Investigation and Optimization of Blended Paraffin-Beeswax Solid Fuels for Enhanced Thermal Stability and Ballistic Performance in Hybrid Rocket Systems

Hybrid propulsion has emerged in recent years as a promising alternative to conventional solid and liquid propulsion systems, offering a combination of their advantages while mitigating many of their drawbacks. Hybrid rockets, besides exhibiting superior performance, possess unique operational characteristics, are less complex, and offer cost-effective solutions. Developing a feasible hybrid system is heavily reliant on the regression rate of the solid fuel. In this study, regression rate studies were carried out with paraffin wax (PW) and beeswax (BW) blended fuels burning in a gaseous oxygen stream. BW was blended with PW in three distinct weight ratios: 25/75, 50/50, and 75/25. Additionally, pure PW was cast as a baseline sample. The prepared fuel formulations were tested for their thermal, surface morphology, mechanical, and combustion characteristics. Laboratory-scale ballistic experiments were conducted at oxidizer mass fluxes between 40 and 95 kg/m2·s. The regression rate of BW was observed to vary between 0.9 and 1.4 mm/s under oxidizer mass flux conditions ranging from 44 to 94.7 kg/m2·s. In contrast, the blended fuels demonstrated regression rates spanning 0.7 to 1.2 mm/s within the same oxidizer flux range. The higher regression rate of BW compared to PW and blended fuels high-lights its potential as a high-performance solid fuel for upper-stage thruster and hybrid rocket system.