Dynamic Characterization of STC Stirling Convertor and Improved Mechanical Integration in SRG110 Power System

Abstract

Listen

Translate article

The U.S. Department of Energy, Lockheed Martin, Stirling Technology Company (STC), and NASA Glenn Research Center (GRC) are developing the 110-Watt Stirling Radioisotope Generator (SRG110) for use as an advanced power system for potential future NASA missions. The launch environment enveloping potential missions is higher than historical radioisotope power system launch levels and presents a challenge for designers. A finite element model (FEM) of the SRG110 system containing detailed representations of the Stirling convertors was used to determine the response of critical components to the launch environment. A prototype STC Stirling convertor was characterized by modal testing at NASA GRC’s Structural Dynamics Laboratory. The understanding of convertor dynamics gained from analysis and testing led to improved mechanical packaging of the convertors in the SRG110. Concepts were evaluated utilizing the FEM; vibration input was applied at the SRG110 mounting interface, and component vibration responses were calculated. An interface isolation mount for the SRG110 was investigated as a means to further reduce system level responses. This paper presents the convertor modal test setup and methodology, the measured convertor modes and frequencies, and component random launch vibration load responses for the baseline SRG110 and for the SRG110 with improvements to the convertor mounting approach and with a vibration isolation interface. The results show a reduction in response due to improved convertor mounting and further reductions through the use of the isolation interface. This enables the SRG110 power system to be considered for a broad range of potential missions, including those with demanding launch environments.