Mixing processes of plasmas in electrothermal-chemical guns

QinetiQ is conducting research into electrothermal-chemical (ETC) guns under contract from the United Kingdom Ministry of Defence. Part of this work has investigated the enhanced gas generation rates (EGGR) that arise from interactions between plasma and solid propellant. As the plasma expansion is important towards exploiting EGGR, a research programme was instigated to investigate mixing processes of plasma under various conditions. The objectives of this research were to understand, firstly, more about the plasma penetration and expansion processes in a combustion chamber and, secondly, how these may affect EGGR in an ETC gun. This paper reports on theoretical work that investigated the influence of the background gas pressure on the plasma penetration for a 155 mm gun. The plasma penetration and expansion were determined at various initial background gas pressures for a breech-mounted capillary plasma generator.