Effect of electromagnetic launch on armature/sabot discard

This paper presents the validation of a sabot discard model, developed at the Institute for Advanced Technology (IAT), for predicting armature/sabot separation, and quantifies the effect of electromagnetic launch on sabot discard as well as on the sub-projectile. The experimental data used to validate the model were obtained at the Army Research Laboratory (ARL) Transonic Experimental Facility at Aberdeen Proving Ground, MD. Five shots were conducted at a nominal velocity of 1350 m/s and armature/sabot petal trajectories were reduced from X-ray images taken at six downrange stations. The residual electromagnetic force on the launch package after muzzle exit was also determined from experimental data. The sabot discard model uses analytical expressions to estimate surface pressure distributions, which are then integrated, in a time-marching algorithm, for linear and angular accelerations, and subsequently for sabot petal trajectories. The most significant attribute of this model is that it does not rely on any empirical data for modeling and is therefore expected to be widely applicable. The results from this study have shown that the comparison between predicted and measured armature/sabot petal trajectories is excellent. Furthermore, the model has demonstrated quantitatively the delayed armature/sabot discard caused by the residual electromagnetic force and the additional deceleration of the sub-projectile due to the delayed mechanical disengagement.