Estimating Ricochet Hazard Zones at Sea

Naval operators commonly report that when projectiles impact the ocean surface, they ricochet mainly to the right but that some rounds ricochet in wildly unpredictable directions. This observation, which leads to considerable uncertainty with regard to the resulting hazard zone for projectiles fired at sea, seems contradictory to observations from controlled experiments where projectiles with similar incident angles tend to ricochet in a more predictable manner. In this paper, we postulate that the likely cause of the discrepancy is ocean waves. Past work examining the effect of waves on ricochet is extended to model the risk area related to projectile ricochet at sea. Ricochet results from controlled experiments are incorporated into a simple model that combines a two-degree-of-freedom ballistic model and a series of analytically derived wave fields with different amplitudes and directions of travel. For the purposes of demonstration in this paper, data for different .50 calibre projectiles are used to populate the model. The results support the notion that waves have a considerable effect on ricochet hazard zones.