Abstract: Under polar ice-covered conditions, the ice-breaking water-entry process of a vehicle involves ice-cover fracture, ice-fragment splashing, cavity formation after the vehicle enters the water, and flow-field disturbances, constituting a typical multi-medium coupled dynamic problem. Compared with conventional water entry through a free surface, the presence of an ice layer alters the pre-entry motion state and load distribution of the vehicle, and significantly affects the subsequent underwater cavity morphology and flow-field evolution. To elucidate the dynamic response characteristics of a projectile during ice-breaking water entry, numerical simulations were conducted for different projectile nose shapes and ice thicknesses, with particular emphasis on impact loads, ice-crack propagation, ice-fragment splashing, and post-entry cavity evolution.The results show that the projectile nose shape significantly influences the projectile-ice contact mode and energy-transfer process. As the nose shape changes from a flat nose to a progressively more streamlined ogive nose, the high-stress region and damaged area within the ice layer become increasingly concentrated around the penetration channel. Accordingly, the failure mode of the ice cover gradually shifts from global bending, radial crack propagation, and intense ice-fragment splashing to localized crushing and perforation. Meanwhile, both the peak axial acceleration and spectral amplitude of the projectile decrease, accompanied by a reduction in high-frequency components, indicating a transition of the impact load from strong transient loading to a smoother and more continuous loading process.With increasing ice thickness, the stiffness and local load-bearing capacity of the ice cover are enhanced, thereby suppressing crack propagation and ice-fragment splashing. At the same time, the reductions in projectile velocity and kinetic energy become more pronounced, while the peak axial acceleration and impact duration increase. After water entry, the flat-nosed projectile generates the largest cavity in the radial direction and induces the strongest free-surface disturbance, whereas the ogive-nosed projectile produces the most slender cavity. However, under intermediate and thick ice conditions, cavity deflection and flow-field asymmetry become more pronounced for the ogive-nosed projectile. As the ice thickness increases, both the cavity size and the propagation range of pressure waves decrease, and cavity closure near the projectile tail occurs earlier.The findings provide important references for the structural design and safety assessment of trans-medium vehicles operating in polar ice-covered environments.