Thermalenergy transport from arc to rails in an arcdriven rail gun
Abstract
A model is developed for examining thermalenergy transfer from the arc to the rails in an arcdriven rail gun. Resistive heating within the rails is also accounted for, though the contribution to the rail temperature from this mechanism is frequently negligible. Melting of the rail surface is allowed in the model, but it is assumed that the melted material is swept away and absorbs no further energy. A set of differential equations is derived which, when solved, yield the temperature, magnetic induction, and current density within the rail, as well as the mass lost from the rail surface. Both numerical and limitingcase analytic solutions to the equations are presented, and approximate expressions are obtained for the time to melting and the steadystate melting velocity of the rail surface. It is found that the governing equations can be written in a form so that they depend only on experimentally measured properties of the arc. The model is then used to analyze rail melting in a recent experiment by Jamison and Burden, for which these properties have been obtained. It is also used to estimate rail damage in other experiments by using arc properties calculated in our previous work. Considerable discussion is given of the probable sources of error in the calculation and recommendations for improvements in future work are made.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 October 1983
 Bibcode:
 1983STIN...8417499P
 Keywords:

 Electric Arcs;
 Electric Propulsion;
 Energy Transfer;
 Heat Transfer;
 Mathematical Models;
 Railgun Accelerators;
 Thermal Energy;
 Damage;
 Differential Equations;
 Equations Of State;
 Hypervelocity Guns;
 Melting;
 Thermal Boundary Layer;
 Thermal Conductivity;
 Electronics and Electrical Engineering