Particle bed reactors (PBRs) have the potential for providing compact power sources for both space power and propulsion applications. The reactors operate in the temperature range of 2000 to 3000 K and, for propulsion systems, utilize hydrogen as a coolant. Given these overall operating conditions, the need exists to develop and verify the performance of various reactor components, particularly those which must operate at the more extreme conditions of temperature and hydrogen flow rate. These components must undergo multiple thermal cycles between cryogenic and exit temperatures. In addition, some of the components are subject to a thermal gradient of thousands of degrees Kelvin over a few centimeters.
A number of approaches directed towards meeting these needs have been developed. These include both monolithic ceramics (e.g. boron nitride) as well as coated composites consisting of refractory carbides (ZrC, NbC and TaC) on carbon-based substrates. Full and partial scale components have been fabricated and tested under prototypic conditions. The results of this developmental effort will be described.