Functional Graded Conductor Rails for Electromagnetic Launchers

The US Navy is pursuing the development of an electromagnetic rail gun (EMRG), which promises to extend naval fire support and increase ship safety. Such guns have been built and operated successfully, however several obstacles prevent them from widespread usage in the field. One specific obstacle is the development of suitable interface between the armature and conductor rails. Abrasion, arcs, molten armature, and balloting loads easily degrade bare surfaces. As a result multiple firings are not possible without repair/replacement of conductor rails. In order to maximize electrical/thermal conductivity, Cu alloys are likely inescapable. In order to minimize damage, a material with a high melting temperature and high density is essential. Therefore, a rail structure that most practically meets these requirements would have a Cu-based core and a refractory metal surface. However, issues associated with thermal expansion mismatch pose significant challenges. The Phase I study demonstrated fabrication of an innovative functional gradient material between the armature and conductor rails. However, additional efforts are needed to perfect the gradient and demonstrate high performance, full-scale conductor rails. A Phase II effort will optimize adhesion of functionally graded rails; investigate non-planar geometries; small caliber evaluation; and fabrication of 5 meter long rails.