#fleeting Spaceships have lots of heat generating things inside them, like humans that convert food to heat... In a vacuum, only radiative heat transfers - not conductive or convective due to the lack of particles. So they often need a radiator system that are optimized for radiating heat. See also the [[Stefan–Boltzmann Law]] The radiators on the [[Space Shuttle]] are in the cargo bay doors, which is why it opens the doors once it reaches orbit. Source: https://www.youtube.com/watch?v=w5fvy1ZcIZk