Search for new possibilities of attaining high launching velocities

The paper is concerned with analyzing the ultimate velocity versus the proj ectile mass at fixed acceleration distance for various methods of decreasin g the current density at the rail-armature interface. The analysis is perfo rmed by numerical solution of the system of equations of unsteady diffusion of a magnetic field and unsteady heat transfer in a two dimensional formul ation. Homogeneous and multilayer armatures, homogeneous rails, and rails with a h igh-resistive layer are considered, The results reported in the paper show that use of a resistive coating on t he conductive side of rails is highly efficient at decreasing a current con centration on the rear side of the armature due to the high-velocity skin e ffect, This ensure a considerable decrease in the heating rate of the armat ure near the contact boundaries. As a result, the maximum velocity to which armature can be accelerated with retention of solid metallic contact with rails in a channel of a given length can be increased by a factor of 2-4, a nd the kinetic energy can be increased by a factor of 4-16 compared to the case of using rails without coating, Use of a multilayer armature with orth otropic electrical conductivity in combination with a resistive coating on the contact side of the rails allows one to attain high velocities and ener gy characteristics of the armature at short acceleration distances.