Analysis of Projectile Motion in Bore and Transfer Efficiency for Electromagnetic Railgun
Electromagnetic railgun (EMG) use a high-current, high-energy electrical pulse to accelerate projectiles to hypersonic velocities. A pulsed power supply (PPS) that employ capacitors as the energy store are typically used to shape the required electrical pulse. In this paper, the differential equations of projectile moving in the bore has been given and solved. The general pattern of projectile moving in the bore has been studied. Considering the influence of current fluctuation on velocity, the stability of armature has been discussed. In order to improving system performance, the efficiency of main energy transfer process has been calculated. The influence of current shape consists of several electrical pulse on muzzle velocity and efficiency has been studied. And some important conclusions have been reached, which provide theoretical references for guiding railgun design and choosing waveform of discharging current.
The effect of rail resistance on railgun efficiency
A time-dependent model of rail resistance based on one-dimensional current diffusion was developed and implemented in a railgun simulation code that can be used to study efficiency and losses in most railgun systems. Results were obtained for simple 500 kA, 2-m gun using metal armature. It is shown that typically 25% of the energy delivered to the gun is dissipated in rail resistance. The energy lost in the rails is about 75% of the final kinetic energy of the projectile. Gun efficiency can be improved by about 7% by simply cooling the rails to 77 K. Resistive voltage drop in the rails accounts for 33% of the breech voltage. Performance as measured by muzzle velocity depends on available power supply energy. >
Design and operation of a self activating crowbar switch
A simple and reliable crowbar switch has been designed and successfully used in the electromagnetic propulsion research program at Materials Research Laboratories. The switch is self activating and has crowbarred a 6211 μF, 8 kV capacitor bank at peak currents in excess of 220 kA. It is manufactured from readily available components and suffers little damage during switching. This paper describes the switch design, and presents results of the crowbarred capacitor currents and voltage. Possible modifications for improved performance are discussed.