Gasdynamic Quantities About Ramjet Projectile While in Transitional Ballistics Region

A study was performed to determine whether the fins of a ramjet projectile are deployed in the reverse flow of the gun blast with adverse consequences. Two muzzle blast simulation schemes were utilized to compute the flow quantities about the rear of the projectile. An estimate of the pressures internal to the projectile was also made because the deployment process for the fins depends upon the relative pressures internal and external to the projectile pusher plate. The calculations show that the deployment process starts before the base of the projectile leaves the jet plume or reverse flow region. Nevertheless the impulse given the pusher plate, which deploys the fins, is so small that the fins do not move back far enough for the reverse flow to harm them. Originator-supplied keywords: Intermediate Ballistics, Computational fluid dynamics, Jet plume flow.