New tube end closure system for the ram accelerator

Abstract

The ram accelerator is a ramjet-in-tube device which has been demonstrated at velocities up to 2.5 km/s, has potential for operation up to 10 km/s, and could be used for direct space launch or large ballistic ranges. The ends of the main ram accelerator tube must have end closures which support substantial pressure differences. There are potentially serious difficulties using solid end closures such as diaphragms pierced by the projectile, explosively removed end closures, or fast acting valves. These include risks of significant damage to the projectile and launch tube and the wasting of tube length. A new end closure system which uses the momentum of an annular axial air jet to support the required pressure differences is described. This system avoids the difficulties of the solid end closure system at the cost of some increase in overall launch system complexity. A preliminary design of such an air jet end closure is presented, and it is concluded that the requirements for airflow rates and storage are reasonable and would likely add only a modest increase to the overall cost of the launch system. If the difficulties with solid end closures prove to be significant, the air jet end closure system may offer a solution.