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Ram Accelerator as an Impulsive Space Launcher: Assessment of Technical Risks

The ram accelerator is a chemically powered hypervelocity mass driver that operates with intube propulsive cycles similar to airbreathing ramjets and scramjets. The launcher consists of a long tube filled with a pressurized gaseous fuel-oxidizer mixture in which a subcaliber projectile having the shape similar to that of a ramjet centerbody is accelerated. No propellants for this launch process are carried aboard the projectile; it effectively flies through its own propellant “tank”. The ram accelerator at the University of Washington has been operated at velocities up to nearly 3 km/s and in-tube Mach numbers greater than 7 in methane-based propellant mixtures. This Mach number capability corresponds to muzzle velocities greater than 7 km/s when using fuel-rich hydrogen-oxygen propellant. The combination of hypervelocity muzzle velocities and the ram accelerator’s inherent scalability to multi-ton payload sizes makes it suitable for direct space launch. Technical issues associated with the implementation of the ram accelerator technology for direct space launch applications are presented here.