Study On The Launch Mechanism Of Rail-Coil Combined Electromagnetic Gun

The electromagnetic (EM) guns launching projectiles by electromagnetic force is a new type of weapons. Compared with traditional artillery, the EM guns have much superiority such as high muzzle velocity, high efficiency, excellent controllability etc. Railgun and coilgun are the basic types of EM guns, and they both have advantages and disadvantages. The combined rail-coil EM launcher, which has integrated the two, is studied in this work, especially the new mechanism caused by combination, new problems, and the improvement.Firstly, a unified theory of mechanism of different EM launchers has been developed upon the basic physical principles to analyze the complicated combined EM launch. The expressions of the drive force with inductance gradient and its applicable conditions are illuminated, and the equivalence between the inductance gradient expression and Ampere force expression is discussed. The conception of Pull EM launch and Push EM launch is defined, and some conclusions about energy conversion efficiency have been obtained. Preliminary analysis shows that there is rail-coil cross interaction in combined EM launchers. Then a special kind of combined EM launchers, which is mainly a coilgun with ferromagnetic armatures, has been studied. It is found that when the armature is saturated in intense magnetic field, the kinetic energy is linearly dependent on the current, and the energy conversion efficiency drops with the current increase. Lastly, the drive force, the rail-coil cross interaction and the system performance of the combined EM launchers with aluminum-copper projectiles have been researched systemically. Since the cross interaction brings considerable transverse pressure and motion instability to the normal two-rail combined EM launcher, a novel structure with four rails distributing symmetrically has been proposed to eliminate the bad effect of the rail-coil cross interaction. The computation shows that in four-rail combined EM launch, not only the transverse pressure is nearly zero, but also the contribution of the cross interaction to the kinetic energy of the projectile is positive, and the system performance is entirely better than two-rail combined EM launch.