Design characteristics and fabrication of radioisotope heat sources for space missions

Abstract

Radioisotope thermoelectric generators (RTGs) have been used by the United States to provide electrical power for spacecraft since 1961. All RTGs that have been launched by the U.S. have used heat sources fueled with the plutonium-238 isotope. Low-power (1 W thermal) Light Weight Radioisotope Heater Units have also been used to maintain spacecraft equipment within their normal operating temperature range. Los Alamos National Laboratory is responsible for fabricating heat sources for current and future space missions. The 238PuO 2 is purified by aqueous processing, fabricated into hot pressed pellets, encapsulated into precious metal cladding material, then the fueled clads are nondestructively tested. NASA currently plans for the potential use of radioisotope power systems for the Europa Orbiter and the Solar Probe missions, which are all scheduled for launch this decade. In addition several Mars Exploration missions over the next decade will employ radioisotope heater units.