Secondary arc formation and evolution in railguns

Summary form only given. A computational code based on simple models has been developed as an aid to understanding the complex physical processes which promote the formation of secondary arcs and control their evolution in plasma armature railguns. A lumped-parameter model with time-dependent parameters is used to describe the dynamic electrical circuit consisting of the railgun and its capacitor power supply. The two arcs in the railgun are modeled as circuit elements having nonlinear current-voltage characteristics. The mechanical equations describing the dynamics of the two arcs include the effects of bore pressure, electromagnetic forces, ablation drag, and viscous drag. The resulting system of equations is solved numerically to obtain the currents and voltages in the railgun circuit, together with the trajectories of the two arcs. It was found that two conditions are required for the formation of distinct secondary arcs in the railgun: The secondary arc must have a significantly greater resistance than the primary, and the secondary arc must accelerate mass ablated from the bore. The detailed trajectories of the arc within the railgun and the resulting division of current between the arcs are strongly dependent on the current-voltage characteristics assumed for the two arcs