Trajectory instability of deep penetration of projectile into soil targets

This paper studies the characteristics of the curvilinear motion and trajectory instability of a rigid projectile in deep penetration. In order to identify the influences of non-axisymmetrical disturbance, impact velocity and mass centre location on penetration trajectory, the curvilinear motion and instability of rigid projectiles with different mass centre locations are analysed. It is shown that both sudden (instable) and gradual (curvilinear) changes of the projectile trajectory may happen under certain conditions of projectile geometry, impact velocity and other attacking parameters. A criterion is introduced to determine the occurrence of trajectory instability. Two characteristic velocities are identified, i.e. (a) the critical impact velocity, beyond which trajectory instability happens, and (b) the characteristic convergent velocity, at which the projectile trajectory turns to straight line from the curvilinear motion. The two characteristic velocities are linearly dependent on the relative mass centre location and independent of disturbance and impact velocity.