Dynamic responses of a kinetic energy projectile under transverse loadings

We report on the effects of launch tube nonstraightness and asymmetric loading on the accuracy performance of a kinetic energy projectile. Modeling the projectile as a rigid body within the launch tube, we obtain and solve the equations of rotary motion to calculate the orientation of the projectile relative to the tube as a function of time. Three launch tube geometries are modeled; curiously, the most severe environment does not produce the most deviant projectile orientations during in-bore travel or at muzzle exit. To determine the effects of asymmetric loading, we model the rod as a nonuniform two-dimensional beam, subject to a transverse blast load. Determined experimentally, the sabot equivalent stiffness is bounded between 10⁶ and 10⁷ N/m. These bounds are used in an elastic boundary condition to the rod finite element model. The ANSYS transient vibration analyses predict a peak transverse displacement of 20 mm and a peak transverse velocity of 75mm/s at muzzle exit. We conclude that: (1) base pressures asymmetry induces transverse vibrations in the projectile, and these vibrations are affected by sabot stiffness; and (2) launch tube profile nonstraightness induces rigid body rotations in the projectile, and these rotations may or may not increase with launch tube severity.