Abstract: A method and apparatus for supersonically accelerating a projectile in a thermally choked subsonic combustion mode. A projectile (50) is initially preaccelerated using either a tank (24) of compressed helium or a chemical propellant charge preaccelerator (152). The projectile enters a portion of a tube (22) filled with a combustible mixture (54) of a gaseous fuel and an oxidizer and is propelled by a ram acceleration process as the mixture burns. In several different embodiments, various devices are used to control the velocity of a shock wave generated as the projectile enters the combustible mixture and the dynamic impulse pressure immediately behind the projectile, so that the shock wave attaches to the projectile along an aft portion, thereby establishing a stable subsonic combustion zone along the aft end (64) of the projectile, in which combustion of the gaseous fuel accelerates the projectile down the bore of the tube.

Abstract: A projectile is initially accelerated to a supersonic velocity and then injected into a launch tube filled with a gaseous propellant. The projectile outer surface and launch tube inner surface form a ramjet having a diffuser, a combustion chamber and a nozzle. A catalytic coated flame holder projecting from the projectile ignites the gaseous propellant in the combustion chamber thereby accelerating the projectile in a subsonic combustion mode zone. The projectile then enters an overdriven detonation wave launch tube zone wherein further projectile acceleration is achieved by a formed, controlled overdriven detonation wave capable of igniting the gaseous propellant in the combustion chamber. Ultrahigh velocity projectile accelerations are achieved in a launch tube layered detonation zone having an inner sleeve filled with hydrogen gas.