Rapid testing for multishot railgun bore life

Bore life is one of the most difficult technical issues confronting railgun development for practical use. Material testing for wear and erosion using a railgun is a very slow and expensive method for developing many shot life data. We have built and used a pin-on-disk contact tester to rapidly and economically accumulate materials performance data under railgun armature/rail interface conditions. The machine can reach sliding speeds of 200 m/s, to simulate armature conditions near the breech of a railgun. The unique feature of this apparatus is the ability to repeatedly place the contactor on the rotating disk (at 200 m/s) and subsequently remove it in less than one disk revolution. This capability permits us to avoid "rewrite" during each simulated shot so that definitive multishot wear data can be accumulated. This apparatus has been used to test a variety of armature contact-rail material combinations, at railgun current density (up to 1.5 GA/m/sup 2/) and pressure levels (up to 150 MPa). Our tests show that different combinations of pressure level, current density, and materials produce results ranging from severe erosion to severe contactor deposition. In the case of contactor deposition after many shots, the per shot deposition rate tends to decline for specific material combinations. This paper describes the apparatus and test results for several material combinations.