Analysis of solid propellant combustion behavior under electrothermal plasma injection for ETC launchers

Abstract

Enhanced burn rates of solid propellants through plasma erosion has been studied showing evidence of increased burn rate with injection of electrothermal plasmas into the propellant. These experiments are designed to evaluate the effectiveness of maximizing energy versus momentum transport, and the influence of geometry on the burn rates of the JA-2 solid granular propellant. A series of experiments has shown evidence of enhanced burn rate at pressures between 55 and 90 MPa (8,000 and 12,000 psi, respectively) over 400 ps pulse length. A 20 to 40% enhancement in the burn rates has been observed when plasma is injected parallel to the surface of the propellant. When plasma is injected normal to the surface, the burn rate increases by about a factor of three. A set of experiments has been designed to measure the burn rates when the electrothermal plasma is injected at various angles, from 0/spl deg/ to 90/spl deg/, to the surface of the propellant. Experiments were conducted at a constant input energy of 5 kJ/spl plusmn/2% to the electrothermal plasma source and constant base pressure of 15 Torr, which provides a 12,300 psi plasma pressure at the source exit close to the surface of the propellant. Results indicate increased burn rates with increased angle of injection. Optical emission spectroscopy measurements revealed a decrease in plasma temperature, at the plasma-propellant interface, with increased angle of injection.