Abstract: A plasma generator (44) for an electrothermal gun cartridge has elongated metallic rod and tube members (58,60) extending along a central axis thereof with the tube member (58) having at least one axial gap (62) and with an elongated annular insulator located between and in engagement with both metallic members to provide support therebetween as an electrical voltage generates an electrical arc at the axial gap to provide a plasma that ignites a propellant (46). Different embodiments of the plasma generator have a plurality of the axial gaps (62) located along the tube member (60) and are constructed for both simultaneous and sequential firing with fuses (74) controlling the timing. Helically extending member portions (78) provide rotation of the electrical arc and hence the plasma generated to distribute it for ignition of the propellent (46).

Abstract: A projectile is accelerated through a gun barrel in response to high pressure gas applied to the rear of the projectile in response to a high pressure plasma discharge. Plasma from the discharge flows transversely of the discharge into a chamber through multiple openings in a passage wall that confines the discharge. The high pressure, high temperature plasma flowing into the chamber causes an exothermic reaction of water and metal particles in a slurry in the chamber to produce high pressure hydrogen gas that flows longitudinally of the discharge against the rear of the projectile. To maintain the pressure of hydrogen gas acting against the projectile relatively constant as the projectile is accelerated down the barrel, electric power applied to the discharge increases substantially linearly as a function of time.