Microwave Plasma Effects on Combustion and Pressure of Composite Solid Propellants

Microwave-assisted combustion is increasingly studied to enhance ignition reliability, regulate burning rates, and improve energy efficiency in solid propulsion systems. However, the interaction mechanisms between microwave plasma and composite propellant combustion under varying pressures remain unclear. This study experimentally investigates the effects of microwave plasma on the combustion performance and pressure sensitivity of composite solid propellants. Results show a progressive increase in burning rate with rising microwave power, exhibiting different enhancement trends across power ranges. At 800 W, the burning rate increased by 22.95% with a reflectivity of 12%. At 1400 W, the gain reached 40.55% with a 36% reflectivity. The burning rate enhancement caused by microwave excitation progressively decreased as chamber pressure increased, with the gain at 1250 W dropping from 17.5% at 1 MPa to 9.7% at 7 MPa. Experiments across various pressure and power conditions showed that microwave power systematically affects the pressure exponent and burning rate coefficient. Specifically, the pressure exponent decreased from 0.412 to 0.376, while the burning rate coefficient increased from 3.25 to 3.81. A modified Vieille’s law was proposed by introducing microwave-dependent and pressure-interaction terms, forming a coupled burning rate prediction model. The model achieved an [Formula: see text] of 0.979 and a mean relative error of 0.0449. These findings provide both experimental insight and predictive capability for plasma-assisted solid propellant combustion, supporting future advancements in controllable, high-performance propulsion.