Google Search

C4: Generators

Skutterudite-based advanced thermoelectric couples for integration into an advanced MMRTG

T. Caillat1, S. Firdosy1, B. C- Y. Li1, C. –K. Huang1, D. Uhl1, K. Smith1, J. Paik1, J.- P. Fleurial1, R. Bennett2, and S. Keyser2
1Jet Propulsion Laboratory/Caltech, MS 277-207, 4800 Oak Grove Drive, Pasadena CA, 911092Teledyne Energy Systems, Inc., 10707 Gilroy Road, Hunt Valley, MD 21301

Radioisotope Thermoelectric Generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric (TE) converter.  RTGs have been successfully used to power a number of space missions including the Apollo lunar missions, the Viking Mars landers, Pioneer 10 and 11, and the Voyager, Ulysses, Galileo, Cassini, and New Horizons outer planet spacecrafts. MSL’s Curiosity rover is powered by the Multi-Mission Radioisotope Generator (MMRTG).  Teledyne Energy Systems Inc. (TESI) and prime contractor, Pratt & Whitney Rocketdyne, working in partnership with the Department of Energy, produced this generator for Curiosity.  RTGs have demonstrated their reliability over extended periods of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. NASA’s Radioisotope Power Systems Technology Advancement Program is pursuing the development of more efficient TE technologies that can increase performance over state-of-practice RTGs, which are limited to device-level thermal-to-electrical energy conversion efficiencies of 7.5% or less, and system-level specific power of 2.4 to 5.1 W/kg.  The Jet Propulsion Laboratory (JPL), under funding from the NASA Radioisotope Power Systems Project, under the Advanced Thermoelectric Couple (ATEC) task, has developed couples based on advanced skutterudite (SKD) thermoelectric materials. Conversion efficiency values on the order of 9% have been demonstrated for SKD-based un-segmented couples when operating at a hot-junction of 873K and a cold-junction of 473K. This represents ~ a 25% improvement over the conversion efficiency of PbTe/TAGS MMRTG couples. JPL, in collaboration with TESI, has initiated a project to transfer the technology to TESI, to further mature this technology, to develop the manufacturing capabilities for SKD TE materials, couples, and modules at TESI, and to demonstrate their performance and lifetime potential for insertion into an enhanced-MMRTG (eMMRTG). This paper provides a status of the technology development at JPL, the initial development work at TESI, as well as a brief description of the technology maturation plan.