Performance optimization of a SCRAM accelerator projectile

Abstract

The optimization of a Supersonic Combustion RAM projectile shape, using a computational analysis is presented. The projectile, flying at hypersonic speeds through a combustible mixture, is accelerated by using the shocks produced by a ring cowl to ignite the flow over the projectile tail. This method could be used to accelerate projectiles to velocities in excess of 2.7 km/sec. The thrust and drag forces on such a projectile are very large and are of the same order of magnitude. Small changes in the projectile design can have a large effect on the net thrust acting on the projectile. A computational analysis using an inviscid CFD code, including chemical reactions, is linked to a gradient based optimizer. The projectile is then optimized for maximum thrust at several different Mach numbers. Multiple CFD solutions were then used to generate a thrust curve used in optimization for other design functions, such as maximum velocity and minimum accelerator tube length. All configurations are compared to determine the best configuration for practical use.