rickman wrote in :

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".


There's still such a thing as radiation resistance, I think, so it wouldn't
stay cold even there. Given the size of a body, there's a limit to how fast
it can get rid of heat at a given temperature.. I don't know the proper
terminology for it though. Anyway, at low tenperature, the rate it can
radiate heat is low, so it will quickly warm up out of low-temp
superconducting state.