Transient modelling of railgun plasma armatures

Simulations are performed with a one-dimensional, time-dependent model to investigate the dynamic behavior of railgun plasma armatures. Specifically, the model is applied to the analysis of three problems: (1) the simulation of the release of a projectile; (2) the simulation of the latter stages of the initiation of an armature, with the initial arc length 50% of its final equilibrium length; and (3) a second initiation simulation where the initial arc length is 10% of its final equilibrium length. For all three simulations, the armature length and projectile acceleration exhibit damped oscillations. After the first armature expansion, the period of oscillation of the armature length can be approximated by 3l_eq/a₀ where l_eq and a₀ are the armature length and acoustic propagation velocity, respectively, calculated for an equilibrium, isothermal plasma whose thermodynamic characteristics are obtained from a mass average of the properties in the nonisothermal simulation. This characteristic period of oscillation is consistent with the period observed in isothermal armature simulations