Reusable Transpiration-Cooled Hydrocarbon Propellant Rocket Engine

Large liquid rocket engine combustion chambers suffer from two key constraints: they incorporate relatively low temperature capability alloys to minimize cost, and require active cooling to prevent excessively high temperatures from weakening the chambermaterials such that they can no longer sustain operating loads. Additionally, operation of engines with hydrocarbon propellants has the added problem of coolant channel coking. Although the high propellant density and high thrust-to weight ratioassociated with hydrocarbon propellants make them very attractive for boost engines, reusable designs must be developed for long-term economic viability. Actively cooled chambers are fabricated either as tube-wall structures or by machining grooves intothe walls. Both methods adversely impact cost, complexity, part count, reliability, and performance. In currently ongoing work, Ultramet and Boeing/Rocketdyne have demonstrated the performance and manufacturing feasibility of an innovative,transpiration-cooled oxygen/hydrogen (O2/H2) engine based on the use of Ultramet's highly porous and structural open-cell foam materials. Although pressure, flow rate, and coolant wall permeability requirements are quite different for hydrocarbon-fueledengines compared to O2/H2 engines, the potential exists to develop an innovative material and design approach for practical use of high-efficiency hydrocarbon propellants in a transpiration-cooled design without coking. In this project, Ultramet proposesto team with Boeing/Rocketdyne to demonstrate the feasibility of a transpiration-cooled hydrocarbon-fueled engine based on the use of advanced structural foam materials. This project will advantageously leverage previous hydrocarbon engine design workperformed at Rocketdyne using more conventional materials and previous engine materials development performed at Ultramet for O2/H2 engines. The use of open-cell foam materials to cool rocket engine combustion chambers by transpiration would substantiallyreduce part count, cost, and mass and increase performance over current regeneratively cooled engines. This design would be further exploited through use with high-efficiency hydrocarbon propellants. The same technology will also find substantialapplication in commercial launch systems as well as advanced heat exchangers, which will benefit from the high heat transfer characteristics and high specific strength of open-cell foams.