Plasma Armatures for Railguns

Renewed interest has arisen in plasma armatures as evidenced by two papers presented at the 2008 EML Symposium. It is hoped that the work at the University of Texas described in these papers succeeds. There may, however, be some uncertainties related to the nature of plasma armatures in that work. The thoughts we offer here may help. It is not yet obvious how the 6-km/s velocity limit encountered in the Canberra railgun can be overcome. In the years following this discovery, a considerable number of experiments were conducted on the subject with no clear outcome. One strategy for overcoming the velocity limit may be to vent the bore behind the armature. In order to do this, it is necessary to find out how long the armature must be to be effective. Too long would make the venting process unwieldy. Too short and the armature losses will rise to unacceptable levels. Further, the method we suggest for implementing the venting strategy may be extended to prevent damage to the railgun rails caused by the arcing current transfer from rails to armature. We examine the possibilities and implications involved in implementing these strategies.