Theoretical modeling of the interior ballistic processes in an electrothermal chemical gun

A comprehensive theoretical model has been developed to describe the interior ballistic processes in an electrothermal chemical (ETC) gun. The model, which takes into account the plasma/working fluid interaction, predicts transient and spatial variations of the gun chamber pressure, instantaneous projectile motion, and gun muzzle velocity. A complete set of governing equations is derived from first principles of physics, and the governing system is solved by an implicit finite difference scheme. Two sets of pulse-forming network (PFN) discharge curves, with various peak power times and total discharge times; are employed to study the ETC gun performance. The numerical results show that a ballistic efficiency of more than 13% can be achieved for an exothermic working fluid (C8H18/H2O2). The breech pressure and projectile-base pressure exhibit double peaks during the ballistic cycle. The first peak is due to the initial discharge of a plasma jet into the gun chamber, whereas the second peak is the result of vigorous interactions between the plasma jet and the working fluid. The calculated maximum breech pressure is on the order of 400 MPa, and a typical muzzle velocity is on the order of 2 km/s. Comparison of present numerical results with limited available experimental data is made and found to be good.