Quantitative expression of sliding contact resistance between armature and rail in railgun

Based on the physical model of the electromagnetic railgun, a quantitative expression of sliding contact resistance of electromagnetic railgun is derived. The expression is related to the rail current, muzzle voltage, in-bore velocity of the armature and the rail configuration. The calculated sliding contact resistances between armature and rail depend on rail current. The resistance is different at different region of the rail current. At flat region, the contact resistance is about 0.2 m and at the rising and falling regions, the contact resistance reaches 3 m.