Washington Research Foundation

David W Bogdanoff

Abraham Hertzberg

Adam P Bruckner

Carl Knowlen

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. In one embodiment, a perforated sabot (52) is used to propel the projectile during preacceleration. The sabot has a plurality of passages (114) extending longitudinally between its front and rear surfaces, which are initially closed with a thin plate (110) during the preacceleration of the projectile. However, the plate is dislodged as the projectile enters the combustible mixture, allowing the dynamic pressure of the shock wave caused by the sabot to dissipate through the open passages.

Method and apparatus for initating stable operation of a ram accelerator

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. An explosive, which is disposed in the annular zone between the inner sleeve and the launch tube, explodes responsive to an impinging shock wave emanating from the diffuser of the accelerating projectile thereby forcing the inner sleeve inward and imparting an acceleration to the projectile. For applications wherein solid or liquid high explosives are employed, the explosion thereof forces the inner sleeve inward, forming a throat behind the projectile. This throat chokes flow behind, thereby imparting an acceleration to the projectile.

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Bellevue, WA, United States of America

David W Bogdanoff