Parameter Analysis and Transient-Feature Study of a Long-Time Working Hybrid Rocket Motor

This study attempts to provide and analyze the performance parameters and transient features of a long-time working hybrid rocket motor (HRM) for its potential applications. To conduct the long-time working HRM firing tests, an experimental system was designed. Two long-time firing tests of HRMs, using hydroxyl-terminated polybutadiene as the base fuel and 98% hydrogen peroxide as the oxidizer, were carried out. The working time of the two tests was 192 and 202 s, respectively. A data-processing program was developed to estimate and deal with the test data, and the transient parameters and motor performances were then determined and analyzed. The results show that chamber pressure and motor thrust decrease with working time, due to the nozzle erosion and regression rate reduction, in which the former has a significant effect. The growth of grain port diameter is the main cause of the decrease of regression rate with time. As the time goes on to 200 s, the regression rate decreases from about 0.5 to 0.1 mm/s. The oxidizer-to-fuel ratio has a large variation during the firing test, which makes it deviate from an optimum condition and therefore reduces the motor working efficiency. The long-time working tests of the two HRMs have a lower specific impulse, which is mainly caused by serious nozzle erosion.