Ram accelerator utilizing active projectile

Abstract

A chemical-propulsion accelerator (either ram- or external-propulsion) system, utilizing a novel, activeprojectile concept is proposed. The projectile comprises the mechanism for compression, storage, and release of high-pressure fluid, that may be either the fuel or the oxidizer used in the ambient combustible gas mixture or inert gas. The shock pattern established by ejection of high-pressure gas from the supersonic projectile into the ambient, combustible-gas mixture serves to ignite the mixture through shock heating and compression, and therefore, to induce the desired propulsive mode (combustion or detonation). The ejected gas then serves to alter locally the ambient mixture, and therefore, can enhance its reactive properties. The present method alse-effers potential application in future aerospace vehicles that will utilize external propulsion modes. A simple model is used to show the practicality of the method and to estimate the lateral size of the combustion zone. The results show that the jet bow shock can ignite the combustible mixture within a radial distance from the body comparable with the barrel radius used in the present ram accelerators. The size of the combustion zone is shown to scale favorably with increasing Mach numbers encountered during the acceleration. The amount of the injectant gas needed is shown to be small. ^