Type XXI submarine

U-2540 in wartime configuration and exhibited at the Maritime Museum in Bremerhaven. It is the only floating example of a Type XXI U-boat.
Class overview
Name	Type XXI
Builders	Blohm+Voss AG Weser Schichau-Werke
Operators	Kriegsmarine Postwar:  French Navy  German Navy  Royal Navy  Soviet Navy  United States Navy
Preceded by	Type VII (patrol submarine) Type IX (oceanic submarine) Type XVIII (cancelled oceanic AIP project)
Succeeded by	Type XXVI (none completed)
Cost	5,750,000 ℛ︁ℳ︁ per boat[1]
Built	1943–1945[1]
In commission	1944–1982
Planned	1,170[2]
Building	267[2]
Completed	118
Cancelled	785[2]
Preserved	1
General characteristics
Type	Oceanic conventional Submarine
Displacement	1,621 t (1,595 long tons) surfaced 1,819 t (1,790 long tons) submerged[1]
Length	76.70 m (251 ft 8 in)[1]
Beam	8 m (26 ft 3 in)[1]
Draught	6.32 m (20 ft 9 in)[1]
Propulsion	Geared Diesel/Geared battery-electric/CODABEL/Diesel-electric beltdrive/Low-noise electric beltdrive. 2× MAN M6V40/46KBB geared supercharged 6-cylinder diesel engines, 4,000 PS (3,900 shp; 2,900 kW), driving: 2× SSW geared GU365/30 double-acting electric motors, 5,000 PS (4,900 shp; 3,700 kW)[1] 2 × SSW GV232/28 "creep motors", 226 PS (223 shp; 166 kW) for silent running, and to keep the boat moving while the batteries are being recharged. 2 shafts
Speed	15.6 knots (28.9 km/h; 18.0 mph) surfaced 17.2 knots (31.9 km/h; 19.8 mph) submerged[1] [4] 6.1 knots (11.3 km/h; 7.0 mph) (silent running motors)
Range	15,500 nmi (28,700 km; 17,800 mi) at 10 knots (19 km/h; 12 mph) surfaced 340 nmi (630 km; 390 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged[1]
Test depth	240 m (787 ft)[1]
Complement	5 officers, 52 enlisted men[3]
Armament	6 × 53.3 cm (21 in) torpedo tubes (bow) 23 G7 torpedoes (or 17 torpedoes and 12 mines) 2 x twin 2 cm (0.79 in) C/30 anti-aircraft guns [3]
Armour	Bridge: 17mm

Type XXI submarines were a class of German diesel–electric Elektroboot (German: "electric boat") submarines designed during the Second World War. One hundred and eighteen were completed, with four being combat-ready. During the war only two were put into active service and went on patrols, but these were not used in combat.

They were the first submarines designed to operate primarily submerged, rather than spending most of their time as surface ships that could submerge for brief periods as a means of escaping detection. They incorporated many batteries to increase the time they could spend submerged, to as much as several days, and they only needed to surface to periscope depth for recharging via a snorkel. The design included many general improvements as well: much greater underwater speed by an improved hull design, greatly improved diving times, power-assisted torpedo reloading and greatly improved crew accommodations. However, the design was also flawed in many ways, with the submarines being mechanically unreliable^[5] and, according to post-war analysis, vulnerable to combat damage. The Type XXI submarines were also rushed into production before design work was complete, and the inexperienced facilities which constructed the boats were unable to meet necessary quality standards.

After the war, several navies obtained Type XXIs and operated them for decades in various roles, while large navies introduced new submarine designs based on them. These include the Soviet Whiskey, American Tang, British Porpoise, and Swedish Hajen III classes, all based on the Type XXI design to some extent.^[6]