How Hedgehog let one escort keep attacking a submarine

Hedgehog launched twenty-four bombs from a bank of four by six spigots, and its small charges needed direct contact with a submarine to destroy it. Firing ahead let the escort retain ASDIC contact through the attack. A stern depth-charge run carried the target into the attacking ship's acoustic blind spot, so other escorts often had to track the submarine and signal its movements. Hedgehog gave one escort a better chance of conducting the attack alone. In an illustrative case of eight attacking submarines and twelve escorts, individual attacks would leave ships available to watch for further threats and remain with the convoy. Squid and the later Limbo used larger charges that did not depend on direct contact. Their smaller salvos still needed enough rounds to cover the target, leading to paired installations firing six projectiles.