Modeling of the electrothermal ignitor metal vapor plasma for electrothermal-chemical guns

The solid propellant electrothermal-chemical (SPETC) gun is a hybrid propulsion concept which uses an ignitor whose electrical energy enhances the performance of standard solid propellant guns. This ignitor is an electrogun which rapidly vaporizes metals such as aluminum. The metal vapor is then ionized to form a dense plasma in which a high current discharge is sustained. Understanding and characterizing the plasma inside the electrogun is one step in understanding the overall performance of the SPETC gun. This paper describes a model to study the electrogun (ignitor) plasma flow field. The plasma flow field equations are solved for parameters that simulate the operational conditions of a small prototype electrogun. Realistic modeling of the plasma flow in the bore is obtained by a consideration of the energy release within the bore and solution of the conservation equations for continuity, momentum, and energy. This obviates the need to model the complicated phenomena at the cathode surface itself. Total potential drops across the electrogun discharge are matched with experimental data to determine values for the cathode surface parameters that yield realistic solutions