Refractory Open-Cell Structural Foams for Advanced Rocket Engine Injectors, Phase II

The Air Force is seeking a highly operable aerospace vehicle that can be ready to launch on demand. Hydrocarbon-fueled vehicles offer certain benefits over other propulsion systems. The vehicle is heavier when fueled with kerosene, but because of the nature of the propellant, it is lighter when empty: a benefit in reduced vehicle weight and cost. Also, kerosene costs less to produce and use. Advanced propellant injector materials and designs are required to promote stable combustion with high mixing efficiency. The potential exists to take advantage of the inherent and tailorable porous open-cell structure contained within refractory ceramic (and metallic) structural foams for propellant injection in hydrocarbon boost engines. Ultramet previously worked with the Air Force Research Laboratory (AFRL) Propulsion Directorate at Edwards AFB to establish the mechanical and fluid flow properties of open-cell silicon carbide (SiC) foam material produced by Ultramet for potential use in injector applications, among others. The flow characteristics showed promise for use with hydrocarbon propellants, but the structures fabricated previously were limited to relatively small sizes (4" diameter x 1.0-1.5" thick). In Phase I, Ultramet demonstrated the feasibility of process scaleup to practical injector components by producing SiC foam structures having an order of magnitude greater volume (12" diameter). The initial material and process development and manufacturing demonstration complements ongoing design and property database development being conducted at AFRL/PRSE and Boeing's Rocketdyne division. In Phase II, Ultramet will team with Rocketdyne to perform comprehensive component design and material optimization, ultimately leading to performance demonstration through hot-fire testing of injector components using a hydrocarbon propellant. The proposed foam injector represents a significant step toward the practical use of hydrocarbon-fueled aerospace vehicles.