Modelling of a Parallel Augmented Railgun with Pspice Validation of the Model and Optimization of the Augmenting Circuit

Summary form only given. Railguns are known for their high muzzle velocity. For a conventional railgun. raising the current is the most efficient way to increase the electromagnetic force on the projectile. But high current densities in the projectile can cause transition of the contact between the rails and the projectile which leads to ablation of the rails. One way to increase the force on the projectile, without raising the current, is by appending an extra pair of rails in order to establish an additional magnetic field. Experiments with LARA, a parallel augmented railgun at the French-German Research Institute ISL. have shown that the augmenting circuit of this railgun was not optimal. Therefore a study of the outer circuit for the next launcher, LARA2, was required. In order to optimize the augmenting circuit of this railgun, we have developed a PSpice model. This model combines an electrical model of the pulse forming network and the rails with a model of the kinematics of the projectile. The electrical model allows us to determine the currents in the inner and the outer rails. With these currents the electromagnetic force on the projectile can be calculated. The cinematic model takes the electromagnetic force on the projectile into account as well as the friction between the rails and the projectile. The calculated position and velocity are at their turn re-entered in the electrical model of the rails. The values of the self inductance and the resistance of the inner rail and the mutual inductance between the rails vary with the position of the projectile. The velocity skin effect is also taken into account. For the experimental validation of the model we compared the results of the simulations with the results of the experimental study on LARA. For the optimization of the augmenting circuit, three different configurations for the outer rails were compared. The outer rails of the first augmented railgun we studied, were both in one piece with all power supp- lies connected to the breech. The influence of the length of the outer rails was examined. The second configuration we have studied was an augmented railgun with segmented outer rails. In this case separate power supplies were connected at the beginning of each segment. The number and the length of the segments were varied. The last configuration we examined was a DES railgun. The outer rails of this railgun are both in one piece as in the first configuration, but there were multiple connection points divided over the length of the rails. The position of these connection points was optimized.