Development of a GOX/ABS Hybrid-Gas Generator System for the NASA Plume Surface Interaction (PSI) Experimental Campaign.

This paper presents results from a high-volume testing campaign of a lab-scale, hybrid rocket system; as developed in support of the NASA's Human Landing Systems (HLS), Plume Surface Interaction (PSI) Program. For the testing campaign, whose results are to be presented in this paper, Utah State University Propulsion Research Laboratory (USUPRL) has modified a legacy 75-mm hybrid rocket propulsion system to act as a high-enthalpy gas-generator, simulating the bi-propellant landing propulsion system for the HLS. Although the PSI hybrid gas-generator system is not specifically designed as an operational propulsion system, the PSI Hybrid Gas-Generator Development program provided rare opportunity to test a Mid- Scale Hybrid Propulsion System over a wide range of ambient and vacuum test conditions, and across three different test facilities. The hybrid system, which uses gaseous oxygen (GOX) and 3-D printed ABS as propellants, has been configured so that the operating the oxidizer-to-fuel ratio (O/F) range results in the maximum plume water content (in simulation of a LOX/ethane Bi-Propellant system), and optimal characteristic velocity. Even with a low-expansion ratio nozzle, vacuum specific-impulse levels exceeding 285 seconds were demonstrated. No hybrid rocket system has reached these performance levels before. To date more than 50 hot-fire tests under ambient conditions and an additional 28 tests under near-vacuum conditions have been performed. An additional 16-20 vacuum tests are planned for Langley Research Center. By the successful completion of this program, the associated hardware will be one of the most-highly-tested, and well-characterized hybrid motor in history.