Empirically Modeling Hypervelocity Sabot Separation

Abstract

The aerodynamic sabot discard process is crucial to the success of hypervelocity testing using less than ideal projectile launch properties or sub-caliber projectiles in smooth bore launchers. Achieving efficient sabot separation is integral to both reaching extreme velocities and capturing distinguishable impact phenomena during testing. In this study, the conical-cup discard technique is investigated for four-petal sabot packages carrying 2-8 mm diameter spherical projectiles launched with the state-of-the-art 2-stage light gas gun located in the Texas A&M University Hypervelocity Impact Laboratory. Image processing techniques are employed to convert images of sabot petal impacts to coordinate entities. The degree of separation for each entity is then characterized by the distance travelled in the radial direction away from the projectile’s nominal launch trajectory. An empirical model relating both environmental and launch parameters to the degree of sabot separation at a fixed distance from the muzzle is developed using polynomial regression. Projectile velocity, nitrogen atmosphere backfill pressure, and sabot geometry are found to be significant regressors in predicting the degree of separation. Additional analysis is conducted to qualitatively understand the model in the context of test results and aerodynamic laws.