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If thermal energy is lost via blackbody radiation, and it's relative to the temperature of the body and its surface area - could you effectively cool a large body by pumping all the thermal energy into a small space, and use blackbody radiation to remove energy from the system (cooling the average large body temperature down)?

For example, you have a space craft in a vacuum with an average body temperature of 500K. Using heat pumps, you bring the average body temperature down to 200K except on a single spot where the temperature is much much higher (defined by he energy previously in the rest of the large body). This would assume you have perfect thermal insulation between the main craft and the hot spot, and no practical upper limit temperature of the 'hot spot'.

I'm thinking about possibility from a physics point of view, ignoring the difficulties in thermal isolation and pumping that much heat around.

EDIT: I think I was being too skeptical, so I'll move to the thing that prompted the question in the first place.

The game 'Elite Dangerous' features battle spaceships, with a veneer of plausible concepts/physics alongside the usual 'because it makes the game more fun' violations.

Dealing with heat is one aspect of the game, and the ships are shown with glowing red 'cooling vents'. When open, these vents make it easier to detect the ship but closing them causes a runaway heat buildup. Now obviously vents is misnomer, because they don't release gas, but could they work by radiation?

On a large, complex craft that generates a lot of heat but a large surface area radiators would be impractical - a small area, but with thermal energy concentrated so it has an extremely high temperature (probably below fusion temperatures though) work to remove thermal energy from the system in a practical way?

Image below shows fictitious spacecraft firing lasers, and radiating excess thermal energy through glowing 'vents'. enter image description here

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  • $\begingroup$ Given that this is currently done on satellites (within some reasonable interpretation of the OP's question), yes it can be done. $\endgroup$
    – Jon Custer
    Jul 5, 2018 at 15:17

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This is exactly how the cooling system works on the Parker Solar Probe. It is surprisingly simple in principle. Water is pumped through the solar panels to cool them and then pumped to a radiator where it cools by black body emission.

I don't think many satellites use active cooling systems like this since in most cases the amount of heat that has to be dissipated is far lower. It is sufficient to paint the satellite with whatever emissivity paint is appropriate. This is described in the answers to Cooling a satellite.

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  • $\begingroup$ I was tempted to mark this question as a duplicate of the linked question, but that question should be closed as too broad. A correct answer to that question would require a book or two or three. There are dozens of books that cover this topic and this topic only. Even this narrower version of that overly broad question is the sole subject of multiple books. $\endgroup$
    – David Hammen
    Jul 5, 2018 at 20:45
  • $\begingroup$ It's not just the Parker Solar Probe that uses active thermal control. The International Space Station, almost every space telescope that looks in the thermal infrared range, and many other spacecraft use cooling loops to transfer excess heat to thermal radiators. $\endgroup$
    – David Hammen
    Jul 5, 2018 at 20:53
  • $\begingroup$ I was aware of radiators on craft/satellites but I hadn't really thought about water pumping heat to them, but now that I think about it how else would they work. $\endgroup$
    – Oliver
    Jul 6, 2018 at 7:00

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