UC Davis

As hybrid rocket propulsion systems continue to be utilized as launch solutions within the small satellite industry, their inherit poor fuel regression rates and low combustion efficiencies possess a notable threat to mission performance. This body of work investigates the practicality of hydrogen co-firing as a novel technique to combat these deficiencies. A hybrid rocket propulsion system of gaseous oxygen (GOx) and nylon 6 thermoplastic fuel grain with a gaseous hydrogen (GH2 ) co-firing configuration was designed and manufactured for preliminary analysis in understanding the internal ballistic effects of hydrogen addition. In order to appropriately characterize the overall combustion event, comprised of both the GOx/nylon 6 and GOx/GH2 burn, NASA CEA (Chemical Equilibrium with Applications) software was utilized. The baseline burning of GOx and nylon 6 yielded a simulated combustion efficiency of 85.67% and an overall system efficiency of 85.95%. The simulated GOx and GH2 burn prompted results of elevated combustion temperatures as well as a surplus of available oxidizing molecules at stochiometric to fuel-lean O/F ratios. No validation experiments were performed; however, it is posited through the analysis that at an optimal O/F ratio of 16, the upstream burn of gaseous oxygen and gaseous hydrogen would expedite the nylon 6 pyrolysis event and supply enough oxidizer for the pyrolyzed thermoplastic hydrocarbons to sustain a healthy flame. This would promote the heat and mass transfer mechanisms that hybrid rocket propulsion systems are limited to and thus improve regression rates and performance efficiencies.