Thrust Modulation in Hybrid Rocket Engines

An experimental investigation of hybrid rocket engines (HRE) is performed to study the throttling performance within a thrust range of 10:1. In order to improve the throttling properties over the entire thrust range, the method of secondary gas injection (gasification) was used. The injection gases were reactive (O2) and inert (N2). High-pressure tests were carried out up to 70 bar to increase the burning rate and the specific impulse. The standard fuel in this study was a composition of aromatic and cyclic amine with red fuming nitric acid (RFNA) as the oxidizer. Controllable, stable, and reproducible throttling properties were demonstrated down to 10% of thrust. The performance with gasification demonstrated the general feasibility of wide-range throttling with fixed-injection geometry. The paper outlines a method for calculating the ballistic behavior of hybrid propellant combinations that is based upon the regression characteristic and the effects of gasification. a A c* F G =m/A m O/F = mn/m PC