Early concepts moved toward the later Hedgehog and Squid family of weapons. The original aim resembled a depth-fuzed Squid-style system, but the available fuze and launcher technology was not ready, so Hedgehog entered service with contact-fuzed projectiles. More reliable Type 122 and Type 124 ASDIC sets made it increasingly practical to turn a detection into fire-control information. A ship passing over a submarine for a stern depth-charge attack lost sonar contact. A second escort could maintain the track, but drawing two ships away from a convoy for every contact rapidly weakened the screen. A forward-thrown attack promised to preserve contact and let one scarce escort prosecute the submarine more efficiently.
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Forward-thrown weapons aimed to free an escort
The drive toward Hedgehog-like weapons came from the problem of losing ASDIC contact during a stern depth-charge attack.