rickman wrote in :

Lol, radiation resistance is from the signal energy *leaving* the
antenna. It does not show up as heat!


I already posted that I wasn't talking about radiation resistance as used in
antennas. I just meant that some object, at some temperature, is limited in
how fast it can get rid of its heat. (Also, assuming that even in space a
thing may get heated a little by something, no matter how well someone tries
to shield it, and that it won't take much to prevent a superconductor
working).