G7es torpedo

The forerunner of the Zaunkönig was the G7e/T4 Falke, codename "Falcon," which was introduced in March 1943, but saw limited use for trial and was rapidly phased out of service in favor of the later model that received a number of significant enhancements. It was faster, had more range, possessed a magnetic or contact detonator and could be equipped with a percussion pistol.

The T5 torpedo was capable of travelling at 24 knots (44 km/h) and had an effective range of about 5000 metres against convoy escorts vessels proceeding at speeds between 10 (18 km/h) and 18 knots (33 km/h). The homing system consisted of two hydrophone receivers and altered the direction of the rudder via an electropneumatic device. The acoustic homing torpedo was specifically designed as to be attracted by the pitch of an escort's propellers and would — even if aimed inaccurately — explode under the ship's stern.^[1]

There were three variants:

• Two flat-nosed versions which contained four sets of magnetostriction hydrophones.
• A round-nosed version which contained two magnetostriction hydrophones inside a funnel-shaped baffle.

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Detonator

Detonator

A detonator, frequently a blasting cap, is a small sensitive device used to detonate a larger, more powerful but relatively insensitive secondary explosive of an explosive device used in commercial mining, excavation, demolition etc.

Acoustic homing

Acoustic homing

Acoustic homing is a system which uses the acoustic signature (sound) of a target to guide a moving object, such as a torpedo. Acoustic homing can be either passive or active in nature. Using passive homing, the system is designed to move either toward or away from a sound, and may also be designed to move only toward certain types of sounds to the exclusion of others, while active homing makes use of active sonar. The system emits a sound pulse that reflects off objects and then back to the system, where the system processes the echos to determine the proper response.

Magnetostriction

Magnetostriction

Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron.

The acoustic homing torpedo required a minimum distance of 400 metres (1,300 ft) to lock onto the target after launch. The detection range of the hydrophones varied much according to circumstance, but 450 m (500 yards) was considered reasonable for a ship moving at 15 knots.^[2] After at least one unconfirmed instance of a U-boat (U-972) sinking after being allegedly hit by its own torpedo, and another circle-back that forced the U-862 to crash-dive, the BdU ordered the submarines to dive to 60 metres (200 ft) and go completely silent after launching acoustic torpedoes to minimize the risk.

The first 80 T5s were delivered on 1 August 1943, and the weapon was first used in a large-scale maneuver against the North Atlantic convoys ONS 18/ON 202 in late September 1943. The commanders reported a number of torpedo strikes and recorded the sinking of nine commercial steamers and 12 escort ships after the battle. In fact, only six merchant ships and three escort vessels, a destroyer, a frigate and a corvette were sunk. However, despite some initial success, in particular sinking destroyers and corvettes, the Zaunkönigs effectiveness was quickly nullified by the introduction of a decoy known as Foxer noise maker. The NDRC worked on countermeasures to an acoustic torpedo long before its introduction by the Germans. At the end of September 1943, it was promptly installed on all transatlantic escort vessels.^[3]

Grossadmiral Dönitz, not satisfied with the development of countermeasures, realized that his brief success against the North Atlantic trade convoys was only a flare up and recorded:

[it is] finally clear that surface warfare for U-boats had come to an end. It was now a matter of filling in time till the new type should be ready for action.^[3]

In spite of highly effective Allied countermeasures, a total of over 700 T5s were fired in combat, sinking 77 ships.^[4]

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German submarine U-972

German submarine U-972

German submarine U-972 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

Befehlshaber der U-Boote

Befehlshaber der U-Boote

The Befehlshaber der Unterseeboote or BdU was the supreme commander of the German Navy's U-boat Arm (Ubootwaffe) during the First and Second World Wars. The term also referred to the Command HQ of the U-boat arm.

Convoys ONS 18/ON 202

Convoys ONS 18/ON 202

ONS 18 and ON 202 were North Atlantic convoys of the ONS/ON series which ran during the battle of the Atlantic in World War II. They were the subject of a major U-boat attack in September 1943, the first battle in the Kriegsmarine's autumn offensive, following the withdrawal from the North Atlantic route after Black May.

Foxer

Foxer

Foxer was the code name for a British built acoustic decoy used to confuse German acoustic homing torpedoes like the G7 torpedo during the Second World War. A US version codenamed FXR was deployed at the end of September 1943 on all transatlantic escort vessels. A Canadian version was also built called the CAAT device. It was replaced in US service by the Fanfare noisemaker.

National Defense Research Committee

National Defense Research Committee

The National Defense Research Committee (NDRC) was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the United States from June 27, 1940, until June 28, 1941. Most of its work was done with the strictest secrecy, and it began research of what would become some of the most important technology during World War II, including radar and the atomic bomb. It was superseded by the Office of Scientific Research and Development in 1941, and reduced to merely an advisory organization until it was eventually terminated during 1947.

Karl Dönitz

Karl Dönitz

Karl Dönitz was a German admiral who briefly succeeded Adolf Hitler as head of state in May 1945, holding the position until the dissolution of the Flensburg Government following Germany's unconditional surrender to the Allies days later. As Supreme Commander of the Navy beginning in 1943, he played a major role in the naval history of World War II.