Development of a Linear Implosion-driven Hypervelocity Launcher

Abstract

A traditional difficulty with high-explosive hypervelocity launching techniques is that extreme loading generally causes hydrodynamic deformation of the projectile either incidentally or by design. The launcher presented in this study uses explosives to operate the pump tube of a two-stage light gas gun via continuous linear implosion. In this configuration, the projectile is cushioned from direct action of the explosives by a light driver gas. The launch cycle is therefore comparable to a conventional two-stage light gas gun but with the shock driven by the rapid linear implosion of the pump tube compressing the gas to a much higher enthalpy. A laboratory scale version of the implosion driven launcher has recently demonstrated the ability to launch a 0.7g projectile to 7.9km/s. This design has successfully been scaled up to launch a 15g projectile to 7.6km/s, a result comparable to large two-stage light gas guns. This study presents the experimental and computational work performed in the ongoing development of this device. The extreme launch conditions lead to a number of unique design considerations, including dynamic confinment of the driver and launcher reservoir, mitigation of the loss of driver gas, and in-bore projectile stability and survivability. These issues are addressed experimentally through a number of focused launcher trials, as well as through the development of a quasi-one-dimensional Lagrangian hydrocode. The development of advanced implementations that involve continuing explosives onto the reservoir and launch tube in order to maintain a high driving pressure are also considered. These “second stage” techniques offer the potential for achieving projectile velocities in excess of 10km/s.