Thermionic Power in Outer Space
Thermionic converters for use in outer space may be heated by the sun, by decaying radioisotopes, or by a fission reactor. Thermionic converters can also be made into concentric cylindrical shells ([Figure 8]a) and wrapped around the uranium fuel elements in nuclear reactors. The waste heat in this case would be carried out of the reactor to a separate radiator[9] by a stream of liquid metal. Since thermionic converters can operate at much higher temperatures than thermoelectric couples or dynamic power plants, the radiator temperature, Tc, will also be higher. Consequently, space power plants using thermionic converters will have small radiators. Once thermionic converters are developed which have high reliability and long life, they will provide the basis for a new series of lighter, more efficient space power plants.