An Advanced Stirling Radioisotope Generator (ASRG) Engineering Unit (EU) is now under extended operation at Glenn Research Center’s Stirling Research Laboratory. The Engineering Unit is a complete generator system including two Stirling convertors, insulation, sealed housing, heat rejection system, and electronic controller. The controller controls and synchronizes the two convertors using power electronics. It also provides telemetry on the ASRG status and accepts commands to adjust convertor operating conditions. The heat input comes from two electric heat sources used in place of General Purpose Heat Source modules.
Lockheed Martin (LM) developed the ASRG EU under contract with DOE. The generator assembly was completed in December 2007 and controller integration followed in March 2008. This unit underwent a series of system-level tests to qualification level thermal and dynamic environments at LM. These included thermal balance, thermal performance, mechanical disturbance, sine transient, random vibration, simulated pyrotechnic shock, and electromagnetic interference. LM delivered the ASRG EU to the Glenn Research Center on August 28, 2008, for the extended operation test. This test will generate data to help validate the life and reliability of the generator and the Stirling convertors.
A special test facility was designed and built at GRC for testing the ASRG EU. In this facility the EU is mounted vertically with cooled air circulating around it to remove heat and maintain desired heat rejection temperatures. Computer systems regulate the heat input to the EU and the controller settings. A data system continuously monitors performance of the EU and rest of the test facility 24/7 and records data for later analysis. The ASRG EU extended operation test continues at GRC with over 30,000 hours accumulated by 2013.