Development of High Efficiency Segmented Thermoelectric Couples for Space Applications

Radioisotope Thermoelectric Generators (RTG) have been used by NASA to reliably power spacecraft for deep space exploration for over 40 years. Current state of the practice systems are limited to device-level efficiencies of 7.5% or less and system level specific powers of 2.8 to 5.1 W/Kg. NASA’s Radioisotope Power Systems Thermoelectric Technology Development Program (TTDP) is pursuing development of more efficient thermoelectric technologies that could increase performance by a factor of 2 to 4x over these state of the practice systems. NASA’s TTDP is developing high-efficiency segmented couples/modules with the following design goals: a) system conversion efficiency ≥ 11% (≥ 60% improvement over MMRTG at BOL) and b) ≥ 6-8.5 We/kg specific power (2-3 x improvement over MMRTG), for a temperature gradient ΔT = 800 K (T_H=1273 K and T_C = 473 K). We will be discussing the state of development of the aforementioned couples and the tools that we use to guide this development.