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Thread: Space combat questions

  1. #1 Space combat questions 
    Forum Masters Degree Numsgil's Avatar
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    So I'm working through a design document for a little space combat simulator/game I'm building, and I'm trying to at least base things on real world data/formulas and only fudge things later as needed. In addition to the questions I bolded, I'd appreciate any comments on things I get wrong.

    This link got me thinking about how most games don't accurately represent what actual space combat might be like, and the real thing would probably be pretty cool in its own right (maybe with some sort of speed up/slow down feature) since it relies so heavily on stealth and not being detected.

    Which brought me to thinking about how you would detect a spaceship if it's thousands to millions of kilometers away. You'd probably try and detect any anomalous EM sources that shouldn't be there. Which brings me to my first question (more of an astronomy question I realize, but the rest are more physics so bear with me): how is background radiation distributed in space? I'm assuming that the lower frequencies are pretty noisy and the higher frequencies (gamma rays) are pretty quiet, but are there any exceptions to that rule?

    Which lead me to think about how to lower your EM signature. Even if your not transmitting or blowing anything up, you still have a base temperature which means you emit EM like a black body. Which means you want to stay as cold as possible. But if your ship uses a electric propulsion method, you'd need to generate electricity, which in a scifi setting probably involves nuclear, thermonuclear, or antimatter power or something like that. Modern nuclear (and coal) power plants generate electricity through a heat engine, which uses the difference in temperature in a cooling tank and a heating tank.

    So I'm using that as a good base give and take for the spaceship. The player wants a large temperature difference between the heating and cooling tanks. Heating the heating tank too hot, though, can damage the ship, so the player needs to keep the cooling tank cool as well. Which led me to think about how you'd cool down a spaceship that gets too hot. There's no convection in space, so a spaceship would probably need to use cooling fins. Which leads me to my second question: what sort of cooling fins would a spacecraft need if it wanted to shed thermal energy? Would it look like the cooling fins on my CPU? Where it's lots and lots of parallel plates? Or is that design more dependent on convection and a different configuration would be appropriate in space? And how would the need to retract the fins (to prevent battle damage and lower the EM signature) affect the design?

    A player's ship could retract fins to temporarily reduce the intensity of the EM signature it produces, but it runs the risk of becoming more conspicuous as it gets hotter and especially when it finally deploys the fins to keep itself cool. I've got Wien's Displacement and the Stefan–Boltzmann law to give me a good starting place and relationship for how fast the ship can cool itself and what sort of EM signature it'd produce while it does.

    So next I moved to weapons. Direct energy weapons and thermonuclear missiles are the only really practical weapons at the distances involved. DEWs more for point defense and missiles for offense. A thermonuclear explosion in space wouldn't have a medium for any concussive damage except at near point blank range, so I'm assuming most of the damage would need to be inflicted from the thermal and ionizing radiation it produces. The medium used in the heat engine to transfer heat (maybe it's water) could also be used as shielding against particle radiation, but it would also heat the medium. The thermal energy from the explosion likewise would be absorbed by some cooling medium. The more energetic EM radiation is a little more problematic, but if the cooling medium is several feet thick, it too would be absorbed and turned into heat.

    All roads seem to lead to a temperature buildup, so my thinking is just to convert the thermonuclear explosion into a flux and determine the intensity per m^2 when it reaches the ship, and multiply that by the ship's exposed surface, to arrive at an energy amount to add to the ship's outer temperature. Likewise DEWs will damage a ship through the exact same method of particle and EM radiation.

    Knowing that EM and particle radiation absorption is going to be the primary method of damage, are there any methods which could be deployed to reflect incoming radiation?. For any EM radiation in the low frequency spectrum, wrapping the ship in tin foil would probably be adequate, so that's pretty easy. What about particle radiation? Alpha and beta particles are pretty easy to deflect, not to mention less effective in space since any cohesive beam would tend to disperse. What about neutron radiation? And what about a neutral particle beam (composed of hydrogen or deuterium accelerated to hundreds of megavolts)? I'm guessing if it's a NPB you couldn't reflect it and would just have to take the thermal heating. And what about energetic EM emissions? Are there any ways to reflect xray or gamma radiation? Which leads to my next question:

    Are there any limitations on building xray and gamma coherent beam weapons (lasers, but in the xray and gamma wavelengths)? I'm thinking specifically if they presently exist. And if they were to exist, what it implies about the ability for a ship to reflect the beam instead of absorbing it. My understanding of lasers is that they work using mirrors, so you'd need a material to reflect xrays or gamma rays to build xasers and grasers. Also, compared with a NPB type weapon (essentially a weapon grade particle accelerator which neutralizes the particles' charge at the end), what sort of energy efficiency would there be?

    Even if there were materials which could reflect gamma rays, it'd still make you more visible to a gamma ray type radar system, so it still balances out for gameplay either way.

    And last, are there any ways to enhance the damage from a thermonuclear explosion in space? this link talks about a "spurt" bomb which uses long rods to act as lasing mechanisms to produce more coherent gamma ray bursts. But I can't find any actual references to such a thing online. Another thought I had: could you focus the blast so instead of a sphere it produced a cone with higher flux? If not, is this just an engineering problem where we don't know of any materials strong enough, or are there other issues at work? Likewise inspired by that link, I was wondering if you could construct a scatter shot type nuclear weapon, wear the blast propels thousands of small projectiles sort of like a shotgun?

    I know this is a long post, so thanks to anyone who made it all the way through


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  3. #2 Re: Space combat questions 
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    Quote Originally Posted by Numsgil
    This link got me thinking about how most games don't accurately represent what actual space combat might be like, and the real thing would probably be pretty cool in its own right (maybe with some sort of speed up/slow down feature) since it relies so heavily on stealth and not being detected.
    I'm afraid the general consensus among people who actually know about detecting objects in space with IR telescopes (I'm not such a person, but I've read their opinions on the subject) is that it's basically impossible for a spaceship to be stealthy. If its engine is running it will stand out like a christmas tree and everyone will see it with little effort. Even it engines aren't running it's still going to be much much hotter than the background, so it would probably take only a few hours to spot it if you did a systematic scan with IR telescopes, even if it was a huge distance away. About the only way you can really hope to hide would be to keep the sun or a planet or something in front of you, but even that won't work if the enemy simply deploys multiple sensor platforms to look from different angles. So there's really no stealth - pretty much everyone who is paying attention will know where everyone else is all the time.
    Which brought me to thinking about how you would detect a spaceship if it's thousands to millions of kilometers away.
    Like I said, the consensus seem to be that you use IR telescopes to look for anything that's warmer than about 4 kelvin.
    There's no convection in space, so a spaceship would probably need to use cooling fins. Which leads me to my second question: what sort of cooling fins would a spacecraft need if it wanted to shed thermal energy? Would it look like the cooling fins on my CPU? Where it's lots and lots of parallel plates? Or is that design more dependent on convection and a different configuration would be appropriate in space? And how would the need to retract the fins (to prevent battle damage and lower the EM signature) affect the design?
    You will need large radiator fins to cool the ship. Since you can't really hide anyway, your best bet is to have the smallest possible fins that you can get away with, running as hot as possible. Retracting the fins to avoid damage is an interesting idea, but you would have limited time before your ship cooks.
    So next I moved to weapons. Direct energy weapons and thermonuclear missiles are the only really practical weapons at the distances involved. DEWs more for point defense and missiles for offense.
    I think it really depends on what sort of missile and laser technology you want your universe to have. If your lasers can easily destroy many incoming missiles before they get close enough to be a threat, missiles might be useless and ships might have to actually close into laser range to hurt each other.
    And last, are there any ways to enhance the damage from a thermonuclear explosion in space? this link talks about a "spurt" bomb which uses long rods to act as lasing mechanisms to produce more coherent gamma ray bursts. But I can't find any actual references to such a thing online.
    Google "bomb-pumped xray laser" and "Project Excalibur SDI"
    Another thought I had: could you focus the blast so instead of a sphere it produced a cone with higher flux?
    They have "lenses" in multi-state fusion weapons that focus the explosion from a fission detonator in order to better ignite a fusion explosion, but I don't have any idea what percentage of the energy they actually divert or focus.


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  4. #3 Re: Space combat questions 
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Numsgil
    This link got me thinking about how most games don't accurately represent what actual space combat might be like, and the real thing would probably be pretty cool in its own right (maybe with some sort of speed up/slow down feature) since it relies so heavily on stealth and not being detected.
    I'm afraid the general consensus among people who actually know about detecting objects in space with IR telescopes (I'm not such a person, but I've read their opinions on the subject) is that it's basically impossible for a spaceship to be stealthy. If its engine is running it will stand out like a christmas tree and everyone will see it with little effort. Even it engines aren't running it's still going to be much much hotter than the background, so it would probably take only a few hours to spot it if you did a systematic scan with IR telescopes, even if it was a huge distance away. About the only way you can really hope to hide would be to keep the sun or a planet or something in front of you, but even that won't work if the enemy simply deploys multiple sensor platforms to look from different angles. So there's really no stealth - pretty much everyone who is paying attention will know where everyone else is all the time.

    Which brought me to thinking about how you would detect a spaceship if it's thousands to millions of kilometers away.
    Like I said, the consensus seem to be that you use IR telescopes to look for anything that's warmer than about 4 kelvin.
    Sure, I'm thinking more in terms of how powerful a telescope you'd need and how long it'd take. Finding an anomalous prick of light among millions of pricks of light is not a mean feat, and would take even super computers some non-negligible time (whether it's seconds to days to months I'm not sure). Or the present method for asteroid detecting, I understand, is to look for moving pricks of light instead of trying to find one which doesn't belong. Plus, as a small ship potentially hundreds of kilometers away, your apparent magnitude would be quite dim, perhaps beneath the threshold of the telescopes the people looking for you are using.

    You're right about hiding behind planets/moons and the difficulty involved if the enemy is using sensor platforms. That's core to the gameplay, I'm thinking.

    Any links you can provide on the subject of spaceship detection would be appreciated. I'm not having much luck. If at 1 Lightsecond even a 100 Kelvin ship is immediately obvious, then stealth is pretty much out the door and I have to rethink things a bit.

    So next I moved to weapons. Direct energy weapons and thermonuclear missiles are the only really practical weapons at the distances involved. DEWs more for point defense and missiles for offense.
    I think it really depends on what sort of missile and laser technology you want your universe to have. If your lasers can easily destroy many incoming missiles before they get close enough to be a threat, missiles might be useless and ships might have to actually close into laser range to hurt each other.
    I'm being vageuly hard sci-fi about this, so I'm a point defense "laser" can eliminate maybe one warhead per second. Would have to do the math and pick some value for how much energy a missile can absorb before it's slag.

    If you're firing missiles you just need to fire a whole lot of them, maybe throw in some dummies just to make too many of them to stop. If they're thermonuclear, you don't have to actually get close for an explosion to hurt. Even thousands of kilometers would deliver a great deal of radiation (or so I've read, haven't done the math yet), which gives you a pretty big sphere for an effective target (something the size of a small planet really). In this regard it's similar to Cold War style games. You just launch as many missiles as possible and have them all arrive at the target at the same time and hope that some get through.

    And last, are there any ways to enhance the damage from a thermonuclear explosion in space? this link talks about a "spurt" bomb which uses long rods to act as lasing mechanisms to produce more coherent gamma ray bursts. But I can't find any actual references to such a thing online.
    Google "bomb-pumped xray laser" and "Project Excalibur SDI"
    Thanks, a wealth of information
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  5. #4  
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    The ISS features several radiator designs. Google images.

    Your game's okay with funless space maneuvers? No dogfighting you know. More like jousting.
    A pong by any other name is still a pong. -williampinn
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  6. #5  
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    Quote Originally Posted by Numsgil
    Sure, I'm thinking more in terms of how powerful a telescope you'd need and how long it'd take. Finding an anomalous prick of light among millions of pricks of light is not a mean feat, and would take even super computers some non-negligible time (whether it's seconds to days to months I'm not sure). Or the present method for asteroid detecting, I understand, is to look for moving pricks of light instead of trying to find one which doesn't belong. Plus, as a small ship potentially hundreds of kilometers away, your apparent magnitude would be quite dim, perhaps beneath the threshold of the telescopes the people looking for you are using.

    You're right about hiding behind planets/moons and the difficulty involved if the enemy is using sensor platforms. That's core to the gameplay, I'm thinking.

    Any links you can provide on the subject of spaceship detection would be appreciated. I'm not having much luck. If at 1 Lightsecond even a 100 Kelvin ship is immediately obvious, then stealth is pretty much out the door and I have to rethink things a bit.
    You'll definitely want to look at this page regarding stealth in space: http://www.projectrho.com/rocket/rocket3w.html

    Remember, the warships that you'll be trying to detect will be a LOT hotter than most asteroids etc, so it will be pretty easy to tell what's a ship and what's a space rock - just tell your computers to look for objects above 250 K or so. Like I said, the consensus seems to be that stealth in space is almost impossible. It makes for less interesting scifi, but that's apparently just the way it is...

    I'm being vageuly hard sci-fi about this, so I'm a point defense "laser" can eliminate maybe one warhead per second. Would have to do the math and pick some value for how much energy a missile can absorb before it's slag.
    Even in a hard scifi setting, it seems very plausible that lasers might be able to knock out missiles well enough to make missiles basically useless.

    let d=the effective range of your laser, v=the incoming velocity of the missile, t=the time it takes the computer controlling the laser to identify a target and point the laser at it, p=the power of the laser and e=the energy needed to destroy a missile.

    You can destroy (d/v)/(t+p/e) missiles before they hit your ship. If the enemy launches more than that, you lose. Now just make up any numbers you want for all those variables. If you have large values of d and p but small values for v and e, missiles are useless. Reverse it, and missiles are practically unstoppable. The nice thing here is that since you can reasonably propose almost any numbers you want for all those variables, you can create whatever balance between missiles and lasers you think would be interesting/fun.
    If you're firing missiles you just need to fire a whole lot of them, maybe throw in some dummies just to make too many of them to stop. If they're thermonuclear, you don't have to actually get close for an explosion to hurt. Even thousands of kilometers would deliver a great deal of radiation (or so I've read, haven't done the math yet), which gives you a pretty big sphere for an effective target (something the size of a small planet really). In this regard it's similar to Cold War style games. You just launch as many missiles as possible and have them all arrive at the target at the same time and hope that some get through.
    I think you're going to have to be a LOT closer than a thousand km for any damaging effects. Probably more like a few km or closer to do any interesting damage. Remember that the energy/area that the weapon will impart on a target falls off as the cube of the distance between the target and the blast, which means your damage will quickly fall to nothing as you separate the warhead from the target.

    One final thing, I think realistically combat between ships would focus very heavily on unmanned drones. Warships would probably mostly be drone carriers, and combat would probably involve ships trying to hide behind planets etc. and launching drones against each other. It would be a lot like navy carrier combat. Drones can survive accelerations that would kill people, can spread out to look for enemies from multiple angles, try to get into weapons range without exposing your big expensive ship to danger, and no one will be too sad if at the end of the combat they've burnt all their fuel and end up drifting forever on their way out of the solar system.
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  7. #6  
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    Quote Originally Posted by Pong
    The ISS features several radiator designs. Google images.

    Your game's okay with funless space maneuvers? No dogfighting you know. More like jousting.
    The best I can find on the ISS cooling system is this. As near as I can tell the thermal fins are just flat metal which can be unfurled like accordion-folded paper. I guess there isn't any fancy shape you can arrange your fins in beyond being flat.

    I don't know if the end result will be fun or not, but it should at least be different enough from most space combat games to be novel. It's an experiment.

    Quote Originally Posted by Scifor Refugee
    You'll definitely want to look at this page regarding stealth in space: http://www.projectrho.com/rocket/rocket3w.html
    Ah, that's a good link. So I guess stealth for a manned craft is out. Drone stealth might possibly be practical, at least so long as the drones don't use engines. The link you provided gives some reasonable equations I can play with.

    I'm being vageuly hard sci-fi about this, so I'm a point defense "laser" can eliminate maybe one warhead per second. Would have to do the math and pick some value for how much energy a missile can absorb before it's slag.
    Even in a hard scifi setting, it seems very plausible that lasers might be able to knock out missiles well enough to make missiles basically useless.

    let d=the effective range of your laser, v=the incoming velocity of the missile, t=the time it takes the computer controlling the laser to identify a target and point the laser at it, p=the power of the laser and e=the energy needed to destroy a missile.

    You can destroy (d/v)/(t+p/e) missiles before they hit your ship. If the enemy launches more than that, you lose. Now just make up any numbers you want for all those variables. If you have large values of d and p but small values for v and e, missiles are useless. Reverse it, and missiles are practically unstoppable. The nice thing here is that since you can reasonably propose almost any numbers you want for all those variables, you can create whatever balance between missiles and lasers you think would be interesting/fun.
    That's an interesting point. I'll mull it over. It might be that space combat ends up being like the Cold War. You have Earth, some L4/L5/Moon colonies, Mars, etc. all with a knife at each other's throat since anyone could destroy anyone else but would be immediately detected doing so. Or maybe space warefare is entirely impractical because you can blow up orders of magnitude more missiles/asteroids coming at you than you can launch.

    I think you're going to have to be a LOT closer than a thousand km for any damaging effects. Probably more like a few km or closer to do any interesting damage. Remember that the energy/area that the weapon will impart on a target falls off as the cube of the distance between the target and the blast, which means your damage will quickly fall to nothing as you separate the warhead from the target.
    Why the cube? Wouldn't it follow the inverse square law? Remember I consider the primary damage to be from the radiation the bomb emits, not from any explosive damage.

    One final thing, I think realistically combat between ships would focus very heavily on unmanned drones. Warships would probably mostly be drone carriers, and combat would probably involve ships trying to hide behind planets etc. and launching drones against each other. It would be a lot like navy carrier combat. Drones can survive accelerations that would kill people, can spread out to look for enemies from multiple angles, try to get into weapons range without exposing your big expensive ship to danger, and no one will be too sad if at the end of the combat they've burnt all their fuel and end up drifting forever on their way out of the solar system.
    Yeah, I realized that, too. My original plan was to have the players run around discretely placing sensor and weapons drones to create a net and wait until the other player is stupid enough to step into the net (creating a cascade as one drone reveals itself to attack, and another reveals itself to counter that attack, etc.). But with stealth out I'll have to rethink things.
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  8. #7  
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    That Atomic Rocket page (www.projectrho.com) is a great link for anyone interested in spaceships of any kind. There's a whole lot of really good info about a number of topics including nuclear bombs, lasers, missiles, armor, shields, heat, engines, and just about anything else you can name. If you intend to make a space game (as you've said) you should read the whole site carefully.
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  9. #8  
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    Quote Originally Posted by Numsgil
    Why the cube? Wouldn't it follow the inverse square law? Remember I consider the primary damage to be from the radiation the bomb emits, not from any explosive damage.
    Sorry, you're right of course, it's the square...don't know what I was thinking there.

    One final thing to consider regarding missiles: you can certainly try to overwhelm an enemy's point defense using lots and lots of missiles, but you can also do it by launching just one or two really fast missiles. Presumably the warships will have some amount of mass allocated to missiles. You can balance that mass between lots of missiles with relatively little fuel that will go fairly slow, or a few huge missiles with a giant amount of fuel that will be able to approach the target at ridiculous speeds. The giant, really fast missiles will be much harder for point defense to intercept (and will get their sooner, which would also be pleasant) but you won't be able to carry as many of them. I'm envisioning big ships that only carry maybe 4-8 missiles that each weigh around 100 tons, 90+tons of which is fuel, with maybe 8-10 warheads per missile. Presumably in the final stage of flight the warheads would scatter slightly and coast in around the target at very high speeds. Maybe one of two of them would be nuclear "jammers" that detonate just as the warheads come into point defense range in order to blind the enemy ship's sensors for the critical fraction of a second it takes the other warheads to reach the target.
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Numsgil
    Why the cube? Wouldn't it follow the inverse square law? Remember I consider the primary damage to be from the radiation the bomb emits, not from any explosive damage.
    Sorry, you're right of course, it's the square...don't know what I was thinking there.

    One final thing to consider regarding missiles: you can certainly try to overwhelm an enemy's point defense using lots and lots of missiles, but you can also do it by launching just one or two really fast missiles. Presumably the warships will have some amount of mass allocated to missiles. You can balance that mass between lots of missiles with relatively little fuel that will go fairly slow, or a few huge missiles with a giant amount of fuel that will be able to approach the target at ridiculous speeds. The giant, really fast missiles will be much harder for point defense to intercept (and will get their sooner, which would also be pleasant) but you won't be able to carry as many of them. I'm envisioning big ships that only carry maybe 4-8 missiles that each weigh around 100 tons, 90+tons of which is fuel, with maybe 8-10 warheads per missile. Presumably in the final stage of flight the warheads would scatter slightly and coast in around the target at very high speeds. Maybe one of two of them would be nuclear "jammers" that detonate just as the warheads come into point defense range in order to blind the enemy ship's sensors for the critical fraction of a second it takes the other warheads to reach the target.
    That's an interesting idea. I think the term used is "dazzlers" instead of jammers, though (though "dazzlers" always makes me think of a missile doing jazz hands :P)
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    How about recycling the heat into electricity? Like This Maybe?.

    As for a power source, why not make the power source integrated into the circuitry throughout the ship? That way there is no power plant to aim at in a fight, among other benefits.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Sadly, you can't just magically turn heat into electricity - you need a resovior of colder material in order to do any work. The problem in space is that there isn't any "colder material," because there basically isn't any material other that your ship.
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    Quote Originally Posted by Scifor Refugee
    Sadly, you can't just magically turn heat into electricity - you need a resovior of colder material in order to do any work. The problem in space is that there isn't any "colder material," because there basically isn't any material other that your ship.
    It does? First they turn heat into sound:

    "Each cylinder, or resonator, contains a "stack" of material with a large surface area -- such as metal or plastic plates, or fibers made of glass, cotton or steel wool -- placed between a cold heat exchanger and a hot heat exchanger.

    When heat is applied -- with matches, a blowtorch or a heating element -- the heat builds to a threshold. Then the hot, moving air produces sound at a single frequency, similar to air blown into a flute."

    Then the sound is directed at a piezoelectric device which produces electricity.

    Am I missing something?
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    I don't know how this invention works or what it does exactly, but I guarantee you that it couldn't just cool down a hot spaceship and turn the heat into electricity - that would violate the laws of thermodynamics.
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    that would violate the laws of thermodynamics
    How so? No more energy is released than is available as heat. The energy is used to create a potential difference that electrifies the spaceship. All it has to do is convert it. The energy ultimately still has to come from a generator of some sort. Are you specifically talking about entropy then? I don't understand what you are saying.
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    Quote Originally Posted by KALSTER
    that would violate the laws of thermodynamics
    How so? No more energy is released than is available as heat. The energy is used to create a potential difference that electrifies the spaceship. All it has to do is convert it. The energy ultimately still has to come from a generator of some sort. Are you specifically talking about entropy then? I don't understand what you are saying.
    Look, I don't want my thread to turn into this kind of thread. It's a law of Thermodynamics. You can't destroy heat. Heat is entropy. You can't turn it in to useful work. You can move it from high temperature to low temperature and extract useful work that way (this is called a heat engine), you can even move it from low temperature to high temperature (this is called a heat pump, though heat pumps require energy input so the net change in the universe is actually more entropy than when you started). If you found a way to extract useful work from entropy (heat), you could build a perpetual motion machine and have unlimited free energy.

    The link you provided is just a clever way of building a heat engine. It works by the gradient of waste heat moving to somewhere cooler. The point isn't that he's extracting energy from waste heat, it's that he's extracting energy from the movement of waste heat into the atmosphere, which is a potential energy source which is often ignored. In that sense he's extracting "free" energy since the waste heat would be produced anyway.

    If you still want to discuss this move it to another thread, please.
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    Quote Originally Posted by KALSTER
    How so? No more energy is released than is available as heat. The energy is used to create a potential difference that electrifies the spaceship. All it has to do is convert it. The energy ultimately still has to come from a generator of some sort. Are you specifically talking about entropy then? I don't understand what you are saying.
    It would violate the second law of thermodynamics. Check out the wikipedia page on it: http://en.wikipedia.org/wiki/Perpetu...Classification
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    Allright then Numsgil, it was not my intention to do so. That device can be used to increase efficiency at least. Final waist heat can then be irradiated away in the form of IR. Maybe one day it could be miniturized to the nanoscale to be used with carbon nano tubes. Who knows.

    Lets move on then.
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    Back to missiles. There's a point where the kinetic energy of the missile is equal to the weight of the missile in TNT. At around this point, a conventional warhead is a waste of resources. Just load the think full of anything to add the desired mass and launch it. Faster and the kinetic energy would be equivalent to turning the whole thing into a nuke. At this point even a nuclear warhead is pointless. Fast enough and the thing becomes an R-Bomb, at which point practically nothing can stop it, sense even the debris will shred your ship, not to mention the trouble of pinpointing something moving that fast. You can read more about this at that Atomic Rocket page.
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    You might also want to look at the w-71 warhead, a nuclear weapon that was actually designed to be used in space.
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    You know, the more I read and work through the math, the more I think combat spaceships will never exist. Freighters, colony ships, space stations, and even permanent mobile space arcs are all within the realm of possibility, but the role of military ship probably won't exist.

    You can't hide in space, so any combat ship will be seen coming (and if it's pulling some strong g's it could be visible as far away as the next star system). If it isn't destroyed before it manages to make it within offensive range, whatever destructive power it manages to bring along will be dwarfed by the offensive capabilities of a planet or moon or permanent space station, which don't have to worry about delta v. Likewise point defense on planet sized target can be quite extensive, even with modern technology. If the dark side of the moon were fitted with hundreds or thousands of square kilometers of modern photovoltaic cells, it could easily generate power in the gigawatts. And since weapons are going to be off most of the time, that power could be stored or even sold back to Earth so it's a highly economical investment. And it's more than enough for a comprehensive, long range laser able to blast anything in the solar system. Putting aside costs of transferring all the equipment to LEO or the Moon, you could build a solar array like that for a few billion dollars today. Well within the operating budget of a country like the US. So every space faring civilization worth its spit is going to have at least one per system. Probably more since it's such a good way to produce power. And since you have all that power handy, you might as well hook it up to a laser and a few mass drivers just in case you need them.

    So instead of combat ships I see planets and moons being the primary weapon carriers. An airless moon covered in photovoltaics can produce more than enough power to fire R-bombs and extremely powerful lasers. Earth or the Moon could easily launch an assault on any other planet in the solar system. And R bombs allow offensive capability against planets in neighboring star systems as well. You wouldn't even need any guidance systems for it, since it's pretty hard for a planet to use evasive maneuvers. And by the time they know it's on its way, it's too late.

    So combat becomes like the Cold War. Any space faring nation can obliterate pretty much any other one, but everyone will know it when something happens. Even with an R bomb, there's going to be a split second at least of warning. More than enough time for the planet being attacked to launch its own R bombs at the attacker. Mutually ensured destruction. It becomes even more stable if there are more than two nations with death rays. Ships with offensive capabilities become completely superfluous.

    Ships still need to get built to move people and goods between worlds, but none of it needs to be guarded by anything more than that death ray on the moon or in low earth orbit. At least against any full scale war. Terrorism and small scale piracy might still be possible, and require marines on those freighters and colony ships to guard against being borded, but if someone blows up a ship in space Earth is going to find out and from there it's an easy matter of tracking the attacking ship, and either blowing it up (once the attacking ship runs out of delta v from evasive maneuvers) or following where it goes and then blowing that up.

    Piracy becomes sort of an Ocean's Eleven. An elaborate heist involving deception and subterfuge instead of pistols and sword fights. You come in, steal the goods, and then flee and blend in to the regular civilian population before anyone knows what happened.
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    Quote Originally Posted by Numsgil
    You can't hide in space, so any combat ship will be seen coming (and if it's pulling some strong g's it could be visible as far away as the next star system). If it isn't destroyed before it manages to make it within offensive range, whatever destructive power it manages to bring along will be dwarfed by the offensive capabilities of a planet or moon or permanent space station, which don't have to worry about delta v. Likewise point defense on planet sized target can be quite extensive, even with modern technology.
    The problem is that your giant 5 terawatt xray laser of doom will have a limited range - if nothing else, eventually moving targets will be so many light seconds away that you can't hit them because they've moved by the time your beam reaches them. Attackers, on the other hand, can effectively attack your immobile weapons installation from infinitely far away.

    Build some really fast missiles with extremely well-insulated warheads. Launch them from a long ways away and let them coast toward the planet/moon/whatever unpowered. Before they get into range of the target's defensive weapons, have the cool warheads separate from the warm missiles. Unlike a crewed ship, your warheads won't care if you cool them down to 4 K. Paint them black and cover them in radar-absorbent materials. It's hard to imagine the target stopping many of them (let alone all of them). And if they don't hit, just sit outside the target's range and try again and again until they do - since you can move, and it can't. Or just keep shooting railguns etc at it until you hit something important. The only solution for the immobile weapons installation would be to send a ship out to stop whoever keeps shooting missiles/railguns/whatever at it.

    Likewise, you will have to worry about your weapons installations being attacked by r-bombs from other people's weapons installations. If someone launches a quartz soccer ball at your weapons platform at 99% C, you probably aren't going to be able to do anything about it (or even know about it much before it hits). You couldn't attack a ship like that so long as it was changing positions occasionally.

    So I think that a government would definitely still want mobile warships to attack other people's weapon platforms from long range, to keep other people's ships from being able to attack their own platforms from long range, and to act as a backup in case their own weapons platforms get smashed by an r-bomb.

    Edit: And of course, it's also entirely possible that there might be some sort of dispute over mining rights etc. in some unclaimed star system where no one has gotten around to building a big weapons installation yet, or where the resources in question aren't valuable enough to justify the cost of such an installation (but might be valuable enough to justify deploying a ship there for however long it takes your robo-miners to stripmine the place).
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    Quote Originally Posted by Scifor Refugee
    The problem is that your giant 5 terawatt xray laser of doom will have a limited range
    A 10^-12 wavelength death ray will have a range of upwards of 40 AU (at 40 AU the radius of the beam expands to roughly .5 meter / radius of lens). That's in the lower gamma ray range. Not strictly possible with current laser technology but nothing stopping it from logically happening. You don't even need a terrawatt laser if you have a gamma ray laser, a few gigawatts is more than sufficient for most purposes. If you make the lens larger you can use less energetic wavelengths even.

    - if nothing else, eventually moving targets will be so many light seconds away that you can't hit them because they've moved by the time your beam reaches them. Attackers, on the other hand, can effectively attack your immobile weapons installation from infinitely far away.
    Right, but all that wiggling around on the part of the attacker burns delta v, which is a precious commodity in space. Eventually they're going to either run out (even if I don't fire at you, you're stuck drifting through space forever), get close enough for me to zap you, or land somewhere. I might not be able to hit you, but I know exactly where you are. You can effectively run but not hide.

    Then I just power up my rail gun and start shooting projectiles at wherever you landed. Depending on how fast I can accelerate these ballistics they may or may not need some sort of warhead. Now a planet the size of Earth has a lot more resources than a space ship. Which means even with the added distances between target and source (allowing time for the target's own death ray to start plasma-fying the incoming ballistics), a planet is able to pump out more kill power than any starship. If the target's point defenses can't overwhelm the incoming ballistics, their planet is dead (even if it's an airless moon, the shots landing will dig up craters and throw micrometeorites around which will damage solar cells.) In this case, spaceships for the attacker aren't necessary. If the target's point defenses can stop all incoming ballistics, then it's a hopeless case for the attacker and no number of spaceships are going to help (offense potential of a planet >> offensive potential of a star fleet, even if the fleet is at point blank range).

    Build some really fast missiles with extremely well-insulated warheads. Launch them from a long ways way and let them coast toward the planet/moon/whatever unpowered. Before they get into range of the target's defensive weapons, have the cool warheads separate from the warm missiles.

    Unlike a crewed ship, your warheads won't care if you cool them down to 4 K. Paint them black and cover them in radar-absorbent materials. It's hard to imagine the target stopping many of them (let alone all of them).
    It's true that a cold ballistic won't be visible from any more than about 1000 km, but something warm has to launch them. Warm missiles = dead from my 40 AU range death ray well before you get to kill speed. Unless they use evasive maneuvers the whole way while they build up speed, and then release submunitions. But the submunitions are going to be about as warm as the main missile when they're first released, so I can track them for that split second before they cool down. After that it doesn't matter if I can see them or not, I can still fire at them, since they can't change their trajectory. But even if I can't track them, and you find some way for a hot missile to launch cold ballistics, I know where they launched from and I can just retaliate cold war style on your planet. If they didn't come from a planet, but from a ship, I just track where the ship came from and still get to retaliate. It's not about being invincible to damage, it's about being able to cause kill damage to anyone at any time. Then it moves into cold war politics and mutually assured destruction.

    And if they don't hit, just sit outside the target's range and try again and again until they do - since you can move, and it can't.
    Lasers have infinite range if I'm desperate enough. They don't have the inverse square law to worry about, just diffraction. Technology within 200 years should easily be able to manage a 40AU graser. More advanced technology should be able to produce lasers with ranges measured in light years. There isn't a way to get outside the range of the laser, and if there is, if you can produce a gamma ray laser in the gigawatts or terrawatts, you can produce a mass driver on that same moon with infinite range and a kill capacity far in excess of anything a meager ship can produce.

    Likewise, you will have to worry about your weapons installations being attacked by r-bombs from other people's weapons installations. If someone launches a quartz soccer ball at your weapons platform at 99% C, you probably aren't going to be able to do anything about it (or even know about it much before it hits). You couldn't attack a ship like that so long as it was changing positions occasionally.
    It's only a 0 warning weapon at point blank range. At 100 lightsecond distance, I get about 100 ms warning. More than enough time for an automated retaliation system to deal with things. Plus your ship has to get close enough, which means I know it's coming and I blast it out of the sky. The farther you try to launch, the more response time I get to retaliate against your home world. The closer you try to launch, the less likely you are to get close enough without me killing you.

    Even if the ship can kill me, I know where it came from, even if it's from another star system. Planets can't evasively maneuver. And you can bet if your space ship can fire a quartz soccer ball at .99 c, I can fire a quartz mountain at .99999c from my planet. There won't be a crater on your home world. It'll just be a new asteroid belt.

    So I think that a government would definitely still want mobile warships to attack other people's weapon platforms from long range, to keep other people's ships from being able to attack their own platforms from long range, and to act as a backup in case their own weapons platforms get smashed by an r-bom
    Mobile ships, no. But multiple death rays on different moons or Lagrange points probably makes sense. The problem really is the delta v necessary for a combat ship to be reasonable. You'll have to constantly maneuver so an enemy laser mounted on a planet or moon can't hit you. And even then, the enemy might just expand the laser to a cross section large enough so you can't escape if you're within some predefined range (maybe a few AUs). It'll take forever for a kill, but you won't be able to escape. And for the ship to be anything more than a pea shooter compared to a planet its mass is going to be absolutely insane. Probably a small moon in its own right. The amount of reaction mass it'd have to carry along will likewise boggle the mind.

    A ship just doesn't make sense in an arena with no stealth. It's not like Earth, there's no such thing as a horizon. Any planet can pretty much destroy any other. Mobility is useful to avoid getting hit, but its prohibitively expensive to keep up long enough to approach another planet.
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    Quote Originally Posted by Numsgil
    Right, but all that wiggling around on the part of the attacker burns delta v, which is a precious commodity in space. Eventually they're going to either run out (even if I don't fire at you, you're stuck drifting through space forever), get close enough for me to zap you, or land somewhere. I might not be able to hit you, but I know exactly where you are. You can effectively run but not hide.
    Come on now. 40 AU is over 5.5 light hours. I don't need to constantly maneuver to avoid your gamma ray cannon, I just need to make a very tiny course alteration a few times a day. It will take 11 hours for you to see where I am, fire, and have your beam reach me. Just 1 m/sec delta v - which is going to be nothing for a space warship that presumably needs many thousands of m/sec of delta v just to get anywhere - will put me out of position by over 40 km by the time your beam reaches me. I could sit 40 au away making a 1 m/sec course change every 11 hours for a year and it would only use about 1.5 km/sec worth of fuel.
    It's true that a cold ballistic won't be visible from any more than about 1000 km, but something warm has to launch them. Warm missiles = dead from my 40 AU range death ray well before you get to kill speed. Unless they use evasive maneuvers the whole way while they build up speed, and then release submunitions.
    If my missiles take an hour to burn through their fuel and release their submunitions, then from 40 AU away they will have been done with their burn for 4.5 hours by the time you even see them, and any weapons you fire won't arrive on target for another 5.5 hours. You are almost certainly not going to be able to formulate a firing solution accurate enough to hit a cold, no longer visible target a few meters across from a distance of 40 AU by analyzing the trajectory data you can collect regarding the missiles' path before their engines shut down and the warheads scatter. Especially since you don't know at what point the warheads were released. Suppose since I'm 5.5 light hours away, I set my missiles to a 5.5 hour burn time with constant maneuvering. You don't even know when in those 5.5 hours I released my warheads. Maybe they all scattered at 5.49 hours, maybe I released one every half hour...you don't know. How are you ever going to hit them?
    But the submunitions are going to be about as warm as the main missile when they're first released, so I can track them for that split second before they cool down.
    You'll note that I said well-insulated warheads. Assuming futuristic insulation technology, there's no thermodynamic reason why you couldn't cool down a warhead, wrap it in insulation, stick it in a warm missile, and have it emerge cool later on. There would surely be some non-zero amount of heat that would leak through, but at 40 AU you're not going to be able to see something a few meters across that's only 10 or 15K. By the time they get closer, they will be even cooler. Of course this will require fantastically advanced insulating material, but I don't know if that's necessarily any more far-fetched than big fusion engines that can move ships around from one planet to another at .1G the entire way.
    After that it doesn't matter if I can see them or not, I can still fire at them, since they can't change their trajectory.
    Even with hypothetical futuristic tracking technology, it seems very implausible that you would be able to hit a target that small at that kind of distance. Like I said, even a 1 m/sec inaccuracy in your tracking data - which is nothing for a target that was probably moving at many hundreds of thousands or millions of km/sec - will throw your shot off by 40 km at a distance of 40 AU. And the uncertainty will only get worse as more time passes and any errors in your tracking are magnified. I suppose you might get a few of them, but certainly not all.

    Lasers have infinite range if I'm desperate enough. They don't have the inverse square law to worry about, just diffraction. Technology within 200 years should easily be able to manage a 40AU graser. More advanced technology should be able to produce lasers with ranges measured in light years.
    So have your story (or game, or whatever) set before the point where civilizations develop lasers that can fry things from lightyears away. Just because it's theoretically possible doesn't mean that people must have figured out how to do it in your fictional universe. And in any case, if my ship isn't comfortable being 40 AU from your planet, I can always just move out to 50 AU or 100 AU. Every time i move farther out it's just a bit more fuel that I have to burn, while for you it means a major engineering challenge to figure out how to double the accuracy of your graser cannon.

    It's only a 0 warning weapon at point blank range. At 100 lightsecond distance, I get about 100 ms warning. More than enough time for an automated retaliation system to deal with things.
    Is it? Even if you vaporize it with a laser or something, the cloud of plasma will still have the same mass, and it will still be moving toward your planet with about the same kinetic energy. It will probably disperse a bit, but I doubt that 100 ms would be enough time for it to disperse enough to matter. I'm not sure that 100 kg of plasma hitting you at .99C is all that better than 100 kg of quartz hitting you at .99C.

    I guess it depends a lot on exactly what sort of setting you're imagining. Are you envisioning a game set in the solar system with pretty much every planet and moon heavily colonized? Or are you imagining a few dozen industrialized star systems and hundreds of others that are "up for grabs"? If there are large areas that no one has claimed and where no one has built any giant planetary defense systems, ships could still be very useful. Or perhaps there are huge corporations that are in intense competition with each other and sometimes blow up each other's stuff, but the planetary governments don't care (and so won't employ their planet-based death rays or r-bomb launcher) so long as the corporations keep everything out on the rim where the fighting won't bother anyone.
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    Quote Originally Posted by Scifor Refugee
    Come on now. 40 AU is over 5.5 light hours. I don't need to constantly maneuver to avoid your gamma ray cannon, I just need to make a very tiny course alteration a few times a day. It will take 11 hours for you to see where I am, fire, and have your beam reach me. Just 1 m/sec delta v - which is going to be nothing for a space warship that presumably needs many thousands of m/sec of delta v just to get anywhere - will put me out of position by over 40 km by the time your beam reaches me. I could sit 40 au away making a 1 m/sec course change every 11 hours for a year and it would only use about 1.5 km/sec worth of fuel.
    But it doesn't cost me anything not to fire my death ray. You'd have to stay constantly moving that whole time, because as soon as you stop I'll know about it. Moreover, I'll know when you're going to run out because I can calculate your mass.

    Plus, 1.5 km/sec is actually quite a bit of fuel. On par with traveling from one planet to another (orbit to orbit). And the whole time you're doing it I know exactly where you are, so you can't hide anywhere. Eventually you're going to run out. So your only hope is to be able to destroy me before you run out. If you can't, your dead. If you can, I know I'm going to die, so instead I just destroy your immobile home, wherever it is. Mars or Ganymede or Alpha Centauri. Distance isn't a big factor in space. It just means you get to live a little longer before you realize you're dead.

    If my missiles take an hour to burn through their fuel and release their submunitions, then from 40 AU away they will have been done with their burn for 4.5 hours by the time you even see them, and any weapons you fire won't arrive on target for another 5.5 hours. You are almost certainly not going to be able to formulate a firing solution accurate enough to hit a cold, no longer visible target a few meters across from a distance of 40 AU by analyzing the trajectory data you can collect regarding the missiles' path before their engines shut down and the warheads scatter.
    Once you turn off the engines your trajectory is locked. Doesn't matter if I still can or can't see it, I know where it has to be. All it takes is knowing the velocity at some moment in time. Even if that moment is 1 ns after the submunitions are launched. After that I can calculate its entire trajectory. So either: a) you can fire your cold submunititions in such a way that I can't determine their trajectory (even here, I know you're probably aiming at me, so I can do a pretty good guess) or b) the missiles will reach me before I can calculate the trajectories and react (effectively unlikely with anything less than an R bomb). And also, if your just cold releasing the submunitions it's going to change the mass of your ship. I'll know something is up the next time your fire your engines, since your mass will have changed. And since I didn't see any munitions firing away, I know those munitions have the velocity that your ship did before it fired.

    And again, if you can launch missiles and I can't stop it, I just aim at your home and take it out as retribution. I don't really care about your ship.

    Especially since you don't know at what point the warheads were released. Suppose since I'm 5.5 light hours away, I set my missiles to a 5.5 hour burn time with constant maneuvering. You don't even know when in those 5.5 hours I released my warheads. Maybe they all scattered at 5.49 hours, maybe I released one every half hour...you don't know. How are you ever going to hit them?
    But I do know all possible trajectories of a released warhead, since once you release them they form a ballistic trajectory. And assuming they aren't R bombs, I'll have at least days to fire my death ray at every possible trajectory a warhead might have taken. Probably more like weeks or months.

    You'll note that I said well-insulated warheads. Assuming futuristic insulation technology, there's no thermodynamic reason why you couldn't cool down a warhead, wrap it in insulation, stick it in a warm missile, and have it emerge cool later on. There would surely be some non-zero amount of heat that would leak through, but at 40 AU you're not going to be able to see something a few meters across that's only 10 or 15K. By the time they get closer, they will be even cooler. Of course this will require fantastically advanced insulating material, but I don't know if that's necessarily any more far-fetched than big fusion engines that can move ships around from one planet to another at .1G the entire way.
    Sure, I'll concede that it's possible. I might not be able to defend against that. But I can still retaliate, which is the important point. I know who decided to kill me, and I have enough time to retaliate.

    Even with hypothetical futuristic tracking technology, it seems very implausible that you would be able to hit a target that small at that kind of distance. Like I said, even a 1 m/sec inaccuracy in your tracking data - which is nothing for a target that was probably moving at many hundreds of thousands or millions of km/sec - will throw your shot off by 40 km at a distance of 40 AU. And the uncertainty will only get worse as more time passes and any errors in your tracking are magnified. I suppose you might get a few of them, but certainly not all.
    For the record, light speed is 300,000 km/sec. If your missile is capable of more than a few thousand km/sec, it becomes an R bomb, which is pretty much unstoppable anyway.

    And present technology is actually pretty able to calculate the motions of asteroids and the like. I think, especially with military funding, I'd be very able to calculate your trajectory accurately enough to aim a laser at it.

    So have your story (or game, or whatever) set before the point where civilizations develop lasers that can fry things from lightyears away. Just because it's theoretically possible doesn't mean that people must have figured out how to do it in your fictional universe. And in any case, if my ship isn't comfortable being 40 AU from your planet, I can always just move out to 50 AU or 100 AU. Every time i move farther out it's just a bit more fuel that I have to burn, while for you it means a major engineering challenge to figure out how to double the accuracy of your graser cannon.
    Well it depends where the ship is coming from. If Mars is at war with Earth, they have no chance to even launch the ship, I'll just fry Mars. More to the point, Earth is never going to allow Mars to develop offensive capabilities. If there's even a hint that Mars is thinking about building its own weapons, we blow up Mars. Same goes for pretty much any planet or moon in the solar system. As soon as there's a hint of someone doing something fishy, we destroy them (whether with a laser or a missile or whatever). Doesn't even need to be advanced technology, since we'll have years before they can actually build anything. The only way this scenario becomes possible is if there's a civil war and some death rays end up on different sides. But then there's no need to launch ships, warfare is just a matter of pointing the lasers at each other.

    If the ship is coming from Alpha Centauri, I'm going to be able to see it launch. You can't build up to a reasonable speed without it being a searchlight visible for potentially dozens or hundreds of light years. I'll know a ship is coming towards Sol, I'll know its mass, and I'll know its path. You couldn't possibly hope to keep up a delta v evasion across a distance of light years. So on Earth I just decide to launch a bunch of my missiles at your ship. Doesn't even have to be anything special, just a few mines designed to create a defensive cloud that your ship has to pass through. At the speeds your ship is traveling at it'll destroy it.

    And if you can manage faster speeds, so I have less warning, then there isn't any point for a ship at all. If you can make your ship go at 25% the speed of light, just aim it at Earth. You've created an R bomb. No need for it to carry anything like a crew or submunitions.

    It's only a 0 warning weapon at point blank range. At 100 lightsecond distance, I get about 100 ms warning. More than enough time for an automated retaliation system to deal with things.
    Is it? Even if you vaporize it with a laser or something, the cloud of plasma will still have the same mass, and it will still be moving toward your planet with about the same kinetic energy. It will probably disperse a bit, but I doubt that 100 ms would be enough time for it to disperse enough to matter. I'm not sure that 100 kg of plasma hitting you at .99C is all that better than 100 kg of quartz hitting you at .99C.
    You misunderstand. I'm not aiming at the R bomb. I'm aiming at where it came from. I'm dead. I know that. But you're dead, too, because I have a similar capability. Again, it's a cold war situation. You can kill me, and I can kill you. Doesn't matter if you fire from a ship or your planet, I know where to aim. Since a ship is expensive but doesn't improve your destructive or defensive capability, there's no reason to have one.

    I guess it depends a lot on exactly what sort of setting you're imagining. Are you envisioning a game set in the solar system with pretty much every planet and moon heavily colonized? Or are you imagining a few dozen industrialized star systems and hundreds of others that are "up for grabs"? If there are large areas that no one has claimed and where no one has built any giant planetary defense systems, ships could still be very useful.
    Well, let's say that only the Moon has a death ray installed. And you're a small star fleet wanting to attack the colony on Titan that has no offensive or defensive capabilities. Earth is going to see your ships approaching Titan, and know that you aren't authorized to do that. They won't be able to get a target lock on you because you're doing evasive maneuvers, but they'll know where you came from. Maybe that colony on Ganymede. Well, Titan is under the protection of Earth (it'd be stupid not to be), so goodbye Ganymede. Or maybe your not from anywhere at all, and you decide to conquer Titan (a roving alien fleet or some such). Once it's obvious what's going on, Earth might decide just to wait until you set down nice and cozy on Titan and then blam, no more Titan.

    So inside the Sol system at least, large scale military endeavors are impossible. The best you can hope for is activities like light piracy or terrorism, which fall more under law enforcement than military operations. And the trick here is not to advertise that you're a pirate or terrorist. Which means no ship mounted weapons.

    Or maybe proxy wars like with Korea, Vietnam, and Soviet era Afghanistan, where lots of ground troops are involved. Maybe there's a war on Titan between corporate and settler interests. They both want Titan, so neither are going to use any large scale weaponry. It's going to be rifles and tanks and airplanes. Your going to have ships transporting those goods to Titan for the ground war. Maybe they build some laser satellites in orbit to fry the other guys transports, so you could maybe end up with some small scale warfare between satellites. But if it gets too hot, Earth comes in and forces a disarmament. Or it just says to hell with it and blows it up. Earth's X Billion people >> Titan's X million people. Earth won't hesitate. Or more likely it'll just give support to one side and force the other to surrender (ala Palestine vs Israel with US backing).

    Or perhaps there are huge corporations that are in intense competition with each other and sometimes blow up each other's stuff, but the planetary governments don't care (and so won't employ their planet-based death rays or r-bomb launcher) so long as the corporations keep everything out on the rim where the fighting won't bother anyone.
    This is more likely, but then you get involved with clandestine operations. If either corporation's fleet starts to look too dangerous for Earth, Earth decides to blow up the fleet and/or the corporation. There's a reason CocaCola Co. doesn't have tanks. Blowing up a starbase isn't going to involve combat ships. It's going to involve one guy, an alarm clock, and a suitcase nuke. The potential for fullscale war will never be allowed to develop, because it becomes too dangerous for the inner planets. More likely corporate war is what it is now: hostile stock takeover. With an enforced pax across the entire solar system, more subtle forms of conflict flourish. You use lawyers instead of battleships.
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    Okay, several things that I want to clear up. First of all, I am quite aware that if you know the position and velocity of an object, you can calculate the exact position of that object at any point in the future. But I don't think it's plausible that you could track the position and velocity of a missile from 40 AU away well enough to hit it with a beam weapon after it burns out. As I said, my missile will be going many hundreds of thousands or million of meters per second (yes, the km/sec in my last post was a typo, I meant that to be m/sec). Of course you will be able to try watch it as its engine burns and calculate where to aim your beam weapon so that it will hit my ballistic warheads in 5.5 hours - but if your estimate of my velocity is off by even 1 m/sec, your beam will be tens of km off target. Heck, if you're off by just 1 cm/sec you will still miss by hundreds of meters. And your uncertainty about the position of my warheads will only get worse as time passes. Of course in addition to tracking technology, how often you can fire your gamma ray cannon and how many you have will also play a big role. If you can fire it continuously and you have 100 of them, you might be able to very quickly systematically "paint" an area of the sky and overcome the uncertainty about my warhead's position. If you only have one cannon and you can only fire it for 5 seconds once every minute, it will be much more difficult for you.

    Now, if you want your game to be set in a future universe were missiles (and warships in general) are useless because tracking technology allows people monitor the velocity of an object 40 AU away to less than a cm/sec and/or where powerful gamma ray cannons are cheap and plentiful and can fire continuously, that's fine. But it's also perfectly reasonable to set your game in a universe where there is a few cm/sec in uncertainly when tracking an object going 3000 km/sec 40 AU away, and where gamma ray cannons that can hit things 40 AU away are giant, incredibly expensive devices that taxpayers don't want to buy very many of - and it would allow you to have interesting interactions between warships and planetary fortifications.
    You misunderstand. I'm not aiming at the R bomb. I'm aiming at where it came from. I'm dead. I know that. But you're dead, too, because I have a similar capability.
    And what, exactly, are you going to retaliate with? If I'm going to carry out an r-bomb attack, I will surely try to destroyed all of your own r-bomb launch sites in my first strike. Which would be easy, because they can't move. You might not be able to figure out where the bombs were coming from and carry out a launch in the very brief moments before the bombs hit. It seems perfectly reasonable that the launchers might need some seconds or minutes (or hours, who knows?) to carry out a launch. In order to preserve your second-strike ability, you will need some sort of mobile launch platforms that's can't be easily targeted by r-bombs. Ie, warships.
    More to the point, Earth is never going to allow Mars to develop offensive capabilities. If there's even a hint that Mars is thinking about building its own weapons, we blow up Mars. Same goes for pretty much any planet or moon in the solar system. As soon as there's a hint of someone doing something fishy, we destroy them (whether with a laser or a missile or whatever). Doesn't even need to be advanced technology, since we'll have years before they can actually build anything.
    Umm...if that's the way you want your fictional universe to be, fine. But there's no reason why Earth would have to be so ruthless and bloody-minded. Maybe the people of Earth wouldn't support genocidal first strikes against colonies that aren't current threats. Maybe Mars and Ceres both demand independence 100 years after they are founded, and Earth agrees. Then 50 years after independence, the people on Mars say that the people on Ceres are jerks and claim that they need deathrays and r-bomb of their own to protect themselves. It's perfectly reasonable that Earth wouldn't be willing to launch a preemptive attack on them just because they don't want other people having such weapons. How many countries have developed nuclear weapons without the U.S. launching preemptive nuclear strikes on them?

    And of course, this assumes that r-bombs are even a factor. You don't have to include them in your universe; just say that people haven't come up with technology to accelerate things to large fractions of the speed of light. That substantially reduces the "I'll kill you if you do anything I don't like" factor.
    So inside the Sol system at least, large scale military endeavors are impossible. The best you can hope for is activities like light piracy or terrorism, which fall more under law enforcement than military operations.
    Why do you assume that Earth will care? Maybe Earth is pissed at Titan over something, and they think it will teach all the other minor colonies a lesson if they let Titan get taken over. Maybe no one has a colony on Titan right now, and both Mars and Ceres want to build a colony there. They're willing to fight over who gets it, but Earth isn't willing to get involved because it has good relations with both, or bad relations with both, or they just don't care...
    This is more likely, but then you get involved with clandestine operations. If either corporation's fleet starts to look too dangerous for Earth, Earth decides to blow up the fleet and/or the corporation. There's a reason CocaCola Co. doesn't have tanks. Blowing up a starbase isn't going to involve combat ships. It's going to involve one guy, an alarm clock, and a suitcase nuke. The potential for fullscale war will never be allowed to develop, because it becomes too dangerous for the inner planets. More likely corporate war is what it is now: hostile stock takeover. With an enforced pax across the entire solar system, more subtle forms of conflict flourish. You use lawyers instead of battleships.
    It's almost like now you're going out of your way to come up with reasons why ship-to-ship combat couldn't happen. Why do you assume this? Maybe the planetary government are too corrupt/afraid of the corporations/whatever to interfere, and so the corporations are allowed to do whatever they want short of actually killing innocent (non-corporate) people or destroying government property? Or maybe the governments don't care what the corporations do so long as they keep it more than 10 AU away from any planets.

    The point I'm trying to make here is that there are plenty of perfectly plausible technological and political situations where you can have combat between ships. You don't have to have r-bombs or 40 AU gamma ray lasers or sensors that can track object light hours away with cm/sec accuracy - a fictional universe without such things would be quite reasonable.
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    Quote Originally Posted by Scifor Refugee
    But I don't think it's plausible that you could track the position and velocity of a missile from 40 AU away well enough to hit it with a beam weapon after it burns out. As I said, my missile will be going many hundreds of thousands or million of meters per second (yes, the km/sec in my last post was a typo, I meant that to be m/sec). Of course you will be able to try watch it as its engine burns and calculate where to aim your beam weapon so that it will hit my ballistic warheads in 5.5 hours - but if your estimate of my velocity is off by even 1 m/sec, your beam will be tens of km off target. Heck, if you're off by just 1 cm/sec you will still miss by hundreds of meters. And your uncertainty about the position of my warheads will only get worse as time passes. Of course in addition to tracking technology, how often you can fire your gamma ray cannon and how many you have will also play a big role. If you can fire it continuously and you have 100 of them, you might be able to very quickly systematically "paint" an area of the sky and overcome the uncertainty about my warhead's position. If you only have one cannon and you can only fire it for 5 seconds once every minute, it will be much more difficult for you.
    I'll admit I don't have any good metrics for guessing at tracking ability. But if high accuracy tracking is possible, it seems far more likely that a planet will be able to guard against a mobile spaceship's missiles than that a spaceship (or ships) could launch enough ordnance to take out a planet. If high tracking isn't possible with the given technology, it does make missiles more attractive, but you'll want to launch your missiles as far away from the target planet as possible to maximize the tracking error. Which puts your missile launchers somewhere near your planet, again making mobile weapon launchers unnecessary.

    Now, if you want your game to be set in a future universe were missiles (and warships in general) are useless because tracking technology allows people monitor the velocity of an object 40 AU away to less than a cm/sec and/or where powerful gamma ray cannons are cheap and plentiful and can fire continuously, that's fine. But it's also perfectly reasonable to set your game in a universe where there is a few cm/sec in uncertainly when tracking an object going 3000 km/sec 40 AU away, and where gamma ray cannons that can hit things 40 AU away are giant, incredibly expensive devices that taxpayers don't want to buy very many of - and it would allow you to have interesting interactions between warships and planetary fortifications.
    I might build some sort of RTS with warships and planetary lasers and just set up some tweakable parameters and see under what circumstances the ability to wiggle outweighs the lower battle potential. But I think the limitations of rocket propulsion are going to make it untenable under all circumstances. The harder the science involved, the less attractive ships become for war as near as I can see.

    And what, exactly, are you going to retaliate with? If I'm going to carry out an r-bomb attack, I will surely try to destroyed all of your own r-bomb launch sites in my first strike. Which would be easy, because they can't move. You might not be able to figure out where the bombs were coming from and carry out a launch in the very brief moments before the bombs hit. It seems perfectly reasonable that the launchers might need some seconds or minutes (or hours, who knows?) to carry out a launch. In order to preserve your second-strike ability, you will need some sort of mobile launch platforms that's can't be easily targeted by r-bombs. Ie, warships.
    It depends how close you can launch the bombs. If I'm paranoid and have been blowing up every single planet within 100 Lightyears, your going to end up launching the missiles from far enough away to give me long enough warning to power up and shoot my own. There's a radius where if you launch outside it I know where you come from and you're dead, and if you launch inside it I'm dead before I can react. So it's in my best interests to be damn sure nothing gets inside that radius that has the power to blow me up. With decent telescopes I know every single ship that comes within 100 LY of Earth. And I'll decide on some arbitrary line (say, 102 LY) which represents my territorial boundaries. If any ship comes within that boundary, I blow up whatever planet it comes from. Again, war ships are mostly superfluous.

    The only way a ship might work is if you're willing to wage war on a timescale of thousands or millions of years. Then you could launch lots of ships at slow speed and maybe get within range. But that's thousands and millions of years for your target to notice you, not to mention the technological improvements in telescopes during that time. And there's no guarantee that a hot Armageddon war won't happen in the mean time.

    Now, if for whatever reason there's a planet inside my die zone which has the ability to destroy me before I can retaliate, well, that's a prisoners dilemma. Game theory says one will strike first, sooner rather than later. No ships necessary here, either.

    More to the point, Earth is never going to allow Mars to develop offensive capabilities. If there's even a hint that Mars is thinking about building its own weapons, we blow up Mars. Same goes for pretty much any planet or moon in the solar system. As soon as there's a hint of someone doing something fishy, we destroy them (whether with a laser or a missile or whatever). Doesn't even need to be advanced technology, since we'll have years before they can actually build anything.
    Umm...if that's the way you want your fictional universe to be, fine. But there's no reason why Earth would have to be so ruthless and bloody-minded. Maybe the people of Earth wouldn't support genocidal first strikes against colonies that aren't current threats. Maybe Mars and Ceres both demand independence 100 years after they are founded, and Earth agrees. Then 50 years after independence, the people on Mars say that the people on Ceres are jerks and claim that they need deathrays and r-bomb of their own to protect themselves. It's perfectly reasonable that Earth wouldn't be willing to launch a preemptive attack on them just because they don't want other people having such weapons. How many countries have developed nuclear weapons without the U.S. launching preemptive nuclear strikes on them?
    That's actually a good place to look. Weapons of mass destruction. The US doesn't mind weapons like this in countries it considers strong allies (France, Great Britain, Israel), or countries without the offensive capabilities to bring those weapons to US soil (South Korea). But the US is more than willing to go to war to destroy a country it thinks is actively working toward such weapons, has a motive to use them against Americans, and has (or is developing) the ability to bring those weapons to US soil.

    So in your scenario, if Mars is friends with Earth, Earth might install that death laser. But they're going to be very careful to have a failsafe to prevent its use on Earth. And Earth is going to be sure that it always has the upper hand. And if Ceres tries to develop a death ray, it means war. You don't want the smoking gun to be a mushroom cloud after all

    If Mars decides some day it doesn't like Earth... And has something like an R bomb so second strike capability doesn't exist... Well, maybe then mobile weapons platforms become viable. But they'd be expensive. You couldn't hide them, you'd just have to keep them in space doing defensive maneuvers for ever and ever. Constantly refuel them with more reaction mass every couple weeks. But they wouldn't really need to travel anywhere. Just wiggle at random.

    And of course, this assumes that r-bombs are even a factor. You don't have to include them in your universe; just say that people haven't come up with technology to accelerate things to large fractions of the speed of light. That substantially reduces the "I'll kill you if you do anything I don't like" factor.
    Even without R bombs you can still easily kill another planet you don't like. We have the offensive capability on Earth today to pretty much destroy the (usability) of the planet several times over. At the end of the day the truth is that if you can reach space, you can blow up a planet. There's too much overlap in the technology.

    So inside the Sol system at least, large scale military endeavors are impossible. The best you can hope for is activities like light piracy or terrorism, which fall more under law enforcement than military operations.
    Why do you assume that Earth will care? Maybe Earth is pissed at Titan over something, and they think it will teach all the other minor colonies a lesson if they let Titan get taken over. Maybe no one has a colony on Titan right now, and both Mars and Ceres want to build a colony there. They're willing to fight over who gets it, but Earth isn't willing to get involved because it has good relations with both, or bad relations with both, or they just don't care...
    If you're within the kill range of Earth, you're within Earth's jurisdiction, and you have to go by what ever rules Earth sets for the conflict. Because Earth doesn't want to get the war too hot they'll probably invent some rules to war which limit the possible damage either side can do. Sort of like the "don't use machine guns against infantry" rule of modern warfare. In this case, it's possible war ships might be practical. But then, anything is practical. Earth gets to decide (explicitly or not) the rules of warfare, which by definition are distorting the natural methods. They could decide that victory is determined by a football match. If a side doesn't like it, tough. You can't rebel against Earth.

    This is more likely, but then you get involved with clandestine operations. If either corporation's fleet starts to look too dangerous for Earth, Earth decides to blow up the fleet and/or the corporation. There's a reason CocaCola Co. doesn't have tanks. Blowing up a starbase isn't going to involve combat ships. It's going to involve one guy, an alarm clock, and a suitcase nuke. The potential for fullscale war will never be allowed to develop, because it becomes too dangerous for the inner planets. More likely corporate war is what it is now: hostile stock takeover. With an enforced pax across the entire solar system, more subtle forms of conflict flourish. You use lawyers instead of battleships.
    It's almost like now you're going out of your way to come up with reasons why ship-to-ship combat couldn't happen. Why do you assume this? Maybe the planetary government are too corrupt/afraid of the corporations/whatever to interfere, and so the corporations are allowed to do whatever they want sort of actually killing innocent (non-corporate) people or destroying government property? Or maybe the governments don't care what the corporations do so long as they keep it more than 10 AU away from any planets.
    Well, it's sort of the whole point for my last several posts, and I didn't want to get too far away from that position and end up debating for arguments sake.

    Anyway, as I said above, Earth can decide on all sorts of rules for engagement, which might make warships useful or not, but it's not the natural state of actual war. If the corporations have the capability to blow up Earth, then they're really the ones in charge and so they'll spend time to make sure Earth doesn't pose a threat. If you're within a star system, there's going to be someone with pure destructive capabilities who gets to call the shots. Either there's a stand off because one guy is in charge, or there are several in charge each with the offensive capability to kill each other, or everyone's defensive capabilities are too great to be killed by anyone. You end up with an uneasy peace in all situations. And if war is declared, there's no reason to dink around with ships, at least in the conventional sense. You just kill each other directly.

    The point I'm trying to make here is that there are plenty of perfectly plausible technological and political situations where you can have combat between ships. You don't have to have r-bombs or 40 AU gamma ray lasers or sensors that can track object light hours away with cm/sec accuracy - a fictional universe without such things would be quite reasonable.
    Possibly there are situations, but I think they're in the minority. If you can get into space, you can destroy yours or anyone else's planets. Think about our own planet. We haven't had a full scale war since World War 2. ICMBs make it just too deadly for both sides. Instead we dick around with infantry and tanks and the like, when pretty much a dozen thermonukes would cripple just about any country on Earth. There's either going to be a single superpower controlling everything (like present day with the US), two large blocs in a cold war, or multiple blocs carefully balanced to prevent anyone from destroying anyone else. You end up with a mostly enforced peace, allowing only relatively small scale warfare for minor strategic positions.

    So in the end if my goal is to build a game around a hard scifi version of future space combat (which it is), most plausible situations seem to suggest a shipless, low stakes battlefield. If there are ships, it's done for ritualistic combat. And the loser of a war doesn't lose much (maybe mining rights to an asteroid or something along those lines), so no one has an incentive to scale it up to full Armageddon.
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    Quote Originally Posted by Numsgil
    I'll admit I don't have any good metrics for guessing at tracking ability. But if high accuracy tracking is possible, it seems far more likely that a planet will be able to guard against a mobile spaceship's missiles than that a spaceship (or ships) could launch enough ordnance to take out a planet. If high tracking isn't possible with the given technology, it does make missiles more attractive, but you'll want to launch your missiles as far away from the target planet as possible to maximize the tracking error. Which puts your missile launchers somewhere near your planet, again making mobile weapon launchers unnecessary.
    Ships can get even farther away than your planet. If I'm on Mars and I want to threaten Ceres, I can move my launchers out past Pluto if I feel like it - much better than launching from Mars.

    I might build some sort of RTS with warships and planetary lasers and just set up some tweakable parameters and see under what circumstances the ability to wiggle outweighs the lower battle potential. But I think the limitations of rocket propulsion are going to make it untenable under all circumstances. The harder the science involved, the less attractive ships become for war as near as I can see.
    Only if you assume that the defenders will have fantastically advanced low-wavelength weapons. There is absolutely nothing that's "soft" about setting your game before such weapons are developed. Such weapons are certainly physically possible, but they're probably right up there with things like efficient, high-thrust fusion engines in terms of how close we are to actually being able to build one. If you're going to simulate it, put it up against a ship with an efficient fusion engine that gets 5000 km/sec + in exhaust velocity. Have a ship with such an engine that's half fuel by mass, and you get over 8000 km/sec delta V to dance around with. That's about three solid months of constant 1 m/sec maneuvering. I suspect that you will have a very hard time hitting it.

    Now sure, if you're going to have your 40 AU gamma ray laser going up against ships with low-tech nuclear thermal engines or something, then yeah, the ships won't stand a chance. But I think that's only because you're assuming a huge disparity in beam weapon technology vs. engine technology.

    It depends how close you can launch the bombs. If I'm paranoid and have been blowing up every single planet within 100 Lightyears, your going to end up launching the missiles from far enough away to give me long enough warning to power up and shoot my own.
    See, there you go again. Like I said, it seems like now you're trying to only come up with scenarios that disallow ships. Why do you assume that one side has been blowing up everything within 100 lightyears? What if Earth and Mars both have great relations for a long time, then they gradually go bad and things get more and more tense until both sides have lots of guns pointed at each other? You would need a second-strike capability, and there's your chance for warships.

    The only way a ship might work is if you're willing to wage war on a timescale of thousands or millions of years.
    Or if you have planets populated by people who aren't willing to launch preemptive extermination attacks against anyone whose ship wanders too close, which seems a lot more likely.
    Now, if for whatever reason there's a planet inside my die zone which has the ability to destroy me before I can retaliate, well, that's a prisoners dilemma. Game theory says one will strike first, sooner rather than later. No ships necessary here, either.
    Uh, what? If the other side has ships then you can't strike, because you won't be able to knock out all their weapons in a single attack.
    That's actually a good place to look. Weapons of mass destruction. The US doesn't mind weapons like this in countries it considers strong allies (France, Great Britain, Israel), or countries without the offensive capabilities to bring those weapons to US soil (South Korea). But the US is more than willing to go to war to destroy a country it thinks is actively working toward such weapons, has a motive to use them against Americans, and has (or is developing) the ability to bring those weapons to US soil.
    Yeah, right. Get back to me when the U.S. gets around to launching a preemptive nuclear strike against North Korea or Iran. And do you really think that the U.S. would have been willing to launch an all-out nuclear attack on Iraq if an invasion hadn't been possible? I very much doubt it. If one planet had r-bombs or death rays and knew that another planet was developing/building them, they would most likely bitch and moan and maybe try to arrange sanctions or something, not launch a preemptive attack of their own. Assuming the planet isn't controlled by a murderous dictator or fanatic.
    So in your scenario, if Mars is friends with Earth, Earth might install that death laser. But they're going to be very careful to have a failsafe to prevent its use on Earth. And Earth is going to be sure that it always has the upper hand. And if Ceres tries to develop a death ray, it means war. You don't want the smoking gun to be a mushroom cloud after all
    Perhaps Mars builds their own death ray and politely declines your offer for help with its construction. Your choices are either 1) attack an ally who only wants to have the same sort of weapons you have or 2) let them build it and be unhappy about it. So you let them build it. Perhaps 50 years later relations will go bad, and crap, now they have that big deathray on Phobos.
    If Mars decides some day it doesn't like Earth... And has something like an R bomb so second strike capability doesn't exist... Well, maybe then mobile weapons platforms become viable. But they'd be expensive. You couldn't hide them, you'd just have to keep them in space doing defensive maneuvers for ever and ever. Constantly refuel them with more reaction mass every couple weeks. But they wouldn't really need to travel anywhere. Just wiggle at random.
    No, you want to move them very far away, so that you only have to occasionally make a tiny course correction. Refuel every few weeks? Like I said earlier, a warship with a fusion engine might have many thousands of delta v worth of fuel. If you move a few tens of AU out, you will only need to tweak your course by a few m/sec ever few hours to make yourself unhittable. Unless some of the other guy's warships start to move uncomfortable close, in which case you might decide to move to a different part of the solar system. Or maybe I'll stand your ground and have a nice tense few weeks/months/whatever while your ships stare at each other from 10000 km apart.
    Anyway, as I said above, Earth can decide on all sorts of rules for engagement, which might make warships useful or not, but it's not the natural state of actual war.
    Actually I could easily see this pushing things TOWARD ships, just not for war with Earth. Perhaps Earth would tell the outer colonies "Do whatever the hell you want, but keep it outside Mars orbit and don't build any r-bombs or death rays, or we'll smash you." Now all the outer colonies have no choice but to build ships to fight each other, because Earth won't tolerate anything heftier.
    If the corporations have the capability to blow up Earth, then they're really the ones in charge and so they'll spend time to make sure Earth doesn't pose a threat.
    I wasn't suggesting that the corporations could destroy the earth (then who would they sell to?) I was suggesting that perhaps the earth will tolerate corporations fighting each other with war ships so long as they keep it "way out there".
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    Quote Originally Posted by Scifor Refugee
    Ships can get even farther away than your planet. If I'm on Mars and I want to threaten Ceres, I can move my launchers out past Pluto if I feel like it - much better than launching from Mars.
    Hmm, yeah, I can see your point there.

    See, there you go again. Like I said, it seems like now you're trying to only come up with scenarios that disallow ships. Why do you assume that one side has been blowing up everything within 100 lightyears? What if Earth and Mars both have great relations for a long time, then they gradually go bad and things get more and more tense until both sides have lots of guns pointed at each other? You would need a second-strike capability, and there's your chance for warships.
    Yeah, if you're talking a civil war situation, things get more dicey, and ships could be useful. Especially if it's a gradual decline. But the weird thing here is that if you're building star ships, it's to get away from your target, instead of getting closer. To preserve your second strike ability. That's... an even more interesting scenario.

    The only way a ship might work is if you're willing to wage war on a timescale of thousands or millions of years.
    Or if you have planets populated by people who aren't willing to launch preemptive extermination attacks against anyone whose ship wanders too close, which seems a lot more likely.
    A certain amount of paranoia is healthy when extinction is the consequence of failure. I subscribe to a more pessimistic view of alien (and human) psychology. Nice guys finish last. What's likely to happen is that people will feel bad afterward about that whole blew up the alien race thing, but it'll still have happened. They'll feel better 200 years later when they learn that it really was an attack cruiser with planet kill technology. :P

    Uh, what? If the other side has ships then you can't strike, because you won't be able to knock out all their weapons in a single attack.
    Yeah, if they have ships a long way off, they can preserve their second strike ability. I hadn't thought of that.

    Yeah, right. Get back to me when the U.S. gets around to launching a preemptive nuclear strike against North Korea or Iran. And do you really think that the U.S. would have been willing to launch an all-out nuclear attack on Iraq if an invasion hadn't been possible? I very much doubt it. If one planet had r-bombs or death rays and knew that another planet was developing/building them, they would most likely bitch and moan and maybe try to arrange sanctions or something, not launch a preemptive attack of their own. Assuming the planet isn't controlled by a murderous dictator or fanatic.
    A full scale attack probably not, but a small scale invasion would be likely. It's not necessary to totally obliterate the enemy if they don't have the ability yet to obliterate you, I suppose. They may or may not even trump up some other reasons and fake the war (a sort of yellow journalism).

    As for modern politics, North Korea is a special case because it's really a satellite of China (and China already has nuclear capability, so the US doesn't really gain anything by pushing the subject), but if it looks like Iran is building up to a nuclear arsenal (not just thinking about it, but in progress), you can bet there'll be more than just sanctions.

    Perhaps Mars builds their own death ray and politely declines your offer for help with its construction. Your choices are either 1) attack an ally who only wants to have the same sort of weapons you have or 2) let them build it and be unhappy about it. So you let them build it. Perhaps 50 years later relations will go bad, and crap, now they have that big deathray on Phobos.
    It obviously depends a bit on the political climate of the day. Either way, you can bet there'll be proponents on both sides of the debate. And a great deal of work to make sure, if nothing else, Earth has second strike capability.

    No, you want to move them very far away, so that you only have to occasionally make a tiny course correction. Refuel every few weeks? Like I said earlier, a warship with a fusion engine might have many thousands of delta v worth of fuel. If you move a few tens of AU out, you will only need to tweak your course by a few m/sec ever few hours to make yourself unhittable. Unless some of the other guy's warships start to move uncomfortable close, in which case you might decide to move to a different part of the solar system. Or maybe I'll stand your ground and have a nice tense few weeks/months/whatever while your ships stare at each other from 10000 km apart.
    Hmm, yes, I hadn't considered that possibility. That's definitely a decent role for a mobile space ship. Not sure if you'd have ship to ship combat or not... There's a lot of space 40 AU out.

    I wasn't suggesting that the corporations could destroy the earth (then who would they sell to?) I was suggesting that perhaps the earth will tolerate corporations fighting each other with war ships so long as they keep it "way out there".
    That's the problem with combat in space, though. There really isn't a "way out there". Even modest technology can reach pretty much everywhere in a system. But yeah, limits on energies involved per ship and things like that could keep Earth safe enough to tolerate that sort of thing.
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    The problem is, acting as a second-strike platform wouldn't make for that interesting of a game. You would probably just go pretty far away and wait for a long time, making minor course alterations while you wait to see if you get the orders to launch this month. If the other guy sends a ship out to follow you around, it would be pretty awkward. How do you know he doesn't have orders to blast you at some prearranged time, taking out your world's second strike ability? But on the other hand, you probably can't just preemptively vaporize him when a war isn't actually going on. You might do some high-g maneuvers and see who has more delta-v to burn. I imagine it would be much like nuclear missile subs and hunter-killer subs.

    I suppose it's always possible that a war could brake out with neither side willing to pull the trigger on full-scale destruction, so you might get orders saying "Assume all Titan ships hostile, destroy if possible, do not launch at this time."
    A certain amount of paranoia is healthy when extinction is the consequence of failure. I subscribe to a more pessimistic view of alien (and human) psychology. Nice guys finish last. What's likely to happen is that people will feel bad afterward about that whole blew up the alien race thing, but it'll still have happened. They'll feel better 200 years later when they learn that it really was an attack cruiser with planet kill technology.
    There's something to that logic, but it's also possible that you will be needlessly pissing off some aliens who would have been friendly, turning them into dangerous enemies. Or that some third race would observe the event and conclude that you were too war-like to be allowed to continue to exist so close by. It's pretty impossible to know what the "best" option would be in terms of ensuring human safety.
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    Quote Originally Posted by Numsgil
    Quote Originally Posted by Pong
    The ISS features several radiator designs. Google images.

    Your game's okay with funless space maneuvers? No dogfighting you know. More like jousting.
    The best I can find on the ISS cooling system is this. As near as I can tell the thermal fins are just flat metal which can be unfurled like accordion-folded paper. I guess there isn't any fancy shape you can arrange your fins in beyond being flat.

    I don't know if the end result will be fun or not, but it should at least be different enough from most space combat games to be novel. It's an experiment.

    Quote Originally Posted by Scifor Refugee
    You'll definitely want to look at this page regarding stealth in space: http://www.projectrho.com/rocket/rocket3w.html
    Ah, that's a good link. So I guess stealth for a manned craft is out. Drone stealth might possibly be practical, at least so long as the drones don't use engines. The link you provided gives some reasonable equations I can play with.
    No.

    Everyone is forgetting one important fact about space: you're not in an atmosphere!!!!

    Only the surface directly facing the detector (IR telescope) matters. If you use a heat pump to cool that surface, then the surfaces behind it can be as hot as you want and the IR telescope won't see them.

    So, you set up a wall between your ship and the telescope, and cool that wall.



    I'm being vageuly hard sci-fi about this, so I'm a point defense "laser" can eliminate maybe one warhead per second. Would have to do the math and pick some value for how much energy a missile can absorb before it's slag.
    Even in a hard scifi setting, it seems very plausible that lasers might be able to knock out missiles well enough to make missiles basically useless.

    let d=the effective range of your laser, v=the incoming velocity of the missile, t=the time it takes the computer controlling the laser to identify a target and point the laser at it, p=the power of the laser and e=the energy needed to destroy a missile.

    You can destroy (d/v)/(t+p/e) missiles before they hit your ship. If the enemy launches more than that, you lose. Now just make up any numbers you want for all those variables. If you have large values of d and p but small values for v and e, missiles are useless. Reverse it, and missiles are practically unstoppable. The nice thing here is that since you can reasonably propose almost any numbers you want for all those variables, you can create whatever balance between missiles and lasers you think would be interesting/fun.
    That's an interesting point. I'll mull it over. It might be that space combat ends up being like the Cold War. You have Earth, some L4/L5/Moon colonies, Mars, etc. all with a knife at each other's throat since anyone could destroy anyone else but would be immediately detected doing so. Or maybe space warefare is entirely impractical because you can blow up orders of magnitude more missiles/asteroids coming at you than you can launch.

    This was actually part of what got discussed in 1969 when they first proposed a Ballistic Missile Defense System. All the enemy has to do is launch more missiles than you're prepared to stop.

    Their plan was to use nukes against nukes, so you'd probably want to use missiles against missiles.

    Remember what I said about covering their heat signature, though. You can't cover a heat signature on Earth because the heat radiates into the nearby air, and the hot air is detectable.

    In space, however, only the heat radiated by the surface facing your opponent's detector matters. If the surfaces hiding behind that surface are hot, it doesn't matter, because the detector can't see them.



    I think you're going to have to be a LOT closer than a thousand km for any damaging effects. Probably more like a few km or closer to do any interesting damage. Remember that the energy/area that the weapon will impart on a target falls off as the cube of the distance between the target and the blast, which means your damage will quickly fall to nothing as you separate the warhead from the target.
    Why the cube? Wouldn't it follow the inverse square law? Remember I consider the primary damage to be from the radiation the bomb emits, not from any explosive damage.
    Don't ignore the value of projectile damage.

    In space, even a tiny little ion accelerator that increases your speed by 10 kmph every ten minutes can be deadly, if you let the object accelerate long enough.

    You want to take out a Mars colony? Drop a meteor on it. Just attach some rocket boosters to an asteroid, and steer it into a collision course.

    As for nukes: See if you can make them like Claymores or fragmentation grenades. The damage from a projectile propelled by the blast doesn't diminish with distance (because you're in space so it's going just as fast if it hits you at 10 miles as it would be if it hit you at 2 feet.) However, the odds of getting hit by any given projectile from the blast drop off as the inverse of the square of the distance. If a person is too far away, then probably all the shrapnel misses. If they're close, they might get hit by more than one piece.


    One final thing, I think realistically combat between ships would focus very heavily on unmanned drones. Warships would probably mostly be drone carriers, and combat would probably involve ships trying to hide behind planets etc. and launching drones against each other. It would be a lot like navy carrier combat. Drones can survive accelerations that would kill people, can spread out to look for enemies from multiple angles, try to get into weapons range without exposing your big expensive ship to danger, and no one will be too sad if at the end of the combat they've burnt all their fuel and end up drifting forever on their way out of the solar system.
    Yeah, I realized that, too. My original plan was to have the players run around discretely placing sensor and weapons drones to create a net and wait until the other player is stupid enough to step into the net (creating a cascade as one drone reveals itself to attack, and another reveals itself to counter that attack, etc.). But with stealth out I'll have to rethink things.
    Well, stealth is in. Just remember that you can only be stealthy from one direction at a time.


    Quote Originally Posted by KALSTER
    Quote Originally Posted by Scifor Refugee
    Sadly, you can't just magically turn heat into electricity - you need a resovior of colder material in order to do any work. The problem in space is that there isn't any "colder material," because there basically isn't any material other that your ship.
    It does? First they turn heat into sound:

    "Each cylinder, or resonator, contains a "stack" of material with a large surface area -- such as metal or plastic plates, or fibers made of glass, cotton or steel wool -- placed between a cold heat exchanger and a hot heat exchanger.

    When heat is applied -- with matches, a blowtorch or a heating element -- the heat builds to a threshold. Then the hot, moving air produces sound at a single frequency, similar to air blown into a flute."

    Then the sound is directed at a piezoelectric device which produces electricity.

    Am I missing something?


    I think you might be on to something. In space, a resonating object has nowhere to transfer its momentum to, so it should just stay resonating for a long time until internal forces of friction (from inside the resonating material) cause the sound to be converted into heat.

    However, the other poster is also right. Heat only works when you have cold (something comparatively colder nearby). What you're missing is that the (initially cool) air has to come from somewhere. On Earth, it exists in a virtually unlimited supply. In space, you'd have to bring it with you.
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    And a note on missiles: You only need to fire the rocket booster to maneuver.
    Otherwise you could just let it coast.

    The best way would be to use something to throw it initially, like a rail gun, and then only fire the rocket booster when its really close to its target (for course correction to make sure you hit).

    In this sense, basically all missiles have unlimited range.
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    Quote Originally Posted by kojax
    No.

    Everyone is forgetting one important fact about space: you're not in an atmosphere!!!!
    I suspect everyone is aware of this...
    Only the surface directly facing the detector (IR telescope) matters. If you use a heat pump to cool that surface, then the surfaces behind it can be as hot as you want and the IR telescope won't see them.

    So, you set up a wall between your ship and the telescope, and cool that wall.
    Your heat pump will only have a net result of making the entire ship even hotter. You're going to be producing a lot of waste heat that you need to get rid of, which means really big radiators. You could theoretically have a "cold side" that was facing one way and a "hot side" that was radiating all your waste heat away in the other direction, but there are many problems. For one thing, if the enemy has more than one telescope and so can look for you from multiple angles, they will still see you. Ships will probably have sensor drones, planets will have multiple telescopes in high orbits. Remember that you need a lot of surface area for the radiators, and you will quickly run into geometry problems trying to design a shield/radiator scheme that gives the radiator enough surface area without exposing some of the radiator surface to anyone looking at an angle of more than a few degrees normal to the "cold shield".

    You want to take out a Mars colony? Drop a meteor on it. Just attach some rocket boosters to an asteroid, and steer it into a collision course.
    The people on Mars will surely see what you are doing and send ships/missiles/whatever out to stop you, or retaliate by lunching missiles against you. Of course you could always cover the asteroid with defensive weapons and whatnot to make it hard for them to divert, but you had better be sure that your own defenses are up to the task of protecting you when they launch every single missile they have at your planet in retaliation.
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    Read this whole article. It really goes through all the arguments you can make about stealth in space, including projecting the heat away in a narrow cone. The only way I see stealth working is if you can magically transport an unmanned drone to some position in space. You could keep it running (maybe as a weapons platform) with minimal juice and keep it at a few Kelvin, and it wouldn't be detectable any closer than a few thousand km.

    Of course, any way of getting it there in the first place is going to alert everyone and their dog of what's going on.
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    Quote Originally Posted by Scifor Refugee
    The problem is, acting as a second-strike platform wouldn't make for that interesting of a game. You would probably just go pretty far away and wait for a long time, making minor course alterations while you wait to see if you get the orders to launch this month. If the other guy sends a ship out to follow you around, it would be pretty awkward. How do you know he doesn't have orders to blast you at some prearranged time, taking out your world's second strike ability? But on the other hand, you probably can't just preemptively vaporize him when a war isn't actually going on. You might do some high-g maneuvers and see who has more delta-v to burn. I imagine it would be much like nuclear missile subs and hunter-killer subs.

    I suppose it's always possible that a war could brake out with neither side willing to pull the trigger on full-scale destruction, so you might get orders saying "Assume all Titan ships hostile, destroy if possible, do not launch at this time."
    Realistically they'd probably be unmanned drones anyway. In a game, it'd either look something like Defcon in space, or you'd concentrate on the politics. Or maybe a game centered around a covert ops squad in that sort of world. Actual ships would be pretty boring, yeah :/

    There's something to that logic, but it's also possible that you will be needlessly pissing off some aliens who would have been friendly, turning them into dangerous enemies. Or that some third race would observe the event and conclude that you were too war-like to be allowed to continue to exist so close by. It's pretty impossible to know what the "best" option would be in terms of ensuring human safety.
    Yeah, it'd be a dilemma. I guess you could always figure if the enemy wanted you dead, they wouldn't have sent a ship.
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    Quote Originally Posted by Numsgil
    Yeah, it'd be a dilemma. I guess you could always figure if the enemy wanted you dead, they wouldn't have sent a ship.
    Actually that might be another good reason to have warships. It would be nice if you could send someone out to meet an unknown ship that was approaching your star system to look the newcomer over and ask "So, uh...who are you and what are you planning to do?" Although I guess you don't technically need a warship for that, since you could always just send out a civilian ship to make contact and wait to see whether or not the newcomer vaporizes it.

    Edit:
    Although the more I think about it, the more it seems like the best way to have "interesting" warships that aren't just second-strike platforms without resorting to somewhat contrived political situations (corporations fighting each other, etc.) would be to have a small number of heavily-industrialized star systems that were in competition for a large number of nearby star systems. You wouldn't want your enemies to get too well-established on in a new system, so when you see them launching a ship toward another star you will probably launch one of your own to intercept them. That way when the ships meet each other the entire system won't already be littered with sensor platforms and huge, long-range lasers. Maybe the side that gets there first will have a little colony or mining installation or something set up, but it would mostly be your ship vs. my ship.
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by kojax
    No.

    Everyone is forgetting one important fact about space: you're not in an atmosphere!!!!
    I suspect everyone is aware of this...
    Only the surface directly facing the detector (IR telescope) matters. If you use a heat pump to cool that surface, then the surfaces behind it can be as hot as you want and the IR telescope won't see them.

    So, you set up a wall between your ship and the telescope, and cool that wall.
    Your heat pump will only have a net result of making the entire ship even hotter. You're going to be producing a lot of waste heat that you need to get rid of, which means really big radiators. You could theoretically have a "cold side" that was facing one way and a "hot side" that was radiating all your waste heat away in the other direction, but there are many problems. For one thing, if the enemy has more than one telescope and so can look for you from multiple angles, they will still see you. Ships will probably have sensor drones, planets will have multiple telescopes in high orbits. Remember that you need a lot of surface area for the radiators, and you will quickly run into geometry problems trying to design a shield/radiator scheme that gives the radiator enough surface area without exposing some of the radiator surface to anyone looking at an angle of more than a few degrees normal to the "cold shield".
    True. This is the limit of your stealth. You're only ever invisible from one side. From the other side, you're twice as visible (or more). You can't enclose your whole ship in cold walls, because you must emit heat toward somewhere.

    The strategy in space would center more on seeing than hiding. The idea is to see them before they see you. Then, once you know where they are, you can hide from them.

    You can close off just the areas of space where you know your enemy to be at, leaving yourself exposed from all other angles..... and just hope you didn't miss spotting one of their drones.

    In real life war games strategy, it isn't much different. The key to ninja-ing is knowing where every possible observer is, and how to elude them.



    You want to take out a Mars colony? Drop a meteor on it. Just attach some rocket boosters to an asteroid, and steer it into a collision course.
    The people on Mars will surely see what you are doing and send ships/missiles/whatever out to stop you, or retaliate by lunching missiles against you. Of course you could always cover the asteroid with defensive weapons and whatnot to make it hard for them to divert, but you had better be sure that your own defenses are up to the task of protecting you when they launch every single missile they have at your planet in retaliation.
    Cover the asteroid in light opaque flat surfaces. They'll have a hard time spotting it. (Flat surfaces is how stealth fighter planes are stealthy, radar beams bounce off at angles that don't return to the radar antenna)

    One key is to launch the attack from behind a planet, and use the planet's gravity to turn its course. The "gravitational slingshot" is how Nasa gets its satellites into the outer edges of the solar system. They bring the satellite's trajectory close enough to a planet that it can dip into its gravity pool and get launched further out into space. (Of course, for that to work, you've got to plan your attack months, maybe even years, ahead of time).
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Numsgil
    Yeah, it'd be a dilemma. I guess you could always figure if the enemy wanted you dead, they wouldn't have sent a ship.
    Actually that might be another good reason to have warships. It would be nice if you could send someone out to meet an unknown ship that was approaching your star system to look the newcomer over and ask "So, uh...who are you and what are you planning to do?" Although I guess you don't technically need a warship for that, since you could always just send out a civilian ship to make contact and wait to see whether or not the newcomer vaporizes it.
    Yeah, you'd probably only want a civilian ship in that role. Don't want to end up with a mild misunderstanding. Worst case scenario you know they're hostile and you've lost only a single ship.

    Edit:
    Although the more I think about it, the more it seems like the best way to have "interesting" warships that aren't just second-strike platforms without resorting to somewhat contrived political situations (corporations fighting each other, etc.) would be to have a small number of heavily-industrialized star systems that were in competition for a large number of nearby star systems. You wouldn't want your enemies to get too well-established on in a new system, so when you see them launching a ship toward another star you will probably launch one of your own to intercept them. That way when the ships meet each other the entire system won't already be littered with sensor platforms and huge, long-range lasers. Maybe the side that gets there first will have a little colony or mining installation or something set up, but it would mostly be your ship vs. my ship.
    It depends on what your interception is trying to achieve. If it's "blow up their colony and everything around it", you probably just use a few guided missiles or something like that. If the objectives are more complex, I could see sending some manned ships out.
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    Quote Originally Posted by kojax
    True. This is the limit of your stealth. You're only ever invisible from one side. From the other side, you're twice as visible (or more). You can't enclose your whole ship in cold walls, because you must emit heat toward somewhere.

    The strategy in space would center more on seeing than hiding. The idea is to see them before they see you. Then, once you know where they are, you can hide from them.

    You can close off just the areas of space where you know your enemy to be at, leaving yourself exposed from all other angles..... and just hope you didn't miss spotting one of their drones.

    In real life war games strategy, it isn't much different. The key to ninja-ing is knowing where every possible observer is, and how to elude them.
    Again, that link earlier talks about all this. Quoting:

    Dr. John Schilling had some more bad news for would be stealthers trying to radiate the heat from the side facing away from the enemy.

    Besides, redirecting the emissions merely relocates the problem. The energy's got to go somewhere, and for a fairly modest investment in picket ships or sensor drones, the enemy can pretty much block you from safely radiating to any significant portion of the sky.

    And if you try to focus the emissions into some very narrow cone you know to be safe, you run into the problem that the radiator area for a given power is inversely proportional to the fraction of the sky illuminated. With proportionate increase in both the heat leakage through the back surfaces, and the signature to active or semi-active (reflected sunlight) sensors.

    Plus, there's the problem of how you know what a safe direction to radiate is in the first place. You seem to be simultaneously arguing for stealthy spaceships and complete knowledge of the position of enemy sensor platforms. If stealth works, you can't expect to know where the enemy has all of his sensors, so you can't know what is a safe direction to radiate. Which means you can't expect to achieve practical stealth using that mechanism in the first place.

    Sixty degrees has been suggested here as a reasonably "narrow" cone to hide one's emissions in. As a sixty-degree cone is roughly one-tenth of a full sphere, a couple dozen pickets or drones are enough to cover the full sky so that there is no safe direction to radiate even if you know where they all are. The possiblility of hidden sensor platforms, and especially hidden, moving sensor platforms, is just icing on the cake.

    Note, in particular, that a moving sensor platform doesn't have to be within your emission cone at any specific time to detect you, it just has to pass through that cone at some time during the course of the pre-battle maneuvering. Which rather substantially increases the probability of detection even for very narrow emission cones.

    (Somebody suggested using a continuous blinding barrage of nearby nuclear detonations in order to hide thrusting)

    The timescale of the radiant emission from a nuclear detonation in vacuum is measured in milliseconds. The recovery time of a good CCD array is measured in microseconds. You'll need to detonate nuclear explosives at a hundred hertz, minimum, to cover an accelerating ship. That's going to get expensive.

    It also rather clearly indicates where the enemy should start looking...

    Ken Burnside said:

    The problem with directional radiation is that you have to know both where the enemy sensor platforms are, and you have to have a way of slowing down to match orbits that isn't the equivalent of swinging end for end and lighting up the torch. Furthermore, directing your waste heat (and making some part of your ship colder, a related phenomena) requires more power for the heat pump - and every W of power generated generates 4 W of waste heat. It gets into the Red Queen's Race very quickly.

    Imagine your radiators as being sheets of paper sticking edge out from the hull of your ship. You radiate from the flat sides. If you know exactly where the enemy sensors are, you can try and put your radiators edge on to them, and will "hide". You want your radiators to be 180 degrees apart so they're not radiating into each other.

    Most configurations that radiate only to a part of the sky will be vastly inefficient because they radiate into each other. Which means they get larger and more massive, which reduces engine performance...and they still require that you know where the sensor is.

    The next logical step is to make a sunshade that blocks your radiation from the sensor. This also requires knowing where the sensor is, and generates problems if the sensor blocker is attached to your ship, since it will slowly heat up to match the equilibrium temperature of your outer hull....and may block your sensors in that direction as well.
    So it just isn't practical. Passive sensors alone are going to be enough to find another ship.

    Cover the asteroid in light opaque flat surfaces. They'll have a hard time spotting it. (Flat surfaces is how stealth fighter planes are stealthy, radar beams bounce off at angles that don't return to the radar antenna)
    But they know that there used to be an asteroid there. And they'll know that some ships from Mars landed there. And they'll definitely know once you fire up those rockets. Heck, the rocket exhaust will probably be visible from Alpha Centauri. Earth will at some point during the process launch some missiles either at the asteroid (blowing up your construction workers), or at Mars itself if they're feeling particularly vindictive.

    One key is to launch the attack from behind a planet, and use the planet's gravity to turn its course. The "gravitational slingshot" is how Nasa gets its satellites into the outer edges of the solar system. They bring the satellite's trajectory close enough to a planet that it can dip into its gravity pool and get launched further out into space. (Of course, for that to work, you've got to plan your attack months, maybe even years, ahead of time).
    All I really have to do to guard against that is launch a sensor platform out past the oort cloud. Voyager managed to get that far out with 1970 technology. We would give it a nuclear reactor and it would sense any blind spots in the system we can't register and relay that information back to Earth. It's just too easy to position enough sensors around a system for there to be any blind spots.

    If you ever fire your engines, I'll be able to see you. That includes launching from a planet. If you ever fire maneuvering thrusters, I'll see you. If you keep your spaceship warmer than a few Kelvin, I'll see you.
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    Quote Originally Posted by kojax
    True. This is the limit of your stealth. You're only ever invisible from one side. From the other side, you're twice as visible (or more). You can't enclose your whole ship in cold walls, because you must emit heat toward somewhere.

    The strategy in space would center more on seeing than hiding. The idea is to see them before they see you. Then, once you know where they are, you can hide from them.
    It would only take a handful of IR telescopes in the right places to cover pretty much the entire solar system. Presumably for a civilization that's building big space warships, an IR telescope the size of a bus with a little engine and some communications gear would not be a very big investment. If I scatter a dozen of them or so around the solar system, you won't have any safe direction to radiate heat. More realistically, I would probably deploy hundreds of them everywhere - some far outside the solar system, some hidden on asteroids, etc. Good luck finding a safe direction to radiate.

    Of course you can try to destroy my sensor platforms, but I'm going to paint them black, cover them with radar-absorbing materials, and let them cool down to near the background temperature, so you're going to have a pretty hard time finding them - unlike your ship, they won't need to radiate a lot of heat.
    Cover the asteroid in light opaque flat surfaces. They'll have a hard time spotting it. (Flat surfaces is how stealth fighter planes are stealthy, radar beams bounce off at angles that don't return to the radar antenna)
    If our planets are unfriendly, I will see you sending ships out to the asteroid and wonder what you are doing there.
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    If you're looking for full proof means that can't possibly fail... well... those don't exist even in terrestrial combat. Your enemy has to be slightly fallible.


    The problem with the discussion from above it is 2 fold:

    1) - The assumption you can't ever find all of your opponent's drones, even using your own drones, may be accurate, but we're talking about a lot of drones. Suppose you set up shop far enough away that you can be confident that all their drones are one side of you. (You're out in interstellar space), and then watch them with your telescope for a long time.


    2) - You can use "moon eclipsing the sun" blockage strategies. You may only have to sacrifice 1% or less of your emitting area in order to stop 250 drones from seeing you (If you see them first, and know where they are, and set up 250 blockers)


    You're not going to get Ninja Stealth. You can get Sniper Stealth, however.

    In space, close proximity has almost no meaning. Bullets travel infinity far to their targets without slowing down. So do missiles. Accuracy is your only limitation.

    The big problem with the distances is the amount of time it takes to traverse them, and problems with the speed of light. A good space battle might take 10 lifetimes to ever complete, if you're not careful.
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    Quote Originally Posted by kojax
    If you're looking for full proof means that can't possibly fail... well... those don't exist even in terrestrial combat. Your enemy has to be slightly fallible.


    The problem with the discussion from above it is 2 fold:

    1) - The assumption you can't ever find all of your opponent's drones, even using your own drones, may be accurate, but we're talking about a lot of drones. Suppose you set up shop far enough away that you can be confident that all their drones are one side of you. (You're out in interstellar space), and then watch them with your telescope for a long time.

    2) - You can use "moon eclipsing the sun" blockage strategies. You may only have to sacrifice 1% or less of your emitting area in order to stop 250 drones from seeing you (If you see them first, and know where they are, and set up 250 blockers)
    Seriously, read this link. Just read it. Don't post until you've read it. Do it. Read. Right now. Every single counterpoint you're making is specifically addressed by that link. Smart people have already thought about all this, and the net conclusion is that it just won't work.

    Please, stop fulfilling Nicoll's Law:
    This is called Nicoll's Law, after it was formulated by James Nicoll: It is a truth universally acknowledged that any thread that begins by pointing out why stealth in space is impossible will rapidly turn into a thread focusing on schemes whereby stealth in space might be achieved.
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    Quote Originally Posted by kojax
    If you're looking for full proof means that can't possibly fail... well... those don't exist even in terrestrial combat. Your enemy has to be slightly fallible.
    No offense, but the solution you have presented is wildly impractical. We're not looking for "full proof means that can't possibly fail." I for one would be perfectly happy with a merely plausible solution, but you haven't given one. For one thing, you are assuming nearly magical heat-pump technology that can keep a surface near 4K while it's right next to another surface that's 270+ K, which is connected to yet another surface that will need some sort of unimaginably high temperature (your radiator). Okay, that seems pretty crazy, but since it doesn't violate thermodynamics we can suppose that our civilization develops such a technology. But even then, it would be very very easy for a network of sensor platforms to spot you since you have to radiate somewhere.
    1) - The assumption you can't ever find all of your opponent's drones, even using your own drones, may be accurate, but we're talking about a lot of drones. Suppose you set up shop far enough away that you can be confident that all their drones are one side of you. (You're out in interstellar space), and then watch them with your telescope for a long time.
    If you want to lurk around far out in interstellar space where I can't see you, fine. I probably won't care until you come closer. But note that I'll still have a pretty good idea of where you are, since I will almost certainly see your ship's engine fire when it was moving you out that far, and I can calculate your position at any given time based on that data until your engine fires again.
    2) - You can use "moon eclipsing the sun" blockage strategies. You may only have to sacrifice 1% or less of your emitting area in order to stop 250 drones from seeing you (If you see them first, and know where they are, and set up 250 blockers)
    I'm not sure you're envisioning this properly. The sensor platforms will all be in some sort of solar orbit. You can't set something up that will constantly stay between you and them - they're always moving, and any orbit you put your blockers into will only keep them between my sensors and you briefly.
    You're not going to get Ninja Stealth. You can get Sniper Stealth, however.
    It's going to more like sitting in your car at night in the desert with the cab light on, and any time you want to actually drive somewhere you turn on the high beams.
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    This argument about stealth is unnecessary. Look how military engagements work today: we employ bogus convergence, countermeasures, decoys... basically flood the enemy with garbage information. This costs relatively little. In space if your main problem is a thermal image, that is so cheap to mask just by spamming crap that generates heat. You do this in a way your own sensors are able to see through. And the enemy answers with same. Escalates. Modern air forces expect it. But it's quite possible to litter a battlefield with so much "smokescreen" and misinformation that both sides lose the advantage - this brings them down to crude combat, plus "atmosphere".

    When the Serbs were getting precision-struck by all those million-dollar NATO smart bombs, they counterattacked with ...microwave ovens. Plug the oven in some distance from the tank or radar etc. leave it on with door open to the sky. Missiles couldn't resist the signature. Cheap. Rumor has it microwave ovens were also responsible for some friendly fire.

    Even strategically you can fire swarms of hot dummies month after month just to keep the enemy guessing. These would cost peanuts to a spacefaring civilization.
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    With a good power source on board, all the heat could be pumped and funneled into an IR laser at one end, which could be used as a weapon, or could be pointed into a direction away from the other ship's sensors.
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    Quote Originally Posted by Pong
    This argument about stealth is unnecessary. Look how military engagements work today: we employ bogus convergence, countermeasures, decoys... basically flood the enemy with garbage information. This costs relatively little. In space if your main problem is a thermal image, that is so cheap to mask just by spamming crap that generates heat. You do this in a way your own sensors are able to see through. And the enemy answers with same. Escalates. Modern air forces expect it. But it's quite possible to litter a battlefield with so much "smokescreen" and misinformation that both sides lose the advantage - this brings them down to crude combat, plus "atmosphere".

    When the Serbs were getting precision-struck by all those million-dollar NATO smart bombs, they counterattacked with ...microwave ovens. Plug the oven in some distance from the tank or radar etc. leave it on with door open to the sky. Missiles couldn't resist the signature. Cheap. Rumor has it microwave ovens were also responsible for some friendly fire.

    Even strategically you can fire swarms of hot dummies month after month just to keep the enemy guessing. These would cost peanuts to a spacefaring civilization.
    Tisk tisk, someone still hasn't read the linked article! Decoys aren't practical - the problem is that you can examine the emission spectra and intensity of any engine to figure out the power output of the engine. By comparing the engine power to the object's acceleration, you can figure out its mass. This means that any decoy would need be the same mass as your warship and have an engine that was as powerful as your warship - in which case it will practically already be a warship itself.

    Now, I will certainly agree that once your warship burns its engine to set itself on a course (say, a course taking it to an enemy planet) it could turn off its engine and deploy some small "decoys" that emitted about the same as your warships black body spectra, so I wouldn't know which of the ten closely-grouped blips on my screen was actually your warship. But I will still know that you only have one ship, and where it it headed. At best, your decoys will only make it somewhat harder for me to shoot at you from a long ways away, not let you hide how may ships you have or where they are going.
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    Quote Originally Posted by KALSTER
    With a good power source on board, all the heat could be pumped and funneled into an IR laser at one end, which could be used as a weapon, or could be pointed into a direction away from the other ship's sensors.
    You can't just build a laser which extracts ambient IR energy. It's just not how lasers work. Read wikipedia on stimulated emissions.

    If there was a way to extract waste heat and fire it off as a laser, maybe stealth would work. It'd be much easier to fire in a direction where nothing is looking. But I don't see any process which would let you do that.
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    Well, I don't want to press this too much, since I obviously don't know that much, but what about the process I suggested earlier? Sufficiently miniaturizing the process could have it be part of the structure (carbon nanotube grid maybe?). The electricity could be stored and used to power the laser. Am I missing something again?
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    You mean that heat engine which used sound?

    Yeah, all heat engines work by extracting useful work from the transfer of heat from high to low temperature areas. Once everything on your ship is the same temperature, you can't produce any more useful work and your ship will cook itself.

    Think of heat engines like a water wheel. It doesn't create or destroy water, it just extracts useful work from it. All that "waste" water still needs to go somewhere. Usually it's carried off down stream but in a spaceship you have to deal with it yourself.
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    Quote Originally Posted by Scifor Refugee
    Decoys aren't practical - the problem is that you can examine the emission spectra and intensity of any engine to figure out...
    Someone ought to tell the air and naval forces about that.


    Just remembered how to perform breakneck maneuvers at high speed. It's the flyby. A great advantage here is that your attack vehicle may enter a system already at speed far outpacing that of any responsively launched defense vehicle. A straight collision course isn't necessary - you can pinball between bodies. Now this would be a pointless show of acrobatics if defenses could just compute your next destination... but they can't because approaching the flyby you may nudge your ship just a little at the last minute, to escape any way you like. You may chicken out and make a U-turn... then come back... And all this while you can outrun any seeking missile, and you're probably thrusting just to keep the edge by wide margin, and milking every flyby for momentum gain.

    I guess the way to counter this is to maintain a similar defense network. That's essentially a perpetually spinning sling, ready to release the shot. Then timing is everything.
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    Decoys are possible in the time frame of seconds, against incoming missiles, but they aren't practical for a long term solution. The decoy would have to have the same engine, the same temperature, and the same mass. Some decoy.

    Seriously, everyone who hasn't, READ THIS LINK before posting on how stealth is possible. Right now. Do it. It's right there. Read it. Now. Right now.

    As for the flybys, that's only useful for a few seconds over the course of a few months' trip. I'll just fire at you when you're coasting for 9 months between Mars and Earth.
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    What if you have a good enough power source so you can use active cooling, like a heat pump, in conjunction with the other system?
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    A heat pump requires energy to operate. You can't use the heat pumps to move heat around and then use a heat engine to extract useful work to power the heat pumps and end up with a net surplus. That would be a perpetual motion machine.

    This is also addressed by this link.
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    Ok, here is the only use I can think of for decoys:

    If I'm coming to attack your star system with my starship, I probably can't stop you from seeing me fire my engine and knowing that I'm coming. But after I burn my engine to reach whatever speed I want, I can launch dozens and dozens of decoys that drift along and mimic my ship's black body spectra. You probably won't be able to tell which one is really my ship, so you won't know exactly where I'll be coming in from, which might make it a lot harder for you to plan your defense. Of course if I want to actually stop in your system I will need to fire my engine eventually, which will give me away, but at least I can keep you guessing about where I'll really be coming from for a long time. If I'm willing to make an "attack flyby" where I just coast past and fire weapons without slowing down, you might not know which blip is really me until I get close enough for you to tell which ones are the decoys by some means other than examining my emission spectra. Of course you will probably star trying to pop the decoys as quickly as possible, but there would at least be some use there - diluting your defensive fire by a factor of 10 or 20 or 50 would probably be pretty appealing.
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    Quote Originally Posted by Numsgil
    Decoys are possible in the time frame of seconds, against incoming missiles, but they aren't practical for a long term solution. The decoy would have to have the same engine, the same temperature, and the same mass. Some decoy.
    Ha! Well you're easy to defeat. I'll send a few decoys just like my old model missiles, and "decoy" them with armed missiles fresh from the factory. You'll be so clever not to waste shots at what are plainly decoys.

    The point is unless you have up-to-date inside knowledge of which signatures correspond to real weapons, your target selection is as good as random. It is not hard to send a bewildering variety of missiles, or make basically random adjustments at last minute.
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    Quote Originally Posted by Numsgil
    A heat pump requires energy to operate. You can't use the heat pumps to move heat around and then use a heat engine to extract useful work to power the heat pumps and end up with a net surplus. That would be a perpetual motion machine.

    This is also addressed by this link.
    No, I mean the heat pumps are powered by the power plant and the heat-sound-electricity thingies convert the guided heat to electricity which powers the laser. You can feed the generated electricity back into the power grid to aid efficiency, can be stored for weapons or used for endothermic chemical reactions or whatever. The waist could then be beamed away or aid in propulsion. The point is that a well thought out integrated system could both increase efficiency and at the same time at least significantly reduce the ship's black body radiation (you can probably never entirely get rid of it).
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    I read the article. I just don't agree with all of its assumptions. Their logic is great, but they assume a few things too many. (Infinity perfect logic cannot rescue a failed assumption).

    For instance, with decoys. They assume that you're going to try and exactly match your ship's signature with them. Why?

    Unless your opponent knows your ship's specs, you might as well use counter measures that have totally random heat signatures. I'm thinking the heat they see is going to be whatever radiates off your fins, or from your thrust, so as long as that's the kind of heat the decoys give off, good luck guessing which object is the real one.

    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by kojax
    If you're looking for full proof means that can't possibly fail... well... those don't exist even in terrestrial combat. Your enemy has to be slightly fallible.
    No offense, but the solution you have presented is wildly impractical. We're not looking for "full proof means that can't possibly fail." I for one would be perfectly happy with a merely plausible solution, but you haven't given one. For one thing, you are assuming nearly magical heat-pump technology that can keep a surface near 4K while it's right next to another surface that's 270+ K, which is connected to yet another surface that will need some sort of unimaginably high temperature (your radiator). Okay, that seems pretty crazy, but since it doesn't violate thermodynamics we can suppose that our civilization develops such a technology. But even then, it would be very very easy for a network of sensor platforms to spot you since you have to radiate somewhere.
    I actually own a "peltier chip" for my CPU processor. They're commonly used by overclockers to keep their chips cool.

    Basically it's a reverse thermal couple. In a thermal couple, you take two pieces of metal, one hot, one cold. Turns out there's always a voltage between the hot and the cold, and you can harness electricity directly from it by running 2 wires (of different composition) between them.

    If, instead of harnessing the electricity, you pump electricity in, then the hot part gets hotter, and the cold part gets colder.

    Of course, this means you'll have to radiate something like 4 times as much heat, just not in the direction of your "wall". The wall doesn't have to be big as long as it's stretched out far enough on a pole between you and the object you want to be out of view of.

    1) - The assumption you can't ever find all of your opponent's drones, even using your own drones, may be accurate, but we're talking about a lot of drones. Suppose you set up shop far enough away that you can be confident that all their drones are one side of you. (You're out in interstellar space), and then watch them with your telescope for a long time.
    If you want to lurk around far out in interstellar space where I can't see you, fine. I probably won't care until you come closer. But note that I'll still have a pretty good idea of where you are, since I will almost certainly see your ship's engine fire when it was moving you out that far, and I can calculate your position at any given time based on that data until your engine fires again.
    Yes, if you were looking for me at the moment I first went out there. If you're watching for me a month before the attack, and I'm the only artificial object (or one of very few) in the sky, then sure.

    On the other hand, it can very complicated if I've employed gravitational slingshot tactics when I was near a planet or large moon.



    2) - You can use "moon eclipsing the sun" blockage strategies. You may only have to sacrifice 1% or less of your emitting area in order to stop 250 drones from seeing you (If you see them first, and know where they are, and set up 250 blockers)
    I'm not sure you're envisioning this properly. The sensor platforms will all be in some sort of solar orbit. You can't set something up that will constantly stay between you and them - they're always moving, and any orbit you put your blockers into will only keep them between my sensors and you briefly.
    From far away, an entire planetary orbit might occupy as little as a tenth an arc second worth of my view of space.

    Besides, why would I ever come close? In space, you're not limited in your ability to strike from afar like on Earth. An artillery cannon that can lob a shell 20 miles on Earth, can lob that same shell infinity miles in space.


    You're not going to get Ninja Stealth. You can get Sniper Stealth, however.
    It's going to more like sitting in your car at night in the desert with the cab light on, and any time you want to actually drive somewhere you turn on the high beams.
    You can to certain lengths on this, if you don't mind poor mass to thrust ratios. You could use a rail gun to lob cryogenicaly cooled rails behind you.

    Suppose I fire off my thrusters bright as a christmas tree to get momentum, but then lob 2 or 3 rails off to the side afterward to adjust my course?
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    Quote Originally Posted by Pong
    Quote Originally Posted by Numsgil
    Decoys are possible in the time frame of seconds, against incoming missiles, but they aren't practical for a long term solution. The decoy would have to have the same engine, the same temperature, and the same mass. Some decoy.
    Ha! Well you're easy to defeat. I'll send a few decoys just like my old model missiles, and "decoy" them with armed missiles fresh from the factory. You'll be so clever not to waste shots at what are plainly decoys.

    The point is unless you have up-to-date inside knowledge of which signatures correspond to real weapons, your target selection is as good as random. It is not hard to send a bewildering variety of missiles, or make basically random adjustments at last minute.
    They aren't decoys then. Those are missiles. So yes, if firing n missiles is good, firing n + 6 missiles is better. I think this is a pretty standard relationship in most of military history.

    The point is that, short of making it an actual missile, a decoy isn't practical because it has to look an awful lot like a real missile. Same temperature, same size, and if the engines fire, same engines and same mass. With all those restrictions you might as well put a warhead on it and make it a real missile.
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    Quote Originally Posted by Scifor Refugee
    Ok, here is the only use I can think of for decoys:

    If I'm coming to attack your star system with my starship, I probably can't stop you from seeing me fire my engine and knowing that I'm coming. But after I burn my engine to reach whatever speed I want, I can launch dozens and dozens of decoys that drift along and mimic my ship's black body spectra. You probably won't be able to tell which one is really my ship, so you won't know exactly where I'll be coming in from, which might make it a lot harder for you to plan your defense. Of course if I want to actually stop in your system I will need to fire my engine eventually, which will give me away, but at least I can keep you guessing about where I'll really be coming from for a long time. If I'm willing to make an "attack flyby" where I just coast past and fire weapons without slowing down, you might not know which blip is really me until I get close enough for you to tell which ones are the decoys by some means other than examining my emission spectra. Of course you will probably star trying to pop the decoys as quickly as possible, but there would at least be some use there - diluting your defensive fire by a factor of 10 or 20 or 50 would probably be pretty appealing.
    Except that those blips are going to have very similar trajectories if they're just ballistics and they're all going to enter the system. I suppose if you do it right you could have some enter orbits around Jupiter and some travel to the inner planets, or something like that (use chaos theory to your advantage), but if it's just a quick flyby all your decoys and you are going to have very similar trajectories and probably all be vulnerable to Kirken mines (I think that's what they're called) and the like.
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    Quote Originally Posted by KALSTER
    Quote Originally Posted by Numsgil
    A heat pump requires energy to operate. You can't use the heat pumps to move heat around and then use a heat engine to extract useful work to power the heat pumps and end up with a net surplus. That would be a perpetual motion machine.

    This is also addressed by this link.
    No, I mean the heat pumps are powered by the power plant and the heat-sound-electricity thingies convert the guided heat to electricity which powers the laser. You can feed the generated electricity back into the power grid to aid efficiency, can be stored for weapons or used for endothermic chemical reactions or whatever. The waist could then be beamed away or aid in propulsion. The point is that a well thought out integrated system could both increase efficiency and at the same time at least significantly reduce the ship's black body radiation (you can probably never entirely get rid of it).
    It just won't work. Waste heat can't be turned into laser power. See, when you extract energy from the heat engine, it doesn't reduce the amount of heat there is. It's that water wheel analogy again. The water isn't destroyed in the process of turning the wheel. With a heat engine, heat isn't destroyed when you extract useful work. You can have a 100% efficient laser, with a perfect Carnot ratio heat engine, but the laser isn't going to cool the space ship even a fraction of a Kelvin.
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    Quote Originally Posted by kojax
    I read the article. I just don't agree with all of its assumptions. Their logic is great, but they assume a few things too many. (Infinity perfect logic cannot rescue a failed assumption).

    For instance, with decoys. They assume that you're going to try and exactly match your ship's signature with them. Why?

    Unless your opponent knows your ship's specs, you might as well use counter measures that have totally random heat signatures. I'm thinking the heat they see is going to be whatever radiates off your fins, or from your thrust, so as long as that's the kind of heat the decoys give off, good luck guessing which object is the real one.
    They won't know which one is the "real" ship, but if engines are firing they'll know each ship/decoy's mass, position, velocity, acceleration, it's engine's thrust, its size, and its temperature. Can you construct a scenario where, even knowing all those things about all your ships, a decoy is still worthwhile over just building a second ship?

    I actually own a "peltier chip" for my CPU processor. They're commonly used by overclockers to keep their chips cool.

    Basically it's a reverse thermal couple. In a thermal couple, you take two pieces of metal, one hot, one cold. Turns out there's always a voltage between the hot and the cold, and you can harness electricity directly from it by running 2 wires (of different composition) between them.

    If, instead of harnessing the electricity, you pump electricity in, then the hot part gets hotter, and the cold part gets colder.

    Of course, this means you'll have to radiate something like 4 times as much heat, just not in the direction of your "wall". The wall doesn't have to be big as long as it's stretched out far enough on a pole between you and the object you want to be out of view of.
    That's called a heat pump. We know they exist. And heat pumps are specifically covered in that link I linked and you apparently read. Presumably you're suggesting that we radiate the waste heat to some "safe" portion in the sky. The problem with that is that realistically I'm going to have thousands of sensor platforms all over and there won't be a "safe" place to radiate your heat.

    Yes, if you were looking for me at the moment I first went out there. If you're watching for me a month before the attack, and I'm the only artificial object (or one of very few) in the sky, then sure.

    On the other hand, it can very complicated if I've employed gravitational slingshot tactics when I was near a planet or large moon.
    Not if I there isn't a sensor blind spot. If I have sensor drones that can see every portion of a planet, you won't be able to do a gravity assist to move in to an unknown trajectory because to do so you have to fire your engines and I'll be able to calculate a new trajectory.

    From far away, an entire planetary orbit might occupy as little as a tenth an arc second worth of my view of space.

    Besides, why would I ever come close? In space, you're not limited in your ability to strike from afar like on Earth. An artillery cannon that can lob a shell 20 miles on Earth, can lob that same shell infinity miles in space.
    Right, that's the logic I used earlier to posit that you'd just keep all your weapons at your base. But then Scifor suggested that you'd use ships to move far away to preserve your second strike ability. So either:

    1. Your planets are far enough way that you wouldn't even use ships (and thus ship stealth is a n/a) -or-
    2. Your planets are close enough that you'd want remote weapons platforms. Which means launching from your planet, which means I can see you.

    Plus, if you can stealth your ships, I can stealth my sensor drones, so you won't know where to build your "sunscreen" anyway. You sure you read that link?


    You can to certain lengths on this, if you don't mind poor mass to thrust ratios. You could use a rail gun to lob cryogenicaly cooled rails behind you.

    Suppose I fire off my thrusters bright as a christmas tree to get momentum, but then lob 2 or 3 rails off to the side afterward to adjust my course?
    How are you refrigerating those cryogenically cooled rails? Especially if it's right after you fired your engines, it means your ship is going to be warm enough to spot even after you fire those rails, even if those rails are undetectable (debatable).
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    Quote Originally Posted by Numsgil
    Except that those blips are going to have very similar trajectories if they're just ballistics and they're all going to enter the system. I suppose if you do it right you could have some enter orbits around Jupiter and some travel to the inner planets, or something like that (use chaos theory to your advantage), but if it's just a quick flyby all your decoys and you are going to have very similar trajectories and probably all be vulnerable to Kirken mines (I think that's what they're called) and the like.
    Any realistic interstellar flight will take at least years, possibly decades. The tiny changes in trajectory that will occur when I jetison the decoys will result in my decoys being scattered all over the place by the time they reach your star system. You won't be able to see the drive signiture if my decoys use some kind of small ion drive to develop a few tens of km/sec in random directions while they're still 5 lightyears out, but 10 years later when they arrive in your star system they will have drifted all over the place.
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Numsgil
    Except that those blips are going to have very similar trajectories if they're just ballistics and they're all going to enter the system. I suppose if you do it right you could have some enter orbits around Jupiter and some travel to the inner planets, or something like that (use chaos theory to your advantage), but if it's just a quick flyby all your decoys and you are going to have very similar trajectories and probably all be vulnerable to Kirken mines (I think that's what they're called) and the like.
    Any realistic interstellar flight will take at least years, possibly decades. The tiny changes in trajectory that will occur when I jetison the decoys will result in my decoys being scattered all over the place by the time they reach your star system. You won't be able to see the drive signiture if my decoys use some kind of small ion drive to develop a few tens of km/sec in random directions while they're still 5 lightyears out, but 10 years later when they arrive in your star system they will have drifted all over the place.
    Yeah, I guess that would work. They'd have to be set up so that I can't automatically guess which is the real one (temperature's would need to be hot for all those decoys). And your weapons would have to be long range enough that I can't just shoot the ones heading for an Earth orbit or whatever.
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    Quote Originally Posted by Pong
    Ha! Well you're easy to defeat. I'll send a few decoys just like my old model missiles, and "decoy" them with armed missiles fresh from the factory. You'll be so clever not to waste shots at what are plainly decoys.

    The point is unless you have up-to-date inside knowledge of which signatures correspond to real weapons, your target selection is as good as random. It is not hard to send a bewildering variety of missiles, or make basically random adjustments at last minute.
    We were talking about using decoys to confuse people about where your ship is. Any decoy that's going to fire its engines will need to be massive enough to plausibly be a ship, and have engines powerful enough that they might plausibly belong to a ship. In which case they might as well just be ships. You can only make a decoy look like your ship if your ship isn't moving, which means you will never be able to really confuse me about where your ship is - at best, I won't know which of the very very closely clustered blips on my screen is your ship, which might make it hard for me to decide exactly where to aim from a long way away. But I'll still know how many ships you really have, where they are, and where they are going. You can only really confuse me about where your ship is and where it's going if your decoys have a VERY long time to slowly drift apart without firing any large engines, which is why I said they could be useful if you wanted to fly up to an enemy star system.

    Regarding mixing decoys in with missiles, yeah, I'll have to just assume that anything coming toward me that looks like it might be a missile, so you could surely fool me with dummy missiles. But if your "dummy missiles" have a mass high enough to plausibly be a missile and an engine powerful enough to plausible belong to a missile, why don't you just stick warheads on them and officially make them missiles?
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    If the engines are good enough, you wouldn't even need to do that. Above a certain speed and them become kinetic kill missiles anyway.

    I think instead of missile decoys, submunitions would be the way to go. Imagine I launch 5 missiles at you. They're big and dangerous looking, so you start trying to shoot them down. If the missile is built right, it'd be able to withstand a little bit of laser fire before being destroyed and would also be able to detect incoming anti-missile-missiles. If it detects either of these, it explodes into 6 submissiles. These can again explode into hundreds of kinetic kill cannonballs. (Each explosion/engine fire, if built right, would increase the velocity of the submunitions.)

    They did this on an episode of Cowboy Bebop once, except the payload of the last round wasn't mass, but a virus. (Not that Cowboy Bebop is exactly hard-scifi, but they do better than most.)
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    Quote Originally Posted by MagiMaster
    If the engines are good enough, you wouldn't even need to do that. Above a certain speed and them become kinetic kill missiles anyway.

    I think instead of missile decoys, submunitions would be the way to go. Imagine I launch 5 missiles at you. They're big and dangerous looking, so you start trying to shoot them down. If the missile is built right, it'd be able to withstand a little bit of laser fire before being destroyed and would also be able to detect incoming anti-missile-missiles. If it detects either of these, it explodes into 6 submissiles. These can again explode into hundreds of kinetic kill cannonballs. (Each explosion/engine fire, if built right, would increase the velocity of the submunitions.)

    They did this on an episode of Cowboy Bebop once, except the payload of the last round wasn't mass, but a virus. (Not that Cowboy Bebop is exactly hard-scifi, but they do better than most.)
    I'd call Cowboy Bebop pretty hard. At least compared to Star Trek and Star Wars and Doctor Who and the like

    So yeah, that's a pretty viable attack strategy. If I see it happening, I either can stop it, or I can't. And it'd be pretty easy for me to determine which one. If I can, great. If I can't, then my best strategy is to fire all my weapons at you. That way, even if you kill me, I've killed you, too. It's a stalemate of the worst kind.

    So warfare becomes mutually ensured destruction, and you end up with Cold War politics.
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    Quote Originally Posted by Numsgil
    Quote Originally Posted by kojax
    I read the article. I just don't agree with all of its assumptions. Their logic is great, but they assume a few things too many. (Infinity perfect logic cannot rescue a failed assumption).

    For instance, with decoys. They assume that you're going to try and exactly match your ship's signature with them. Why?

    Unless your opponent knows your ship's specs, you might as well use counter measures that have totally random heat signatures. I'm thinking the heat they see is going to be whatever radiates off your fins, or from your thrust, so as long as that's the kind of heat the decoys give off, good luck guessing which object is the real one.
    They won't know which one is the "real" ship, but if engines are firing they'll know each ship/decoy's mass, position, velocity, acceleration, it's engine's thrust, its size, and its temperature. Can you construct a scenario where, even knowing all those things about all your ships, a decoy is still worthwhile over just building a second ship?
    Yeah, the trouble with your decoy is that it has to match your ship's approximate mass.

    However, if you do this (expend 10 times the thrust to bring 9 decoys with you), they can push off of each other initially, before firing their thrusters so that when they first become visible they're all already headed in slightly different directions.



    I actually own a "peltier chip" for my CPU processor. They're commonly used by overclockers to keep their chips cool.

    Basically it's a reverse thermal couple. In a thermal couple, you take two pieces of metal, one hot, one cold. Turns out there's always a voltage between the hot and the cold, and you can harness electricity directly from it by running 2 wires (of different composition) between them.

    If, instead of harnessing the electricity, you pump electricity in, then the hot part gets hotter, and the cold part gets colder.

    Of course, this means you'll have to radiate something like 4 times as much heat, just not in the direction of your "wall". The wall doesn't have to be big as long as it's stretched out far enough on a pole between you and the object you want to be out of view of.
    That's called a heat pump. We know they exist. And heat pumps are specifically covered in that link I linked and you apparently read. Presumably you're suggesting that we radiate the waste heat to some "safe" portion in the sky. The problem with that is that realistically I'm going to have thousands of sensor platforms all over and there won't be a "safe" place to radiate your heat.
    Well, if you're talking about already having thousands of sensors in every part of the sky, then you're kind of talking about defensive overkill. Nobody can come up with a way to defeat that, even in Earth combat.

    If you've got 1000 soldiers watching a quarter square mile area base, well. . ... the best ninja in the world couldn't sneak through them all and assassinate the base commander. They'd either need a diversion, an inside man, or some kind of sci-fi invisibility device.

    If we're talking about an attack from within the solar system, are we suggesting that you've got drones further out than the Kuiper belt? Why not just find the outermost limit of your drones perimeter, set up shop further out than that, and just watch for a while? (At that point, you only have to block, at most, 1/2 of your heat signature)


    Yes, if you were looking for me at the moment I first went out there. If you're watching for me a month before the attack, and I'm the only artificial object (or one of very few) in the sky, then sure.

    On the other hand, it can very complicated if I've employed gravitational slingshot tactics when I was near a planet or large moon.
    Not if I there isn't a sensor blind spot. If I have sensor drones that can see every portion of a planet, you won't be able to do a gravity assist to move in to an unknown trajectory because to do so you have to fire your engines and I'll be able to calculate a new trajectory.
    As I was saying about ejecting rails and gravitational slingshots. There will probably be a moment in your approach to any planet or moon when one ejected rail's worth of lateral acceleration can multiply to quite a large change in final trajectory.




    From far away, an entire planetary orbit might occupy as little as a tenth an arc second worth of my view of space.

    Besides, why would I ever come close? In space, you're not limited in your ability to strike from afar like on Earth. An artillery cannon that can lob a shell 20 miles on Earth, can lob that same shell infinity miles in space.
    Right, that's the logic I used earlier to posit that you'd just keep all your weapons at your base. But then Scifor suggested that you'd use ships to move far away to preserve your second strike ability. So either:

    1. Your planets are far enough way that you wouldn't even use ships (and thus ship stealth is a n/a) -or-
    2. Your planets are close enough that you'd want remote weapons platforms. Which means launching from your planet, which means I can see you.

    Plus, if you can stealth your ships, I can stealth my sensor drones, so you won't know where to build your "sunscreen" anyway. You sure you read that link?
    I read it. I was questioning their assumption that you need to block out the whole sky. I agree that there's no way a ship could ninja its way to your inner perimeter (at least without knowing where each of your observer drones are).

    However, your division of the two possibilities into just two doesn't seem warranted.

    In the first place, you might use a moon or large asteroid instead of a planet. You might set up a few of them. If you use magnetic launch methods, then you don't have to fire any rockets to leave a small moon or large asteroid.

    When you send supplies between these places, they might not be in ships at all. Just big massive objects (devoid of thrusters of any kind) that have been ballistically hurled into space, and drift to their destinations. In fact, you might even move people in these shipments. (Especially if you could cryogenicaly freeze them)


    You can to certain lengths on this, if you don't mind poor mass to thrust ratios. You could use a rail gun to lob cryogenicaly cooled rails behind you.

    Suppose I fire off my thrusters bright as a christmas tree to get momentum, but then lob 2 or 3 rails off to the side afterward to adjust my course?
    How are you refrigerating those cryogenically cooled rails? Especially if it's right after you fired your engines, it means your ship is going to be warm enough to spot even after you fire those rails, even if those rails are undetectable (debatable).
    Why would I eject the rails *right* afterwards? It doesn't matter when I do it. The effect is the same if I wait a month to eject the rails as it is if I do so immediately.

    From the moment they're ejected onward my heading will have moved, and while you may still know where I am down to within a range, you won't know well enough to shoot at me.

    However, I must admit that, unless I've got a gravitational object nearby, the course change would be too small to make my location totally unknown.
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    Quote Originally Posted by Scifor Refugee
    Regarding mixing decoys in with missiles, yeah, I'll have to just assume that anything coming toward me that looks like it might be a missile, so you could surely fool me with dummy missiles. But if your "dummy missiles" have a mass high enough to plausibly be a missile and an engine powerful enough to plausible belong to a missile, why don't you just stick warheads on them and officially make them missiles?
    Why? Economics. Politics aside, wars are economic contests. Suppose each defense missile always knocks out one incoming missile. Attacker fails? Not necessarily. If each brute-force attack missile costs an average 2 billion centauris, and the defense missile system loses 3 billion centauris per "success", defender loses by attrition. I guessed warheads possibly add significant cost, because these warheads are pure sci-fi speculation. And fear alone tends to activate expensive defenses. But whatever. What we do know for certain is fuel. Then we want to force the defender to burn as much fuel as possible.

    How can an attacker from another system possibly win a fuel war? I think it can be done, by forcing the defender to burn fuel wastefully (essentially defending up from a gravity well). The defender sees something scudding into the system at mad velocity, aiming for a game of planetary pinball as described above, and must quickly intercept by accelerating and possibly chasing around after that object. A probably benign signature must be answered with the same vigor as a clear threat. Attacker may even psy-op decorate the objects with neon flashing "WE COME IN PEACE" or whatever. Everything must be intercepted by thrusting at it. This is hugely expensive for a defender.

    Guns don't help, because attacker may switch from trickling attacks to massed attack. That's real easy to set up, real hard to anticipate, and certainly overwhelming to a quality-not-quantity defense strategy.

    And of course the overhead to maintain vigilance costs even while attacker pauses.

    I dont' consider beam weapons like interplanetary lasers because I have no clue about them and guess they'd totally unhinge the discussion.

    In conclusion I believe, economically, attacker has the "high ground".


    Kojax good call on the "thousands of sensor platforms all over". It's not playing fair.
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    It just won't work. Waste heat can't be turned into laser power. See, when you extract energy from the heat engine, it doesn't reduce the amount of heat there is. It's that water wheel analogy again. The water isn't destroyed in the process of turning the wheel. With a heat engine, heat isn't destroyed when you extract useful work. You can have a 100% efficient laser, with a perfect Carnot ratio heat engine, but the laser isn't going to cool the space ship even a fraction of a Kelvin.
    Ok. I'm opening a new thread.
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    Quote Originally Posted by Pong
    I dont' consider beam weapons like interplanetary lasers because I have no clue about them and guess they'd totally unhinge the discussion.
    Good guess Beam weapons and lasers have a really long range. Not quite as long as ballistics, but they can be run on just electricity, which comes pretty cheap if you have the technology for space flight.

    If you know that I have beam weapons, you have to evasively maneuver so that the light speed lag means I won't be able to hit you. Doesn't matter if I actually ever fire or not, you have to burn delta v so I can't hit you. If you're as far out as the edge of the solar system, it's relatively cheap. You just need to slightly alter course every 11 hours or so. But this increases quickly as you approach a target. So that provides a balancing economic force for the attacked vs. the defender. Don't know which side it's more economic for, but there you are.

    And a quick second point: if you can fly around in space, you can probably obliterate any planetary target just from dropping small needles at it from space (needle shape so that it can reach the ground at high speed). If a planet is your target warheads aren't necessarily required, so if they're the expensive part of your missile system, you might just be better off not using any and building more missiles with that money.

    But in the end it comes down to two scenarios: I can defend against you or I can't. And both scenarios lead to stalemates (just with some more stable than others).
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    I think a needle would have to be pretty heat resistant to make it to the surface of a planet like Earth before it burns up in the atmosphere (besides that the atmosphere will slow its fall a little), but small moons would certainly be vulnerable.



    Another interesting possibility is to hide most of your operation underground on a large moon. How much of the surface do you think they could afford to nuke before they run out of nukes?
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    That's an interesting idea. If your bunker is 1km below the surface, it'd be pretty hard to hit you, even if I know where you are. I'd be able to take out your solar generators, but probably not a whole lot else. Of course digging down is always more expensive than building up, so it's probably more for military outposts than civilian colonies, unless underground offers other benefits (maybe geothermal?).

    Of course this assumes fairly contemporary sorts of weapons. If I'm chucking multiple 1 kg slugs at you at .15c, that's a lot of boom. I don't think you're going to be able to dig your way to safety.
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    Actually, underground does offer a lot of other benefits. The two I can think of off the top of my head are radiation shielding and thermal insulation.
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    Quote Originally Posted by Numsgil
    If you know that I have beam weapons, you have to evasively maneuver...
    Why dodge a gift? If you're going to send free energy my way I'll gladly take it and use it, or reflect back what I don't want. How can you ensure any kind of beam is destructive? You have no control over it once released. I'd concede attack vehicle provisions to defend against radiation might be costly or inadequate. Might be. :?


    A cute trick possible with lasers fakes FTL travel. What you do is, project an apparent object. By wagging your projectors, you make the apparent object zip through space at amazing speed. There's no way to actually do anything useful or communicate superluminally with that, though it would seem plausible intuitively. Still it does create an illusion, which could matter very much in war.

    Quote Originally Posted by Numsgil
    Doesn't matter if I actually ever fire or not, you have to burn delta v so I can't hit you
    You see my earlier point then. Yeah it cuts both ways.
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    Quote Originally Posted by Pong
    Quote Originally Posted by Numsgil
    If you know that I have beam weapons, you have to evasively maneuver...
    Why dodge a gift? If you're going to send free energy my way I'll gladly take it and use it, or reflect back what I don't want. How can you ensure any kind of beam is destructive? You have no control over it once released. I'd concede attack vehicle provisions to defend against radiation might be costly or inadequate. Might be. :?
    You'd have to line your hull with super-thermally conductive substances, and I know of no such substance, either real or theoretical. Otherwise the heat won't disperse across your ship fast enough and I'll burn a whole in your ship. Or if I use a solid beam instead of a pulse, I could make your hull actually explode.

    And even imagining that you could build a ship capable of transmitting heat fast enough, I have a planet based laser. I can potentially put the entire power output of a small moon behind my laser. Lasers right now are capable of outputting in the petawatt range (1000000 Gigawatts). Future lasers could be orders of magnitude larger, especially for military purposes. I'd have to do the math, but something tells me the steady state between the laser and the black body radiation your ship emits is going to be on the order of thousands to tens of thousands of Kelvin. More than enough to fry any sensitive electronics, not to mention melt your hull and cause you to lose containment on your reaction mass. And if your fuel is, say, antimatter. There won't even be man sized chunks left

    So no, you'll want to be dodging those laser beams.

    A cute trick possible with lasers fakes FTL travel. What you do is, project an apparent object. By wagging your projectors, you make the apparent object zip through space at amazing speed. There's no way to actually do anything useful or communicate superluminally with that, though it would seem plausible intuitively. Still it does create an illusion, which could matter very much in war.
    Um, what is your laser reflecting off of? There aren't any giant white walls in space to use your ship based laser pointer on. And what if the teacher catches you? She's going to confiscate your ship and you won't get it back until the end of the year. And then when the principal gets involved...
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    Quote Originally Posted by Numsgil
    Lasers right now are capable of outputting in the petawatt range (1000000 Gigawatts).
    No laser has a time-average output anything like that high. The lasers you're thinking of usually pack a few hundred joules into a pulse that lasts less than a picosecond. The power is only in the petawatt range for the very very brief instant when it's actually firing, and then it takes seconds or minutes to recharge. Over a time scale of seconds, their average power is in the tens of watts.

    I still think you're waaaay underestimating 1) how difficult it would be to build these things and 2) how difficult it would be to actually hit anything with it over long distances. I'm not saying it's physically impossible and I'm not saying that large planet-based laser installations won't be important, but actually building something like that would be a colossal project that could easily end up costing more than entire fleets of ships - assuming you even have the technology to do it.
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    Not at all. Laser power has been increasing tremendously over the last 30 years. We're talking at least another 100 years before Earth technology would be even remotely capable of space combat (without just being a sitting duck). Extrapolating tells us we should expect a several order of magnitude increase in laser power in the next 100 years.

    As I see it the main limiting factor wouldn't be the laser's power (if nothing else you can always just build thousands of lasers and point it at the same ship), but it's wavelength. Larger wavelengths have more diffraction, which means their range is shorter than smaller wavelengths.

    Or, if lasers aren't your cup of tea, what about neutral particle beam weapons? Roughly light speed, with a similar punch.

    And of course if you can use a telescope to zoom in on your target, you can pretty much use a laser to fry it, assuming it doesn't wiggle. I don't see tracking technology being a problem.

    Or if you're being extremely hard with your science, and you refuse to use any technology not available right this minute, then yes, you're talking about a purely missile to missile arena.
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    This thread is suffering mission creep isn't it Numsgil? You opened it, but now your role is largely dismissing fresh ideas. I get the sense you have a pre-established vision, you want corroborated.
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    I'm playing devil's advocate to new ideas. Scifor played devil's advocate when I suggested a combat spaceship-less universe. It's a conflict of interest for a person to try and poke holes in their own idea, so this way you can get a good debate going and explore all sides of an issue.

    I have no personal ego tied to any of this. Please don't take anything I say as anything more than an exploration of why any given idea might be right or wrong. There is absolutely no emotion involved beyond a certain amount of playful argumentativeness.
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    Quote Originally Posted by Pong
    Quote Originally Posted by Numsgil
    If you know that I have beam weapons, you have to evasively maneuver...
    Why dodge a gift? If you're going to send free energy my way I'll gladly take it and use it, or reflect back what I don't want. How can you ensure any kind of beam is destructive? You have no control over it once released. I'd concede attack vehicle provisions to defend against radiation might be costly or inadequate. Might be. :?
    Well, all you could harness is the heat.

    Solar panels are only able to capture a very narrow range of light frequencies from sunlight. Unless the laser is coming at exactly the right frequency, you won't be able to convert it directly to electricity. And, it's likely you won't know what frequency to expect until it's already hit you.



    A cute trick possible with lasers fakes FTL travel. What you do is, project an apparent object. By wagging your projectors, you make the apparent object zip through space at amazing speed. There's no way to actually do anything useful or communicate superluminally with that, though it would seem plausible intuitively. Still it does create an illusion, which could matter very much in war.

    Quote Originally Posted by Numsgil
    Doesn't matter if I actually ever fire or not, you have to burn delta v so I can't hit you
    You see my earlier point then. Yeah it cuts both ways.
    You project your image onto a moon, maybe. Or maybe throw out some mirrors and project something off them. Maybe the mirrors would be your decoys? Project a computer calculated image onto the mirror so it will be reflected toward your opponent's detectors?

    Quote Originally Posted by Numsgil
    Not at all. Laser power has been increasing tremendously over the last 30 years. We're talking at least another 100 years before Earth technology would be even remotely capable of space combat (without just being a sitting duck). Extrapolating tells us we should expect a several order of magnitude increase in laser power in the next 100 years.

    As I see it the main limiting factor wouldn't be the laser's power (if nothing else you can always just build thousands of lasers and point it at the same ship), but it's wavelength. Larger wavelengths have more diffraction, which means their range is shorter than smaller wavelengths.

    Or, if lasers aren't your cup of tea, what about neutral particle beam weapons? Roughly light speed, with a similar punch.

    And of course if you can use a telescope to zoom in on your target, you can pretty much use a laser to fry it, assuming it doesn't wiggle. I don't see tracking technology being a problem.

    Or if you're being extremely hard with your science, and you refuse to use any technology not available right this minute, then yes, you're talking about a purely missile to missile arena.
    I like that you're taking into account the direction that technology is moving in. The trouble with lasers is that I think they still follow the inverse square law, so you need a really powerful laser to pack sufficient punch at large distances.

    With particle weapons, on the other hand, I think you're basically just hurling particles at somebody at insane speeds. They'll continue to drift in that direction forever until they hit something, losing none of their power along the way.
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    Quote Originally Posted by kojax
    Well, all you could harness is the heat.

    Solar panels are only able to capture a very narrow range of light frequencies from sunlight. Unless the laser is coming at exactly the right frequency, you won't be able to convert it directly to electricity. And, it's likely you won't know what frequency to expect until it's already hit you.
    True, but heat can still be useful if you can maintain a cool sink. Then you can build a heat engine and extract that incoming laser's power. So the real issue is dispersing that heat faster than its coming in, or you'll end up with part of your hull in a plasma form.


    You project your image onto a moon, maybe. Or maybe throw out some mirrors and project something off them. Maybe the mirrors would be your decoys? Project a computer calculated image onto the mirror so it will be reflected toward your opponent's detectors?
    I was thinking about this yesterday (the mirrors that is). The main issue would be that even if the enemy doesn't know it's a mirror, your reflection is going to look like it's the sum of the distance from your ship to the mirror, and the mirror to the enemy (since the image will fade with inverse square law).

    I like that you're taking into account the direction that technology is moving in. The trouble with lasers is that I think they still follow the inverse square law, so you need a really powerful laser to pack sufficient punch at large distances.
    Lasers don't suffer from the inverse square law, actually. It's one of the neat things about lasers. Instead, they suffer from Diffraction. From Atomic Rocket:

    Laser beams are not subject to the inverse-square law, but they are subject to diffraction. The radius of the beam will spread as the distance from the laser cannon increases.

    RT = 0.61 * D * L / RL
    where:
    RT = beam radius at target (m)
    D = distance from laser emitter to target (m)
    L = wavelength of laser beam (m, see table below)
    RL = radius of laser lens or reflector (m)
    Or in other words, they drop in power per square meter linearly with distance, with higher frequency lasers falling off slower. If you do the math, a gamma ray laser (at 10^-12 meter wavelength) would easily have a range of anywhere in a solar system. If you're stuck with lower wavelengths, that range drops unless you can build some really big lenses.

    With particle weapons, on the other hand, I think you're basically just hurling particles at somebody at insane speeds. They'll continue to drift in that direction forever until they hit something, losing none of their power along the way.
    So yeah, NPB weapons don't have diffraction issues, and don't lose power over distance. However, they're harder to aim. A laser can be aimed a little bit if you can build another mirror which can swivel, and redirect the beam through some given arc (with higher frequencies more difficult to aim because it's harder to build a mirroring surface which can tolerate more acute angles). But a NPB pretty much has to be pointed at what you're firing at.
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    Thanks for clearing that up. I knew there was something special about lasers. I didn't know they broke the inverse square law, but now that you mention it it makes sense.

    I've got one of those laser pens and sometimes I'll project it off of things miles away. The dot clearly grows a little bit, but the apparent brightness of the reflection seems to only barely diminish.

    Quote Originally Posted by Numsgil
    Quote Originally Posted by kojax
    Well, all you could harness is the heat.

    Solar panels are only able to capture a very narrow range of light frequencies from sunlight. Unless the laser is coming at exactly the right frequency, you won't be able to convert it directly to electricity. And, it's likely you won't know what frequency to expect until it's already hit you.
    True, but heat can still be useful if you can maintain a cool sink. Then you can build a heat engine and extract that incoming laser's power. So the real issue is dispersing that heat faster than its coming in, or you'll end up with part of your hull in a plasma form.
    True. I wonder if you'd want to use some kind of semi-transparent material to capture the heat, so most of the light passes through, but some of it also stays and generates heat?

    Are any transparent crystals good for that? (With a good combination of heat resistance and transparency?)


    You project your image onto a moon, maybe. Or maybe throw out some mirrors and project something off them. Maybe the mirrors would be your decoys? Project a computer calculated image onto the mirror so it will be reflected toward your opponent's detectors?
    I was thinking about this yesterday (the mirrors that is). The main issue would be that even if the enemy doesn't know it's a mirror, your reflection is going to look like it's the sum of the distance from your ship to the mirror, and the mirror to the enemy (since the image will fade with inverse square law).
    You'd need a computer generated image that accounted for that. And the original image would have to be really, really, bright.

    If you knew the exact distance between you and the mirror, you might be able to pass the light through a lens that counts on the mirror to act as a second lens? (Or maybe the mirror has a second lens)

    I mean like how a telescope has two lenses. And, the cut of the lenses counts on the distance between them to focus the light just right so an image forms in front of your eye. The mirror and projector could *kind of* form a telescope with a very, very long pathway between lenses?




    With particle weapons, on the other hand, I think you're basically just hurling particles at somebody at insane speeds. They'll continue to drift in that direction forever until they hit something, losing none of their power along the way.
    So yeah, NPB weapons don't have diffraction issues, and don't lose power over distance. However, they're harder to aim. A laser can be aimed a little bit if you can build another mirror which can swivel, and redirect the beam through some given arc (with higher frequencies more difficult to aim because it's harder to build a mirroring surface which can tolerate more acute angles). But a NPB pretty much has to be pointed at what you're firing at.
    Yeah, it makes sense they'd be hard to aim.

    Do you think it would help to set them in motion at one place, and then, maybe 2 or three miles out, have some kind of steering magnet that does course correction? (Kind of like the way a TV set works, only bigger)
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    The point of a NPB is that they don't respond to either magnetic or electric fields. While this means that they don't scatter, it also means that you can't steer them. (TVs use electron beams, BTW.)
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    About projecting ghost threats. I had in mind a space war environment with plenty of debris and clouds, from say exploded planets. At some stage no one side could track all those "fog of war" particles, so they'd be looking for suspicious ones. An image would only be a heat signature. Anyway it's just a minor possible mid-game strategy.
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    So, the idea is that you find a piece of debris drifting through space with your telescope, and then hit it with a laser to super - heat it so it will give off a heat signature?


    Quote Originally Posted by MagiMaster
    The point of a NPB is that they don't respond to either magnetic or electric fields. While this means that they don't scatter, it also means that you can't steer them. (TVs use electron beams, BTW.)
    I guess that kind of rules that out.

    I'm curious, though: is scattering the basic problem with other kinds of beams then? Like, an electron beam, for example?
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    Quote Originally Posted by kojax
    Quote Originally Posted by Numsgil
    Quote Originally Posted by kojax
    Well, all you could harness is the heat.

    Solar panels are only able to capture a very narrow range of light frequencies from sunlight. Unless the laser is coming at exactly the right frequency, you won't be able to convert it directly to electricity. And, it's likely you won't know what frequency to expect until it's already hit you.
    True, but heat can still be useful if you can maintain a cool sink. Then you can build a heat engine and extract that incoming laser's power. So the real issue is dispersing that heat faster than its coming in, or you'll end up with part of your hull in a plasma form.
    True. I wonder if you'd want to use some kind of semi-transparent material to capture the heat, so most of the light passes through, but some of it also stays and generates heat?

    Are any transparent crystals good for that? (With a good combination of heat resistance and transparency?)
    Diamond has unusually high thermal conductivity, and is pretty transparent (at visible wavelengths anyway). Its melting point isn't great (roughly 3800 Kelvin), but about in line with many other common substances. Plus it's strong and durable against kinetic damage. I don't know if it's transparent as frequency increases, though. It might be that with xrays or gamma rays, diamond is entirely opaque. It would still have that high thermal conductivity of course.

    So if you're going to be capturing laser energy instead of reflecting it (or avoiding it), diamond would be a good bet among "common" substances.

    I was thinking about this yesterday (the mirrors that is). The main issue would be that even if the enemy doesn't know it's a mirror, your reflection is going to look like it's the sum of the distance from your ship to the mirror, and the mirror to the enemy (since the image will fade with inverse square law).
    You'd need a computer generated image that accounted for that. And the original image would have to be really, really, bright.

    If you knew the exact distance between you and the mirror, you might be able to pass the light through a lens that counts on the mirror to act as a second lens? (Or maybe the mirror has a second lens)

    I mean like how a telescope has two lenses. And, the cut of the lenses counts on the distance between them to focus the light just right so an image forms in front of your eye. The mirror and projector could *kind of* form a telescope with a very, very long pathway between lenses?
    It might work. I think in practice there are too many issues for the enemy not to figure out it's a ruse, but I don't see anything immediately impossible with the setup.

    Of course, you'd have that annoying issue of the phantom ship facing the wrong way. As soon as the real ship turns the engines on, the ruse is up.

    Yeah, it makes sense they'd be hard to aim.

    Do you think it would help to set them in motion at one place, and then, maybe 2 or three miles out, have some kind of steering magnet that does course correction? (Kind of like the way a TV set works, only bigger)
    Before you neutralize the charge? Hmm, I don't know enough about how the charge neutralizing mechanism works. But if you could construct it like a TV, with your proton gun firing a charged particle beam at a giant TV screen mesh which can neutralize the charge, then you'd get some decent firing arcs.
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    Quote Originally Posted by Pong
    About projecting ghost threats. I had in mind a space war environment with plenty of debris and clouds, from say exploded planets. At some stage no one side could track all those "fog of war" particles, so they'd be looking for suspicious ones. An image would only be a heat signature. Anyway it's just a minor possible mid-game strategy.
    The problem here is that if your dust cloud absorbs and then re-emits the energy, it's not going to look like a space ship, it's going to look like a hot dust cloud. You can tell what an emitting substance is made of if you check it's emission spectra. We did it in my highschool physics class years back.

    However if you replace dust cloud with ship debris field, then maybe you're on to something. You couldn't make the phantom ship move at all (the debris wouldn't cool fast enough to look like a coherent heat signature), but you could probably make it look like a fleet is hiding in the debris field.
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    Quote Originally Posted by kojax
    So, the idea is that you find a piece of debris drifting through space with your telescope, and then hit it with a laser to super - heat it so it will give off a heat signature?
    Exactly. This might be most effective as missile decoy after loss of some wingmen. Throw out a bomb that dazzles missiles so they need to re-fix on some likely signature, at the last second. Project decoys onto friendly ship debris if necessary.

    A FTL illusion would require dense field of untracked debris, like an asteroid belt from recently destroyed planet. I doubt it useful.

    Numsgil we can assume craft emissions would be tweaked not necessarily for stealth but also for deception. Like torpedoes that "sound like" motorboats. Military deception is more about sending misleading or garbage information than invisibility.
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    Well, if you're assuming that the primary method of detection is looking for a spaceship's heat signature, there are real physical limits. The inverse square law means I can tell how far away it is. Emission Spectra mean I know what the object is made of. Black body radiation means I know its temperature (and probably incident surface area). Doppler Shift means I know how fast it's going, and how fast it's changing speed (acceleration). The Doppler Shift of the Emission Spectra of the spaceship's exhaust tells me how much thrust the engines are producing. Thrust / Acceleration gives me the mass of this ship.

    That's a lot of information, but still a lot of wiggle room for deception. For instance, if you manage to make your war ships look like colony ships, with similar mass and engines and size, you can fool the enemy into thinking that your ships are harmless. Or if you make your ships look like freighters you might be able to disappear into civilian ship traffic.
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    Quote Originally Posted by kojax
    I'm curious, though: is scattering the basic problem with other kinds of beams then? Like, an electron beam, for example?
    Yeah. The individual electrons repel each other since they are all negatively charged. This makes them spread out pretty quickly. There's some work done on keeping the beam coherent in an atmosphere due to some really complicated interactions with air, but that won't work in space.
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    Quote Originally Posted by Numsgil
    Well, if you're assuming that the primary method of detection is looking for a spaceship's heat signature, there are real physical limits. The inverse square law means I can tell how far away it is. Emission Spectra mean I know what the object is made of. Black body radiation means I know its temperature (and probably incident surface area). Doppler Shift means I know how fast it's going, and how fast it's changing speed (acceleration). The Doppler Shift of the Emission Spectra of the spaceship's exhaust tells me how much thrust the engines are producing. Thrust / Acceleration gives me the mass of this ship.

    That's a lot of information, but still a lot of wiggle room for deception. For instance, if you manage to make your war ships look like colony ships, with similar mass and engines and size, you can fool the enemy into thinking that your ships are harmless. Or if you make your ships look like freighters you might be able to disappear into civilian ship traffic.
    Well, if we go back to mirror projection decoys, then what I'm assuming is that you have a very advanced image generation computer, that knows not only how to generate an apparent ship image, but also knows how to make that image appear to change, for instance, to give the impression of firing its rockets.

    Whatever a detecting computer to can think to look for, a projecting computer can think to imitate. The question is how accurate an image can you generate, and what tell tale signs would a mirror decoy give off? Can you mask them?

    In the first place, I'm guessing you couldn't use an RGB projector, because the detector is going to know how to tell the difference between mixed RGB colors and real true colors. That could make your projector pretty hard to build.


    Quote Originally Posted by Numsgil
    Quote Originally Posted by Pong
    About projecting ghost threats. I had in mind a space war environment with plenty of debris and clouds, from say exploded planets. At some stage no one side could track all those "fog of war" particles, so they'd be looking for suspicious ones. An image would only be a heat signature. Anyway it's just a minor possible mid-game strategy.
    The problem here is that if your dust cloud absorbs and then re-emits the energy, it's not going to look like a space ship, it's going to look like a hot dust cloud. You can tell what an emitting substance is made of if you check it's emission spectra. We did it in my highschool physics class years back.

    However if you replace dust cloud with ship debris field, then maybe you're on to something. You couldn't make the phantom ship move at all (the debris wouldn't cool fast enough to look like a coherent heat signature), but you could probably make it look like a fleet is hiding in the debris field.
    So, couldn't you throw out a dust cloud near your ship to mask (or at least distort) your own signature a little? The deep space equivalent of a smoke screen?

    If the distortion is confusing enough, then you might equip your decoys with dust cloud emitters too, so the small differences between projected and real ship images become harder to distinguish from dust-related noise.
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    Quote Originally Posted by kojax
    Well, if we go back to mirror projection decoys, then what I'm assuming is that you have a very advanced image generation computer, that knows not only how to generate an apparent ship image, but also knows how to make that image appear to change, for instance, to give the impression of firing its rockets.

    Whatever a detecting computer to can think to look for, a projecting computer can think to imitate. The question is how accurate an image can you generate, and what tell tale signs would a mirror decoy give off? Can you mask them?

    In the first place, I'm guessing you couldn't use an RGB projector, because the detector is going to know how to tell the difference between mixed RGB colors and real true colors. That could make your projector pretty hard to build.
    No, I don't think you could use some sort of "primary light color" beams and mix and match for a final image. I'm pretty sure if you did an emission spectrum analysis on a Television image you could determine what gas is being excited in the electron gun. In other words there isn't a way to confuse a TV image with the real thing since even elementary tests will determine that it's an image of a apple instead of an actual apple.

    If you're going to try faking an image, you'll need a way to fake the emission spectra for some arbitrary image. I don't know if that's possible (don't know if it's impossible either, of course). Then you need a way of faking the black body radiation. I also don't know if this is possible.

    If you can fake those two things, you might have a fighting chance of fooling your enemy (meaning I can't think of anything else that would give you away).

    So, couldn't you throw out a dust cloud near your ship to mask (or at least distort) your own signature a little? The deep space equivalent of a smoke screen?

    If the distortion is confusing enough, then you might equip your decoys with dust cloud emitters too, so the small differences between projected and real ship images become harder to distinguish from dust-related noise.
    When the dust cloud absorbs your radiation, it warms and then re-emits that radiation, probably at a lower frequency. Telescopes will probably be able to extrapolate how much energy the cloud is radiating, and thus how much energy is being inputted from your star ship, and thus how hot your star ship is. They'll know the difference between an empty dust cloud and a dust cloud with a ship inside.

    On the other hand, they might not know exactly where in the cloud your spaceship is, making kinetic kill weapons and beams less attractive. A gamma ray blast from a nuclear explosion will still be pretty effective, though. And it might be possible to create a fake cloud somewhere and heat it remotely with a laser to simulate a ship hiding inside. I don't know enough about it to say if it would be a convincing dummy, but it's the best proposal I've seen yet.

    Also, the dust cloud will probably lower your ability to cool yourself, since much of the radiation your cooling fins emit ends up reflected back at your ship. And of course your ship couldn't accelerate at all, or the cloud wouldn't follow it and you'd be exposed.

    It all depends on whether it's more like an actual smoke screen or a candle in a light fog.
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    When talking about decoys etc. everyone really needs to start specifying 1) how far away you are and 2) how long you plan the deception to last. If you are far away and I'm watching you through my telescopes, it won't really do you and good to throw out a dust cloud or something because I'll still basically know where you are (since the dust cloud can't be all that big) and the dust cloud will dissipate very quickly. So if you're trying to confuse the people in my command center, it's not going to work. If you're trying to confuse my missiles moments before they hit you, then yeah, the dust thing might work.

    One a side note, for anything not set in the far future where there's plentiful antimatter or something, nuclear salt-water rocket engines seem like the engine of choice for missiles. They're very high thrust and high specific impulse, but they're also hideously wasteful with valuable uranium - so you probably wouldn't want to push a huge ship around with them, but relatively small missiles wouldn't be such a big deal.
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    So what happens if you use a slightly magnetic cloud?

    Have two magnetic devices (rings around your ship, I guess), one of them is closer to your ship's hull and exerts a very strong attractive force on the particles (say they're negatively charged and it's positively charged). Then one that's a little bit further out and exerts a slightly weaker repulsive force (so it's negatively charged and they're negatively charged).

    And, I don't mean just one ring each. More like 2 cages of rings.

    The idea is that the particles are repulsed if they get close to the outer cage (because the near distance makes its repulsive force stronger, from the particle's perspective, than the attractive force of the inner ring that's further away, even though the inner ring is actually pulling harder in total) However, they won't drift too far away either (unless they reach escape velocity).

    Basically, if I'm right, this means you can keep your cloud near you. In some ways it's almost the beginning of a "force field" of sorts, except it's using actual particles instead of pure energy and it isn't exactly a solid protection, because the particles can only be traveling so fast in order to remain held.
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    The outer cage is going to be larger in volume than the dust cloud, which means instead of hiding yourself you've just made yourself an even bigger target.

    Also, you'd probably want both cages repelling the dust. If one cage is attracting the dust, it's going to stick on the cage like, well, dust. Really sticky dust.
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    Quote Originally Posted by Scifor Refugee
    nuclear salt-water rocket engines
    Interesting, I'll look into that.

    ***

    What I said about deception and fog of war and such, is assuming this sci-fi war plays out the way wars do: Stuff happens. Plans fall apart. It gets messy. Finally there's just so much accumulated noise and smoke (figuratively) that the direct approach works best. I don't buy the image of omniscient fortress solar system. Why not start the ball bouncing by just overrunning an outpost? That should pull defenders into the thick and thicker, easy. And let's not forget this is supposed to be a game. Like, fun?
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    Quote Originally Posted by Pong
    What I said about deception and fog of war and such, is assuming this sci-fi war plays out the way wars do: Stuff happens. Plans fall apart. It gets messy. Finally there's just so much accumulated noise and smoke (figuratively) that the direct approach works best.
    This works only if the debris in space is also warm like a ship. But you could maybe construct a handwavium science where war weapons cause matter to slowly disintegrate and release radiation, which would keep spaceship debris warm enough to make detection of an active ship more difficult amid all the noise.

    I don't buy the image of omniscient fortress solar system.
    I think the science holds up pretty well. If firing your engines means I can see you anywhere in the solar system (and the consensus of what I've read seems to indicate this), then war becomes a game of perfect information, at least if it's between only two countries/alliances/species. And also adjusting for the light speed lag.

    Add to that the fact that weapons in space can have extreme ranges, and it means an omniscient fortress solar system, where your only hope of not being 'sploded is using light lag to your advantage.

    And let's not forget this is supposed to be a game. Like, fun?
    Sure, but the whole point of this thread is to examine the actual science involved. Knowing that, it wouldn't be hard then to tweak the science to make whatever sort of combat is fun.
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    Quote Originally Posted by Numsgil
    This works only if the debris in space...
    No I meant more generally "stuff happens". Like a lot of refugees getting in the way, the need to protect or retrieve POWs, strategic outer planets or resources get captured, etc. War is always messier than planned on paper. Expect the unexpected.

    Maybe the attackers hunker down behind twenty kilometers of comet slush and ride in?

    Maybe they block traffic to a system that depends on trade?

    Maybe insurrection is brewing and won't end until the enemy is wiped out?

    Maybe the defenders are really geared for attack not defense?
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    Quote Originally Posted by Numsgil
    The outer cage is going to be larger in volume than the dust cloud, which means instead of hiding yourself you've just made yourself an even bigger target.

    Also, you'd probably want both cages repelling the dust. If one cage is attracting the dust, it's going to stick on the cage like, well, dust. Really sticky dust.
    Ok, I haven't explained myself properly then. The dust never gets inside the outer cage. It's always outside of both cages.


    Suppose we have two charged cages. A+ is the inner cage, B- is the outer cage. (your ship is inside the inner cage)

    Ship______A+________B-________Dust-

    Suppose A+ is stronger than B- in total. Because of the inverse square law of magnetic attraction/repulsion, when the dust drifts close to B-, it's still pretty far from A+, so the Repulsive force of B- still has more effect.

    Ship______A+________B-_ Dust-


    So, in the above case, the Dust- will be repelled, because it's close to B-, but far from A+, meaning that the net force on it is more repulsive than attractive. (It's being both repelled and attracted at the same time, but the repulsive force is stronger.)


    Ship______A+________B-______________________Dust-


    In this above case, the Dust- is far from both A+ and B-, and if A+ is a stronger overall charge (stronger by enough of an amount, I mean) , then the Dust- will be attracted, because the net force on it is more attractive than repulsive. (Again: it's being both repelled and attracted at the same time, but the attractive force is stronger. )

    I'm talking about manipulating the inverse square law. It's just like how if you're closer to the Moon than the Earth, the Moon's gravity dominates, even though the Moon is smaller than the Earth. It's the same principle. It's just that with magnetism you can have repulsive forces too, instead of just attractive forces.

    Basically, in this analogy, B- is kind of like the Moon. If you're closer to the Moon than Earth, the Moon dominates. If you're far away from both, you'll probably feel more of the Earth's gravity than the Moon's.
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    Well, let's check the math on that one, assuming that you could make a perfect enough sphere of a magnetic field like that. (I'm pretty sure you can't, but that's another question.)

    So, you have field strengths S and T, and magnet distances a and b. That totals up to: and the goal is to assign numbers such that there is a dip somewhere just outside of the outer magnet. Just looking at the equation, I'm not sure you could do that. I'd have to check more closely to be sure though.

    Edit: Actually, I think you might could get the right shape out of that. I don't have numbers to back that up though.
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    Oh, that's an interesting idea. What you're talking about is a lot like a L3 Lagrange point, but slightly different since you have an attractive and repulsive force. And the fact that it represents a stable equilibrium.

    If you replaced the dust with some low temperature plasma (keeping the cloud's mass low), you could probably effectively increase your resistance to laser weapons and EM bursts pretty cheaply, and also make it difficult for the enemy to know where exactly your ship is inside the "cloud". Of course kinetic and particle beam weapons will slice through your "shield" like a hot knife through butter. I'm not even sure what a charged particle beam weapon would do. The plasma would be extremely conductive... Also, a "shield disrupter" would be pretty easy to build: essentially a giant permanent magnet which collects material from your cloud to thin it out.
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