OBSERVATION OF SOLID ARMATURE BEHAVIOR

High efficiency railgun armatures require metal-on-metal sliding of armature on rail without arcing. A succession of armatures has been constructed and tested in a 25 mm square bore railgun. The first armature tested was a single leaf copper staple having 12 fingers per side, of the type pioneered in the Canberra railgun. At moderate currents (250 kA) the staple armature performed well, but at higher currents transition to arcing contacts occurred as current was falling. The effects of modifying rail surfaces was also tested, including the use of transverse mini-grooves to enable friction to be calculated, angled lands to improve armature contact, and insulating inserts to trip transition. This led to a design in which a polycarbonate ''spring'' was used to carry 11 wires, 2 mm in diameter. This armature, when using copper wires, carried 360 kA without premature transition. Various other designs have also been tested, including monolithic aluminum alloy armatures, which successfully carried currents of 600 kA.