Conceptual study of hybrid rocket fuels and port geometries : A comparative analysis with system-level scaling towards CAMUI-based launch stages

The growing demand for orbital launch capabilities has renewed interest in hybrid rocket propulsion as a potentially safe, throttleable, and cost-effective alternative to conventional solid and liquid engines. However, hybrids are limited by low fuel regression rates and scalability challenges. This study evaluates the feasibility of the Cascaded Multistage Impinging-jet (CAMUI) fuel grain design developed by Letara Ltd. by comparing it against conventional single-port and wagon wheel geometries using different fuel materials (HDPE, HTPB, and paraffin wax). A MATLAB-based sizing model was implemented to assess grain length-to-diameter ratios (L/Df) across multiple engine classes. Results show that while paraffin wax provides high regression rates, structural limitations reduce its practicality, and single-port designs become impractical at high thrust levels. In contrast, the CAMUI geometry significantly reduces L/Df, particularly when paired with HDPE, demonstrating strong theoretical potential for scalable hybrid launch-stage applications pending experimental validation.