Fuel grain modeling and optimization for hybrid propulsion systems using additive manufacturing

Hybrid propulsion systems have garnered significant interest in recent years due to their potential to offer a safer and cheaper alternative to traditional solid and liquid rocket engines. A key component of these systems is the fuel grain, which plays a vital role in the performance and efficiency of the propulsion system. However, the practical feasibility of hybrid propulsion has been hindered by the low regression rates. This thesis focuses on the improvement of regression rates in hybrid rocket fuel grains through the utilization of additive manufacturing. Acrylonitrile Butadiene Styrene (ABS) exhibits a lower regression rate than conventional fuels like paraffin or HTPB, making it a promising candidate for this study. Additive manufacturing allows the production of complex geometries that were previously unattainable with traditional manufacturing techniques. This study explores the impact of the grid infill structure with different densities on the performance of ABS fuel grains. Single port fuel grains with infill densities of 70\%, 90\%, and 100\% are fabricated using a 3D printer. A small-scale test setup was employed for the static fire tests of the fuel grains with nitrous oxide. The test results show that utilizing a lower infill ratio inside the fuel grain increases the regression rate significantly while ensuring combustion stability and structural integrity.