[Retric]

Closed loop steam power is actually not that unreasonable in space.

Concentrated solar cells have been considered for a range of space operations. They generate a lot of waste heat, which opens the way for a range of heat engines. Currently, non concentrated solar is a clear winner but serious effort went into studying combined systems.

Long term several space mining concepts involve using concentrated sunlight to heat and refine asteroids. This would tend to make quite a bit of waste heat and steam power is one method to utilize that waste heat.