Skin and heating effects of railgun current

Abstract

The authors present a calculation in a simplified geometry for the current distribution in the rails of a railgun, taking into account the motion of the armature and the time variation of the current. Closed-form, asymptotic results for the current density are obtained for arbitrary time-dependent currents and velocities, in the limit in which the length scale k/sub 0//sup -1/ is small, where k/sub 0/=( mu sigma nu ), sigma is the electrical conductivity of the rails, and nu is the speed of the armature. Because of eddy-current effects the rail current may reverse in portions of the rails when the total current decreases. The current is used as a source of Joule heating to find the temperature distribution in the rails. The heat diffusivity is negligible. Numerical results concerning melting are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>