Modeling of the 105-mm Rarefaction Wave Gun

Report No. ARL-TR-4897
Authors: Terence P. Coffee
Date/Pages: August 2009; 36 pages
Abstract: The Rarefaction wAVE guN (RAVEN) is designed to reduce the recoil momentum of a gun while having a minimal effect on the projectile velocity. The recoil reduction is achieved by venting gas out the breech through an expansion nozzle. This is similar to a recoilless rifle. The difference is that the venting is delayed until the projectile is some distance down tube. The opening of the breech creates a rarefaction wave that travels down the bore of the gun. If the timing is done correctly, the rarefaction wave will not reach the projectile until at or after muzzle exit. Hence, the projectile does not know the breech has opened, and the venting has no effect on the muzzle velocity. As a proof of principle, a 35-mm RAVEN gun was designed, built, and fired. The breech is a moving piston. When the piston moves a specified distance, it opens a vent into an expanding nozzle. There is a small reduction in the muzzle velocity due to the motion of the breech, i.e., the chamber becomes larger than for a fixed breech gun. If the timing is correct, there is no additional reduction in the muzzle velocity from venting. In a previous report, a one-dimensional model of the RAVEN was presented. The model covered the interior ballistics, motion of the projectile and the breech, opening of the vent, flow through the nozzle, and blow down of the gun. The model was validated against the 35 mm RAVEN data. In this report, an updated version of the model is discussed. The modified model is compared with the old 35-mm RAVEN data. The model is then applied to a proposed 105-mm demonstrator. The demonstrator has not yet been built.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2009