Oxidation Resistant, Hafnium-Carbide-Tantalum-Carbide Rocket Thrusters for High Performance Propellants

An innovative approach for producing dense adherent, protective oxides for radiatively-cooled C/HfC-TaC ceramic matrix composite (CMC) rocket thrusters capable of handling a broad spectrum of higher performance propellant-oxidant reactants is outlined. HfC- TaC CMCs of varying composition will be combined with unique CVI and mixed oxide sol gel post treatments. These CMC specimens will be evaluated for oxide compositional and microstructural changes between 1500 @C and 2200 @C as a function of time. Cyclic thermal stress tests using a computer controlled, translational 02-C2H2 torch will be used to determine which HfC-TaC composition and CVI or sol gel densification combination provides the best overall performance. Parabolic rate constants will be defined so thruster lifetimes at 4000 @F can be estimated. A 251bf HfC-TaC CMC thruster will be fabricated from the most promising materials system and delivered to LERC for H/O rocket testing.