High acceleration experiments using a multi-stage ram accelerator

Abstract

Methods of maximizing projectile acceleration to obtain high velocities with the thermally choked ram accelerator have been investigated. A low mass (50 gm) projectile geometry was developed that can be reliably accelerated up to the Chapman-Jouguet detonation speed of the propellant in a 38 mm bore ram accelerator. Experiments were performed in CH₄/O₂/He propellants wherein Mach number and heat release of combustion were varied to obtain very high projectile acceleration. Using 5.0 MPa fill pressure in a 2-m long first stage, average accelerations of over 38,000 g were routinely achieved, allowing the projectile to be accelerated from 1320 to 1800 m/s. Two and three-stage ram accelerator investigations culminated in a staging configuration that produced an average acceleration of ≈ 35,000 g over three 2-m long stages, resulting in a peak velocity of 2404 m/s in a distance of 6 m.