German submarine U-480
|Ordered:||10 April 1941|
|Builder:||Deutsche Werke, Kiel,|
|Laid down:||8 December 1942|
|Launched:||14 August 1943|
|Commissioned:||6 October 1943|
|Fate:||Sunk between 29 January and 20 February 1945 in minefield "Brazier D2" in the English Channel, with the loss of the entire crew of 48.|
|Class and type:||Type VIIC submarine|
|Height:||9.60 m (31 ft 6 in)|
|Draught:||4.74 m (15 ft 7 in)|
|Complement:||4 officers, 40–56 enlisted|
|Identification codes:||M 53 621|
|Commanders:||Oblt.z.S. Hans-Joachim Förster|
|Victories:||Four ships sunk|
U-480 was an experimental Kriegsmarine Type VIIC U-boat of World War II. Considered by many to be the first stealth submarine, it was equipped with a special rubber coating (codenamed Alberich, after the German mythological character who had the ability to become invisible), that made it difficult to detect with British ASDIC (sonar).
The U-boat was laid down in the Deutsche Werke in Kiel as yard number 311 on 8 August 1942, launched on 14 August 1943 and commissioned on 6 October 1943 under Oberleutnant zur See Hans-Joachim Förster. U-480 carried out three war patrols, all under Förster's command. Because of its coating, the boat was sent to the heavily defended English Channel. The Alberich worked; U-480 was never detected by sonar.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-480 had a displacement of 769 tonnes (757 long tons) when at the surface and 871 tonnes (857 long tons) while submerged. She had a total length of 67.10 m (220 ft 2 in), a pressure hull length of 50.50 m (165 ft 8 in), a beam of 6.20 m (20 ft 4 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.74 m (15 ft 7 in). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two Siemens-Schuckert GU 343/38–8 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged. She had two shafts and two 1.23 m (4 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 17.7 knots (32.8 km/h; 20.4 mph) and a maximum submerged speed of 7.6 knots (14.1 km/h; 8.7 mph). When submerged, the boat could operate for 80 nautical miles (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 8,500 nautical miles (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph). U-480 was fitted with five 53.3 cm (21 in) torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm (3.46 in) SK C/35 naval gun, (220 rounds), one 3.7 cm (1.5 in) Flak M42 and two twin 2 cm (0.79 in) C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
On the second patrol, Förster departed from Brest in occupied France on 3 August 1944, and sank two warships and two merchantmen:
- the Canadian Flower-class corvette HMCS Alberni (925 tons) on 21 August
- the British Algerine-class minesweeper HMS Loyalty (850 tons) on 22 August
- the Fort Yale (7,134 GRT), sailing in convoy ETC-72, on 23 August
- the Orminister (5,712 GRT) on 25 August
U-480 left Trondheim, Norway, on 6 January 1945 for its third and last patrol. It did not return. In 1997, the wreck of a Type VIIC U-boat was discovered by accident by divers at Coordinates: , 20 kilometres (12 mi) southwest of the Isle of Wight. The following year, it was correctly identified as the Alberich-coated U-480 by nautical archaeologist Innes McCartney. Subsequent research by the Naval Historical Branch established that it had fallen victim to the secret minefield 'Brazier D2' some time between 29 January and 20 February. A mine had damaged the stern of U-480, sending it to the bottom 55 metres (180 ft) down. The entire crew of 48 was lost. Helmsman Horst Rösner only survived because he had been left behind in Norway for training.
The Germans developed a 4-millimetre (0.16 in) thick sheet of synthetic rubber anechoic tile. The coating reduced echoes by 15% in the 10 to 18 kHz range. This frequency range matched the operating range of the early ASDIC active sonar used by the Allies. The ASDIC types 123, 123A, 144 and 145 all operated in the 14 to 22 kHz range. However, this degradation in echo reflection was not uniform at all diving depths due to the voids being compressed by the water pressure. An additional benefit of the coating was it acted as a sound dampener, containing the U-boat’s own engine noises.
The rubber contained a series of holes, which helped break up sound waves. There were problems with this technology: the material performed differently at different depths, due to the holes being compressed by water pressure, and securing the tiles to the submarine's hull required a special adhesive and careful application. The first tests were conducted in 1940, but it was not used operationally until 1944, with U-480. According to the Naked Science television episode "Stealth Submarine", U-480 had a perforated inner rubber layer covered by a smooth outer one. This formed air pockets with the right separation and size to muffle sonar waves.
Summary of ships sunk
|21 August 1944||HMCS Alberni||Royal Canadian Navy||925|
|22 August 1944||HMS Loyalty||Royal Navy||850|
|23 August 1944||Fort Yale||United Kingdom||7,134|
|25 August 1944||Orminster||United Kingdom||5,712|
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