Voltage regulated burning rate of solid propellants via ionic liquids

Controlled thrust of solid rocket engines can provide more reasonable power distribution for spacecraft. The burning rate of conventional solid propellants are largely predetermined by the propellant formulation and combustion chamber pressure, which limits their adjustability after ignition. This paper studies the effect of introducing ionic liquid as electronic control component into solid propellants on the combustion heat, conductivity, and electrically enhanced burning rate performance of solid propellants. The results indicate that with the increased content of ionic liquid in solid propellants, the combustion heat improves from 12,649 J/g to 14,149 J/g, and the conductivity improves from 0 to 0.35 S/m. The enhanced conductivity is the key to achieving electrically enhanced burning rate of solid propellants. Specifically, for the H4 formulation, the burning rate increased from 1.36 mm/s at 0 V to 1.89 mm/s at 10 V, corresponding to a voltage-induced increase of approximately 39% relative to the 0 V condition of the same formulation. Furthermore, the electrochemical decomposition of the ionic liquid and the thermal decomposition of ammonium perchlorate (AP) were investigated by microstructural characterization and gaseous product analysis. Based on the results, an electrically enhanced combustion mechanism of solid propellants is proposed to elucidate the principle of electrically enhanced burning rate.