G7es torpedo

The G7es(TV) Zaunkönig (English: Wren^[1]), also known as T5 Zaunkönig or T5 torpedo, was a passive acoustic torpedo developed by Germany during World War II.^[2][3][4] The basic design was a development of the straight-running G7e, equipped with an acoustic homing seeker head developed by Atlas Werke.^[5] It got the nickname GNAT (German Navy Acoustic Torpedo) by the British.

G7es torpedo
A G7es Zaunkönig exhibited alongside U-534 at Woodside Ferry, Birkenhead.
Type	Heavyweight anti-surface ship torpedo
Place of origin	Nazi Germany
Service history
In service	1943
Used by	Kriegsmarine
Wars	World War II
Production history
Produced	1943-1945
Specifications
Mass	1,495 kg (3,296 lb)
Length	7.163 m (23.50 ft)
Diameter	534.5 mm (21.04 in)
Warhead weight	274 kg (604 lb)
Engine	Electric batteries
Operational range	5,700 m (3.1 nmi)
Maximum speed	24 kn (44 km/h)

Description

Diagram of various German submarine torpedoes: T1, T3 & T5

The forerunner of the T5 Zaunkönig was the T4 Falke which was introduced in January 1943.^[6] While initially restricted in its use, after several modifications, the T4 Falke was ready for general operational use on 1 July 1943.^[7] However, the T4 saw limited use as a result of the introduction of the T5 in August 1943.^[8] This torpedo was faster, had more range, possessed a combined magnetic and contact detonator 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.^[9]

There were five variants of the passive acoustic seeker mounted in front of the warhead:^{[citation needed]}

• The initial round-nosed version "25 degree storch" which contained two magnetostriction hydrophones inside a funnel-shaped baffle
• The later flat-nosed versions "vierfach storch" which contained four sets of magnetostriction hydrophones which came in four different arrangements.

Variants

Germany

• T5 Zaunkönig: the original T5 Zaunkönig acoustic torpedo.^[2][1]
• T5a Zaunkönig: motor torpedo boat (MTB) variant of the T5 Zaunkönig.^[2] This modified T5 had a range of 8000 meters at 22 knots.^[6]
• T5b Zaunkönig: U-boat variant of the T5 Zaunkönig.^[2] Had the same range as the T5a Zaunkönig.^[6]
• T11 Zaunkönig II: improved version of the T5 Zaunkönig.^[10] This improved version had modifications that were intended to allow the torpedo to bypass enemy decoys and be less vulnerable to jamming.^[7][11]

Soviet Union

• SAET-50: first acoustic homing torpedo of the Soviet Union and based on the German T5 torpedo.^[12][13] The torpedo was developed as a result of Soviet engineers gaining access to German torpedo technology during and after the Second World War.^[13] The SAET-50 entered service in 1950.^[13] Later modified with an improved battery; this torpedo entered service in 1955 as SAET-50M.^[12]

Use

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 significantly according to circumstance, but 450 m (500 yards) was considered reasonable for a ship moving at 15 knots.^[14] After at least one unconfirmed instance of a U-boat (U-972) sinking after being hit by its own torpedo, and another circle-back that forced the U-862 to crash-dive, the BdU ordered 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 noise making decoy known as Foxer. 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.^[15]

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.^[15]

In spite of highly effective Allied countermeasures, a total of ca 650 T5s were fired in combat, sinking 77 ships.^[16]

See also

• G7e torpedo
• List of World War II torpedoes of Germany