Influence of high loading density charge configurations on performance of electrothermal-chemical (ETC) guns

Experiments have shown that an electrically-generated, ablation-stabilized plasma is an effective ignition stimulus in electrothermal-chemical (ETC) guns. The current generation of ETC concepts in the United States utilizes a small amount of electrical energy during the ignition process of the order of the chemical energy in conventional igniters. Thus, in order to obtain the significant muzzle kinetic energy increase that has been demonstrated in the US with ETC guns in comparison to fielded systems, a new generation of energetic materials has been developed with increased impetus and improved packing properties. The propelling charge loading density (propellant mass/initial free volume in the combustion chamber) his risen concurrently in direct fire applications from the conventional 0.85-0.95 g/cm³ to a value up to 1.35 g/cm³ in experimental firings. The increase in loading density and concomitant decrease in initial ullage in the combustion chamber changes the sensitivity of the charge and the multi-phase properties of the interior ballistic flow. In this paper the authors present comparisons between high and low density cases for a number of ballistic parameters. Experimental data are also examined to compare the pressure gradient in conventional guns versus high loading density cases