Calculating the liquid film effect on solid armature rail-gun launching

In existing EM launchers with solid electroconductive armatures the achievement of high velocities is limited by the velocity skin-effect (VSE) and wearing of contact surfaces due to inhomogeneities of the electric current, and frictional tearing and heating. Inevitably, a liquid phase appears that is considered usually to be undesirable. We believe the deliberate injection of electroconductive liquid in the gaps between the armature and rails is capable of significantly decreasing friction between these surfaces and the resulting wear, of improving electric contact and reducing armature overheating in zones of electric current concentration caused by imperfectness of surface manufacturing or by the VSE. We present the calculation of temperature fields in the armature/rail interface with due account of VSE, energy release, and heat transfer in a continuous liquid film that completely covers the contacting surfaces. The motion of viscous liquid in the gap is considered with due regard to Ampere forces and inertial forces caused by acceleration of the armature. We have found that the rate of the armature heating, which ultimately leads to melting in a region at the trailing edge, depends essentially on thickness and material of the film. By optimizing these parameters it is possible to delay the crisis phenomena associated with melting of the armature material and subsequent transition of the armature/rails contact into the plasma mode of operation.