Abstract: A high pressure plasma initially formed from a fluidizable substance in a confined region of a passage behind a projectile in the passage initially accelerates the projectile toward an open end of the passage. The plasma is intially derived by supplying a discharge current to an electrode in the substance. The plasma in the confined region is ohmically heated by an azimuthal current generated in the plasma by an AC magnetic field that is coaxial with the passage or by a discharge current flowing longitudinally through the passage and projectile. A cartridge includes the projectile and a wall of the passage that is evaporated after the projectile has been fired so the evaporant flows out of the passage after the projectile.

Abstract: A high pressure plasma initially formed from a fluidizable substance in a confined region of a passage behind a projectile in the passage initially accelerates the projectile toward an open end of the passage. The plasma in the confined region is ohmically heated to a higher pressure by a discharge current flowing longitudinally through the passage and the projectile.