Performance predictions for electromagnetic launching with multi-fibre solid brush armatures and resistively layered rail accelerators

In the literature on EM launcher research, number of proposals have been made to suppress the negative influence of the velocity skin effect on the performance of solid armatures during electromagnetic launch. In this paper, the results of a study of two of these methods, i.e. the application of multi-fibre solid brush armatures and the use of accelerator rails with a resistive layer, are presented. This study is performed by means of two-dimensional finite element computer simulation of the electrothermal behaviour of the armature and the rails during the launch process. A description of the electrothermal mode used in the simulation is given. Here, the fibre armatures are regarded as made of materials with an anisotropic electrical and thermal conductivity. The results for the current distribution in a rectangular multi-fibre solid brush armature obtained from the simulations agree with the results of an analytical method. It is shown that fibre armatures have a more homogeneous current distribution during the acceleration process than monobloc armatures. U-shaped molybdenum multi-fibre solid brush armatures are good candidates for arc erosion-free launching if the electrical insulation of the fibres can be maintained at increasing temperature. Simulations also show that the skin depth in monobloc and fibre armatures can be increased by using rails with resistive layer with suitable material properties.<
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