In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling converter 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 earlier termination of the mission. An alkali‐metal Variable Conductance Heat Pipe (VCHP) can be used to allow multiple stops and restarts of the Stirling convertor. A sodium VCHP with a Haynes 230 envelope was designed and fabricated for the Advanced Stirling Radioisotope Generator (ASRG), with a baseline 850° C heater head temperature. When the Stirling convertor is stopped, the heat from the GPHS is rejected to the Cold Side Adapter Flange using a low‐mass, carbon‐carbon radiator. The VCHP is designed to activate with a AT of 30° C. The 880° C temperature when the Stirling convertor is stopped is high enough to avoid risking standard ASRG operation, but low enough to save most of the heater head life. The VCHP has low mass and low thermal losses for normal operation. The design has been modified from an earlier, stainless steel prototype with a nickel radiator. In addition to replacing the nickel radiator with a low mass carbon‐carbon radiator, the radiator location has been moved from the ASRG case to the cold side adapter flange. This flange already removes two‐thirds of the heat during normal operation, so it is optimized to transfer heat to the case. The VCHP was successfully tested with a turn‐on ΔT of 30° C in three orientations: horizontal, gravity‐aided, and against gravity.
Sodium VCHP with Carbon‐Carbon Radiator for Radioisotope Stirling Systems
SPACE, PROPULSION & ENERGY SCIENCES INTERNATIONAL FORMUM SPESIF‐2010: 14th Conference on Thermophysics Applications in Microgravity 7th Symposium on New Frontiers in Space Propulsion Sciences 2nd Symposium on Astrosociology 1st Symposium on High Frequency Gravitational Waves ; 2010 ; Huntsville (Alabama)
AIP Conference Proceedings ; 1208 , 1 ; 42-54
2010-01-28
13 pages
Conference paper
Electronic Resource
English
Modular Stirling Radioisotope Generator
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