Americium fuelled radioisotope stirling generator for lunar surface mobility systems

Abstract

Radioisotope Power Systems (RPS) are an invaluable resource for the exploration of our Solar System. Providing both heat and electricity, spacecraft using RPS can operate where it is impractical to use solar arrays and/or battery systems because of either limited solar illumination or mission durations which make a standalone battery impractical. Dynamic Radioisotope Power System (DRPS) have been designed using the decay of Plutonium-238 (238Pu) in the form of the General-Purpose Heat Source (GPHS) coupled with Stirling convertors, and Stirling-based generator technologies are being developed by NASA's RPS Program in an effort to realize high efficiency RPS. This paper describes the development of a new generator design based upon the European Large Heat Source (ELHS). The ELHS uses Americium-241 (241Am) rather than 238Pu as the heat producing isotope. The ELHS dimensions and shapes were optimized for use with thermoelectric power conversion and are different compared to a Step-2 GPHS Module, which impact implementation into the DRPS generator design. This ELHS-DRPS design assumes that the ELHS would be coupled to the same Stirling convertors under development for existing GPHS-based DRPS designs. Trades are performed on the number of convertors, fin lengths, housing configuration and hot-end temperature. Finally, this ELHS-DRPS design is compared with the existing GPHS-DRPS generator design completed by Aerojet Rocketdyne, along with the advantages and disadvantages of using americium as a heat source for RPS.