Nuclear Electric Propulsion

Nuclear Electric Propulsion (NEP) uses a nuclear reactor to generate electricity to power an Ion thruster. It requires some kind of converter from heat to electricity and is subject to thermodynamic limitations. The reactor usually needs to be cooled using radiators. The exhaust velocity is generally higher than for Nuclear Thermal Propulsion so the engine requires less propellant. However, the mass of the required radiators and energy conversion systems reduces the overall effectiveness.

NEP is in direct competition with Solar Electric Propulsion (SEP). As technologies change and evolve either SEP or NEP are advantageous. For missions past the asteroid belt and Jupiter, SEP is no longer viable du to the reduced solar constant and NEP is the most likely solution for larger scale missions that require stopping and maneuvering at the target planet. Near Earth and towards the inner solar system SEP is usually less expensive in terms of mass and is more advantageous in terms of development costs, as there are currently no nuclear reactor available for space propulsion, while photovoltaic solar is a mature technology, readily available.