LOX/hydrocarbon auxiliary propulsion for the Space Shuttle Orbiter

The completed phases of a study evaluating LOX/hydrocarbon auxiliary propulsion system concepts for a second generation Space Shuttle Orbital Maneuvering Subsystem (OMS) and Reaction Control Subsystem (RCS) are presented. The results of the preliminary system evaluation phase are summarized, and efforts regarding the in-depth system evaluation phase are described. Ethanol and methane are considered to be the best fuel candidates as both are non-coking, non-corrosive, and offer high performance capability. Ethanol affords the highest dV and total impulse capability because of its high density-specific impulse product, while methane affords the lowest system wet weight when the system is sized for a fixed dV or total impulse requirement. The LOX/ethanol system allows the use of a simple non-insulated RCS feed system, and is the most attractive LOX/hydrocarbon OMS-RCS. Its operational costs would be substantially less than the current N2O4/MMH system.