Spacecraft are often required to operate in the outer reaches of the solar system and beyond where sunlight is very faint. Nuclear Power Systems (NPS), which includes both Radioisotope Power Systems (RPSs) and Fission Power Systems (FPS, Nuclear Reactors), are the only available power sources that can operate without constraints in these environments for the long periods of time needed to accomplish many missions. Efficient heat to electric conversion technology is needed to provide more power from significantly smaller and lighter weight sources that use less Pu238 and that require less structure for mechanical support and thermal management.

The Johnson-Thermo-Electrochemical Converter (JTEC) is a solid-state heat engine that has the potential for converting NPS heat into electricity at net efficiency levels as high 30 to 40% net, 70 to 80% of Carnot based on typical RPS heat source operating temperatures. Over the past five decades, conventional thermoelectric converters (Seebeck) have not been able to exceed 15% of Carnot (6% to 8% net). As a more efficient replacement for existing thermoelectric technology, JTEC will provide NASA with an attractive alternative for addressing the ever present need to minimize the amount of mass that must be delivered to space using expensive launch vehicles. A laboratory proof-of-concept demonstration has been successfully completed and an initial application analysis has been performed to understand the technology and its potential impacts at maturity. JTEC represents an opportunity to develop common technology that feeds both FPS and RPS and, thereby, support a full spectrum of space power requirements.