Power Converters for Spacecraft

For over 30 years, NASA has used radioisotope thermoelectric generators (RTGs) to provide electrical power on a range of space exploration missions. Currently, Creare engineers are working with NASA on the Radioisotope Power Conversion Technology (RPCT) project. This activity is an ambitious attempt to improve the power conversion efficiency and reduce the weight and cost of the next generation of radioisotope power systems.

Creare is developing two alternative power conversion systems, one dynamic and the other static, that promise to improve conversion efficiency by a factor of two to four and reduce weight by a factor of two to three. Both of these projects include demonstrations of breadboard power converters.

In one project, our dynamic power conversion concept is based on miniature turbomachinery technology used to compress and expand the working gas in a Brayton cycle at high temperature. The technical challenge is fabrication of miniature, high-speed (>150,000 rpm) rotating turbomachinery that operates at high temperature (1100 K) at the turbine end of the common shaft and at near-ambient temperature (350 K) at the compressor end.

In the second project, Creare’s power conversion system uses thermophotovoltaics (TPV) to convert the radiant energy from the radioisotope heat source directly into electricity. Technical challenges here include fabrication of high-temperature (1350 K) emitter structures and thermal design, development and fabrication of converter hardware, advanced photovoltaic cells and advanced filters to maximize efficiency.