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I am aware of methods such as heatsinks, radiators, and thermoelectric generators, but I was wondering if there are any alternative methods to dissipate heat on a military vessel in combat. Preferably without dumping raw mass into deep space for no other purpose than heat management, although if it serves an alternate purpose as well(decoys, munitions, etc), I'm fine with it. The technology level is fairly high, with many well-developed systems on par with Earth. technologies such as extremely efficient magnets, EXTREMELY power-hungry gravity manipulation, FTL travel, etc.

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Fundamentally, if a spacecraft's reactor produces one megawatt of heat, there will be one megawatt eventually leaving the spacecraft, and with very little conduction or convection, the only way that heat is getting disposed of is radiation.

extremely efficient magnets

I don't know what your research on radiators has entailed. Are you familiar with the Curie-point liquid-drop radiator? It's a system that pumps heat into small ferromagnetic pellets or droplets until they stop being ferromagnetic, sprays them out into space to lose their heat by radiation (a thin sheet-cloud of tiny spheres is extremely efficient at shedding heat!), and then pulls the cooled-down ones back in with a magnet since they become ferromagnetic again.

There's little to no net mass loss, strong magnets can keep the pellets under control even while under acceleration, and it doesn't present the same kind of target for enemy weapons that a large wing-style radiator panel does, so it would be a natural fit for a military spacecraft.

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    $\begingroup$ Cooling a spaceship with a giant marble-machine radiator is, to be honest, incredibly metal. $\endgroup$
    – Mermaker
    Apr 18 at 20:53
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    $\begingroup$ The book Saturn Run by John Sandford and Ctein (2015) features these in a neat way (to run help run a ship based around a VASIMIR engine). Also, the game Terra Invicta has them and they are some of the best radiators you can get for the reasons described here (tin droplet radiator plus some variants) -- mass efficient and not very vulnerable to fire. I think there's some question of intense maneuvering causing you to lose your marbles but that's manageable (w/ magnets as described), and at worst something you plan for $\endgroup$
    – Wavedash
    Apr 19 at 3:00
  • $\begingroup$ When I first read the question, I had the idea of pumping heat into the ammunition. This might be an excellent vehicle for that. $\endgroup$ Apr 20 at 1:00
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The ruthless truth of physics as we understand it today

  1. Heat happens.
  2. Heat sucks.

What can we do?

  1. Yours is a future tech where FTL is possible. That lets us make some assumptions that aren't just convenient, they're kinda required.
  • Energy efficiency is much higher than today.
  • The ability to move heat around is much better.
  • Material science is much more advanced.
  1. We need two, maybe three "stages" of heat dispersal. What can we do right now? vs. what must we do later?
  • You need radiation shielding anyway, and one such solution is to use water. This is also convenient for space combat as compartmentalized water between the hull and interior can give you an ablative defense (for a while). In the mean time, each time you use the FTL or fire your favorite spinal mount and generate a boat load of heat, you simply channel that heat into the water tanks. You can put an unbelievable amount of heat into (for lack of a better term) a boiler. Funny thing about boilers — they can drive electrical turbines. However, full disclosure, the energy recovered this way is a drop in the bucket compared to what you're using to generate the heat in the first place. Still, every joule counts, right? Besides, extracting kinetic energy from the steam pressure cools the water. In fact, it's akin to the process that artificially makes ice.

  • But! You can only cool that steam down so fast and once you've maxed it out you've gotta do something. You can begin by covering your ship with any of the radiators you can read about. It almost doesn't matter which because they're based on the limits of science today. Remember, better thermal transfer! Better material science! That means you'll start dumping the heat quite well. But it might still be insufficient. IMO, you don't want it to be sufficient.

  • So eventually you just need to dump vast amounts of heat. This will obviously be in a non-combat situation when you're not immediately generating it and can't risk what might happen to your get-rid-of-the-heat solution when laser bursts and bullets hit it. What can you do? I'm fond of what I'll call the "slippery-slide technique." Let's roll out a 500km long fairly thin sheet that drags behind the ship. Water flows down one half then back via the other half. When it gets back is chilled to a comfortable 33℉ so that it's still liquid.

Why am I advocating such a complex solution?

Because things are rarely simple. Want simple energy? Light a fire. Want to power a nation? Use a nuclear reactor. Fires are simple. Nuclear reactors ain't. A complex solution to a complex problem will be more realistic to readers than the best technobabble one-step-to-magic solution.

On top of that, the complexity gives you hooks to use for crises in your story.

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