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Comment by wmil | Hacker News Reader

Most people assume that, and most sci-fi reinforces that opinion. But a generic Thermos is a vacuum flask.

Space is an incredible insulator. The only way to cool things is to radiate heat.

The sci-fi game series Mass Effect had a good explaination for this, and tied it in with the notion of ships having recognizable "signatures":

http://masseffect.wikia.com/wiki/Codex/Ships_and_Vehicles#St...

It also works similarly in Eve Online, btw.

Indeed, whenever corp-mates would ask why there are brightly lit "windows" on their ships I would point out that they were actually heat dissipation panels.

A major mechanic in Elite Dangerous is managing your ship's internal heat and heat signature.

Thank you. TIL, actually not learned realized, space is actually a good insulator out of earth conditions too. Prejudices. We can never know what if something we thing is a reality or prejudice. Science and skepticism is that important.

Also of note is that while a vacuum doesn't necessarily have a temperature (it's just a medium), space does.

Even if you go far away from anything else, you will still reach thermal equilibrium at the Cosmic microwave background (CMB) temperature, which is 2.7K -- it's essentially the "temperature of the universe", radiation which has been emitted as far back as the first moments of the universe.

And of course, if you create a vacuum chamber on Earth, any object inside will always reach equilibrium at ambient temperature (in the lack of any heat engines on the body -- even then the fuel would deplete some time).

Technically interplanetary space is a hot plasma too. The particles emitted by the Sun are very hot according to kinetic theory (which only depends on the mean velocity of particles) since they have a lot of energy. It's a plasma because the particles are charged and accelerated by the Sun's magnetic field.

Of course the density of these particles is very low, so if your definition of heat factors those in then space is cold.

Why did it get so cold inside of Apollo 13 then?

My understanding is that the spacecraft was designed to radiate large amounts of heat, with the expectation that systems inside the spacecraft would be producing a lot of it. Apollo 13 shut down much of the equipment inside the spacecraft, which meant that it was no longer producing as much heat as was expected.

Evaporative cooling ought to work really well?

It would with an unlimited supply of coolant, but bringing mass is expensive. Unless you start grabbing asteroids and using your waste heat to vaporize them or something....

Bolt habitat to asteroid heatsink, profit.

That's what we have Planetary Resources for ;).

But that would use up material, all of which has to be trucked up to orbit at great expense.

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