch drives. But in my estimation, it's going to take something magitechnic to get to that place where everybody seems to want to go.
(SA Phil)
I dont think that reactor fuel is going to be a significant problem for the laserstar.
The ship is going to be designed for months of continuous electric drive thrust at the same electrical power level the Laser/Capactior system will need.
So by definition it would be able to shoot its laser for months.
Raymond:
While I agree with most of your analysis, I wish to address the following statement:
Lasers are really the only good defense against incoming kinetics.
This is not clear to me. Low mass, low delta-V seeker heads seem like they would also make an effective defense against kinetics. You just interpose them between yourself and the incoming kinetic, and the kinetic's own speed destroys it in the resulting impact. These 'mines' will act in a complimentary way to the laser. The laser can burn out kinetics at long range, can burn down an indefinite number of kinetics, and and can perform area defense to protect other assets. However, the laser can be saturated if the kinetics arrive at a high enough rate. Meanwhile, the mines are only good for point defense and cannot take out more kinetics than there are mines, but whether or not they are saturated is independent of the rate at which the kinetics come in.
SA Phil:
"I dont think that reactor fuel is going to be a significant problem for the laserstar.
The ship is going to be designed for months of continuous electric drive thrust at the same electrical power level the Laser/Capactior system will need."
The ship is presumably going to have to use fuel to get to the battlespace. The ship is presumably going to have to use fuel to get home. The ship is going to have to maintain a amenuvering reserve. The ship is going to have to generate ship's service power over the duration of the mission. After that, any fuel left over is going to be available to power weapons and sensors. Think of it as a similar dynamic to that of a submarine or aircraft time on station.
Another thing -- space lasers may have to use expendable coolants in order to support a practicale rate of fire. When you run out of coolant, you go down to a low rate of fire or (if your design doesn't use radiators in combat mode, in order to preserve compactness) you stop shooting altogether.
Tony:
Inexpensive launch with non-torch drive performance presumes huge investments in megastructures
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.
And Yes, I know I'm invoking magitech when I presume portable (in the sense of small and light enough to put on a launch vehicle), high thrust torch drives. But in my estimation, it's going to take something magitechnic to get to that place where everybody seems to want to go.
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)?
Post a Comment