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I know they have systems that flow water through there suits to keep them cool. But how do they block out the coldness that is space? What materials do they have for this?

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  • $\begingroup$ It's only cold in the shade. $\endgroup$
    – gerrit
    Jun 30, 2016 at 0:25
  • $\begingroup$ Well, how do they stay warm in the shade. $\endgroup$
    – LostPecti
    Jun 30, 2016 at 1:14

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Space isn't actually hot or cold. Here on Earth, you're radiating heat away all the time, although not very fast. Other things around you are radiating heat at you, as well (usually slower). Those processes are very small compared to the way the air and evaporation are cooling you.

In space, nothing is radiating back at you and you will get cold if the sun isn't shining on you, but it shouldn't take much insulation to make it so the outside of your suit is much cooler than the inside, so your losses by radiation will be much smaller.

Being in the sun, absorbing all that heat with no good way to get rid of it, is going to become a problem much faster than cooling off in the shade, I'd imagine. Add a little insulation, so the outside of your suit can get very hot and radiate heat away more quickly without heating up the inside, and that will help as well.

Of course, if you're perfectly insulated, your own body heat will cook you. I suspect that enough insulation to let you withstand the full sun will also keep you from cooling off fast enough in the shade, so you'll need some sort of cooling mechanism in addition to the insulation. You could bleed off some of the air you exhale, maybe, or carry some water and let that boil off into space.

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  • $\begingroup$ Thanks for the detailed answer. I read from a NASA PDF file that outline there suit, they use a polyester film for insulation and have a water flow system to keep then cool. $\endgroup$
    – LostPecti
    Jun 30, 2016 at 1:21
  • $\begingroup$ Sublimation of water. $\endgroup$
    – user
    Jun 30, 2016 at 13:09
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There are three ways of losing heat:

  1. Conduction (two bodies touching each other, the warmer transferring heat to the colder until both are equally warm/cold)
  2. Convection (warmer gas/liquid rising up, taking heat away)
  3. Radiation (giving off heat in the form of electromagnetic radiation, e.g. infrared light)

In space, nothing is touching you, and there is no air or liquid, which means #1 and #2 are out. And #3 is extremely inefficient. That's why, for example, the ISS needs huge radiators to get rid of the excess heat, otherwise the astronauts would literally be cooked pretty soon.

So, in other words: yes, space is really cold, but the mechanism for losing heat to the cold space is so inefficient that getting rid of, not preserving, your own body heat will be the actual problem. You will die of a heatstroke, not hypothermia.

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