Thomas, James C (2014-12). Hybrid Rocket Burning Rate Enhancement by Nano-Scale Additives in HTPB Fuel Grains. Master's Thesis.
Low regression rates in hybrid rockets limit their use and capability, but additive aluminum nano-particles represent a possible solution to this problem. In this thesis, aluminum nano-particles were characterized and added to hybrid motor grains to assess their effects on the combustion behavior of hybrid rocket fuel grains. Procedures for the fabrication of 6-inch-long motors with combustion port diameters of 1 cm and 2.54 cm (1 inch) were developed for formulations with and without additive particles. The implementation of commercial aluminum particles at a mass loading of 5% as a burning rate enhancer was assessed on a lab-scale burner. Traditional temporally and spatially averaged techniques were applied to determine the regression rates of plain and aluminized HTPB motors burning in gaseous oxygen. Resistance-based regression sensors were embedded in motor grains and used to determine instantaneous and averaged burning rates. The resistive-based sensors exhibited good accuracy and unique capabilities not achievable with other regression measurement techniques, but still have limitations. The addition of commercial nano-aluminum, with a diameter of 100 nm, to hybrid motors increased the motor surface regression rate for oxidizer mass fluxes in the range of 0-15 g/cm2-s. Future testing will focus on the evaluation of motors containing novel aluminum particles manufactured in situ with the HTPB at a mass loading of 5%, which are expected to perform better than similar commercially aluminized motors.