INVESTIGATION OF PARAFFIN-BASED FUELS IN HYBRID COMBUSTORS

Hybrid propulsion is a promising alternative for space propulsion; however, due to the low regression rate and hence low thrust levels of the classic polymeric fuels, new alternatives are sought. In recent years, liquefying, paraffin-based fuels have been investigated for their much higher regression rate compared to that of polymeric fuels. This paper presents experimental and theoretical research conducted at the Technion. Both plain paraffin fuel and paraffin-polymer mixtures have been tested. Plain paraffin exhibits a high regression rate but poor mechanical properties. The addition of polymer improves the mechanical properties but lowers the regression rate compared to plain paraffin fuel. Nevertheless, it indicates a promising direction to pursue a relatively high burning rate fuel of good mechanical properties. A model accounting for heat and mass transfer in the presence of liquefying fuel has been developed to predict the regression rate of the paraffin-based fuel. The model developed includes an additional mass loss mechanism, i.e., the liquid melt flowing along the grain. It is shown that this mechanism might have a noticeable effect on the overall regression rate and a potential for decreasing system performance. The test results exhibit good correlation with the model predictions.