Performance Optimization of a Supersonic Combustion Ram Accelerator Projectile

Abstract

The optimization of a supersonic combustion ram projectile shape, using a computational analysis, is presented. A projectile e ying at hypersonic speed is passed through a combustible mixture. Shocks generated by a ring cowl surrounding the projectile ignite the e ow over the projectile tail, causing it to accelerate. This method could be used to accelerate projectiles to velocities in excess of 2.7 km/s. 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 computational e uid dynamics (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 are used to generate a thrust curve used in optimization for other design functions, such as maximum velocity and minimum accelerator tube length. All cone gurations are compared to determine the best cone guration for practical use. Optimized cone gurations are capable of higher velocities, but the main benee t gained is the reduction in the length required to reach that maximum velocity.