Electromagnetic Propulsion

Abstract

Sporadic attempts have been made for more than 150 years to use electrical energy to launch projectiles at high velocities. Throughout the world during the last 20 years, most of the funding invested in electromagnetic (EM) launcher development has been for military applications. In most cases, the perceived advantage has been attaining higher velocities than can be achieved with propellant guns, leading to enhanced lethality. The elimination of gun propellants would also reduce vulnerability as well as allowing an increased number of stored rounds and enabling extended missions. The EM rail gun has been the preferred choice for this application because it has already repeatedly demonstrated muzzle velocities well above those of conventional guns—typically 2500 m/s versus 1750 m/s. The military challenge is to fit the electric pulsed power equipment into a battleworthy vehicle, especially if it needs to be compact. The main potential applications are direct fire tank guns, long‐range artillery, and air and missile defense. Several electrical or electromagnetic (EM) concepts have been suggested, as described here, but their potential for space applications is, as yet, limited. However, the technological bases are now being created on which future EM launch systems for space exploration could be based in the twenty‐first century. Such systems could include launch to space from the surface of Earth, the Moon or asteroids, Maglev launch assist for large rocket systems and, possibly, EM thrusters for space transportation. Electrical ion engines have been used in space, and the Hall plasma thruster is under development for NASA. The interest in electric launchers for military applications has led to improved understanding and advances in many technical areas. Most military applications for EM launchers require gigawatt power levels for pulse lengths of a few milliseconds to accelerate a useful projectile in a launcher of acceptable length. Coupled with the need for compact and robust equipment, this is a challenging goal for the pulsed power system. The desire to achieve muzzle velocities significantly greater than those of conventional guns—from 2–3 km/s—also requires developing the launcher and projectile. Recent progress in these areas could be the basis for future space applications.