Investigation of the behavior of a plasma-arc armature inside a two-stage railgun and methods for preventing arcing

Results from a recent hydrogen pellet acceleration study using a 3.2-mm-diam two-stage electromagnetic railgun are reported. By installing a pressure-relieving coupling piece between the first-stage gas gun and the second-stage railgun and thereby controlling the pressure distribution inside the railgun bore, spurious arcing that prevented operation of the railgun at high voltages (and therefore high currents) was eliminated. Consequently, voltages and currents as high as 10 kV and 23.5 kA, respectively, could be used to operate the gun. A record output velocity of 2.2 km/s and an acceleration of 2.92×106 m/s2 were achieved for a solid hydrogen pellet, 3.2 mm in diameter and 4 mm in length, using a railgun of 1-m length.