Experimental investigation of barrel damage mechanisms in electromagnetic railguns

Electromagnetic railguns suffer from several major sources of damage. The first is transition to arcing contact, in which the sides of the armature wear away, leaving a gap in which an arc forms between the armature and the rails. The second is startup damage that appears as grooving near the rail edges in the armature startup region. Using the 40mm square bore Medium Caliber Launcher at the Institute for Advanced Technology, we analyzed the results from several shot series, each on the same set of rails with 1, 3, 7, and 20 shots. We discovered that the damage from both mechanisms is cumulative with increasing number of shots, making them both serious hurdles to overcome before railguns can be practically fielded. Furthermore, we studied the aluminum layer deposited by the armature onto the rail surface in pre-transition locations, where the rails displayed no damage. Thus, the layer is a key indicator as to whether the rails have suffered damage. A similar aluminum layer exists in the startup region and additional experiments that involved etching it away between shots showed that the layer also helps to protect the rails from startup damage, but does not prevent it completely.