Power for Deep-Space Missions: High-Specific-Power Nuclear Energy

Electric propulsion can provide very large total velocity increments but its capabilities are directly constrained by the power and mass of the power system. For deep-space missions, the specific power of the complete power system therefore becomes particularly important. The system includes the heat source, energy conversion, heat transport and waste-heat rejection. This paper presents a concept for nuclear power systems using static thermoelectric (TEG), thermophotovoltaic (TPV) and thermionic energy converters (TEC) integrated directly with the radiator. The proposed approach is intended to reduce thermal-control-system mass by using the same large-area structure for both energy conversion and heat rejection to space. Design targets of approximately 50 W/kg are considered for TEG and TPV systems while the prospect of achieving 500 W/kg is examined for high-temperature thermionic converters. Requirements for the reactor, operating temperatures, converter area and deployable structures are also discussed together with the principal materials and mechanical challenges. Achieving these specific-power levels could transform nuclear electric propulsion from a supporting technology into the foundation for new classes of deep-space missions.