Performance of Mixture-Ratio-Controlled Hybrid Rockets for Nominal Fuel Regression

Abstract

This paper discusses the impacts of oxidizer-to-fuel mass ratio () shifts on the flight performance of single-stage sounding rockets using the flight simulations of three scales of -controlled and -uncontrolled hybrid rockets under a nominal fuel regression behavior without uncertainty. The flight simulation code includes three factors dependent on the : thermodynamic states of the burned gas (theoretical ), shifts in efficiency, and nozzle throat erosion. In the flight simulations, a thrust control law was applied to increase the apogee and evaluate the effects of shifts in the thrust curve including throttling. For the best cases in each scale, -controlled hybrid rockets slightly improved the performance by 2.03–2.42% in the averaged specific impulse. However, the performance of the -controlled sounding rockets is essentially the same as the -uncontrolled type under the median regression behavior: especially when considering the slight increases in the mass and complexity of the oxidizer feed system needed for control. Considerable scale effects on the throat erosion and theoretical were observed, but that of the efficiency was negligible. The improvement of the theoretical was the primary contributor to flight performance, which was responsible for a larger than 70% share in the total increase. The second largest contribution was the improvement of the efficiency with a share of 21.8–24.3%. The control gave an improvement of throat erosion corresponding to 5.75% in the total increase for the smallest scale; but, with increasing of the scale, the throat area increase ratio became small so that the throat erosion improvement contribution was reduced to 1.21%.