Thermoelectrodynamic loss of material by a solid armature in a railgun as a cause of velocity limitation

It is shown that even when monolithic electrically conducting bodies (armatures) are accelerated in a railgun, redistribution of the current as a result of Joule diffusion allowing for the drop in the electrical conductivity with heating may lead to the appearance of negative mechanical stresses in the object. Assuming that the strength of the material is reduced or melting occurs, this causes a loss of material which can initiate shunting arcs behind the armature at a velocity of similar to 1 km/s. (C) 1999 American Institute of Physics. [S1063-7850(99)00404-8].