## Does physics forbid such a device; a heat destroyer

 Quote by bahamagreen Have you not read "The Gods Themselves" (1972) by Isaac Asimov? You want to employ a mechanism whose conception is yet outside known science, so you need to refer your basis to an interpretation that comes from known science but is not yet known to be true or false. The arguments against your idea are based on thermodynamics and conservation in a closed system... explore a way to employ the parallel worlds interpretation of QM to override these problems. Your basis will then have plausible deniability for as long as it takes science to settle on one interpretation of QM...

I haven't, I'll take a look at The Gods Themselves, thanks.

Mentor
 Quote by Deeviant A relativistic projectile would initiate a fusion reaction on contact. It would literally hit with the force of a hydrogen bomb...
Yes, the energy and force is on the order of a nuclear weapon, but the momentum is vastly different. The point is that you are focusing on the former and neglecting the latter, which tends to decrease the effectiveness.

 Quote by Deeviant Your gravitation defense is an interesting angle though. I think the biggest problem I foresee is that most defensive systems seem to ...
That is an engineering problem. If future tech can be allowed to solve the engineering problems of offense then "what is different in defense"? Particularly considering that we can already build bunkers to withstand a nuclear attack.
 Clearly the best solution is not to be stupid enough to start a war in the first place. edit: I actually think the future of this is a swarm of smaller drone-controlled units that can somehow co-ordinate their actions. I believe it's already a given that "human" pilots are history. This is however not fun to write about.

 Quote by Deeviant 1 kilogram projectile traveling at .99 C represents 10.52 MEGATONS of energy
I noticed wrong equation. KE=1/2mv**2 is classical physics. There's a different one for relativistic, but I do not recall it. Google or the other members here will know it. The actual energy is much higher as your mass increases as you approach light speed. For reference "1 megaton TNT equivalent blast" is 4.18 petajoules.

 Quote by rorix_bw I noticed wrong equation. KE=1/2mv**2 is classical physics. There's a different one for relativistic, but I do not recall it. Google or the other members here will know it. The actual energy is much higher as your mass increases as you approach light speed. For reference "1 megaton TNT equivalent blast" is 4.18 petajoules.
You right, I redid the math with the relativistic kinetic equation. It would be 1503.3 megatons for a 1 kilogram at .9999C projectile and 128.9 megatons for a 1 kilogram at .99C.

But that is only the KE. The actual amount of energy released could be more. For one, the projectile could be made of anti-matter and it's density combined with it's velocity with guarantees high amount of particle-anti particle annihilation. 1 kilogram of matter turns into 21.481 megatons of energy, of course this is assuming a 100% annihilation figure which isn't even close to the actual, however, this energy would not be solely directed in path of the projectile, but radiate outward throughout the ship(in fact much of the KE energy would do this as well). If anybody is picturing such a projectile to simply knock a neat hole right through a ship, they would be horrible mistaken, there would be little left. In fact, it would not take many of such projectiles to render earth inhabitable.

In effect, a relativistic mass-driver such as the .9999 C 1 kilo of antimatter design as outlined above would functionally be a laser that shoots planet killer level thermonuclear bombs. It is this fact, combined with that fact that a relativistic mass driver is on the lower end of the weapons theoretically possible that has led me to that classical sci-fi defensive mechanisms would be useless; armor isn't going to cut it, high maneuverability evasion of relativistic weapons doesn't seem likely at all without some sort of physics breaking propulsion engine(warp drive/higgs field blocker/etc) and there is no credible way to make a star-trek like shield with known physics(that I know of).

I will say that swarms of small expendable unmanned drones would certainly be effective, but than again, you certainly wouldn't want such a swarm to find your ship, would you...

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 Quote by Deeviant this energy would not be solely directed in path of the projectile, but radiate outward throughout the ship
This is simply false and yet again shows that you are neglecting the momentum.

It is well known in PET imaging that matter antimatter annihilation conserves momentum. The result is that the photons released do not simply radiate outward, but are angled toward the direction of the momentum. In this case, because the momentum is so high, they would be tightly collimated, and any that did go radially would have quite low energy.

 Quote by Deeviant If anybody is picturing such a projectile to simply knock a neat hole right through a ship, they would be horrible mistaken, there would be little left.
And I suppose that you have done some rigorous simulations (including momentum) of such a device that would support this extremely dubious claim?

Mentor
 Quote by DaleSpam 3) Military ships could be equipped with a material of very high specific heat capacity which is actively cooled down to a few μK (requiring substantial work) during "off duty" times. Then during operations that material could be used as the cold reservoir and the hull kept at 2.7 K without radiating. That would limit the time that they could be stealthed by the amount of time that it would take to heat up the material.
Btw, I ran some math on this. It turns out that the time depends linearly on the mass of heat sink material and the specific heat capacity, and inversely on the power. For a 1 kg heat sink made from a 100 J/kgK material you get 42 min at 1 kW.

Interestingly, the dependence on the starting temperature of the heat sink is very non-linear. The above calculations are for 1. μK. For 2.7 K, a factor of ~3 million change, the time is 11 min, only a factor of ~4 change.

 Quote by DaleSpam This is simply false and yet again shows that you are neglecting the momentum. It is well known in PET imaging that matter antimatter annihilation conserves momentum. The result is that the photons released do not simply radiate outward, but are angled toward the direction of the momentum. In this case, because the momentum is so high, they would be tightly collimated, and any that did go radially would have quite low energy. And I suppose that you have done some rigorous simulations (including momentum) of such a device that would support this extremely dubious claim?
As far as my best research can dig up, matter/antimatter annihilation does indeed conserve momentum but not in the way in which you describe. Any particle/anti-particle pair will have the exact behavior you describe but photon's conserve momentum in the form of photon pairs traveling in equal but opposite vectors, but in the end, it would not much matter, simple engineering could render the point moot; for instance the projectile could burst into a web of filaments after being launched, resulting in the ship being sliced into many different pieces, violently. And that is just one idea, but there would be a great many ways to tweak the projectile to get more of a "shotgun" effect.

As far as the launcher itself, it would be trivial; on a ship that is traveling at a relativistic speed(which is not trivial, but certainly possible, especially with the fact that the ship can take a long amount of time to accelerate). The ship could also be a kill vehicle and be consisting of independent highly modular autonomous vehicles that could break apart into many different guided sections and/or launch an almost arbitrary number of filament bombs. Such a weapon would not have any difficulty at all rendering a solar system uninhabitable and/or destroying any detectible structures/ships, and moreover, such a vehicle is not fantastical in the least within the realm of hard sci-fi. It just seems like the only defense in space would be stealth(or perhaps diplomacy, but we all know how well that works in today's world).

 Quote by DaleSpam Btw, I ran some math on this. It turns out that the time depends linearly on the mass of heat sink material and the specific heat capacity, and inversely on the power. For a 1 kg heat sink made from a 100 J/kgK material you get 42 min at 1 kW. Interestingly, the dependence on the starting temperature of the heat sink is very non-linear. The above calculations are for 1. μK. For 2.7 K, a factor of ~3 million change, the time is 11 min, only a factor of ~4 change.
So a 1 kg 100 J/kgK heat sink at 1. μK. would absorb 1 kW for 42 before reaching 2.7k? If that is true I don't understand the second part in which assumes the heatsink starting at 2.7k.

My current best design uses heat pumps to pull heat from across the ship and concentrate, then use a black-body pumped laser to lase energy in a very focused direction that I hope nobody will be listening, in addional to using heat sinks as you have suggestion with standard black-body radiator design when not in "stealth mode".

Mentor
 Quote by Deeviant As far as my best research can dig up, matter/antimatter annihilation does indeed conserve momentum but not in the way in which you describe.
Then your best research isn't very good. Google the terms "relativistic beaming" and "relativistic aberration".

 Quote by Deeviant So a 1 kg 100 J/kgK heat sink at 1. μK. would absorb 1 kW for 42 before reaching 2.7k? If that is true I don't understand the second part in which assumes the heatsink starting at 2.7k.
It absorbs heat for 42 min before reaching 1275 K, at which point the engine efficiency is 0 and no more work can be extracted.

 Quote by Deeviant My current best design uses heat pumps to pull heat from across the ship and concentrate, then use a black-body pumped laser to lase energy in a very focused direction that I hope nobody will be listening, in addional to using heat sinks as you have suggestion with standard black-body radiator design when not in "stealth mode".
Since you are using heat pumps work is being done and the second law of thermo should be OK. I don't know much about blackbody pumped lasers. I would be surprised if they cool the blackbody at all.

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 Quote by Deeviant As far as the launcher itself, it would be trivial; on a ship that is traveling at a relativistic speed(which is not trivial, but certainly possible, especially with the fact that the ship can take a long amount of time to accelerate).
With 10g of acceleration (too much for any humans), an acceleration to .1c requires ~4 days and ~500 million km. You would need the whole inner solar system to accelerate and break, and .1c is far away from any relativistic effects.

In addition, your system to accelerate the ship is a weapon of mass destruction on its own. And you probably want a really powerful energy source. Direct antimatter annihilation would have the capacity, but is hard to store and handle (and imagine your storage getting hit by anything!) and probably give an exhaust visible even from other stellar systems (while this is not an issue due to the delay, it means that it is easy to spot for everything in the same system). Hawking radiation might be useful but gives a lot of heat to radiate away, and it is tricky to accelerate the black hole with 10g.

 My current best design uses heat pumps to pull heat from across the ship and concentrate, then use a black-body pumped laser to lase energy in a very focused direction that I hope nobody will be listening, in addional to using heat sinks as you have suggestion with standard black-body radiator design when not in "stealth mode".
Your current best design violates basic laws of physics.

Mentor
 Quote by mfb With 10g of acceleration
Railguns designed with today's technology could produce ~2000 g.

http://en.wikipedia.org/wiki/Railgun
 Mentor Deeviant was talking about a ship, not a projectile. As the ship should have its own railgun, I would assume that it is too large to be launched by regular railguns. In addition, even with an insanely oversized railgun, capable of accelerating a whole spaceship with 2000g, and a spaceship which can handle this, the acceleration track would be more than 1 million km long. At this size and in the inner solar system, the inhomogeneous gravity from the sun becomes significant. And it cannot "catch" the spaceship afterwards.

Mentor
 Quote by mfb Deeviant was talking about a ship, not a projectile.
D'oh! I completely missed that. I was entirely focused on the projectile discussion.

 Quote by Deeviant I will say that swarms of small expendable unmanned drones would certainly be effective, but than again, you certainly wouldn't want such a swarm to find your ship, would you...
That is the ship. I don't know why you need a pilot? If it isn't the ship, then you just re-invented are playing carrier war in space and my original post applies.

PS: If you think relativistic projectiles will induce fusion or antimatter reactions by virtue of the energy they deliver (which they might or might not do), then even one loose hydrogen atom, or one tiny grain of space dust, would cause detonation.

How to ensure the projectile does not go BOOM inside, or close to, the launcher? (Also a crop sprayer on the front of the ship would be an effective defence while closing...)

Also I think you really need to think about the engineering "difficultes" inherent with getting up to even 1/10th of light speed. Those are not simply going to go away with bigger drives. There is the Tsolikov Rocket Equation to consider.

http://en.wikipedia.org/wiki/Tsiolko...ocket_equation

In laymans terms, top speed of a ship in space is proportional to the exhaust velocity of the drive, and the fuel system has to conserve momentum. Which means the ship is going to be like 99.99% fuel or something and you need a drive with relativistic exhaust velocity. (Which will of course explode unless you concede say that relativistic mass driver weapons don't cause fusion by kinetic energy transfer)

edit: Actually i think that equation doesnt apply to relativistic speeds, upon reading further I see there is a relativistic version of it presented, however.

 Quote by mfb With 10g of acceleration (too much for any humans), an acceleration to .1c requires ~4 days and ~500 million km. You would need the whole inner solar system to accelerate and break, and .1c is far away from any relativistic effects. It doesn't have to be manned(and in this case it would not be, considering it will turn itself into a projectile). Secondly, you are assuming that humans in the future will be like the humans of today, this is a bad assumption. There are no physical laws forbidding the complete resign of the human body and/or integration with technology, and even more so, we have every reason to believe that humans will continue to "improve" our design. If a human is re-engineered to live in liquid for example, the possible acceleration could be enormous as accelerating the whole tank would not put a lot of strain of the person inside, since the force would be evenly distributed as a pressure gradient in the liquid. A complete redesign of the human body using genetic code like we use software code today plus integration of technology is already part of the world I am building. Also, it does not break, it collides, the whole thing is a projectile In addition, your system to accelerate the ship is a weapon of mass destruction on its own. And you probably want a really powerful energy source. Direct antimatter annihilation would have the capacity, but is hard to store and handle (and imagine your storage getting hit by anything!) and probably give an exhaust visible even from other stellar systems (while this is not an issue due to the delay, it means that it is easy to spot for everything in the same system). Hawking radiation might be useful but gives a lot of heat to radiate away, and it is tricky to accelerate the black hole with 10g. There are no laws forbidding a ship traveling at sub-light speed, it is well accepted in the hard sci-fi canon, and really nothing to be gained by trying to argue against it. It is an engineering problem, I have my own ways I will theorize how they can be solve and many others have their own, but it is truly irrelevant to this discussion. The ship could start acceleration far out-system and "Buzz" by, destroying everything in sight. Your current best design violates basic laws of physics. It is perfectly compatible with physics. I use a heat pump, which takes energy to move heat and concentrate it into a black-body chamber, the photons are then used to pump a laser(remember I could just radiate the heat right into space via black-body if I wanted, the only thing that is different is that I want to do so in a focused beam to reduce detection) Here is a patent for a black-body pumped laser with a good description of it's operation http://www.freepatentsonline.com/3614663.html

 Quote by mfb Deeviant was talking about a ship, not a projectile. As the ship should have its own railgun, I would assume that it is too large to be launched by regular railguns. In addition, even with an insanely oversized railgun, capable of accelerating a whole spaceship with 2000g, and a spaceship which can handle this, the acceleration track would be more than 1 million km long. At this size and in the inner solar system, the inhomogeneous gravity from the sun becomes significant. And it cannot "catch" the spaceship afterwards. The ship accelerates itself to high relativistic speed out-system, undetectably. It then fires it's projectiles in intercept vectors when it nears or enters the system, it is almost moving at relativistic speeds the only thing the launcher would have to do is set the projectiles into intercept vectors, for added effect the entire ship can collide into a planet to sterilize it or it could split up into independent vehicles (a la MIRV) and spread the destruction
 Quote by rorix_bw Also I think you really need to think about the engineering "difficultes" inherent with getting up to even 1/10th of light speed. Those are not simply going to go away with bigger drives. There is the Tsolikov Rocket Equation to consider. http://en.wikipedia.org/wiki/Tsiolko...ocket_equation Once again, these are all arguments for why it is difficult to get a ship up to relativistic speed, in hard sci-fi, it can be assumed this enormously complex but theoretically possible feat has be achieved. .
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Mentor
 Quote by Deeviant It is perfectly compatible with physics. I use a heat pump, which takes energy to move heat and concentrate it into a black-body chamber, the photons are then used to pump a laser(remember I could just radiate the heat right into space via black-body if I wanted, the only thing that is different is that I want to do so in a focused beam to reduce detection) Here is a patent for a black-body pumped laser with a good description of it's operation http://www.freepatentsonline.com/3614663.html
I didn't see anywhere in the patent that the lasing would cool the blackbody. On the contrary, they had to use a coolant to keep the lasing material cooler than the blackbody cavity.

However, you could just use mirrors and optics to radiate the heat in a focused beam. So that isn't an "in principle" problem, just a "best practice" problem.

 Quote by DaleSpam I didn't see anywhere in the patent that the lasing would cool the blackbody. On the contrary, they had to use a coolant to keep the lasing material cooler than the blackbody cavity. However, you could just use mirrors and optics to radiate the heat in a focused beam. So that isn't an "in principle" problem, just a "best practice" problem.
Yes, it wouldn't be coherent but it would at least be directional, somewhat controlled and far more efficient...