New 5 kW free-piston Stirling space convertor developments

Abstract

The NASA Vision for Exploration of the moon may someday require a nuclear reactor coupled with a free-piston Stirling convertor at a power level of 30–40kW. In the 1990s, Mechanical Technology Inc.'s Stirling Engine Systems Division (some of whose Stirling personnel are now at Foster-Miller, Inc.) developed a 25kW free-piston Stirling Space Power Demonstrator Engine under the SP-100 program. This system consisted of two 12.5kW engines connected at their hot ends and mounted in tandem to cancel vibration. Recently, NASA and DoE have been developing dual 55 and 80W Stirling convertor systems for potential use with radioisotope heat sources. Total test times of all convertors in this effort exceed 120,000h. Recently, NASA began a new project with Auburn University to develop a 5kW, single convertor for potential use in a lunar surface reactor power system. Goals of this development program include a specific power in excess of 140W/kg at the convertor level, lifetime in excess of five years and a control system that will safely manage the convertors in case of an emergency. Auburn University awarded a subcontract to Foster-Miller, Inc. to undertake development of the 5kW Stirling convertor assembly. The characteristics of the design along with progress in developing the system will be described.