Status of an advanced radioisotope space power system using free-piston Stirling technology

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:20000397

White, M A; Qiu, S; Erbeznik, R M; Olan, R W; Welty, S C

This paper describes a free-piston Stirling engine technology project to demonstrate a high efficiency power system capable of being further developed for deep space missions using a radioisotope (RI) heat source. The key objective is to develop a power system with an efficiency exceeding 20% that can function with a high degree of reliability for 10 years or longer on deep space missions. Primary issues being addressed for Stirling space power systems are weight and the vibration associated with reciprocating pistons. Similar weight and vibration issues have been successfully addressed with Stirling cryocoolers, which are the accepted standard for cryogenic cooling in space. Integrated long-life Stirling engine-generator (or convertor) operation has been demonstrated by the terrestrial Radioisotope Stirling Generator (RSG) and other Stirling Technology Company (STC) programs. Extensive RSG endurance testing includes more than 40,000 maintenance-free, degradation-free hours for the complete convertor, in addition to several critical component and subsystem endurance tests. The Stirling space power convertor project is being conducted by STC under DOE Contract, and NASA SBIR Phase II contracts. The DOE contract objective is to demonstrate a two-convertor module that represents half of a nominal 150-W(e) power system. Each convertor is referred to as a Technology Demonstration Convertor (TDC). The ultimate Stirling power system would be fueled by three general purpose heat source (GPHS) modules, and is projected to produce substantially more electric power than the 150-watt target. The system is capable of full power output with one failed convertor. One NASA contract, nearing completion, uses existing 350-W(e) RG-350 convertors to evaluate interactivity of two back-to-back balanced convertors with various degrees of electrical and mechanical interaction. This effort has recently provided the first successful synchronization of two convertors by means of parallel alternator electrical connections, thereby reducing vibration levels by more than an order of magnitude. It will also demonstrate use of an artificial neural network to monitor system health without invasive instrumentation. The second NASA contract, begun in January 1998, will develop an active adaptive vibration reduction system to be integrated with the DOE-funded TDC convertors. Preliminary descriptions and specifications of the Stirling convertor design, as well as program status and plans, are included.

• Research Organization: Stirling Technology Co., Kennewick, WA (US)
• OSTI ID: 20000397
• Country of Publication: United States
• Language: English

Related Subjects

07 ISOTOPE AND RADIATION SOURCES
42 ENGINEERING
DEMONSTRATION PROGRAMS
DESIGN
MECHANICAL VIBRATIONS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
RADIOISOTOPE HEAT SOURCES
SPACECRAFT POWER SUPPLIES
STIRLING ENGINES
WEIGHT