Performance characteristics of a high velocity, 25 mm railgun

Abstract

This paper documents a series of tests in a 4.8 m long, 25 m m square bore railgun that characterize plasma armature behavior in a hypervelocity regime. Projectile masses ranging from 15 to 23 grams were accelerated to velocities of 2.5 to 5.6 W s . A linear decrease in momentum transfer efficiency with velocity was observed. This performance degradation was greater than predicted, and may be caused by the failure of the plasma armature to remain compact. Secondary arcs were noted when copper alloy rails were used, and au expanding primary arc was observed when molybdenum rails were used. In an attempt to circumvent armature expansion, the railgun configuration was modified to include a muzzle shunt resistor; this modification is a type of augmentation, such that the ratio of armature magnetic force to armature current is increased. Muzzle shunt augmentation (MSA) had little effect on the plasma armature's behavior.Measurements of the momentum transfer efficiency during acceleration show a slight but significant increase in efficiency of the MSA configuration over the simple breech-fed configuration. This paper describes an effort to quantify the various loss mechanisms by comparing experimental performance (velocity) to model predictions.

Resonant deformation of barrel in plasma - dynamic launchers

“…It is generally accepted that considerable degradation of EML performance at projectile velocities above 3-4 km/s is explained by essential increasing of the total accelerated mass due to thermal destruction of the barrel and restriking of secondary arcs in the breech of the railgun [1][2][3]. It should be noted that these assumptions have not been proved until now.…”

Electromagnetic Launch to Space

“…Researchers involved in that research were met with a great deal of challenge and difficulty, especially in getting plasma armatures to accelerate payloads to muzzle velocities in excess of 6 km/s at acceleration levels under 1 MG [1]. In those experiments, velocities of only 4-5 km/s were achieved for medium--bore (25-50 mm) railguns operating at typical accelerations of 400-600 kG [2,3], and velocities of 6-7 km/s were achieved in smaller bore guns operating at 1 MG or greater [4,5]. The researchers involved proposed a * corresponding author; e-mail: david wetz@iat.utexas.edu number of theories to account for the velocity ceiling and even proposed a number of solutions that could be used to overcome the obstacles, but no significant effort was put into implementing them.…”

Electromagnetic launchers - the new concept

“…For example, the maximum projectile velocity was near 4.3 km/s with copper electrodes, and 5.5 km/s with molybdenum electrodes [5]. The application of refractory electrodes allows to reduce to the certain degree the relative contribution of erosion of conducting walls to formation PP and, accordingly, to increase velocity of a sound in it.…”

“…The value of ratio p m /p is closed within the limits of 0.3 -3 at conditions of experiments [2][3][4][5].…”

“…The tested designs of EML according to (2) should provide projectile velocity v m above 15-20 km/s [2,5]. However really measured projectile velocities have been obtained much less, than follows from the equation (2).…”