FUNDAMENTAL STUDY AND DEVELOPMENT OF A HYDROGEN PELLET ACCELERATOR USING A FUSELESS TWO-STAGE PLASMA-ARC-DRIVEN ELECTROMAGNETIC RAILGUN

A detailed experimental study has, for the first time, successfully demonstrated the acceleration of frozen hydrogen pellets by means of a fuseless two-stage electromagnetic railgun system. This system consists of a pneumatic hydrogen pellet injector, which freezes and pneumatically pre-accelerates (with high-pressure helium as the propellant gas) cylindrical 1.6-mm-dia. by 1.75-mm-long hydrogen pellets, and a 60-cm-long 1.6-mm-dia. circular-bore electromagnetic railgun. The pellet is introduced into the railgun by means of a coupling piece, and a plasma-arc armature is created from the propellant gas by means of a very unique, fuseless, arc-initiation scheme. A slightly different, yet equally effective fuseless arc-initiation scheme was employed in a prototype room-temperature two-stage railgun system. Railgun-accelerated hydrogen pellet velocities of 1.6 km/s were achieved from pneumatically-accelerated injection velocities of 800 m/s. Streak-camera and current-probe data showed that the plasma-arc armature moves at a velocity proportional to the railgun current, I, and not to the often-quoted I('2). Insight to this I-dependence has been gained through the use of streak photography and current probes for varying bore geometries and gas pressures.