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To compensate the growing losses of submarines from the mid 1943, Germany had to face the challenge of creating a "true" submarine.
The Walter submarines propelled by hydrogen-peroxide turbines were too unreliable for service - nor to say too expensive - even
if they were built in certain quantity. The other - more successful - alternative, adopted in the oceanic submarines of the Type
XXI and the coastal submarines of the Type XXIII, rendered more hydrodynamical the external surfaces and widely increased the power
of the batteries. New shapes were given to the hulls and for the first time better prestations were achieved underwater than in the
surface. But, even if both projects were intended for extensive production and a large number of units was built, very few units carried out
operative patrols. Ironically, the true contribution of these submarines took shape in the first postwar years, when they were used
by the victorious nations to build their new classes of submarines.
The advanced Type XXI entered production in 1943. These were the first submarines designed to operate primarily submerged, unlike the
"submersibles" built until then, which had to spend most of their time in surface. The key was a greatly enhanced capacity in the
batteries (three 124-cell units) and a more streamlined hull of cleaner surfaces. Apart from the hydrodynamical advantage, noise emissions were reduced
as well in comparison with previous models. Another useful utility was the hydraulic torpedo loader, which allowed for a much faster
rate of launching. In comparison with the Type VIIC, the Type XXI had three times higher battery capacity, more than twice speed while
submerged and six times higher torpedo reload speed. Electronic equipment included a high-sensitivity passive sonar, a FuMB Ant 3 Bali radar
detector, a FuMO 65 Hohentwiel U1 maritime patrol radar with Type F432 D2 radar transmitter and a plan position indicator.
Between 1943 and 1945, 118 of these submarines were assembled, but only four were made ready for combat before the end of the war.
A minor part of the submarines built was taken by the Allied nations at the end of the war, being commissioned for service and used
as well for trials and tests until being scuttled or used as targets. France scrapped its unit in 1967 but Great Britain had scrapped
its unit already in 1949. United States used one as target in 1951 and scrapped the other in 1956. It was the Soviet Union
which showed more interest in the design. This country acquired an uncertain number - probably fifteen - of units and conquered the
production centers. Later, they would use the Type XXI as a reference point for the submarines of the Whiskey class.
Type XXI: 118 units
Type: Attack submarine
Length: 76.7 meters
Beam: 8 meters
Draught: 6.3 meters
Displacement (surfaced): 1621 tonnes
Displacement (submerged): 1819 tonnes
Propulsion: 2 shaft, 2 x Diesel engine MAN 2200 horsepower, 2 x electric motor Siemens-Schuckertwerke
2500 horsepower, 2 x silent electric motor Siemens-Schuckertwerke 325 horsepower, 372 x battery cell 44 MAL 740 33900 amperes/hour
Speed (surfaced): 15.6 knots (28.9 kilometers/hour)
Speed (submerged): 17.2 knots (31.9 kilometers/hour)
Speed (silent mode): 6.1 knots (11.3 kilometers/hour)
Range (surfaced): 15500 nautical miles (28700 kilometers) at 10 knots
Range (submerged): 340 nautical miles (630 kilometers) at 5 knots
Test depth: 240 meters
Armament: 6 x 533-millimeter torpedo tube (at prow), 23 x torpedo reload (or 17 x torpedo and 12 x TMC mine),
2 x 20-millimeter twin cannon