Projectile acceleration apparatus and method

摘要

A high pressure pulsed gas source for accelerating a projectile along a gun barrel comprises a structure including a high voltage electrode for establishing axial electrical discharges in corresponding axial gaps behind an outlet where the projectile is located. Plasma flows at right angles to the discharges into a propellant mass that is converted into a high pressure component of the gas pulse. The gaps are arranged so that after the projectile moves away from its initial position and is in the barrel, power applied to the plasma via gaps close to the outlet is greater than power applied to the plasma via gaps farther from the outlet. To avoid damage to the gun, the gaps are arranged so power applied to the plasma is substantially the same in the discharges when plasma is initially produced. The gaps include walls that are eroded differently by the discharges so gap walls close to the outlet erode faster than gap walls farther from the outlet. The plasma has sufficient pressure so it tends to flow out of a confining structure for it into contact with the electrode via a secondary flow path other than the flow path through the outlet. The confining structure includes a cavity located in the secondary flow path. A soft, non-electrically conducting material in the cavity expands in a direction at right angles to the secondary flow path and compresses in the direction of the secondary flow path against walls of the cavity to form a seal to overcome a tendency of the plasma to flow into contact with the electrode. <IMAGE>