Design considerations for an electromagnetic railgun firing intelligent bursts to be used against anti-ship missiles

Railguns can reach higher muzzle velocities and fire rates than conventional guns. Muzzle velocities up to 2400 m/s and fires rates of more than 50 Hz have already been demonstrated with projectiles having a mass of 140 g and a square calibre of 25 mm. We investigated if a Close In Weapon System (CIWS) based on a railgun performs better against incoming anti-ship missiles than a conventional CIWS such as the Goalkeeper and propose solutions to optimize the performance of such a railgun. CIWS are operational systems that defend a ship against incoming subsonic anti-ship missiles. However, future anti-ship missiles will be supersonic and more difficult to defeat with conventional gun systems. Railguns are expected to perform better against these future threats thanks to their higher muzzle velocity and fire rate. Furthermore, the muzzle velocity within a single burst can be varied easily from shot to shot, generating a so-called intelligent burst. It allows varying the velocity of each projectile such that all projectiles arrive on the target at the same time. The number of projectiles and thus the electrical energy required to achieve a target kill with an intelligent burst is expected to be lower than for railguns firing at constant muzzle velocity. In the first part, the performance of an electromagnetic CIWS is discussed using simulation models calculating the hit probability of a burst of projectiles fired with muzzle velocities ranging from 1200 m/s to 2400 m/s and fire rates ranging from 75 rounds per second to 300 rounds per second. The geometry of the target is that of a typical anti-ship missile, its velocity ranges from subsonic (300 m/s) to supersonic (600 m/s). The influence of the projectile mass on the performance of the system and the required electric energy was also investigated. We confirmed that the concept of intelligent burst reduces the required electric energy, especially against supersonic targets. The second part deals with some technical aspects of high fire rate railguns. We have shown experimentally that an automatic loading system allows increasing the fire rate of a medium calibre railgun from 50 Hz to 75 Hz.