Supporting Technology at GRC to Mitigate Risk as Stirling Power Conversion Transitions to Flight

Abstract

Stirling power conversion technology has been reaching more advanced levels of maturity during its development for space power applications. The current effort is in support of the Advanced Stirling Radioisotope Generator (ASRG), which is being developed by the U.S. Department of Energy (DOE), Lockheed Martin Space Systems Company (LMSSC), Sunpower Inc., and the NASA Glenn Research Center (GRC). This generator would use two high-efficiency Advanced Stirling Convertors (ASCs) to convert thermal energy from a radioisotope heat source into electricity. Of paramount importance is the reliability of the power system and as a part of this, the Stirling power convertors. GRC has established a supporting technology effort with tasks in the areas of reliability, convertor testing, high-temperature materials, structures, advanced analysis, organics, and permanent magnets. The project utilizes the matrix system at GRC to make use of resident experts in each of the aforementioned fields. Each task is intended to reduce risk and enhance reliability of the convertor as this technology transitions toward flight status. This paper will provide an overview of each task, outline the recent efforts and accomplishments, and show how they mitigate risk and impact the reliability of the ASC's and ultimately, the ASRG. Nomenclature

Advanced Stirling Convertor (ASC) Development for NASA RPS

“…Specifically, the ASC-E2 required the development of a new heater head assembly design and manufacturing process making use of high temperature nickel superalloy 247-LC that would allow 850°C operation with long-life and reliability. GRC performed a variety of key technology support activities 3…”

Recent Stirling Conversion Technology Developments and Operational Measurements at NASA Glenn Research Center

“…In the case of ac magnetic field, measurements are typically made relative to 1 picoTesla (pT). With this, the ac magnetic field can be expressed using Equation (1).…”

Extended Operation of Stirling Convertors at NASA Glenn Research Center

“…1). Free-piston Stirling conversion offers a thermal-to-electric conversion efficiency of greater than 25 percent at the system level, which is a factor of four greater than thermoelectric conversion.…”