Performance testing of the EU & QU MMRTG

Abstract

The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) Lifecycle Testing Laboratory is operated by the University of Dayton Research Institute (UDRI), which is dedicated to conducting life-cycle testing of electrically heated versions of the MMRTG. Since there are only two MMRTG electrically-heated thermoelectric generators (ETG) available for testing, a Test Plan Development Working Group was established to determine and prioritize the performance testing that is being conducted with the Engineering Unit (EU) and Qualification Unit (QU) ETGs. This working group is comprised of subject matter experts from the U.S. Department of Energy (DOE), the National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC), NASA Jet Propulsion Laboratory (JPL), Idaho National Laboratory (INL), Oak Ridge National Laboratory (ORNL), UDRI, Aerojet Rocketdyne, and Teledyne Energy Systems. The highest priority testing was concluded by the working group to be: 1) To determine the impact of thermal cycling on thermoelectric components by characterizing the evolution of the thermoelectric/electrical properties of the EU as a result of thermal cycling the ETG through a Martian Sol repeatedly; 2) to characterize the effect of a simulated cruise-phase environment on the QU by evaluating the change in performance of the ETG before and after a cruise-phase simulation; and 3) characterize and clear any potential MMRTG internal shorts to chassis by integrating the JPL derived active short technique between the internal electrical power circuit and chassis frame of the MMRTG. The data and risk mitigation techniques derived from this testing can potentially be incorporated into future missions that would employ the MMRTG or successor thermoelectric radioisotope power systems.