Modeling of the Plasma-Propellant Interaction

Plasma-propellant interaction for application to an electrothermal gun is studied theoretically. Electrothermal-chemical (ETC) guns are used for enhancement of the ignition and combustion of the energetic propellant. A detailed understanding of the dynamics of the plasma-propellant interaction is considered one of the key elements to the future success of practical ETC gun implementation. A model of the propellant ablation under plasma effect is developed based on the kinetic theory of ablation. The ablation model is coupled with a model of the plasma generation in the capillary discharge that allows calculation of the effective heat flux from the plasma. Calculations are performed for specific experimental conditions in which ablated mass of a double-base and a nitramine composite propellant are studied. An ablation model is used to predict the ablation rate of the propellant for different bulk plasma densities. An effective heat flux from the plasma is found which yields the experimentally determined ablated mass. One representative solution reproduces the experimentally determined ablated mass for the double-base propellant of 5.3 mg via an effective heat flux on the order of 4times10⁸ J/m²s. The effective heat flux that corresponds to the experimentally measured ablated mass is determined for different propellants. Differences in the calculated effective heat flux between different propellants indicate that although heat convection from the plasma is the dominant source of energy, plasma radiation, and the optical properties of the propellants themselves cannot be ignored. The difference in plasma heat flux between propellants can readily be explained by partial absorption of plasma radiation consistent with the optical properties of the propellants