3-D field analysis in tubular induction launchers with armature transverse motion

In this paper the transition between the sections of a generator driven induction launcher is investigated. During the transition a possible mismatch of the currents in the sleeve with the driving coils currents can give rise to strong braking force. If the sleeve is not in coaxial position with the barrels, forces in the transverse direction of motion can produce contacts with the flyway tube. Transverse motion of the sleeve has to be considered. The equations of motion are derived assuming a rigid projectile and a flyway restoring force that is proportional to the local deformation. A full 3-D analysis, required because of the departure from the coaxial configuration, has been performed by means of a computer code based on an integral formulation of the Maxwell equations; the resulting equations are those of an electrical time-varying network. Simulations of the behaviour of the system have been performed to search for the optimal initial position of the sleeve in the second section. The results show that smooth transition between the sections is obtained if the energization of the coils of the second section is done in correspondence with the proper positions of the sleeve. Under these conditions the motion is characterized by the greater muzzle velocity.