Advanced Radioisotope Space Power Systems JAMES A. TURI & ROBERT T. CARPENTER Summary As the US Space Program moves into its fourth decade of highly successful utilization and exploration of space, even more ambitious missions are being undertaken and planned. Many of the significant accomplishments of the past and those planned for the future have been, and will continue to be, made possible by the use of radioisotope space power systems. As mission power levels, lifetimes and other performance requirements, such as operation in increasingly hostile environments, become more demanding, the Department of Energy’s program for advancing the technology of radioisotope space power systems will continue to support the needs of the NASA and DOD space programs. This paper describes the present state-of-the-art radioisotope thermoelectric generators (RTGs) which the DOE has developed for use on the upcoming Galileo and Ulysses space exploration missions, as well as the technology improvements planned in the areas of heat sources, thermal insulation, thermoelectric conversion and dynamic energy conversion for advanced radioisotope space power systems to be used in future applications. Such applications include NASA’s Mariner Mark II spacecraft missions (Comet Rendezvous Asteroid Flyby and Cassini Saturn Orbiter/Titan Probe) in the mid-1990s and the Mars Rover/Sample Return Mission in the late 1990s, as well as higher power civilian and/or highly survivable military spacecraft programs over the next decade. Introduction Since before the first Sputnik was launched into space, the US Department of Energy (and its predecessor agencies) has been developing the technology for, and providing radioscope space power systems for, use on US military and civilian space missions. Later this month we will celebrate the 28th anniversary of the first use of nuclear power in space, a plutonium-238 (Pu-238) fueled 2.7 We thermoelectric generator designated SNAP-3. SNAP is the acronym for Systems for Nuclear Auxiliary Power. It was launched on the Navy’s Transit-4A navigation satellite. Between 1961 and 1977, the USA launched over 36 radioisotope thermoelectric generators (RTGs) on 22 different spacecraft (8 military and 14 NASA spacecraft). The spectrum of RTG-powered missions has been quite diverse, including those in high and low Earth orbit, on the lunar surface, Mars landers and outer-planet flybys. Power levels have varied from 2.7 to 160 We/RTG and 1-4 RTGs were used per spacecraft. All of these RTGs met or exceeded their predicted power performance. For James A. Turi, US Department of Energy, Washington, DC 20545, USA; Robert T. Carpenter, Fairchild Space Company, Germantown, MD 20874, USA.
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