Heat-pipe development for the SPAR space-power system

The use of alkali metal heat pipes to provide redundant, reliable, and low loss heat transfer at high temperatures is described. Three sets of heat pipes are used in the system. These include sodium/molybdenum heat pipes to transfer heat from the reactor core to the conversion system, potassium/niobium heat pipes to couple the conversion system to the radiator in a redundant manner, and potassium/titanium heat pipes to distribute rejected heat throughout the radiator surface. The designs of these units are discussed and fabrication methods and testing results are described.