Rail Accelerator as Continuous Commutation Process

The problem of armature transition in a rail accelerator is considered in this paper from the position of analysis of the commutation process realized by a moving armature. The needed electrical conductivity of the surface layer of the rails to avoid arc excitation has been calculated for each step of armature motion using the simple model of the transient electromagnetic process. Conductivity must be changing depending on the path of armature transportation along the rails. The efficiency of variable conductivity and multilayer structure of the rails has been demonstrated by 2-D simulation of the field and current density distribution using the finite-element software Comsol and FlexPDE6. It was concluded that the main problem of railgun (armature transition, i.e., current concentration and extra-voltage appearance near the trailing edge of the armature resulted in the local melting of both the rails and the armature) can be resolved successfully when 2-D gradient of the electrical conductivity of the rails near the contact surface is provided jointly with the reduced conductivity of the armature contact surface.