NASA Technical Reports Server (NTRS) 20070010453: Summary of Stirling Convertor Testing at GRC

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by  NASA Technical Reports Server (NTRS)

Summary of Stirling Convertor Testing at GRC
Jeffrey G. ~chreiber*
NASA Glenn Research Center at Lewis Field, Cleveland,O hio,4 41 35
The NASA Glenn Research Center (GRC) has been testing free-piston Stirling
convertors for potential use in radioisotope power systems. These convertors tend to be in
the 35 to 80 watt electric power output range. Tests at GRC have accumulated over 80,000
hours of operation. Test articles have been received from Infinia Corporation of Kennewick,
WA and from Sunpower of Athens, OH. Infinia designed and built the developmental
Stirling Technology Demonstration Convertors (TDC) in addition to the more advanced Test
Bed and Engineering Unit convertors. GRC has eight of the TDC's under test including two
that operate in a thermal vacuum environment. Sunpower designed and developed the EE-
35 and the Advanced Stirling Convertor (ASC). GRC has six of the EE-35's and is
preparing for testing multiple ASC's. Free-piston Stirling convertors for radioisotope power
systems make use of non-contacting operation that eliminates wear and is suited for long-
term operation. Space missions with radioisotope power systems are often considered that
extend from three to 14 years. One of the key capabilities of the GRC test facility is the
ability to support continuous, unattended operation. Hardware, software, and procedures
for preparing the test articles were developed to support these tests. These included the
processing of the convertors for minimizing the contaminants in the working fluid,
developing a helium charging system for filling and for gas sample analysis, and the
development of new control software and a high-speed protection circuit to insure safe,
round-the-clock operation. Performance data of Stirling convertors over time is required to
demonstrate that a radioisotope power system is capable of providing reliable power for
multi-year missions. This paper will discuss the status of Stirling convertor testing at GRC.
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