Influence of Boron on the Performance of Solid Fuel Ramjet Propulsion: A Reduced-Order Modeling Approach

Abstract

This study investigates the flight performance of a solid-fuel ramjet missile, comparing a conventional hydroxyl-terminated polybutadiene propellant against a formulation enriched with 33% boron. A computational framework was developed in Python, coupling NASA Chemical Equilibrium with Applications-based thermochemical equilibrium data with a high-fidelity flight dynamics model that accounts for atmospheric variability, instantaneous aerodynamic drag, and continuous mass depletion. To ensure a realistic assessment of energetic potential, a semi-empirical boron combustion efficiency model – sensitive to combustion chamber pressure and temperature – was integrated into the simulation. Results indicate that the boron-loaded propellant significantly expands the operational envelope, yielding a 34.3% increase in specific impulse and extending the effective range by approximately 15.2%. Furthermore, sensitivity analysis across varying payload masses (150 kg to 220 kg) demonstrates that boron’s superior energy density provides a performance buffer; notably, a 220 kg boron-fueled missile maintains higher cruise Mach numbers than a lighter conventional counterpart. These findings underscore the strategic utility of metallic additives in enhancing the tactical flexibility and range of next-generation supersonic propulsion systems.