Current scaling of projectile velocities with and without a snowplow effect in electromagnetic launchers

Scaling laws are studied, with and without a snowplow (SP) effect, for macroparticle projectile velocities in electromagnetic launchers (EMLs) as a function of the peak EML current. Analytical formulae to predict the instantaneous position and velocity have been derived for both phases of rising and constant EML currents. The SP effect altered the scaling law of the short-pulse muzzle velocity (ν_xw), but not of the long-pulse muzzle velocity (ν_xm). The absolute values of both ν_xw and ν_xm are, however, seriously reduced in the SP regime, depending on the newly introduced parameter, ∈, which is a mass ratio of the armature/projectile system to the gas in the barrel. The critical ∈ s with which the SP effect alters the muzzle velocity and time by more than 10% are presented. Numerical examples are given for possible applications of EMLs on calibrated impact damage testers and impact thermonuclear fusion, where short (1 m) and long (1 km) barrels are to be used for projectiles of several grams to achieve the maximum velocities of 1 and 130 km/s, respectively