All the artificial satellites launched in space have a series of solar cells attached to them. When in use, these panels absorb a lot of radiation from the Sun and put it to use. So, do these panels get hot with exposure to radiation as on Earth? Since there is no medium available in space to dissipate the heat, how is it relieved?
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2 Answers
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Convection isn't a usable heat dissipating function in space, because there is no convecting medium.
Radiation, however, works extremely well. Any body in space will radiate in a wide range of wavelengths, and will also absorb radiation.
So any part of a space craft or satellite facing the sun will absorb heat (a net gain) and any facing away will radiate heat (a net loss).
Satellite designers minimise the absorption of energy by the use of reflective foil wherever possible, and provide heat radiating fins in order to dissipate excess heat on the dark side of the satellite.
answered Dec 6, 2013 at 9:23
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$\begingroup$ I think I remember some insulation that's layers of foil (with a very low emissivity) spaced out with a very low conductivity mesh. If (for example) each layer of foil reflects 98% of the radiation, and the spacer is negligible, the heat is reduced by 2 orders of magnitude for each layer $\endgroup$– Nick TCommented Dec 11, 2013 at 16:57
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To add to Rory's answer, satellites also use heat pipes to transfer heat from the hot side to the cold side; they are highly thermally conductive.
Consider a cube-shaped satellite, with one side facing the sun. By using heat pipes or otherwise distributing the heat, the radiative area can be increased to up to 6 times the sun-facing side.
Keeping the temperature difference between different parts of the craft low is important, as a higher gradient induces greater mechanical stress (one side expands without the other side doing so).
