Jeff wrote in :

...or looking at it another way the dissipation in the radiation
resistance is not in the form of heat it is the power radiated into space.


Well, I did say I didn't know the terminology. On the other hand, I'm not
talking about antenna's radiation resistance. The only thing I'm sure of here
is that some body, at some temperature, can not emit heat faster than some
rate, and that superconductors in space will warm up too fast to stay
superconducting without support to cool them.

This discussion looked like it had strayed some way from the earlier talk of
antennas and radiation resistance.