@stux well you can still get the heat off of things. But you are limited to one of the three heat transfer methods, radiation. Ther eis no convection or conduction.

@freemo And that's slooww, hoomans will become like a big beef jerky in plain space right ​

@stux Attached you can see the giant heat radiators the ISS needs to use. This helps cool off the ISS systems using radiative heat (they are designed to be black-bodies and radiate it as IR)

Humans in space would essentially turn into astronaut ice cream but it would take some time. They would freeze dry.. so first your blood boils (though this isnt very fast since your enclosed in a meat sack). The boiling off of water will cool you until you freeze (likely hours), then your frozen corpse will sublimate (the ice turns direct to gas).. over days youd eventually be jerkey.

@stux interesting fact. You could, in theory, take your helmet off in space and survive for a hot minute. You probably will be pretty beat up when you get back in. But death isnt as fast as they show in movies.

@freemo @stux you'll only be conscious for about 10 seconds of that

@icedquinn

15 second conscious time or more, 90 second survival time more if you want actual numbers. That is based off tests on dogs. but all ddogs survived <90 seconds and they all stayed conscious for at least 15 seconds.

@stux

@icedquinn

Also fuck whatever scientist stuck dogs in hard vacuums, thanks.

@stux

@freemo @stux for our next trick, spacefauci will see how many peppers you can eat with your eyeballs while hanging upside down on the ISS.

@icedquinn

Wordsmith quinn is at it again :)

By the way the dogs bloated up like " bloated goatsskin sacks" but recovered enough to walk and be normal after only 15 minutes.

@stux

@freemo @stux i mostly remember this because people were nerding out about the space jump in bebop and people found out you can actually do this

@icedquinn

Hahaha yea, a quick trip through space is possible but it sounds absolutely awful. You would have instant bends, go blind before you go onconscious probably from occular pressure. You would literally feel your tongue boiling off as it freezes. You would bloat up and couldnt really move easily.... it sounds awful.

@stux

@icedquinn

Oh and did I mention that if you tried to hold your breath, as would be your instinct, you would have completely destroyed your lungs and no chance of survival at that point... to survive you MUST exhale. We know this even in scuba, if i hold my breath and ascend a few feet I die.

@stux

@freemo @stux

You can also evaporate something (but only as long as you have something to evaporate). Surprisingly many spacecraft used evaporative cooling at least sometimes (Gemini had an evaporator that seemed to have been used at low flow continuously, Apollo LM was cooled purely by evaporation, Apollo CSM had an evaporator to allow higher heat rejection rates than by radiators alone and as the sole way to dispose of heat after the SM was gone, Shuttle had an evaporator to cover high heat load intervals and, I assume, to help in the case the payload doors won't open).

@robryk

Yes very true but evaporative coolin can be tricky since it can freeze and slow the heat transfer. Plus as you say, it requires a "fuel" that is expended to do it.

@stux

@freemo @stux

Actually I forgot one "spacecraft": Apollo portable life support backpack used a sublimator. I _think_ all the spacecraft I mentioned previously used evaporators, but am less sure than previously (esp. about the LM, which had to support very low power levels). Funnily enough, in some cases the evaporator (or the steam piping from it) actually had an electrical heater to prevent freezing.

Apollo CSM, late Gemini, and Shuttle had an overabundance of water (because they were powered by hydrogen-oxygen fuel cells), but that water had to be condensed from steam first, so the evaporator was essentially part of "negative heat storage" system. Apollo LM was constrained to a very short period of operation by many other constraints (e.g. the descent engine would become inoperable IIRC 72h after it was first used, and something like a week after launch).

@robryk @freemo @stux There's also things like liquid droplet radiators, which allow you to have radiators running at much higher temperatures than the materials would allow for a solid radiator, but you lose radiator material if you accelerate while using them.

@izaya @stux @freemo

Wikipedia doesn't say anything about water droplet radiators behind able to handle higher temperatures. I also don't understand how would that be possible: the liquid, before being sprayed has to be pumped through pipes, so we need to have a material that can withstand that temperature (and I naively expect that adding the "has reasonably high thermal conductivity" requirement doesn't narrow things that much; does it?).

@robryk @stux @freemo not water, liquid
like liquid metal
https://en.wikipedia.org/wiki/Liquid_droplet_radiator

@izaya @stux @freemo

Sure, but you still need to pump it through the device you're cooling, so you still need pipes that can withstand the operating temperature of your coolant.

@robryk @stux @freemo sure, but you can use bizarro materials that don't radiate heat well but can handle high temperatures to make the pipes
(There's probably ways to rules laywer thermodynamics to get the cooling fluid higher temperatures than would otherwise be allowed but I'm smol brain)

@izaya @stux @freemo

Hm~ I'll need to look up examples of materials used for high-temperature pipes. I had a baseless impression that they're always metal (well, not completely baseless -- they need to be flexible or to have very small thermal expansion coefficient).

What kind of rules you'd want to lawyer? My impression is that the temperature of the coolant is limited by the temperature the device being cooled can handle. Ah, we could try pumping heat from the device into the coolant, thus increasing the cooling power (because coolant's hotter), while paying some penalty in having generated some additional heat (because efficiency of heat pumps is thermodynamically limited)? Thanks, I'll need to think about it.