By comparison , only a few space vehicles have been launched using full - fledged nuclear reactors : the Soviet RORSAT series and the American SNAP - 10A .
RTGs were also used for the Nimbus , Transit and LES satellites .
Only a few space vehicles have been launched using full - fledged nuclear reactors : the Soviet RORSAT series and the American SNAP - 10A .
RTGs were also used for the Nimbus , Transit and LES satellites .