Improved Rhenium Thrust Chambers for In-Space Propulsion

Radiation-cooled, bipropellant thrust chambers are being considered for the ascent/descent engines and reaction control systems (RCS) for future NASA missions such as Mars Sample Return. Currently, iridium-lined rhenium combustion chambers are the state-of-the-art for in-space engines. NASA's Advanced Materials Bipropellant Rocket (AMBR) engine, a 150-lbf rhenium-iridium chamber produced by Plasma Processes, Inc. (PPI) and Aerojet, recently set a hydrazine specific impulse record of 333.5 seconds. To withstand the high loads during terrestrial launch, rhenium chambers with improved mechanical properties are needed, i.e., 40ksi yield strength and 10% elongation at room temperature. Recent electrochemical forming (EL-Form) work has shown considerable promise for improving the mechanical properties of rhenium by producing a multi-layered deposit comprised of a tailored microstructure, i.e., Engineered Re. In addition, the multi-component processing ability of the EL-Form process has the potential to significantly reduce the cost of producing advanced rhenium-iridium thrust chambers. Therefore, PPI and its industry partner, Aerojet, will work together to develop rhenium based in-space engines with improved mechanical properties at a reduced cost.