The influence of mechanical preload on muzzle speed in solid armature railgun

Electromagnetic railgun is one of the most important new concept weapons. It is very important and necessary to maintain adequate contact pressure between rail and armature for avoiding transition in solid armature railgun. Based on Marshall´s “one gram per amp” rule, the mechanical preload is analyzed. The lower limit of mechanical preload is about 0.1kN in both small and large caliber railgun. Based on Newton´s second law, the upper limit of mechanical preload is also analyzed in different caliber railgun. The result shows that the mechanical preload permits very wide range of values. The influence of mechanical preload on rate of muzzle speed change is analyzed. The influence is remarkable in small and medium caliber railgun, which is larger than that in large caliber railgun. When rate of muzzle speed change is lower than 1%, the upper limit of mechanical preload is 38.6kN in 30mm×30mm caliber railgun and 1150kN in 90mm×90mm caliber railgun. When rate error of muzzle speed is lower than 0.1%, the upper limit of mechanical preload is 8.36kN in 30mm×30mm caliber and 251.02kN in 90mm×90mm caliber, which are still larger than 0.1kN in various calibers.