The Hunt Intensifies
Attacking the U-505
On June 4, 1944 at 11:10am, the USS Chatelain reported a sonar contact and the Task Group jumped into action. The USS Guadalcanal could not attack without damaging itself so Captain Gallery moved the ship quickly out of harm's way. Supported by the Destroyer Escorts USS Pillsbury and USS Jenks, the USS Chatelain swiftly attacked.
As the sonar crew maintained contact with the submerged U-505, the USS Chatelain attacked with a salvo of hedgehogs that missed. While the USS Chatelain opened the range to turn and make another attack, two fighter planes from the USS Guadalcanal fired their guns into the water to help mark the location of the submerged U-505. The USS Chatelain then fired a pattern of depth charges, forcing U-505 to the surface.
Depth Charges & Hedgehogs
Depth charges and hedgehogs were two of the most important weapons the Allies used to attack U-boats hiding underwater. Depth charges were powerful explosive devices that were dropped into the water after being preset to detonate at a specified depth. They didn't have to hit a sub to cause damage — by striking close enough, the blasts could shatter equipment inside a U-boat and even damage its hull. Hedgehogs detonated only upon direct contact with the targeted sub, or with the seafloor in the case of a miss. In 1943, the U.S. Navy started packing depth charges and hedgehogs with a new explosive called Torpex, which was 50% stronger than the previously used Trinitrotoluene (TNT).
The Mark 9 and Mark 4
Mark 9 depth charges and Mark 4 hedgehogs were used in the attack against the U-505. Mark 9 depth charges had a pressure-activated fuse that detonated 200 pounds of Torpex at a predetermined depth anywhere from 30-600 feet below the surface. Mark 4 hedgehogs were filled with 35 pounds of Torpex. They were launched in a salvo, or cluster, 24 at a time, from spiked fittings that gave the launcher a hedgehog-like appearance.