
Nuclear power in space is the use of in , typically either small systems or for electricity or heat. Another use is for scientific observation, as in a . The most common type is a , which has been used on many space probes and on crewed lunar missions. Small fission reactors for Earth observation satellites, such as the , have also been flown. A

Passive nuclear safety is a design approach for safety features, implemented in a , that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a safe shutdown state, in the event of a particular type of emergency (usually overheating resulting from a or loss of coolant flow). Such design features tend to rely on the engineering of components such that their predicted behavio.