Influence of the armature-rail geometry on results of launch experiments of fibre armatures with railguns

To increase the transition velocity of solid fibre brush armatures, launch experiments have been performed with an increased armature height of about 15%. However, results of experiments under equal launch conditions did not show higher transition velocities up till now. In order to find an explanation for the disappointing results, a number of 3D-computer simulations has been performed to calculate the current density distribution and Lorentz force in the forward direction in monolithic solid armatures for different armature-rail height ratios. It appears the Lorentz force is influenced by relatively small changes in the armature-rail geometry. The results of the 3D-computer simulations of two armature-rail combinations of different geometry have been verified with (quasi) static experiments in the armature test bed and launch experiments with segmented copper fibre armatures in the 2.4 m long, 20 mm square bore rail accelerator. The results of computer simulations and armature test bed measurements are presented. Furthermore, results of the launch experiments for two different rail heights are discussed.