Thermal and mechanical stress in induction coilguns

The aim of this paper is to define a procedure for the design of induction coilguns in order to obtain thermal and mechanical stress that do not exceed the allowed values in the sleeve. The magnetic vector potential is determined considering a cylindrical sheet current model both for the barrel and the sleeve and solving the related modified Bessel equation. Then the flux, the current density and the propulsive force for each section are determined. By considering the constraints due to mechanical and thermal stress, the maximum muzzle velocity for a one-section launcher is determined. Supposing that the muzzle velocities in the first and in the last section are established, and assuming that all sections, from the second to the last, work with the same mean slip and the same relative velocity, the number of sections and their length are determined. Moreover the surface current density in the barrel is calculated. The design criterion is compared with other criteria, and then used to design an 8 km/s muzzle velocity launcher.