XXI type submarines

Since 1941, submarines have become the main striking force of the German fleet. The list of victories of German submariners is very impressive, but the measures taken by the allies during the battle for the Atlantic , began to lead to great losses of German submarines. Thus, in February 1943, 19 submarines were killed, in May of the same year, 41 submarines were killed immediately, after which the Germans were forced to return their boats to the bases. Of course, the question immediately arose of changing the design of submarines and the tactics of their use. The existing submarine structures at that time were more likely to be diving than submarines, and were vulnerable to attacks by aircraft and anti-submarine ships. Already in April 1943, grand-admiral Karl Dönitz, in an interview with the Minister of Armaments Albert Speer, stated: "... if we do not improve the design of submarines, then we will be forced to practically end the submarine war." In addition to improving the existing types of submarines, the Germans developed several types with fundamentally new engines. We are talking about the Walter engine installed on experimental boats of the XVII series. These boats showed a record underwater speed for that time, but they were extremely uneconomic and had a limited cruising range. Therefore, it was decided on the basis of the type XVIII with the engine of Walter to create "electrobots", placing in the bottom of the robust case, made in the form of a vertical "eight", instead of a large stock of hydrogen peroxide increased batteries. The project of the boat of the XXI series under the working title “Elektroboot” was developed by Professor Olfken, who worked in the design bureau of the firm “Gluckauf”. The boat had dimensions and displacement similar to ocean boats of the IX series, but had much better tactical and technical characteristics.

The command of kriegsmarine , proceeding from the capabilities of industry, proposed a construction program, according to which, by August 1945, no less than 12 boats would be put into operation every month. Grand Admiral Dönitz made an official presentation to Speer, Minister of Arms, with a request to speed up the construction of a new submarine fleet. After a detailed analysis of the situation, Speer appointed Otto Merker, an automotive manufacturer who had previously established himself as a developer of fire trucks, responsible for building boats of the XXI series.

On July 5, 1943, Merker proposed a new construction program. Instead of building a boat from beginning to end, the shipyard proposed to build a boat in sections along with all the equipment at various factories within the country, and then finally assemble it on the stocks. According to calculations, each boat was supposed to be on the slipway for no more than a month, and the monthly output would be 33 boats. Already during the development work industrialists were given orders.

Permanent bombing caused disruptions in supply. Haste in the manufacture of sections of the body led to inconsistencies in the assembly. As a result, instead of the planned 18 boats , only one was launched in July 1944 , but it also had to be returned to the shipyard for revision. However, in 1944 6 boats were launched and tested. In March 1945, U-2516 was commissioned, followed by another 330 boats, which were in different states of readiness (many passed acceptance or were mastered by crews). But in the spring of 1945, a massive raid on Hamburg of allied aviation took place, during which a large number of submarines at the docks were destroyed. As a result, in April 1945, only two boats U-2511 and U-3008 were able to go on a military campaign.

The robust submarine hull type XXI was divided into seven compartments. The numbering in the German fleet began from the stern:

• Aft compartment : hydraulic cylinders for rudder drives, high-pressure air cylinders and a ship's workshop.
• Electromotor compartment : main electric motors , creeping motors and control panels.
• Diesel compartment : diesel engines, gearboxes, bulky snorkel locks and exhaust pipes.
• Aft battery compartment : crew accommodation and living quarters in the upper part, battery holes in the lower part.
• Fifth compartment : the central post and pull-out devices in the upper part, ship devices, high-pressure cylinders and replacement tanks in the lower.
• Nasal battery compartment : crew accommodation and living quarters in the upper part, accumulator pits in the lower part.
• Bow compartment : torpedo tubes , spare torpedoes .

Corps

Submarines type XXI had a polutorakorpusnuyu design. Durable hull boats had a complex shape. The 1st, 2nd, 3rd and 5th compartments had a cylindrical conical shape, whereas the compartments from the 4th to the 6th, which occupied 40% of the length of the robust case, had a cross section shape close to the figure "8" - with a round top and a semicircular bottom. In addition, the upper part of these compartments was further divided into two decks. Asylum compartments, unlike the earlier series of submarines, did not have type XXI ^[1] . The bollards were not inside, but outside the strong case, which more rationally allowed the use of the internal space. The durable hull was fully assembled by welding ^[2] , the thickness of its parts, made of St52KM steel with a yield strength of 3400 kg / cm², reached 26 mm. The maximum immersion depth reached 220 m, including that achieved by testing - 200 m, the calculated breaking depth was 330 m, with safety factors for the maximum and breaking depths, respectively 1.5 and 2.5 ^[3] .

The shape of the light hull type XXI was created with the expectation of minimizing underwater resistance while maintaining good surface seaworthiness ; for this, it was given the most streamlined shape, and the number of its protruding parts was minimized. A much more streamlined form, in comparison with earlier submarines, was attached to the fencing ^[4] .

Powerplant

Submarines type XXI belonged to diesel-electric. The structure of their power plant included two in-line 6- cylinder four - stroke diesel engines of the model M6V 40/46 , manufactured by MAN , each with a capacity of 2,000 liters. with. at 520 rpm The engines were equipped with a retractable snorkel with a radar absorbing surface coating.

The two main electric motors are GU 365/30 models, each with a capacity of 2500 liters. with. at 1675 rpm ^[5] . This is 5 times more than the power of electric motors similar to the displacement of boats of the IX series. To reduce the mass and size of the main electric motors, the supply voltage was increased to 360 volts due to the series connection of three groups of batteries. The weight of each engine was 10.33 tons, a length of about 3 meters and a diameter of 1.3 meters. In addition to them, the boats had two sneaking motors, models CV 323/28, which developed a capacity of 113 liters. with. at 350 rpm each and attached to the propeller shafts through a V-belt drive . On sneaking engines with a 6-node stroke, the boat could move 48 hours. Up to a speed of six knots, the boat under the sneaking engines did not practically make noise, which was heard by hydroacoustic equipment of that time ^[6] . After the war, the comparative tests of the XXI series with a 6-node course on sneak engines showed the same level of noise as the American boats at a speed of 2 knots. The boat batteries consisted of six groups of 62 cells of type 44-MAL 740 each, their total weight was 225 tons ^[7] , the capacity was 33,900 ampere-hour ^[8] . Rechargeable batteries occupied about a third of the durable case and were located in two tiers.

Habitability

The crew of the XXI type submarine consisted of 58 people: 6 officers , 19 foremen and 33 sailors ^[5] . The living quarters of the boat occupied the upper part of the 4th and 6th compartments. The berths of the submariners were placed on 49 beds , while the living quarters were, as far as possible, exempted from walking through them by the crew members involved in their duties ^[6] . Other innovations used on type XXI submarines to improve habitat conditions included an air conditioning system , desalination plant ^[4] , a hot water shower cabin, sanitary cylinders that allow the use of latrines in the underwater position, gateway devices for removing waste and garbage, refrigerators.

Armament

Torpedo

Torpedo armament of type XXI boats were six torpedo tubes of 533 mm caliber, placed in two vertical rows in the bow of the boat, inside a solid hull. Torpedo tubes - steel, tubular type, ensuring the launch of torpedoes from a depth of 50 meters.

The standard ammunition of the boats was 30 torpedoes , including 6 that were in the torpedo tubes and 24 located on the rack lay in front of them. The submarines were equipped with an electromechanical device for fast loading, consisting of charging carriages moving along the rails and allowing to give the second after 4 minutes a second volley after 4 minutes.

Artillery

The anti-aircraft armament of boats of the XXI type was 4 (2 * 2) 20-mm automatic guns Flak C / 38 . The guns were placed in tower installations, which had a light bulletproof, splinterproof booking, and were located in the extremities of the cabin fence, being inscribed in its lines. In a submerged position the towers were automatically retracted inside the cabin. Management of the towers could be carried out both directly and with the help of electromechanical drives from the inside of a sturdy building. The ammunition of the guns was 4000 (1000 per 1 gun) shells.

Electronic and navigation equipment

The boats of the XXI series were equipped with the latest hydrophones , which allowed detecting targets over a distance of 100 km, sonar and “balcony devices” (essentially the first phased sonar arrays) located in the nose section under the torpedo tubes. This made it possible to fix, identify, separate and attack group targets in the absence of visual contact.

• Sonar "Nibelung" with a power of 5 kW and an operating frequency of 15 kHz. The pulse duration is 20 ms. For transmission, magnetostrictive emitters installed in the bow of the wheelhouse were used. Received echoes were processed by an analog computer, and data for firing was entered directly into the torpedoes. The viewing angle was about 100 degrees in the forward direction, with an accuracy of determining the direction to the target of about 0.5 degrees. Depending on the state of the water, the target determination range was two to four nautical miles with an accuracy of 2%. The target was displayed on a cathode ray tube. To measure the relative velocity of the target, the Doppler effect was used, the determination of the direction to the target was calculated from the phase difference.
• The GHG-Anlage noise-detecting station, whose antenna consisted of 144 hydrophones and was located in the keel of the nose under the fairing (“balcony” device). Under favorable conditions, the noise finder detected single targets at a distance of up to 20 km, and group ones up to 100 km, with an average accuracy of 1 degree.
• Gyrocompass with 6 repeaters.
• 30 KHz echo sounder with ranges of measured depths from 0 to 1000 meters.
• Binocular periscope with a length of 5000 mm and a vertical angle of inclination from −10 to +90 degrees.
• Underwater telephone at a frequency of 4120 Hz.
• Direction finder receiver with retractable loop antenna.
• Shortwave receiver T8K44 "Cologne".
• Long-wave receiver T3Pl Lä38 (Telefunken) with ranges of 15-33 KHz and 70-1.260 KHz.
• Transmitter 200 W in the range of 3-23 MHz
• 40 watt transmitter for 3-16.5 MHz
• 150 watt transmitter for longwave.
• 10W transceiver on VHF (radio)
• Radar "FuMO65", which could be used only in the surface position. In the future, it was planned to use a radar with a retractable antenna, which could operate at periscope depth.
• Enigma cryptographic machine with four rotors (planned with five).
• A device for compressing radio data .

The only submarine of type XXI, which went on a military campaign under the flag of Kriegsmarine , was U-2511 . On April 30, 1945, under the command of A. Schnee, she left the port of Bergen in Norway to hunt convoys in the western Atlantic .

On May 1, off the east coast of Great Britain , moving at the periscope depth, she met with a group of British submarine hunters , but thanks to effective navigation aids and speed advantage she managed to escape from them. On May 4, the order was given to end the submarine war, and U-2511 fell back. In the region of the Faroe Islands, she met with a group of British ships that included the heavy cruiser "Norfolk" and several destroyers . The boat, moving on the motor of stalking, took the position to attack the cruiser, but the commander did not give an order to open fire, and the U-2511 disappeared, and remained unnoticed by the British ^{[9] [10]} .

In addition to her, U-3008 , passing through the Skagerrak Strait off the coast of Norway, tried to launch an attack on an unidentified large British ship, but, like U-2511, abandoned its intentions. About a dozen more boats of type XXI, attempting to leave for Norway these days, were sunk in the Baltic straits by the anti-Hitler coalition aviation ^[10] .

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  Type XXI Submarine Chart

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  U-3008 in the US Navy during sea trials

Submarines of the XXI series had an impact on all post-war submarine shipbuilding.

A number of revolutionary innovations were used in the project - electromechanical charging of torpedo tubes, a sonar complex that allows attacking without visual contact, enlarged rechargeable batteries, a rubber coating hindering the operation of enemy sonars, and a bubble curtain . The frames for the first time were taken out of a strong hull, this allowed to increase the space inside the boat and simplify the conduct of all kinds of communications and equipment placement. For the first time, submarines were designed for scuba diving throughout the entire autonomous trek.

Project Development

After the war, the following submarine projects were created on the basis of type XXI:

•   USSR - project 611 , project 613
•   Sweden - type "Hayen"
•   Great Britain - modernization of T-type boats
•   France - type "Narwhal"
•   USA - type "Tang" (1949-1952) and further work on the programs GUPPY .

In the Soviet Union, the captured submarines were given the name "Project 614." U-3515 was renamed to N-27 (N - German), then to B-27. U-2529 respectively in the N-28 and B-28, U-3035 in the H-29 and B-29, U-3041 in the H-30 and B-30. These four submarines lasted until 1957-1958, then they became training, and the B-27s were scrapped only in 1973.

After the war, four boats of type XXI remained. U-2540 , raised in 1957, named Wilhelm Bauer and served as an experimental vessel, has been a museum in Bremerhaven since 1984 ^[11] .

Three more boats of type XXI ( U-2505 , U-3004 and U-3506 ), which were considered missing , were found in 1987 in the Elbe II bunker that was blown up in Hamburg . All three boats were in poor technical condition, in the 1950s, diesel engines and electric motors were partially removed from the boats by American troops. U-3506 is crushed and damaged by fallen concrete floor beams. In the same year, the remains of the Elbe II were demolished and buried, together with three boats, for the construction of port facilities ^[12] .

• XXIII type submarines

• А. М. Антонов. Германские электролодки XXI и XXIII серий. — Санкт-Петербург: Гангут, 1997. — 48 с. — (Корабли мира № 1). - 1500 copies — ISBN 5-85875-112-9 .
• S. Breyer. German U-Boat Type XXI = Elektro-Uboot Typ XXI. — Этглен: Schiffer Publishing (Podzun-Pallas Verlag), 1999. — 48 с. — ISBN 0-76430-787-8 .

U-Boot Type XXI in Detail. Фотогалерея и описание на английском