Nuclear Heat Source for Cryogenic Refrigerators in Space

To supply the heat input required by space-borne Vuilleumier refrigerators, a possible design for a reliable Pu-238 radioisotope heat source, based on state-of-the-art technology, is described. The isotope heat source would replace electrical heaters powered by solar panels and batteries, and would be adaptable to existing VM refrigerators without redesign. The heat source contains all necessary safety features, and also a simple thermal control system to permit refrigerator shut-down for indefinite duration. A system for thermal interfacing with the spacecraft, the booster, and ground support is also described. The isotope heaters are compared with solar-electric heaters for the same application, and found to result in very significant weight and size savings.