Comments on Rocketpunk Manifesto: World of Two Suns

LOL

2011-10-27T20:46:01.576-07:00

LOL

OK, my posts lately have been hit-or-miss, but ...

2011-10-27T20:29:53.610-07:00
OK, my posts lately have been hit-or-miss, but here goes..

HIT! You sunk my space battleship!

OK, my posts lately have been hit-or-miss, but her...

2011-10-27T18:48:48.695-07:00
OK, my posts lately have been hit-or-miss, but here goes...My opinion of space warfare is that it will be dominated by either orbital combat or high speed fly-by intercepts. Most combat spacecraft will probably mount a mix of weapons; lasers, missiles, and ballistics; each will cover the other's weak points and concentrate on their strengths. Versitility is very important to millitary success, no matter what the battlefield is. The only other space combat mission is likely to be convoy escort/attack, but that would likely blur into the other two.

Ferrell

Rick: "But my mental image of an expediti...

2011-10-27T09:30:31.070-07:00
Rick:

"But my mental image of an expeditionary 'capital ship' is something on the lines of one keel-mounted main mirror, a couple of secondary mirrors (port/starboard or dorsal/ventral, the distinction being arbitrary), and payload capacity for kinetics, 'gunships,' or whatever."

As I've stated before, space warships are likely to resemble fighter-bombers than they are to be like dreadnought battleships. So I have serious doubts about the subordination of everything to a spine mounted weapon system. And even as secondary or co-primary weapons, lasers are too narrow in application.

Thucydides, the thread you're thinking of was ...

2011-10-26T20:25:55.981-07:00
Thucydides, the thread you're thinking of was Further Battles of the Spherical War Cows.

The ships I have in mind are big, but not humongous - on order of 1000 tons departure mass, 500 tons dry mass, perhaps 200 tons gross payload, give or take.

If you are fighting demi-operatic deep space wars at all, you should be able to afford capital ships on this scale, whatever armament you choose to provide.

Also bear in mind that the 'ideal' spherical-cow laserstar is a conceptual exercise, not a service proposal. I can see a 'monitor' vehicle - designed purely to defend a planet's orbital space against intruders from Somewhere Else - coming fairly close.

But my mental image of an expeditionary 'capital ship' is something on the lines of one keel-mounted main mirror, a couple of secondary mirrors (port/starboard or dorsal/ventral, the distinction being arbitrary), and payload capacity for kinetics, 'gunships,' or whatever.

Re: Thucydides That's kind of how I figured i...

2011-10-26T10:53:34.165-07:00
Re: Thucydides

That's kind of how I figured it -- lasers with thousands or tens of thousands of kilometers of effective range are prohibitively large, expensive, and nowhere near as effective as the armchair admirals imagine.

The spin on the EFP projectile isn't to provide any kind of laser energy resistance. The device is only going to be about the size of a modern antitank missile, maybe smaller. If it gets hit, it gets hit all over. The point of the spin is to minimize attitude control system mass. With a spinning object, any attitude change WRT the spin axis can be accomplished with a couple of burns of a single thruster, providing that thruster is acting along a vector that doesn't pass through the object's CG.

I seem to recall that one thread here (or was it A...

2011-10-25T18:36:33.264-07:00
I seem to recall that one thread here (or was it Atomic Rockets?) actually tried to work out the mathematical relationship between incoming warheads and laser weapons of "stupendous power".

My Google Fu seems weak today, but the magnitude of kinetic vs WSP laser was in the order of thousands of warheads needed to be launched to ensure overmatch against a single laser weapon. I suppose it would be fair to ask Tony what his ship is giving up to operate as a huge missile carrier?

Indeed, the tradeoff would seem to be favouring size; Luke Campbell's Xaser with its kilometer long LINIAC would be a large and robust ship (the optical train would have to be held in a massive truss, with power and cooling units mounted on vibration isolating "rafts"). This would be more than sufficient space to mount hundreds of VL cells carrying the thousands of missiles desired.

Even smaller ships would still be large in our terms; there is a proposal for a megawatt class FEL capable of fitting into a 747 (much like the ABL, but a tunable, electric weapon rather than a chemical laser). This implies the smallest spacecraft capable of fighting with a laser weapon would be at least as large as a 747, and probably much larger once the reactor, tankage and so on were added; plenty of room for missile batteries as well.

Rick: "That's true of every military ...

2011-10-25T08:27:56.801-07:00
Rick:

"That's true of every military capability, and the penalty for this one is a few percent of combat mass. What did you sacrifice to carry those marbles you're tossing at me?"

Just so. I was simply forestalling one of those well-then-I-pull-out-my-vorpal-blade-that-goes-snicker-snack type arguments by pointing out that there are limits.

"Huh? These are unguided projectiles - the longer the flight time, the longer my jink time, and the less delta v I need to cover whatever deflect radius I estimate to be enough to make a hit difficult."

It's like any other long range gunnery exercise. A dodging target is just part of the problem. I only have to hit you a few times out of several thousand projectiles.

"How do you propose to give your attack 'depth in three dimensions?' Your grapeshot has to be deployed from ships or missiles that are basically easy to track - I will know hours in advance what the threat vectors are."

Certainly you will. But with proper timing I can have attacks arriving within a few seconds of each other from different directions, so that you simply can't re-orient your shielding quickly enough.

"Did you mean 'waive'? Or am I missing something?

In any case, this is basically a target seeker, since it needs to be oriented the right way and set off at the right time in order to hit. I'll engage them as I would any other target seeker."

They're not quite like any other target seeker. They wouldn't maneuver, so they wouldn't have to be much bigger than the warhead, a sensor-control package, and a small attitude thruster plus about a second of remass. (You only need one attitude jet because you spin the projectile on launch.)

"I'm not claiming that such an attack can't throw me off, just as the German torpedo attack at Jutland threw off the Grand Fleet and allowed the HSF to bail."

Oh, it's intended to do much more than throw you off.

If you have extra margin for jinking, it's ...

2011-10-24T20:56:30.515-07:00
If you have extra margin for jinking, it's because you skimped somewhere else. Tell me what you traded off, and let's see if I can't exploit it.

That's true of every military capability, and the penalty for this one is a few percent of combat mass. What did you sacrifice to carry those marbles you're tossing at me?

The flight time is almost immaterial.

Huh? These are unguided projectiles - the longer the flight time, the longer my jink time, and the less delta v I need to cover whatever deflect radius I estimate to be enough to make a hit difficult.

How do you propose to give your attack 'depth in three dimensions?' Your grapeshot has to be deployed from ships or missiles that are basically easy to track - I will know hours in advance what the threat vectors are.

Things get different in low orbit, but that is no place to take a laserstar anyway; they are intended for more open space - say, geosynch and beyond. (If there's no reason to fight out there, I wouldn't build laserstars.)

I wave the dumb kinetics and have my attackers shoot EFPs at you on the way by.

Did you mean 'waive'? Or am I missing something?

In any case, this is basically a target seeker, since it needs to be oriented the right way and set off at the right time in order to hit. I'll engage them as I would any other target seeker.

I'm not claiming that such an attack can't throw me off, just as the German torpedo attack at Jutland threw off the Grand Fleet and allowed the HSF to bail.

jollyreaper: "That's possible. On th...

2011-10-24T11:30:09.022-07:00
jollyreaper:

"That's possible. On the other hand, how far would aeronautics have gone if the European powers were able to settle their differences peacefully in 1914? If R&D was only paid for by private concerns and not public money, it's not inconceivable that we could still be looking at piston and prop aircraft even now."

By 1909, all major governments in Europe and the US were already financing aviation development. Planes were first used for bombing in 1911 (by the Italians in the Italo-Turkish War). Many advances were also made between the wars. Many more advances were made after WWII. Wartime accelerates things somewhat, but the fact is that anything with even marginal military utility is developed to its maximum extent, with or without war.

So, what am I saying here? Well...maybe lasers...

2011-10-24T10:29:01.855-07:00

So, what am I saying here? Well...maybe lasers are just never going to be all that. Maybe we've really pretty much plumbed their depths. We won't know whether we have or haven't for several decades, but based on the recent history of engineering technologies, I think maybe -- just ma-a-aybe -- we have.

That's possible. On the other hand, how far would aeronautics have gone if the European powers were able to settle their differences peacefully in 1914? If R&D was only paid for by private concerns and not public money, it's not inconceivable that we could still be looking at piston and prop aircraft even now.

While not wanting to get into a tech stagnation debate, it does seem to be the case that each development requires more people and more research and more money but how much of this is driven strictly by the requirements of the task at hand and how much is bureaucratic inertia? I have no idea.

I'm pretty agnostic on the whole idea. I won't say for sure whether X is possible or X is impossible, I'm simply prepared to see it go either way or just muddle along kicking the answer-can down the road.

Rick: "If I don't have ~100 m/s of OM...

2011-10-24T06:04:42.391-07:00
Rick:

"If I don't have ~100 m/s of OMS delta v available I have no business zapping people, and ought to work on mutual understanding through dialogue."

If you have 100 m/sec of attitude control available, that's becaue you need it for attitude control. If you have extra margin for jinking, it's because you skimped somewhere else. Tell me what you traded off, and let's see if I can't exploit it.

Also, if you jink in orbit, you have to reestablish your orbit after the fighting's done (presuming you're still around). Whether you do that with your electric motors or with your attitude thrusters, you still gotta carry extra remass for that eventuality too.

"At this sort of range, flight time of kinetics will be hundreds of seconds, and getting more than a few degrees of spread would be problematic."

The flight time is almost immaterial. The projectiles, if unguided, are going to be golf ball sized at largest, but probably more like marbles, and number in the thousands. If you can engage enough of them to avoid getting hit, be my guest. I don't think you can.

WRT dispersion, we have to remember that we're operating in three dimensions. My solution to your shielding is to give my attack depth in three dimensions. When the orbits of the attack and your ship intersect, some projectiles may in fact be absorbed by your shielding, but unshielded parts of your ship facing in the direction of your orbit will run into projectiles as they pass by.

Or I can be a little more efficient and arrange for depth in time, so that the first attack hit's you from off orbit, while the second one you run into because it's timed for you to run into it, instead of it running into you. Or variations of this theme. The problem you're faced with is that you can't re-orient your shielding that quickly.

Or, borrowing from emerging (in 2011, not SFnal) AFV point defense technologies, I don't worry about the particular aspect of attack, I wave the dumb kinetics and have my attackers shoot EFPs at you on the way by. Surely a few of them will hit from an unshielded angle.

That's kind of my whole point -- lasers are good for shooting at something along a straight line. Kinetics and chemical energy explosives can be made to do all sorts of fun things to screw up the best laid plans of lasermen.

If I don't have ~100 m/s of OMS delta v availa...

2011-10-23T21:20:30.402-07:00
If I don't have ~100 m/s of OMS delta v available I have no business zapping people, and ought to work on mutual understanding through dialogue.

That gives me 10 evasion burns at 10 m/s.

And bear in mind that even with pretty conservative assumptions my zapping range is impressive. Suppose that my main mirror performance is degraded by 90 percent, i.e. my 10 meter main mirror delivers the spot size of an ideal 1 meter mirror.

If I am zapping at 1200 nm in the IR, my spot size is 1.83 m at 2500 km. With 100 MW average power, I can burn through various armor materials at rates on order of 1 cm/minute - and keep on zapping more or less as long as I can hold down the trigger.

Remember that this is with a range degradation of 90 percent - comparable to the difference between the bench range of an assault rifle and typical firefight range.

At this sort of range, flight time of kinetics will be hundreds of seconds, and getting more than a few degrees of spread would be problematic.

Chemical attitude control thrusters used for maneu...

2011-10-23T15:59:15.723-07:00
Chemical attitude control thrusters used for maneuvering is a pretty limited resource. You can't just burn all of your attitude control juice, even in survival mode. You'll need it later. I doubt it would be smart to use them except to face your shielding/armor in the appropriate direction.

Also, you really can't point your shielding armor in the direction of the attack, unless it's coming from up or down orbit (WRT your orbit). The smart attacker will arrange his salvo so that it intersects your orbit from an off angle. With careful timing he can have an attack arrive over a pretty wide sector, maybe 50-60%.

Stay outside of zapping range and attack it wit...

2011-10-23T15:00:18.683-07:00
Stay outside of zapping range and attack it with small, hard-to-hit, unguided kinetics until the radiators are shredded.

That is a pretty easy tactic to defeat. I don't have what I think of as 'tactical maneuvering power' (e.g. to choose the time and place of engagement). But I surely have chemfuel thrusters good for dozens of meters per second.

And I'll have a approximate idea of viable trajectories, because the kinetics have to be launched from a ships/missiles on a collision course. I only need to sidestep by a few hundred meters to render non-guided kinetics ineffective.

Also, for most geometries I can position myself so that my radiators are end-on to your attack, minimizing cross section (and making a Whipple shield a worthwhile investment).

You could theoretically defeat these defensive measures by engaging me simultaneously along widely separated axes. But that is VERY hard to arrange unless I am totally asleep at the switch.

Ferrell: "Also, since lasers are so versi...

2011-10-23T12:25:47.627-07:00
Ferrell:

"Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons."

Lasers as a class are very versatile. Individual lasers are extremely limited, since they have to be optimized for operating frequency and power output.

Rick: "So a nuke electric ship loses noth...

2011-10-23T12:18:04.848-07:00
Rick:

"So a nuke electric ship loses nothing by diverting its full electric output to a laser (bank), even for an hour or more of steady zapping."

Stay outside of zapping range and attack it with small, hard-to-hit, unguided kinetics until the radiators are shredded. It's not like the ship will be maneuvering to complicate the targetting. If the ship elects to maneuver, because it doesn't have other ships to shoot at, it becomes a better target for guided kinetics that it can't shoot at while maneuvering.

This is one of the big reasons lasers just strike me as way oversold and unlikely to be viable. They just represent a ridiculous vulnerability in the form of large and fragile power systems. Or if you choose to use consumable power generation and cooling, well, they're just another gun.

=Milo= Ferrell: "Also, since lasers ar...

2011-10-23T10:28:58.256-07:00
=Milo=

Ferrell:

"Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons."

Well, we're looking into laser communication today. They could be used against asteroids. I guess lasers could have scientific uses for vaporizing samples. Or you could just bounce them off something to measure its distance.

But a laser designed for communication is going to work very differently from one designed as a weapon. They aren't interchangeable.

Of course, ships will have numerous micro-lasers onboard for a variety of purposes, such as in the DVD reader for playing the in-flight movie, but no-one is actually going to count those as ship-mounted lasers.

Perhaps the best use of space lasers would be as p...

2011-10-23T10:16:25.611-07:00
Perhaps the best use of space lasers would be as point defense weapons; short range and either causing the seeker heads to be 'pulled' off target, or generating a jet of super-heated gas that knocks the projectile off course. Also, since lasers are so versitile, I would expect them to be included on many deep-spacecraft for a variety reasons; not just weapons.

Ferrell

Meta note that it is very odd to be defending a we...

2011-10-23T09:01:51.644-07:00
Meta note that it is very odd to be defending a weapon tech that I don't particularly like on 'aesthetic' grounds, and certainly have no SF-sentimental attachment to!

Note also that I'm not arguing for laser small arms, field artillery, naval guns, or whatever - my interest in laser weapons is strictly as a long range space weapon.

just because you have propulsion power, that doesn't mean you have beam weapons power

For most propulsion systems I would agree, but nuclear (or solar) electric space propulsion seems to be a notable exception. Electric spacecraft have available onboard power equal to their thrust power, with radiators capable of shedding the waste heat. And their milligee acceleration is so modest as to be pretty much irrelevant to tactical maneuver.

So a nuke electric ship loses nothing by diverting its full electric output to a laser (bank), even for an hour or more of steady zapping.

A few provisos, from technical to rather meta:

1) While the main radiators can shed the waste heat, the cooling system that takes heat from the laser to the radiators may well be so noisy as to produce excessive beam jitter. This topic is pretty deep into the technical weeds.

2) A case an be made that the techlevel of milligee electric drives is not conducive to the sort of warfare in which laserstars would have any mission. (Such as combat between terrestrial powers in Earth orbital space.)

3) More futuristic/speculative electric drives have different characteristics. A torch-level drive almost certainly does NOT have plug power equal to anything like its (outrageous) thrust power.

I wanted to add: Beam weapons, laser or otherwise,...

2011-10-22T22:06:31.655-07:00
I wanted to add: Beam weapons, laser or otherwise, are something we hold close because they are right at the center of long cherished canon. But like the family nuclear interplanetary rocket, or the geosynchronous Earthport One space station, they may just be another thing that reality has overtaken. In fact, given the way reality has overtaken much of the rocketpunk canon, it seems to me to be somewhat quixotic to hold onto beam weapons so dearly.

I evaluate it this way: Lasers have been adapted ...

2011-10-22T21:52:36.557-07:00
I evaluate it this way:

Lasers have been adapted to every possible application over the last fifty years. Who in 1960 would have predicted fiber optics or CDs, for example. If lasers haven't been adapted into weapons, it seems to me that, in this age of rapid technological development, it's a reasonable question to ask if they can be.

And in all honesty, I really don't see where it has been demonstrated that they will ever be practical as weapons. They've been shown to work technically. But they haven't been shown to be practical. And the limit to practicality (for rail guns as well, BTW) is the portability and reliability of a combat power supply. Even in shipboard applications, it turns out that one would have to add large and heavy auxiliary generators, plus their cooling systems and fuel supply, because you can't use propulsion power for weapons.

As I have stated before, this last is something that people seem to be systematically missing about space lasers -- just because you have propulsion power, that doesn't mean you have beam weapons power. That takes other power. The big attraction to guns, missiles, and explosive warheads is that all of the energy they use is put in by commercial power plants that don't have to be brought along on the mission.

Simply put, I just don't think lasers will ever achieve the level of practicality to be even complimentary weapons.

I would side with Thucydides in this case. Militar...

2011-10-22T18:40:36.184-07:00
I would side with Thucydides in this case. Military lasers have not been pursued with any great consistency. Even more to the point, there has been rather little effort put into space-to-space weapons in general, for strategic rather than technological reasons.

Also note that there have been some very major developments in optics in the last 25-odd years. Much larger telescopes, adaptive optics, and so on.

I would not count out lasers quite so easily. The ...

2011-10-22T12:28:35.812-07:00
I would not count out lasers quite so easily. The on again/off again R&D effort may have made it seem like lasers have taken 50 years to mature, but in reality, many programs were stopped in the 1980's at the end of the Strategic Defense Initiative, and newer programs start and stop as well. The US Navy had funding cut to both laser weapons and electromagnetic railguns, despite having demonstrated excellent test results. The USAF's airborne laser efforts are hitting a similar "wall" despite successful tests as well.

Short bursts of effort followed by longer funding lulls, and the inevitable "reinventing of the wheel" as programs are restarted or new programs pick up where old programs ended suggest to me that high power lasers are really about halfway to maturity.

New ideas, like ganging high efficiency diode lasers (Lasermotive) are appearing all the time, so I think we could be in for some surprises. (Perhaps the biggest surprise may be which nation fields the first viable tactical lasers...)

Anyway, the argument is a bit moot, lasers and kinetics are complimentary, and the decision by Fleet HQ will be deciding what proportion of laser to kinetic will be used, and how that will be balanced across ship classes and the fleet as a whole. Factors such as nuclear electric or nuclear thermal will be a big factor in guiding the decision.

=Milo= Rick: "Classic nuclear electric...

2011-10-22T10:42:51.979-07:00
=Milo=

Rick:

"Classic nuclear electric propulsion, IMHO, favors laser armament because you've already got beaucoup electrical power, plus radiators and so forth. So all you need is the laser (bank) and targeting optics. At the same time, this propulsion is too sluggish for much tactical oomph.

On the other hand, orbital combat with chemfuel or nuke thermal propulsion favors kinetics because there is no handy built-in power supply for lasers, and the combination of high accelerations and strong gravity fields makes it fairly easy to deploy fast kinetics."

I disagree when it comes to nuclear-thermal - bimodal nuclear-thermal engines can be made, and while less efficient than power plants designed exclusively for electricity production, they should be pretty good for laser purposes.

I do, though, conceptually appreciate the idea of different weapons being optimal in different tactical environments, and getting to use both lasers and kinetics.

Comments on Rocketpunk Manifesto: World of Two Suns

LOL

OK, my posts lately have been hit-or-miss, but ...

OK, my posts lately have been hit-or-miss, but her...

Rick: "But my mental image of an expediti...

Thucydides, the thread you're thinking of was ...

Re: Thucydides That's kind of how I figured i...

I seem to recall that one thread here (or was it A...

Rick: "That's true of every military ...

If you have extra margin for jinking, it's ...

jollyreaper: "That's possible. On th...

So, what am I saying here? Well...maybe lasers...

Rick: "If I don't have ~100 m/s of OM...

If I don't have ~100 m/s of OMS delta v availa...

Chemical attitude control thrusters used for maneu...

Stay outside of zapping range and attack it wit...

Ferrell: "Also, since lasers are so versi...

Rick: "So a nuke electric ship loses noth...

=Milo= Ferrell: "Also, since lasers ar...

Perhaps the best use of space lasers would be as p...

Meta note that it is very odd to be defending a we...

I wanted to add: Beam weapons, laser or otherwise,...

I evaluate it this way: Lasers have been adapted ...

I would side with Thucydides in this case. Militar...

I would not count out lasers quite so easily. The ...

=Milo= Rick: "Classic nuclear electric...