Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?

PhD Candidate Talks About the Physics of Space Battles 361

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."


This discussion has been archived. No new comments can be posted.

PhD Candidate Talks About the Physics of Space Battles

Comments Filter:
  • by WillAdams ( 45638 ) on Thursday December 17, 2009 @03:28PM (#30477452) Homepage

    that I've found thus far in her Merchanter / Alliance-Union books ---esp. Heavy Time / Hellburner --- though I'd be very interested in suggestions on other authors to read who've put forth a similar effort to have realistic physics and effects thereof.


  • Not much surprising (Score:5, Interesting)

    by JoshuaZ ( 1134087 ) on Thursday December 17, 2009 @03:32PM (#30477514) Homepage

    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.

  • by sznupi ( 719324 ) on Thursday December 17, 2009 @03:36PM (#30477582) Homepage

    More powerful weapons, with greater range. Any direct hit with intended kind of weapon knocks out of the action at the least. Mostly only active countermeasures are effective, unless you can exploit the environment somehow or are good at camouflage. Never stay put. One big cat & mouse game. And so on.

    The factors that shaped this will be even more pronounced in space, with the added fun of predicting position (speed of light limit). Which makes majority of SciFi depictions that more disappointing; limited in popular formats to somewhere between WW1 and WW2 state of affairs.

  • by alen ( 225700 ) on Thursday December 17, 2009 @03:37PM (#30477608)

    just like fighter pilots use energy and physics today, you'll need to use gravity in space combat. it's everywhere and if you use it properly you'll be able to maneuver faster than the other guy and probably kill him

  • Re:Video games? (Score:1, Interesting)

    by Anonymous Coward on Thursday December 17, 2009 @03:46PM (#30477762)

    Independance war games have fairly convincing space physics, most of what you describe is present, including infinite acceleration and should you turn off your stabilizers or have them damaged look out....

  • not quite (Score:4, Interesting)

    by wizardforce ( 1005805 ) on Thursday December 17, 2009 @03:50PM (#30477826) Journal

    we'll be able to tell exactly what trajectories our enemies could take between planets: the launch window.

    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.

    to point high-power radar-reflection surveillance satellites at certain empty reaches of space

    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.

    Second, there are only a few ways to maneuver the attitude of a spacecraft around – to point it in a new direction. The fast ways to do that are to fire an off-center thruster or to tilt a gyroscope around to generate a torque. Attitude maneuvers would be critical to point the main engine of a space fighter to set up for a burn, or to point the weapons systems at an enemy. Either way, concealing the attitude maneuvers of the space fighter would be important to gain a tactical advantage. So I think gyroscopes ("CMGs," in the spacecraft lingo) would be a better way to go

    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.

    A kinetic impactor is basically just a slug that goes really fast and hits the enemy fighter, tearing through the hull, damaging delicate systems with vibrations, throwing gyroscopes out of alignment so that they spin into their enclosures and explode into shards

    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.

    lets just go with a tool that we already use to cut sheet metal on Earth: lasers. In space, laser light will travel almost forever without dissipating from diffraction

    Lasers ablate material off the hull which obscures the target. Not quite the most effective weapon.

    Deflector shields like those in fiction are not possible at present, but it would still make sense to armor combat spacecraft to a limited extent.

    modified plasma window technology can function as a shield in a sense. Thick armor on the hull impedes the ship's ability to rotate.

    What do we do to hit them on the ground? Well, strategic weapons from space are easy: kinetic impactors again.

    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.

    So, I think the small fighter craft would be nearly spherical, with a single main engine and a few guns or missiles facing generally forward.

    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.

  • by Chris Burke ( 6130 ) on Thursday December 17, 2009 @03:55PM (#30477902) Homepage

    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.

  • by c6gunner ( 950153 ) on Thursday December 17, 2009 @03:57PM (#30477962)

    The problem is that reducing the profile in one direction means you have to make it larger in a different dimension. Now, that's not much of a problem when you're fighting 2D land-battles, but zero-gravity gives you the ultimate 3D battle-space. If your enemy is smart enough to put one fleet directly in front of you while having another flank from the top or bottom, all you've done is make your ships easier to hit.

    If you're looking at it purely from the perspective of presenting the smallest profile possible, your best bet would be a needle-shape. Very long, and as thin as possible. However, that runs into other problems, such as maneuverability.

  • in the war of 1812 (Score:5, Interesting)

    by circletimessquare ( 444983 ) <circletimessquare&gmail,com> on Thursday December 17, 2009 @04:01PM (#30478020) Homepage Journal

    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 []

    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)

  • Re:Video games? (Score:1, Interesting)

    by Anonymous Coward on Thursday December 17, 2009 @04:16PM (#30478278)

    Have you tried the Evochron series?

    It's an indie game made by a one-man team, but it's very impressive. Evochron uses Newtonian physics primarily, but also has an optional thrust dampening system which utilizes your thrusters to make the ship control as if there were an atmosphere.

    It's a real joy to fly the ship, but there is a bit of a learning curve.

  • by lgw ( 121541 ) on Thursday December 17, 2009 @04:24PM (#30478400) Journal

    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.

  • by Anonymous Coward on Thursday December 17, 2009 @04:29PM (#30478472)

    Joe Haldeman wrote a few books based on the idea of soldiers travelling at relativistic speeds to fight battles. IIRC, there were times when an invasion force arrived long after a treaty was signed. That kind of war sort of has to end in ripples, it seems to me.

  • by dakohli ( 1442929 ) on Thursday December 17, 2009 @04:32PM (#30478512)
    I enjoyed Hamilton's work as well, of course the ending was not satisfying at all. I suspect he just ran out of plot, and finished it up quickly.

    How about Larry Niven's "Protector" which featured dueling Bussard Ramjets if memory serves?

  • by lgw ( 121541 ) on Thursday December 17, 2009 @04:36PM (#30478566) Journal

    but aiming at something hundreds of miles away, moving at thousands of mph, the slightest vibration in the ship will send the beam several feet off course by the time it gets there. You won't be able to steadily drill a hole in the enemy ship, you'll just illuminate different parts of the hull w/o much heating or impacting any specific area.

    The Airborn Laser program has to cope with the same problem, and shoot through an atmosphere. It's not that hard once you realize that you lens doesn't have to be made of glass. When you can change your lens geometry microsecond-by-microsecond, you can easily keep the beam on target over distances as short as hundreds of miles (and ever correct for atmospheric turbulance). If you dump enouh energy into the target it won't matter much that it's spead out a little. Of course, you want your laser to deliver its energy as fast as possible, but lasers are pretty good that way.

    Or just use a nuke-pumped x-ray laser.

  • by bluecoffee ( 1702800 ) on Thursday December 17, 2009 @04:42PM (#30478664)
    wrap the thing in polystyrene and depleted uranium rods boom hypersonic kinetic energy penetrators, fuck yo armour
  • by Chris Burke ( 6130 ) on Thursday December 17, 2009 @04:59PM (#30478944) Homepage

    Wouldn't it tend to vaporize anything nearby, and melt things that are a little farther away, but still within like a mile or two?

    Well, let's think about this using the power of the maths! Let's assume a 300 kT TNT =~ 1300 TJ yield bomb (most common in our arsenal today, and bigger thermonuclear devices are probably impractical to carry into space), detonating at 1km from the target. Let's assume a normal warhead with a spherical energy dispersion pattern, and that's an energy density of 103 MJ/m^2 at the target.

    The specific heat of aluminum is 897 J/(Kg*K) according to WP, though it would change with temp I'll use that figure as a constant. The mass of 1 m^2 of aluminum hull is 27kg/cm of thickness. Assuming all the energy is absorbed as heat and that it also magically heats the hull evenly through that's 4256 K*cm. Aluminum melts at 993K. So, whatever the starting temperature of the hull, you'd need at least about 5cm thick armor to prevent it from melting all the way through.

    Now I actually have no idea how thick hulls are, but that seems pretty hefty.

  • by Rei ( 128717 ) on Thursday December 17, 2009 @05:04PM (#30479026) Homepage

    It depends on what axis of maneuverability you're talking about. A vehicle will have a low moment of inertia around its narrow axes but poor about its long axes. Of course, that's why the flak concept is so important -- to make it harder to miss. One concept that the US military threw around for a bit was launching what basically amounted to a missile full of sand/grit into orbit, esp. one counter to the Earth's rotation. You want to ensure damage -- how about being nailed by hundreds of chunks of rock moving at a relative velocity of over 15,000 meters per second? It'd render LEO inaccessible for years.

    As for your comments about making yourself more exposed in one axis while decreasing it in others, I think the author actually addressed that point well. Until we have tech that allows for virtually unlimited thrust at virtually no cost, there *will* be orientation implicit in space. You don't just go whatever direction you want in a gravity well, you still need to factor in launch windows, etc.

    On that front, I'm reminded of an old game I used to play, called VGA Planets. A very fun multiplayer game, although everyone's empires tended to become too unwieldy to manage after many turns, and players would start to drop out until there was nobody left. In the game, you built various starships (freighters, warships, crew transports, etc) and dispatched them to various star systems to colonize their planets. Your planets and starbases had long-range radar and could detect incoming ships (some being stealthier than others) -- the closer it came, the more data you could get about it. By paying attention to the ship's trajectory and velocity, you could forecast where it was likely to be in future turns, and dispatch warships for an intercept and capture. A clever countermeasure, therefore, was to not always take the optimal route between planets, but to slightly offset your angle and velocity each turn so that if someone tries to set up an ambush, you sail past it. As a counter to the countermeasure, some players would send multiple warships and spread them out along the route, since capturing an unescorted Large Deep-Space Freighter didn't exactly require a powerful fleet. And I would have fun by setting the callsign for my most powerful warships, "Large Deep-Space Freighter", hoping that people who weren't paying enough attention to what they were seeing would mistake the callsign for the ship class (it actually worked several times).

    Any way, the reality with space combat is much more boring. There's no way a Mars colony could become truly independent from Earth for many, many centuries. Try to trace back the resources needed to, say, run a CPU fab, or even a nuclear fuel cycle. Modern technology is produced from an unfathomably large web of interconnected part and resource dependencies that we have spread across the entire Earth. And future tech will be even more complicated to produce. So the reality is that if Mars wants to rebel, all Earth needs to do is cut off shipments to them and they'll slowly wither away as things break that they can't replace.

  • by earlymon ( 1116185 ) on Thursday December 17, 2009 @05:23PM (#30479364) Homepage Journal

    I read the article - despite many correctly spelled words, it is absolutely devoid of strategic or tactical thought and shows evidence that the author has no combat planning experience - and I'll go out on a limb and say that there are so many artificial constraints that I very sincerely he ever read - or understood if he did - the Art of War.

    You're a Mars Colonist. You revolt. OK - you're _expecting_ an attack. You won't wait for anything orbital from Earth - you'll pre-position killer drones - a mine field if you will - beginning at the LaGrange point between Earth and Mars and in layers anticipating the attacking fleet. Somewhere within the field - or to its edges - you'll arrange tracker-transmitters that will generate fake attack messages seemingly from Earth friendlies in an effort to steer the attackers into the mine field.

    You're an Earth administrator and you're not idiot - your agents on Mars tells you that not only is the violent revolt coming, deep space assets are being prepared to thwart your approach.

    You're a Mars propagandist - you shape public messages in order to inflame Earth, but one of your messages is seeming fuck-up, and you accidentally give away a secret regarding your strategic forces - but it's a plant to entrap Earth forces at a point besides the (kinda) mid-flight-point minefield - you're actually planning to outflank Earth.

    You're a Mars agent - you seize an Earth civilian spaceliner and announce terrorist demands. You're not Earth, so you're not evil, it's a complete distraction, so your partner agents already on Earth can try to mess up launch logistics for Earth forces while paying attention to the wrong crisis.

    And after a mile of more text like this - you can have all the space opera that the author wanted.

    Space is simply not Earth.

    TFA reads to me like Mars is supposed be some kind of Fort Apache - and I don't buy it.

  • by Rei ( 128717 ) on Thursday December 17, 2009 @05:48PM (#30479806) Homepage

    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.

  • by WarlockD ( 623872 ) on Thursday December 17, 2009 @06:05PM (#30480032)

    A decent amine called Starship Operators [] had some interesting concepts. I like the idea that the warp engines don't work inside of a sun gravity well and a majority of the weeks of travel was between the outer edge of a gravity well to the planet itself. No force fields just really good heat plating designed to reduce heat. It could be said that the whole point of these space battles was just trying to microwave the other side faster:P

    How most ships were built around a decent long range weapon designed to insta-kill the other ship once its in range. Having a complete observatory on a ship because you had to magnify visual sight so much it took very powerful telescopes. Even if you had visual sight, it takes close to 8 minutes for a plasma or projectile to hit.

    Its based off some novels that makes me really wish I could read Japanese. My main complaint about the anime is the ending. After all this time of staying fairly true to physics they seemed to just make some stuff up at the end to end the series.

    As for the plot points for the characters? Meh. Nothing I haven't seen in any other semi-political amine in space. They could of expanded the charters a bit more but in the end, they went with a short and sweet simple anime series.

  • by citizenr ( 871508 ) on Thursday December 17, 2009 @06:19PM (#30480212) Homepage
    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.
  • Atomic Rockets (Score:3, Interesting)

    by Nyrath the nearly wi ( 517243 ) on Thursday December 17, 2009 @06:48PM (#30480646) Homepage

    I have a few notes on space combat, lasers, railguns, stealth, tactics, delta v, nuclear shaped charges, ship design, and whatnot on my website. I am not a Ph.D, but many of the people who contributed are.

    Atomic Rockets (index) []

    Space War: Introduction []

    Space War: Detection []

    Space War: Weapons Intro []

    Space War: Weapons: Conventional []

    Space War: Weapons: Exotic []

    Space War: Defenses []

    Space War: Warship Design []

    Space War: Strategy and Tactics []

  • by Anonymous Coward on Friday December 18, 2009 @12:26AM (#30483544)

    My word, where to begin?

    -There is no network of telescopes dedicated to finding NEOs that approaches the equivalent of a warship's omnidirectional sensors.
    -NEOs are near the background temperature. A launched weapon will not be, for a variety of reasons.
    -Earth based sensors have to detect NEOs through thousands of meters of atmosphere. A spacecraft will not have that problem.
    -And, finally, a warship is much smaller than the Earth. The volume of space within 100 miles of a warship is microscopic in comparison to the volume within 100 miles of the Earth's surface.

    Your argument demonstrates you fail to understand the science and engineering of the matter completely.

Kill Ugly Processor Architectures - Karl Lehenbauer