PERFORMANCE PREDICTIONS FOR ELECTROMAGNETIC LAUNCHING WITH MULTIFIBERSOLID BRUSH ARMATURES AND RESISTIVELY LAYERED RAIL ACCELERATORS

In the literature on EML research, a number of proposals have been mad e to suppress the negative influence of the velocity skin effect on th e performance of solid armatures during electromagnetic launch. In thi s paper, the results of a study of two of these methods, i.e. the appl ication of multi-fibre solid brush armatures and the use of accelerato r rails with a resistive layer, are presented. This study is performed by means of two-dimensional finite element computer simulations of th e electrothermal behaviour of the armature and the rails during the la unch process. A description of the electrothermal model used in the si mulations 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 sol id 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 armat ures are good candidates for arc erosion-free launching if the electri cal insulation of the fibres can be maintained at increasing temperatu re. Simulations also shown that the skin depth in monobloc and fibre a rmatures can be increased by using rails with a resistive layer with s uitable material properties.