Whay would real-life war spacecraft look like?

[EzinX]

I've been musing on the heat issue and wondered about whether that "waste" heat can be piped somewhere and used for something. Obviously we can't make a perpetual motion machine, but there's no reason I can't heat my shower water with waste heat from a nuclear reactor (ignoring radiation).

Taking a shower with heated water doesn't change the basic need for heat generated = heat radiated. Essentially, over time, 100% of the heat generated must be radiated somehow. Firing a laser weapon that is 20% efficient radiates 20% of the energy as laser light, so you need to radiate the other 80% via radiators of some kind. Ditto for the nuclear electric engine case.

Since the surface of your spacecraft hull radiates heat at a rate proportional to the T^4 (temperature raised to the fourth power), any parts of your ship that are not high temperature radiators can be ignored as they don't radiate enough heat to matter.

This is just the overall theory. In practice, using foreseeable future tech, heat management is an even bigger problem because a lot of the nifty gadgets you need require very low temperatures to work. Sensitive infrared detectors to spot enemy ships - better cool that detector down to reduce thermal noise in the sensor element and also use a cooled shroud to protect it from IR from your own ship. Want a coilgun? All those magnets need to be cold, even if room temp superconductors are possible, superconductors work better when cold. Want a fusion reactor and your design uses magnets? Ditto for the cooling need. Want a free electron laser? About half the laser is superconducting magnets FTW. Are you storing hydrogen slush onboard for use as propellant, since it is frequently the most efficient possible propellant? Better keep that tank at under 20 kelvin.

Edited December 5, 2014 by EzinX

[Sandworm]

"American manned combat spacecraft. Study 1973. The space cruiser was a US Navy design for a single-place crewed space interceptor designed to destroy Soviet satellites used to track the location of US warships.

In the first half of the 1970's the US Navy began serious development work on a space cruiser - a single-place crewed space interceptor intended for "scientific and military applications". The Navy was specifically interested in knocking out Soviet satellites used to track the location of US warships. The space cruiser was to have been launched into orbit by a Poseidon missile from a ballistic missile submarine."

http://www.astronautix.com/craft/spauiser.htm

At one point there were extensive plans for a USAF version of Shuttle to be launched from Vandenberg. They actually build the launch facilities for this before it was canceled.

[Kibble]

Super long post divided into neat little chunks!

I’d imagine a real space war being kind of like our methods of detecting dangerous asteroids, if we started putting a bunch of money into it. Asteroids and spacecraft that aren’t actively talking to you have a lot in common – they are small, radiate softly in the infrared spectrum, and often on unstable, not-entirely-predictable solar orbits. You would probably launch telescopes a lot like the proposed Sentinel Space Telescope, with liquid helium-cooled sun-shaded detectors hunting the sky for anything that stands out. If they spot something, mission control will track it, figure out its orbit, and judge whether it’s a bad guy’s spacecraft. Alot of these telescopes will be in similar positions to Sentinel – i.e. a low enough solar orbit that it can look away from the Sun to see things, because you can’t look at or around the Sun without your temperature-sensitive telescope optics burning out. But the best place to be is at the Sun-Badguyville L1 point – you’re always looking away from the Sun, and always looking right at all the fishy things the bad guys are doing on orbit. So that spacecraft you detected heading for you might be a telescope headed for your Sun-El-Wun.

What about all the violent parts? Well this is where it stops resembling combatting dangerous space rocks. We can assume functioning spacecraft are flimsy (not made of rock) and in one piece. First of all nobody is never going to come anywhere near low orbit of an enemy planet, unless they absolutely have to. If you’re in LEO, you’re going to be ASATed by Earthicans. We have launched ASATs practically for fun. If you’re in LMO or LVO, you’re going to be ASATed by Martians or Venusians (Venerians?). If you’re in LLO, you might be ASATed by Moon men, but without an atmosphere to hide in or send airplanes thru, it might not be entirely practical. It is extremely likely that ASATs will be launched from airplanes, so that you can match the enemy inclination, and there is precedence for air-launched ASATs. These airplanes might even be manned! “But that’s not space combat!â€Â, you may be complaining. Well you’re right, its not! The good news is, that probably won’t happen very often, there is no real reason to go into Low Badguyville Orbit.

So how do you deal with that baddie headed for your Butt Lagrange? Earth’s SEL1 is 1.8 million kilos away – ASATs are no-go. Well you have a few different options, but the most likely one I will call by Rick Robinson’s wonderfully evocative name – Killer Bus! It will be on a solid-fuel air-launched rocket like Pegasus, again to match inclinations, avoid bad weather, all that stuff. It consists of three major parts: a little hypergolic tug like Fregat to put it on a trajectory that will roughly intersect with the enemy. Mounted on top is a modified P-Pod, built to carry at least 4Us of Cubesat. And then the Killer Buses themselves, at least two Cubesats, probably at least 2U each to carry enough maneuvering fuel to rendezvous with the bad spacecraft. With multiple operating in tandem like sheepdogs, likely at least one will get really close. Then it detonates a charge, becoming a small cloud of lethal space debris. This is just to really make sure you get em – you’ll be as close as possible, but even docking with a cooperative target is hard! Much less docking with an uncooperative target at high relative velocity.

Another option is pre-positioned Laserstars, a laser emitter looking thru an infrared space telescope with the biggest mirror you can afford. These will look a lot like James Webb Space Telescope, but with bigger solar panels and bigger radiators to power the laser. If you had infinite money and infinite rockets, the best way to use these would be the way you use Killer Bus, but without having to have near as precise aiming. Unfortunately these things are probably way to expensive to regularly eject onto solar orbits. But even at low power, laserstars are the natural enemy of telescopes (including other laserstars). It eats flimsy, temperature-sensitive, finely tuned mirrors for breakfast. (If low power lasers are also good at frying solar panels, laserstars rule the solar system until we start regularly launching nuclear-powered spacecraft, but I don’t know if they are.)

This is where it starts to get complicated. We can assume the ultimate targets are the enemy’s space infrastructure, which varies with each planet. Earth has that awesome (water-rich?) Moon for some complex weak stability trajectories and stuff, but most or all infrastructures will probably center on Keck Institute-style redirected asteroids. Little Philae-looking Kuck Mousquitos will drill for water ice to keep as drinking water, crack into oxygen for breathing, crack into hydrogen to resupply Sabatier reactions, crack into hydrogen and oxygen for rocket fuel, and to make hydrogen peroxide. They will also drill for ammonia ice, and using the peroxide process (with that hydrogen peroxide), to make hydrazine, and with catalytic oxidation, to make nitrogen tetroxide. For rocket fuel. Hydrogen doesn’t keep for very long, so any maneuver not falling under the category “rocket stage putting something on a transfer trajectory†will be done with hypergolics.

The Kuck Mosquitos will probably be teleoperated by astronauts in a space station somewhere in the vicinity of Keckistan. Mining is a difficult and unpredictable process, and mining in space will probably require constant supervision, and ocaissionally quick reactions to imminent problems. It is also one of the few cases in which it is probably easier to send astronauts to fix the probes that break, rather than just launch new ones. It is natural to assume that this is where the probes return to offload their freshly extracted ices, and where those ices get turned into something useful. It is equally natural to assume that there will be many of these stations, each supervising a rock, or a set of rocks. It is possible that this station will actually be on the surface. This simplifies protection against radiation, if most planetoids end up having enough regolith to make Mooncrete with.

Those rocks will be fiercely protected, there might be some big fighting landers, and maybe Laserstars keeping station. They would be regularly serviced by the nearby astronauts, as station-keeping requires non-trivial amounts of fuel. Once you have reliable data from L1 telescopes (protected by friendly Laserstars?), you need to immediately launch a large expedition, before this advantage gets Killer Bussed away. Ultimately the goal is to get your astronauts to those asteroid stations, and get their astronauts out, so this expedition will be manned. It will probably consist of a big central command spacecraft with a habitat, ferries, landers, and enough delta vee to brake onto orbit. The rest of the constellation will probably include some more telescopes, maybe some Laserstars, and lots of Killer Bus. The latter will stay on hyperbolic trajectories, and impact as much of the bad guy’s stuff as possible. If they aren’t successful enough, the manned segment of the mission might be aborted. Otherwise the command spacecraft brakes onto High Badguyville Orbit, and launches astronauts to start boarding and taking over the bases. Depending on how successful this part is, their space infrastructure is taken over, and the interplanetary war is won!

[Mazon Del]

Welcome to the forums Kibble!

[EzinX]

Good stuff Kibble. I see you've read up on Spherical War Cows. One comment : wouldn't it be a good idea for the badguy pwnboat to have it's own lasers to deliver a nice hefty zap on any incoming killer buses?

[Kibble]

Welcome to the forums Kibble!

Thank you! I've actually been a lurker for awhile, and these forums are awesome.

Good stuff Kibble. I see you've read up on Spherical War Cows. One comment : wouldn't it be a good idea for the badguy pwnboat to have it's own lasers to deliver a nice hefty zap on any incoming killer buses?

Thanks - it just seemed to me like there are too few discussions of space strategy that don't assume super crazy future technologies. Re: your comment I guess that depends on how effective lasers would be against them. I'm sure most satellite components can be ruggedized against high temperature variations, and we probably won't have lasers that can actually vaporize metal until we have lots of fissioning in space (which I don't think will be for a long while). However if low-powered lasers can fry solar panels, then the Killer Bus would have to have an alternate power source, like an RTG, which IIRC can be fairly heavy, maybe even heavy enough (when you have to launch at least two plus the propulsion bus) that it defeats their main advantage over sending a Laserstar.

[Mazon Del]

The situation that you have outlined though Kibble ends up having an interesting issue. So, like I had pointed out in my post, the defender has something of an advantage against missiles in that he knows where the enemy is trying to go. Lets say the laser sats in the lagrange point that you mention have redeployable solar sails on them. Once an attack is though to be on its way (early stages), then they could open these up and start nudging themselves in random directions. Considering the distance between Earth and the lagrange points in question, this means your rocket is going to need to adjust its course to match. Now, the acceleration is likely not to be too much if its just a base solar panel, and a small size is probably what it gets if it is redeployable. That's fine! We've known for a while that laser pumped solar panels can do quite a lot of interesting things when it comes to acceleration. You can utilize the main beams from the other satellites (I am assuming you have a few in the general area) to give each other shoves in different directions that could be quite powerful (NASA conducted a microwave beam test on a small solar sail in a lab on Earth and calculated that if you scaled the system up to its likely size, it could quite easily reach full G levels of acceleration from the beam).

Meanwhile, you have some other laser sats (probably using solar sails themselves to maintain position relative to the lagrange points) that can fire their beams towards the lagrange point sats so they can 'reverse' to some extent. Of course, once the killer sats start coming in, pack up the sails, present your thinnest feature to them and hope for the best. Chances are unless you sucked at this game, you will probably survive if the incoming are unable to manage a fairly precise intercept. Clouds of shrapnel tend not to work over the ranges most likely to be experienced in space. It's one of the reasons that the US' defense missiles are kinetic impact rather than gravel slingers.

[Kibble]

Huh, laserstars pushing each other around using solar panels as sails? It would definitely save you some precious toxic explosive, meaning the Killer Bus couldn't run you out. But I imagine anything sitting precariously at a Lagrange point would wait to jink as long as possible, considering how unstable Halo and Lissajous orbits are. On debris clouds, IIRC thats how Istrebitel Sputnikov worked, and was effective up to 1 km away. I think with at least two sheep-dogging vehicles, one could rendezvous within 1 km.

I just noticed that I got rep from Nyrath - Atomic Rockets Nyrath! OmigoshOmigoshOmigosh!

Edited December 6, 2014 by Kibble
Don't wanna double-post

[OlivierRevilo]

Well, in The Expanse, it is an important topic, and they say a dreadnought would actually look like a huge building ( long and the etages vertically to the thrust vector) and they're equipped with modern projectile weapons there (railguns, coilguns and some kind of machine guns, they don't use lasers since they require too much energy

[NSEP]

I always thought spacewarfare would be from afar, because if an enemy spacecraft wants to rendezvous you and shoot you, you can just predict their trajectory in a reasonable amount of time and escape to another orbit or something to get away with them. No dogfighting without a mothership at least. Elimanting stuff from a distance is more plausible, like missles and lazers.

Thats my opinion.

[DDE]

Oi! @OlivierRevilo, you necroed a really old thread.

On a really old topic. The only two combat spacecraft ever flown looked like this:

[SuperFastJellyfish]

https://en.wikipedia.org/wiki/Almaz

Almaz (Diamond)

Quote

Defense measures

In addition to reconnaissance equipment, Almaz was equipped with a unique 23mm Rikhter (factory index 261P or 225P) rapid-fire cannon mounted on the forward belly of the station. This revolver cannon was modified from the tail-gun of the Tu-22 bomber and was capable of a theoretical rate of fire of 1800-2000 (up to 2600) rounds per minute. Each 168 gram (ammo 23-OFZ-D-R ) or 173 gram (ammo 23-OFZ-G-R) projectile flew at a speed of 850 m/s relative to the station. The cannon had a supply of 32 rounds and was tested at the end of the mission, when the station was operating in unmanned mode. To aim the cannon, which was on a fixed mounting, the entire station would be turned to face the threat.^[7] The Almaz series remain, to this day, the only armed, crewed military spacecraft ever flown.

 

Edited June 4, 2017 by SuperFastJellyfish

[Nibb31]

14 hours ago, NSEP said:

I always thought spacewarfare would be from afar, because if an enemy spacecraft wants to rendezvous you and shoot you, you can just predict their trajectory in a reasonable amount of time and escape to another orbit or something to get away with them. No dogfighting without a mothership at least. Elimanting stuff from a distance is more plausible, like missles and lazers.

Thats my opinion.

Any projectiles fired from a distance still need to rendez-vous with the target, which requires a reasonably cooperative target.

[NSEP]

15 minutes ago, Nibb31 said:

Any projectiles fired from a distance still need to rendez-vous with the target, which requires a reasonably cooperative target.

Well yeah, unless they are really fast. Like REALLY fast.

[shynung]

2 hours ago, NSEP said:

Well yeah, unless they are really fast. Like REALLY fast

You're talking about a relativistic projectile. These move at considerable fractions of light-speed, and needs large amounts of energy to throw. Nevertheless, going this route, even a small projectile can impart a considerably large kinetic energy.

[NSEP]

22 minutes ago, shynung said:

You're talking about a relativistic projectile. These move at considerable fractions of light-speed, and needs large amounts of energy to throw. Nevertheless, going this route, even a small projectile can impart a considerably large kinetic energy.

Yup. maybe solar sails with a lazer, i dont know if they are accurate enough.

[shynung]

3 minutes ago, NSEP said:

Yup. maybe solar sails with a lazer, i dont know if they are accurate enough.

To be fair, no one has built anything like that.

[NSEP]

10 minutes ago, shynung said:

To be fair, no one has built anything like that.

Yeah, thats true.

[wumpus]

18 hours ago, DDE said:

Oi! @OlivierRevilo, you necroed a really old thread.

On a really old topic. The only two combat spacecraft ever flown looked like this

The above are the only crewed combat spacecraft.  There have been plenty otherwise (for various degrees of "flown").

The V2 could achieve ~200km altitude (should qualify as spacecraft) if launched vertically but for long range use could only get 88km (not spacecraft).  No idea if any where launched from close enough to their target to break the Karman line.  There were also thousands of ICBMs deployed, but none so far has been launched armed (and presumably never tested with actual warheads).

There have been at least two successful tests of anti-satellite weapons.  I'd be shocked silly if there weren't plenty more orbiting the Earth.

[ChainiaC]

1 hour ago, NSEP said:

Yup. maybe solar sails with a lazer, i dont know if they are accurate enough.

Actually, it's a laSer. This stands for Light Amplified by Stimulated Emission of Radiation. Sorry for being pedantic

 

[NSEP]

11 minutes ago, ChainiaC said:

Actually, it's a laSer. This stands for Light Amplified by Stimulated Emission of Radiation. Sorry for being pedantic

 

Did not know that. Thanks

[Canopus]

I would recommend to check out the game "Children of a Dead Earth" on Steam, as it not only simulates Space combat but also the Spaceships and their different systems. And it allows you to create spaceships in a manner similar to KSP.

[whoshotdk]

If it's a war between nations on Earth or within the Solar System, my guess on an effective way to win that war might just be to do as the Neanderthals did - throw big rocks at each other. Unmanned probes with the ability to impart enough delta-v to an asteroid to deflect it into a collision with the opposing forces' infrastructure / cities. Man-made Tunguska events, if you like.

[wumpus]

59 minutes ago, whoshotdk said:

If it's a war between nations on Earth or within the Solar System, my guess on an effective way to win that war might just be to do as the Neanderthals did - throw big rocks at each other. Unmanned probes with the ability to impart enough delta-v to an asteroid to deflect it into a collision with the opposing forces' infrastructure / cities. Man-made Tunguska events, if you like.

Pretty much the point of Robert Heinlein's classic "The Moon is a Harsh Mistress".  At one point the targeting computer asks for a new target.  The operator asks why.  It points out that Cheyenne Mountain is now Cheyenne Plain and continued bombardment would produce Cheyenne Crater (I think this was written in the brief moment that Cheyenne Mountain was considered impervious to atomic attack).  This mainly worked because one side (The Moon) held the high ground and the Earth didn't.

The catch is that between any Earth nations (or really any two or more enemies in the same gravity well), it is quite possible that any diverted asteroid would be detected, followed by a tug-of-war where various nations try to impart enough last minute delta-v to drop the asteroid on an enemy nation (or at least not their own).  Since the delta-v to divert an asteroid to Earth >> the delta-v needed to change the location on Earth such an asteroid will land, it seems a dangerous strategy.  This would make a lot more sense for two planets (in the same solar system) attacking each other.  Also consider the issue of having a large body scheduled to collide at a later date: what do you do when your enemy surrenders?

[whoshotdk]

I love the idea of two nations playing tug-of-war 'til the last moment

However, I'm not sure how possible the detection or prevention of impending doom would be... I'm really not thinking too hard here, but if for example Combatant A found a NEO in a highly inclined orbit, currently viewable only from the southern hemisphere and heading earth/sunward; would it be a matter of taking out Combatant B's southern hemisphere telescopes and using information control and misdirection to hide it's existence from them?

Could it be also that the asteroid be given enough delta-v so that no nation on earth could possibly counteract it? I dont know. Maybe a high yield explosive would do the job when the 'roid is in its 'terminal interdiction' stage (i.e nearly here anyway). It's a totally reckless and as you say, dangerous strategy regardless and would indeed make more sense for in-system planetary bombardment. However I can imagine a world where some insane leader (I'm looking at you, Kim) has decided "enough is enough, let's end it all" and surrender in that case is simply not an option for anybody.

All this is under my assumption that we want to start flinging rocks at each other today, with chemical rockets and nuclear bombs.

 

 

All of the above is random crap from my thoughts and in no way is intended to insult, offend, coerce, patronize or indeed make any sense at all.