The SP-100 was an ambitious American program to develop a nuclear reactor for spaceflight applications carried out from 1983 to 1994. The SP-100 program resulted in a realistic design for a system that could deliver 100 kilowatts of electric power using a reactor with 140 kilograms of uranium-235 (in uranium nitride). The modular construction of SP-100 would enable the reactor to be used either as a power source for a large ion propulsion system or as an electric power station for a manned lunar or planetary base.