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Alkali Metal Backup Cooling for Stirling Systems - Experimental ResultsIn a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.
Document ID
Document Type
Technical Memorandum (TM)
Schwendeman, Carl
(Advanced Cooling Technologies, Inc. Lancaster, PA, United States)
Tarau, Calin
(Advanced Cooling Technologies, Inc. Lancaster, PA, United States)
Anderson, William G.
(Advanced Cooling Technologies, Inc. Lancaster, PA, United States)
Cornell, Peggy A.
(NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
August 19, 2014
Publication Date
October 1, 2013
Subject Category
Spacecraft Propulsion And Power
Report/Patent Number
Paper 6733
Meeting Information
Meeting: Proceedings of Nuclear and Emerging Technologies for Space 2013
Location: Albuquerque, NM
Country: Mexico
Start Date: February 25, 2013
End Date: February 28, 2013
Sponsors: American Nuclear Society
Funding Number(s)
WBS: WBS 138494.01.99.01
Distribution Limits
Public Use Permitted.
Stirling Convertor
Stirling Radioisotope Power System
Variable Conductance Heat Pipe
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