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PhD Candidate Talks About the Physics of Space Battles
darthvader100 writes "Gizmodo has run an article with some predictions on what future space battles will be like. The author brings up several theories on propulsion (and orbits), weapons (explosives, kinetic and laser), and design. Sounds like the ideal shape for spaceships will be spherical, like the one in the Hitchhiker's Guide movie."
That'll be boring: round ships, round planets, round explosions, and round movie goers.
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When the future Enterprise flew at the other ship all perpendicular?! That was crazy.
The point that nukes wouldn't generally be useful is a good one. And the point that kinetic weapons would be ideal also makes sense. However, I'm not completely convinced by the emphasis on orbital mechanics. In order for that make sense, one needs space travel to be cheap enough and convenient enough that one can easily have lots of ships in space. If that's the case, one needs efficient enough propulsion systems that will make orbital mechanics not matter as much. They'll still matter probably (and certainly matter more than they do in standard scifi) but I'm not at all convinced they'll matter as much as he makes it out.
Also, he doesn't address the issue that long-range kinetic impactors can make most space combat irrelevant if they are going fast enough. There's not much Earth could do if there were large mass drivers on say Demos and Phobos sending fairly small projectiles at targets on the Moon or Earth or targeting large space installations. Again in this situation orbital mechanics would matter. But when the planets are in the correct positions, such setups would render local space combat irrelevant.
Assuming technology exists to accelerate space ships to interplanetarily practical speeds, what's to stop warring planets from accelerating an asteroid in the same way and in the direction of the enemy planet? Or take that acceleration technique and speed up some ball bearings to ridiculous speeds and send them on their way towards something with a predictable position like a space station? Hell, you could use millions of ball bearings like a mine field, because any ship traveling through the bearings will have such a high speed relative to them. I just wonder that if we currently get so butthurt about orbiting space debris, a space war will focus on simple kinetic weapons at huge speeds and from huge distances.
That assumes that there aren't technological advances that allow spacecraft to brute force the problem. Launch delays in terms of orbits mostly occur because of energy and fuel requirements. If you've got propulsion licked, you can pretty well launch when you wish.
That isn't going to work for stealth spacecraft which are a trivial engineering problem next to propulsion. Space is huge, you're going to need very very powerful sensors to find anything the size of a ship.
Correct. Burning fuel just to change the ships' direction is a waste. Utilising conservation of angualar momentum with a gyroscope is efficient and technologically feasible. Sapcecraft that are large and non-sperical are going to be very difficult to manoeuvre. Concentrating most of the ships mass in tight near the center is the way to mitigate this problem.
I don't think kinetic impactors are the way to go here. A high energy neutral particle beam is demonstrated to work effectively and doesn't spread out too much over a vast difference. (not more than a few cm over 1000 km) There is no hope of stopping it either. A few GEV beam of particles shows no mercy and can punch through several meters of shielding.
Lasers ablate material off the hull which obscures the target. Not quite the most effective weapon.
modified plasma window technology can function as a shield in a sense. Thick armor on the hull impedes the ship's ability to rotate.
Ammo is a problem. How many impactors can you have on an orbital defense platform? Just use particle beam technology to wipe out the ground force.
Only if you don't plan on re-entry as a sphere is non-optimal for utilising the effect that shaceship one was supposed to use; that is using a flat surface to force a ubble of air to pool in front of the craft and buffer against the heat.
Sigs are too short to say anything truly profound so read the above post instead.
I thought Neal Stephenson's Gap series had very good handling of space battles. Outside of lasers the weapons were pure fantasy physics, but the battle tactics that resulted from them were pretty realistic. Battles took place at distances on the order of light-minutes, such that your knowledge of the enemy ship's position was perhaps minutes old, your light-speed weaponry took minutes to reach them, and it took that much time again for you to know if you scored a hit. Defensive tactics consisted of trying to move your ship in unpredictable patterns. Ships were often cylindrical so they could have rotational gravity, but this was off for battle. Kinetic weapons existed, but were rarely used since at distances where they had a chance of hitting anything, it would have been basically like two old ships broad-siding each other only with deadly energy beams and in space.
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They said this after the American Civil War. They said this after the first world war, the war to end all wars.... War will never end. "Let him who wishes for peace prepare for war" ~ Vegetius
the peace treaty was signed in december 1814. but a major battle in the war, the one that made andrew jackson's name, took place in new orleans AFTER the peace treaty. the combatants didn't hear about the peace until february 1815
http://en.wikipedia.org/wiki/Battle_of_New_Orleans
i think we'll see a return of that in space warfare. sure the wide open vacuum of space changes everything, but so does the sheer vastness of it all. in future space battles, it wouldn't be surprising for a peace to be signed, the agreement beamed to combatants at light speed... and yet the battle still rages on for weeks, months, maybe even years. the battlefield might be lightyears away from the capitols
i don't even know if the idea of central command will work. we're used to modern tom clancy style special operations nowadays where forces engage the enemy while analysts watch them in realtime in pentagon/ cia warrooms as infrared images on massive screens, caught from spy satellites high above
but you can't do that in space
so warfare in space will deevolve from this sort of highly vertically integrated command and control aspect. you can't, for example, have a commander on earth relaying instructions to his troops on mars in real time, simply because the radio signal takes 10-20 minutes, one way (depending upon orbital locations)
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Do you mean Stephen Donaldson?
I'm reasonably familiar with Stephenson's work and do not recognize his 'Gap series'.
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There's little radiant thermal energy directly from a nuke, and even in the atmosphere where there's a lot more, a sheet of bright white posterboard would be 100% eccective as a defense. Drop and cover.
The energy directly from a nuke is mostly expresses as gamma and x-rays. These are planty damaging, but fall off with the square of distance. You'd need to get a pretty large nuke in pretty close to your target to produce more radiation than bad weather. Space this close to the Sun is harsh, radiation-wise.
So the solution is to use the energy of a nuke, but overcome the range^2 thing: nuke-pumped X-ray lasers. This is not a new idea - it's why Reagan's missile defense program was called "Star Wars". For all I know, we have this weapon in orbit already.
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Sounds like the premise of Heinlein's "The Moon Is a Harsh Mistress". Revolutionaries on the Moon take control of a mass driver and start flinging multi-ton barges at Earth, with just enough remote-control maneuvering that the shooters can call up Earth afterward and ask if they'd like to surrender.
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Those gamma and X-rays are bad news when absorbed by stuff like a spacecraft hull. The photon flux is so high that even transparent substances like air absorb ghastly amounts of those. That's the source of the atmospheric shock from a nuke, and the source of the distinctive thermal double-flash: initial infrared pulse, occluded after a few nanoseconds by the atmosphere flashing into opaque plasma, and the resuming after the shockwave begins to dissipate the opacity. Any substance more opaque than air will just immediately flash to plasma and create its own shockwave in the rest of the target.
Yes, the inverse-square law applies to the photon burst from a nuke in space, so a nuke is not the large-area weapon it is in atmosphere. But to write off the huge pulse of ionizing radiation is mistaken. A contact or near-contact nuke would hurt bad.
A perfect x-ray laser would be immune to the inverse-square law, but a perfect laser doesn't exist. Every real-world laser will have a divergence angle; that would give the beam with an inverse-square behavior with a constant coefficient based on the ratio of the divergence angle as a solid angle and the solid angle of a unit sphere (4 pi).
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That is absolutely correct. The author seems to be unfamiliar with just how devastatingly destructive nuclear weapons are in space.
First, re. the airblast: the reason nuclear weapons have an airblast on earth is that the X-rays from the explosion are so intense that they superheat every piece of atmosphere (and ground, and ocean, and so forth) around the explosion, leading to rapid expansion. So if the detonation is near the ship, the ship itself will become just as superheated as the air that turns into the airblast on Earth. More, actually, because there's nothing to get in the way of the X-rays from the explosion.
Furthermore, the lethal range of the radiation from nuclear weapons in space is tremendously large -- many hundreds, if not thousands, of miles. While a kinetic kill vehicle has to actually hit you, a nuclear explosion doesn't have to be even close. And some of it may actually turn your kinetic shielding against you -- for example, bremsstrahlung.
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Actually, nuclear weapons are likely to be far more lethal at great distance in space than in the atmosphere. The atmosphere absorbs most of the radiation from a nuclear weapon. The vacuum of space doesn't. It continues on and on, at dangerous levels for hundreds or even thousands of miles.
A ~50 megaton blast releases ~1e18 joules of energy. At 1000 miles, that's spread over 12.6 million square miles, or about 30 joules per square meter. 1 rad is 0.01 joules per kilogram, so a 100kg mass taking up 0.5 square meters would receive 15 rads. If we assume a Q factor of 5 for a nuclear weapon, that's 75 rem. That's enough to cause radiation sickness. Cut the distance in half (500 miles) and that's 300 rem -- the LD50 for humans.
The danger radius for nuclear weapons in space is *big*. Even if you add in enough shielding to reduce radiation exposure by 95%, and drop the nuclear weapon yield tenfold to 5 MT, you'd still kill over half the crew of the spacecraft from a dozen miles away. You don't really need to be even close. And radiation poisoning is not a nice way to go.
Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
As far as I know Independence War series (1 & 2) are the only PC games that implemented 100% true Newtonian physics. They took care of movement, heat issues, detection by heat and visual, whole shebang.
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