Three-Dimensional Numerical Simulation of the Joule Heating of Various Shapes of Armatures in Railguns

This paper reports the results of 3-D numerical simulations of the Joule heating of armatures and rails in railguns. Armatures of various shapes with homogeneous and orthotropic electrical conductivity, homogeneous rails, and rails with a resistive coating are considered. It is shown that the maximum current density is reached at the perimeter of the rail-armature interface. The current-density value and, hence, the armature-heating dynamics are significantly affected by the armature shape and the electrothermal properties of the armature and rail materials, as well as by the acceleration dynamics, which, in turn, is determined by the total current value in the electromagnetic launcher and the total mass of the projectile. The ultimate projectile velocities are obtained when the Joule heating of the rails and armature by electric current during the shot does not tend to increase the temperature at any point of the railgun above its melting point. By controlling the structure and properties of rail materials, it is possible to reach ultimate (in terms of heating conditions) velocities much higher than those with homogeneous materials.