What's the difference between SF rocket ships and real spacecraft? Fantasy rocket ships almost never have radiators. Go to your local used book store and look at the cover art of SF novels. Do they ever have radiators on them? I've only seen it a couple of times in 30 years of reading SF, e.g. the "Lying Bastard" in "Ring World". Take a look at the JIMO spacecraft: It's almost ALL radiator. The artist's conceptions of the interstellar spacecraft that were studied by the British Interplanetary Society and Lawrence Livermore National Lab were also almost all radiator. The radiator was a significant design feature in the Space Shuttle's bay doors and on the side of the Apollo Service Module.

Gary