An Investigation Into Muzzle Velocity Repeatability of a Railgun

Muzzle velocity repeatability of electromagnetic railgun has been identified as a potential development issue for several years. The muzzle velocity is sensitive not only to initial parameters, such as charged voltage of capacitors, mass of armature, and starting position, but also to dynamic parameters, such as electric contact resistance and friction between the armature and rails. This paper analyzes the effects of initial and dynamic parameters on muzzle velocity. It is found that the most sensitive parameter is the charged voltage of capacitors. A series of two 20-shot bursts was performed with two sets of rails, respectively. The details of the experimental setup and velocity measurement are described. The maximum deviation of the muzzle velocity is 3.8% with 8.47-g armatures at a mean velocity of 1913 m/s in the first 20-shot burst, and 0.92% with 10.50-g armatures at a mean velocity of 2373 m/s in the second 20-shot burst. It indicates that the greater armature mass and larger contact area probably advance the repeatability of the railgun muzzle velocity. The effects of rail current and muzzle voltage on repeatability are discussed. The relations between repeatability of the muzzle velocity and the rail current and/or muzzle voltage are not obvious.