Transpiration-Cooled Hydrocarbon-Fueled Scramjet Engine

The Air Force is seeking advanced cooling concepts for scramjet engines for use in hypersonic cruise missiles, Mach 8-10 strike/reconnaissance aircraft, and affordable, on-demand access to space. In current work for the Air Force, Ultramet and Boeing/Rocketdyne are demonstrating the performance and manufacturing feasibility of a transpiration-cooled oxygen/hydrogen rocket engine for boost applications, based on the use of Ultramet's open-cell foam materials. The design is much less complex and offers lower weight than conventional regeneratively cooled engines. The high propellant density and high thrust-to-weight ratio associated with hydrocarbon propellants make them very attractive; however hydrocarbon propellants can cause coolant channel coking. Although pressure, flow rate, and coolant wall permeability requirements are quite different for hydrocarbon-fueled engines compared to oxygen/hydrogen engines, the potential exists to develop an innovative material and design approach for practical use of high-efficiency hydrocarbon propellants without coking issues. In this project, Ultramet will team with Pratt and Whitney to demonstrate the feasibility of a transpiration-cooled, hydrocarbon-fueled scramjet engine based on the use of advanced structural foam materials. This project will take advantage of the substantial scramjet development work performed at Pratt & Whitney and previous rocket engine materials development performed at Ultramet.