| The dissertation describes research into the uncertainty in thrust and performance design calculations for conventional hybrid rocket motors ranging in size from small labscale motors to large Space-Shuttle class boosters of more than three million pounds thrust. The premise is that the design calculation parameters and design data base used to size a hybrid rocket propulsion system contain varying degrees of uncertainty and that these uncertainties propagate into the results of performance calculations.; An examination of the effects and propagation of design parameter uncertainty is accomplished by considering an idealized hybrid rocket motor as a baseline case. The hybrid rocket model assumes quasi-one-dimensional, steady-state flow with adiabatic combustion, and isentropic expansion of a perfect gas mixture through a converging-diverging conical fixed nozzle.; The uncertainty analysis is conducted by sequentially perturbing each nominal design parameter and calculating uncertainties in the rocket thrust and other performance predictions. The numerical value of uncertainty assigned to each design parameter is based on analysis of data and recommended practices found in the open literature for hybrid-, solid-, and liquid-rocket propulsion design.; Results of the uncertainty analysis model applied to 27 numerical test cases show that the uncertainties in hybrid rocket vacuum thrust range between {dollar}pm{dollar}6% to {dollar}pm{dollar}13% ({dollar}pm{dollar}9% common), in vacuum Isp from {dollar}pm{dollar}5{dollar}{lcub}1over4{rcub}{dollar}% to {dollar}pm{dollar}22% ({dollar}pm{dollar}7% common), and in total vacuum impulse from {dollar}pm{dollar}6% to {dollar}pm{dollar}12% ({dollar}pm{dollar}8% common). An uncertainty analysis performed with normalized parameter sensitivities shows that 10 out of 20 parameters are key to performance. However, all normalized sensitivities are not greater than unity. Upon assigning each parameter a specific uncertainty, only 8 parameters provide a significant relative contribution. The research shows that combustion efficiency, propellant c*, and oxidizer mass flow rate are the key parameters in hybrid rocket motor performance uncertainty for any size motor. The uncertainty analysis is a useful tool in both determining performance uncertainty in a hybrid rocket motor design and in managing design parameters. |
