System Integration of Stirling Convertors into a Dynamic Radioisotope Power System

Free piston Stirling convertors offer increased efficiency over radioisotope thermoelectric generators at the potential expense of increased risk to reliability and robustness. Steps in reducing that risk are system studies that integrate Stirling convertors into a generator. System integration of a Stirling convertor into a generator requires trade studies and in depth system analysis of a variety of subsystems. Subsystems focused upon here are the GPHS to convertor heating mechanism, convertor and system level heat rejection system, and the overall physical/mechanical configuration. An overview of several system design options and rationale for the down selection of the final configuration are presented. Included in the analysis is several off-nominal conditions and effects of failed convertors upon the system. Initial simulations showed a system efficiency of 21% and specific power of 3.9 W/kg, updated higher fidelity models and details indicate a system efficiency of 23% and a specific power of 3.0 W/kg for the reference condition are possible.