Progress in Developing a New 5 Kilowatt Free-Piston Stirling Space Convertor

Abstract

The NASA Vision for Exploration of the Moon envisions a nuclear reactor coupled with a free‐piston Stirling convertor at a power level of 30–40 kWe. In the 1990s, Mechanical Technology, Inc.'s Stirling Engine Systems Division (now a part of Foster‐Miller, Inc.) developed a 25 kWe free piston Stirling Space Power Demonstrator Engine under the SP‐100 program. This system consisted of two 12.5 kWe engines connected at their hot ends and mounted in tandem to cancel vibration. Recently, NASA and DoE have been developing dual 55 We and 80 We Stirling convertor systems for use with radioisotope heat sources. Total test times of all convertors in this effort exceed 120,000 hours. Recently, NASA began a new project with Auburn University to develop a 5 kWe, single convertor for use in the Lunar power system. Goals of this development program include a specific power in excess of 140 We/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 5 kWe Stirling Convertor Assembly. The characteristics of the design along with progress in developing the system will be described.