Numerical Parametric Study of the Capillary Plasma Source for Electrothermal–Chemical Guns

This paper expands upon previous research into developing a numerical model of a capillary plasma source for application to electrothermal-chemical (ETC) guns. The capillary model is comprised of a kinetic model simulating polyethylene ablation coupled to a 1-D time-dependent hydrodynamic model to determine the capillary outflow parameters. As input, the simulation requires the capillary internal radius, length, and applied electrical current. Previous work found that best agreement with experimentally measured ablated mass could be achieved with the application of a backflux parameter, representing the percentage of the ablated material that was allowed to return to the polyethylene surface and form a film. Using the model, a parameter study is conducted to determine the effects that varying the peak electrical current, internal capillary radius, and backflux parameter has on the plasma temperature, peak outflow pressure, and total ablated mass. A sinusoidal electrical current is assumed in this paper, with the peak current and discharge time taken over a range typically encountered in ETC gun application. An analysis of the dependence of total ablated mass and peak capillary pressure on the deposited electrical energy yields insight into nonlinearities in the capillary energy equation.