Electromagnetic Acceleration: Asynchronous Linear Induction Motors

A coil-gun uses pulsed currents of large magnitude to propel ferrous projectiles at high speeds. The various problems associated with high currents and magnetic fields are discussed, as well as the components and design of my experimental coil-gun. I tested the coil-gun at various charge voltages and different projectile sizes, then calculated the efficiency of the coil-gun with measured values of muzzle speed, projectile weight, and discharge energy. INTRODUCTION The first projectiles known to mankind were simple rocks thrown by hand. Eventually, devices like the catapult, slingshot, and bow were invented to propel projectiles with pure mechanical forces that were far greater than a man's arm and hand were capable of producing. These mechanical devices that use stored potential energy were limited to the strength of the elastics or springs that store the energy, and were not capable of propelling objects at supersonic speeds. The invention of black powder, and eventually the modern smokeless gunpowder, allow rifles like the Barrett M82 to fire a projectile at about 2.5 times the speed of sound [2]. However, as time progresses, so does the search for technology to propel projectiles at higher speeds. Electromagnetic accelerators like rail-guns and coil-guns are not limited by the properties of gas expansion, and thus have no theoretical limits on velocity [3]. The US Navy has ongoing research, and even a few operational experimental rail-guns for use on battle ships. The advantages of such high projectile velocities is that effective ranges are