Pardon my potential ignorance, but I’m under the assumption that radiating heat in vacuum is NOT easy. Normally, heat escapes from sources into the surrounding atmosphere, whereas in space, only radiant heat (IR?) can bleed off into vacuum. The conductive heat from, say, a cycling loop of water still needs a radiator that vents into surrounding volume. Without atmosphere, radiators can’t conduct efficiently, right?

Please set me straight if possible.