The stability and the conditions for initiation of electric-arc discharges in railguns

Characteristic physical features of plasma formations in high-velocity sliding electric contacts are treated, in particular, those in railguns with both electric-arc and metal armatures. Comparison is made of the effect of a number of MHD instabilities (superheating, Rayleigh-Taylor, and erosion-dynamic) on the working capacity of plasma armature. It is demonstrated that the armature compactness may be disturbed both in the case of fairly intensive abrupt drop of current and in the case of increase in the associated mass of the armature, which is defined by the processes of erosion and ablation of the electrodes, walls, and dielectric projectile. The theory of transition of metal contact is generalized in view of the presence of transition electric resistance and external magnetic field.