Non-steady phenomena in railgun plasma armatures

We report some recent diagnostic measurements of the early-time behavior of a railgun plasma armature, and the development of a one-dimensional, fully time-dependent model to account for this behavior. The experimental measurments describe both the initiation of the arc and its subsequent collision with a projectile located down bore. The intent of the experimental work is to provide the appropriate initial conditions for the theoretical treatment, as well as to provide a basis for comparison with the theoretical calculations. The formalism included in the model is discussed in some detail and the results of some preliminary calculations are presented. The extent to which they support the experimental observation is discussed.