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C4: Generators
Thermoelectric power sources have consistently demonstrated their extraordinary reliability and longevity for deep space and planetary missions (67 missions to date, more than 30 years of life) as well as terrestrial applications where unattended operation in remote locations is required.
The successful application of high temperature thermoelectric technology has relied on only a few materials, PbTe, GeTe-AgSbTe2 (TAGS) alloys and Si-Ge alloys, identified in the late 1950s and 1960s. The NASA spacecraft Voyager 1, which rose from Earth on a September nearly 37 years ago, has traveled farther than anyone, or anything, in history. Thanks to its Multi-Hundred Watt Radioisotope Thermoelectric Generator (MHW-RTG) based on Si-Ge alloys, Voyager 1 has now entered interstellar space. A General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG), also based on Si-Ge alloys, is currently one year away from Pluto on board the New Horizons spacecraft (launched in 2006) while the PbTe/TAGS-based multi-mission radioisotope thermoelectric generator (MMRTG) is currently on the Martian surface on board the Mars Science Laboratory Rover (Since August 2012).
An overview is provided for key materials, technologies and system approaches that have enabled such an excellent track record, and the discussion reflects on some key lessons learned as new higher performance materials are being considered for possible infusion into next generation radioisotope and fission power systems. The potential for application of recent technological advances made for space power systems into large scale terrestrial opportunities for producing electricity from waste heat recovery is described.