A model for rigid asymmetric ellipsoidal projectiles penetrating into metal plates

A theoretical model is presented for penetration of asymmetric ellipsoidal projectiles which are proposed to fit the lift-generating outline of hypersonic vehicles. The projectile is composed of two triaxial quarter ellipsoids with one different semiaxis, and four geometric parameters are required to decide the shape. The model is based on two-term drag equation and a stress distribution relation of elliptical boundary with hole enlargement mechanism. Verification of the model is completed by simulation cases of six different projectiles with initial velocity between 600 m/s to 1000 m/s. Ballistic characteristics of asymmetric ellipsoidal projectiles including acceleration and residual velocity are derived from the model and analyzed to acquire the effects of geometric parameters on penetration results. Two decisive factors of cross section shapes, asymmetry and flatness, are specially discussed in contributions to residual velocity. Comparations with traditional circular cross-sectional cases are also presented, which indicates that same penetration capacity could be retained in the asymmetric ellipsoidal projectiles as in the circular cross-sectional one by selecting the shape controlling factors.