A Stirling Radioisotope Generator supplying over 100 W of electric power (SRG110) is being developed by Lockheed Martin Astronautics (Valley Forge, PA). This development effort is under contract to the Department of Energy (Germantown, MD). The generator will be a high-efficiency electric power source for NASA space science missions with the capability to operate in the vacuum of deep space or in a gaseous atmosphere like that found on the surface of Mars. The generator converts heat into electric power as the heat is supplied by a plutonium heat source.
The NASA Glenn Research Center is supporting Lockheed Martin Astronautics and the SRG110 project by providing key data to enhance performance and mitigate risk for what will be the first dynamic power system used in space. High system efficiency was achieved through the use of free-piston Stirling power-conversion technology. Long life has been achieved through the use of noncontacting moving components: there are no wear mechanisms. The Glenn tasks include in-house testing of Stirling convertors and advanced controllers, materials evaluation and heater head life assessment, structural dynamics testing and analysis, assessment of organics, and reliability analysis. A parallel effort to develop an advanced technology Stirling convertor with reduced mass and increased efficiency complements the SRG110 project.
To demonstrate the capability for long life, Glenn is conducting extended-operation tests of flight-prototype Stirling power convertors known as Technology Demonstration Convertors (TDC’s) that were developed by Infinia Corporation (formerly known as the Stirling Technology Company, Kennewick, WA). TDC’s #13 and #14 recently passed 2 years of operation and now have over 18,400 hr of extended operation. The power output and efficiency have remained nearly constant throughout this test. TDC’s #15 and #16 began testing at Glenn earlier this year and have accumulated over 4200 hr of extended operation. TDC’s #5 and #6 have been operating in a thermal vacuum environment intended to simulate operation in deep space and have accumulated over 4600 hr. The total operating time of all the convertors at Glenn has surpassed 58,000 hr with no failures to report. Operation is continuing in support of Lockheed Martin Astronautics and the SRG110 project. This effort is supported by NASA’s Science Mission Directorate, Radioisotope Power Systems.
Left: SRG110. Right: TDC’s #13 and #14 on extended operation test at Glenn. (Photograph courtesy of Lockheed Martin Astronautics; used with permission.)
Thieme, Lanny G.; and Schreiber, Jeffrey G.: Advanced Technology Development for Stirling Convertors. Proceedings of the Space Technology and Applications International Forum, Albuquerque, NM, 2004.
Schreiber, Jeffrey G.; and Thieme, Lanny T.: Accomplishments of the NASA GRC Stirling Technology Development Project. AIAA-2004-5517, 2004.
Find out more about the research of Glenn’s Thermo-Mechanical Systems Branch: http://www.grc.nasa.gov/WWW/TECB/
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Jeffrey G. Schreiber, 216-433-6144, Jeffrey.G.Schreiber@nasa.gov
Author:
Jeffrey G. Schreiber
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Last updated: October 16, 2006
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