Submarines of the 21st series of the Kriegsmarine. Type XXI submarines. Radioelectronic and navigation equipment

By April 1945, the Germans managed to launch 118 submarines of the XXI series. However, only two of them were able to achieve operational readiness and go to sea in the last days of the war.

Our allies were very lucky that all the forces of Germany were sent to the Eastern Front - the Germans did not have enough resources to release a flock of fantastic “Electric Boats” into the sea. If they appeared a year earlier, that would be it! Another turning point in the Battle of the Atlantic.

The Germans were the first to guess: everything that shipbuilders in other countries are proud of - large ammunition, powerful artillery, high surface speed of 20+ knots - is of little importance. The key parameters that determine the combat effectiveness of a submarine are its speed and cruising range when submerged.

Unlike its peers, “Electrobot” was focused on being constantly under water: a maximally streamlined body without heavy artillery, fences and platforms - all for the sake of minimizing underwater resistance. Snorkel, six groups of batteries (3 times more than on conventional boats!), powerful electric. Full speed engines, quiet and economical electric. "sneak" engines.

The Germans calculated everything - the entire Elektrobot campaign moved at periscope depth under the RDP, remaining difficult to detect for enemy anti-submarine weapons. At great depths, its advantage became even more shocking: 2-3 times greater range, at twice the speed of any wartime submarine! High stealth and impressive underwater skills, homing torpedoes, a set of the most advanced detection means... “Electrobots” opened a new milestone in the history of the submarine fleet, defining the vector of development of submarines in the post-war years.

The Allies were not prepared to face such a threat - as post-war tests showed, the “Electrobots” were several times superior in mutual hydroacoustic detection range to the American and British destroyers guarding the convoys.

Type VII boats, Germany
The number of submarines built is 703.
Surface displacement - 769 tons; underwater - 871 tons.
Crew - 45 people.
Working immersion depth - 100 m, maximum - 220 meters
Full surface speed - 17.7 knots; submerged - 7.6 knots.
Cruising range on the surface is 8,500 miles (10 knots).
Submerged cruising range 80 miles (4 knots).
Weapons:
- 5 torpedo tubes of 533 mm caliber, ammunition - 14 torpedoes;
- 1 x 88 mm universal gun (until 1942), eight options for superstructures with 20 and 37 mm anti-aircraft mounts.

The most effective warships ever to roam the world's oceans.
A relatively simple, cheap, mass-produced, but at the same time well-armed and deadly weapon for total underwater terror.

703 submarines. 10 MILLION tons of sunk tonnage! Battleships, cruisers, aircraft carriers, destroyers, corvettes and enemy submarines, oil tankers, transports with aircraft, tanks, cars, rubber, ore, machine tools, ammunition, uniforms and food... The damage from the actions of German submariners exceeded all reasonable limits - if only Without the inexhaustible industrial potential of the United States, capable of compensating for any losses of the allies, German U-bots had every chance to “strangle” Great Britain and change the course of world history.

The successes of the Sevens are often associated with the “prosperous times” of 1939-41. - allegedly, when the Allies appeared the convoy system and Asdik sonars, the successes of the German submariners ended. A completely populist statement based on a misinterpretation of “prosperous times.”

The situation was simple: at the beginning of the war, when for every German boat there was one Allied anti-submarine ship, the “sevens” felt like invulnerable masters of the Atlantic. It was then that the legendary aces appeared, sinking 40 enemy ships. The Germans already held victory in their hands when the Allies suddenly deployed 10 anti-submarine ships and 10 aircraft for each active Kriegsmarine boat!

Beginning in the spring of 1943, the Yankees and British began to methodically overwhelm the Kriegsmarine with anti-submarine equipment and soon achieved an excellent loss ratio of 1:1. They fought like that until the end of the war. The Germans ran out of ships faster than their opponents.

The whole history of the German “seven” is a formidable warning from the past: what threat does a submarine pose and how high are the costs of creating an effective system to counter the underwater threat.
Surface displacement - 1620 tons; underwater - 1820 tons.
Crew - 57 people.
Working depth of immersion is 135 m, maximum depth is 200+ meters.
Full speed in the surface position is 15.6 knots, in the submerged position - 17 knots.
Cruising range on the surface is 15,500 miles (10 knots).
Submerged cruising range 340 miles (5 knots).
Weapons:
- 6 torpedo tubes of 533 mm caliber, ammunition - 17 torpedoes;
- 2 Flak anti-aircraft guns of 20 mm caliber.

German submarines of the XXI series, without exaggeration, are the best ships of this class in the world of that era. They became role models in all leading naval powers. What was revolutionary about them? The creation of the XXI series submarines began in 1943. Then the “wolf pack” tactics, based on group night attacks by submarines operating from the surface, ceased to bring results. Boats pursuing convoys on the surface were detected by radar and subjected to preemptive counterattacks. Submarines forced to operate from the surface, since underwater they were inferior to convoys in speed and had a limited supply of energy resources, were doomed to lose.



Structure of the XXI series submarine:
a - longitudinal section; b - location of propulsion motors; c - deck plan.
1 - vertical steering wheel; 2 - fairing of the hydroacoustic station (HAS) “Sp-Anlage”; 3 - life raft containers; 4 - creeping electric motor; 5 - a device for operating a diesel engine under water (“snorkel”); 6 - diesel; 7 - living quarters; 8 - air supply shaft for diesel engines; 9 - fenders of the first shots; 10 - 20 mm artillery mount; 11 - gas exhaust shaft; 12 - retractable radio antenna mast; 13 - radar antenna; 14.15 - commander and navigation periscopes; 16 - sonar fairing “S-Basis”; 17 - torpedo loading hatch; 18 - spare torpedo; 19 - torpedo tube; 20 - sonar fairing “GHG-Anlage”; 21 - battery pits; 22 - propeller shaft gearbox; 23 - propulsion motor; 24 - hydroacoustics cabin; 25 - radio room; 26 - central post; 27 - stabilizer; 28 - aft horizontal rudders

The solution to the problem lay in radically improving the quality of the submarine, and specifically the quality of the submarine. And this could only be achieved by creating a powerful power plant and large-capacity energy sources that do not require atmospheric air. However, work on new gas turbine engines proceeded slowly, and then a compromise decision was made - to create a diesel-electric submarine, but focusing all efforts primarily on achieving the best performance of the elements of underwater navigation.

A feature of the new boat was the use of powerful electric motors (5 times more than the previous large submarines of the IX series, which had the same displacement) and batteries with a tripled number of cell groups. It was assumed that the combination of these proven solutions and perfect hydrodynamics would provide the submarine with the necessary underwater qualities.

The submarine was initially equipped with an improved device for operating a diesel engine under water, the snorkel. This allowed the boat, while under the periscope and sharply reducing its radar signature, to charge the battery while making transitions under diesel engines. The approach of the anti-submarine ships conducting the search was detected by the submarine using the signal receiver antenna of operating radar stations installed on the snorkel. The combination of these two devices on one retractable mast made it possible to promptly warn submariners about the appearance of the enemy and evade them by diving to depth.

The total mass of the battery installation was 225 tons, and its share in the displacement reached 14%. In addition, the capacity of cells previously created for Series IX submarines was increased through the use of thinner plates by 24% in a two-hour discharge mode or by 18% in a twenty-hour discharge. However, at the same time, the service life of the batteries was halved - from 2-2.5 to 1-1.5 years, which approximately corresponded to the average “life expectancy” of submarines participating in combat operations. In this regard, the XXI series boats were considered by the designers as wartime ships, as a kind of “consumable” with a relatively short life cycle, the same as a tank or an airplane. They did not have the excess resources typical of peacetime ships that have been in service for 25-30 years.

Placing such a powerful battery became possible only thanks to the original shape of the durable case with cross sections in the form of a “figure of eight”. On boats of the XXI series, the battery pits occupied about a third of the length of the durable hull and were located in two tiers - in the lower segment of the “eight” and above it, with a central passage between the batteries.

The durable hull of the XXI series submarine was divided into 7 compartments. But, unlike the previous boats of the VII and IX series, it refused to highlight shelter compartments with spherical bulkheads of increased strength, which, as a rule, were the end compartments and the central post compartment. War experience has shown that in combat conditions the concept of rescuing submariners from shelter compartments is practically impossible to implement, especially for boats in the ocean zone. The abandonment of shelter compartments made it possible to avoid the technological and layout costs associated with spherical bulkheads.

The contours of the stern end adopted to achieve high speed qualities did not allow the placement of feed devices. But this did not in any way affect the methods of using the new submarines. It was assumed that, having discovered the convoy, it should take a position in front of it, and then, approaching underwater at the maximum possible speed, break through the guards and take a place under the ships inside the order (the relative position of the ships during the sea crossing and during the battle). Then, moving along with the convoy ships at a depth of 30-45m and hiding behind them from anti-submarine ships, the boat, without surfacing, carried out attacks with homing torpedoes. Having fired the ammunition, she went to greater depths and, with low noise, evaded the stern of the convoy.

Artillery weapons were intended only for air defense. Two twin 20-mm artillery mounts were located in turrets, organically integrated into the contours of the wheelhouse fence. Unlike previous ships, the XXI series submarines were for the first time equipped with a fast loading device, which made it possible to reload all torpedo tubes in 4-5 minutes. Thus, it became technically possible to fire with a full load of ammunition (4 salvos) in less than half an hour. This became especially valuable when attacking convoys that required a large expenditure of ammunition. The depth of torpedo firing was increased to 30-45 m, which was dictated by the requirements for ensuring safety from ramming attacks and collisions when the boat is in the center of the order, and also corresponded to the optimal operating conditions for surveillance and target designation equipment when performing periscope-less attacks.

The basis of the hydroacoustic armament was a noise direction-finding station, the antenna of which consisted of 144 hydrophones and was located under a drop-shaped fairing in the keel of the bow, and a sonar station with an antenna installed in the bow of the wheelhouse enclosure (view sector up to 100° on each side). Primary detection of targets at distances of up to 10 miles was carried out at a noise direction-finding station, and accurate target designation for firing torpedo weapons was provided by sonar. This allowed the XXI series boats, unlike their predecessors, to carry out attacks from underwater based on hydroacoustic data, without surfacing under the periscope for visual contact.

To detect the most dangerous opponents - anti-submarine aircraft - the boat was armed with a radar station, which was used only on the surface. Subsequently, on the boats scheduled for delivery to the fleet in the summer of 1945, it was planned to install a new radar with an antenna on a retractable mast, raised in a periscope position.

Much attention was paid to hydrodynamic properties. The shape of the hull ensured low resistance underwater, but at the same time made it possible to maintain good surface seaworthiness. The protruding parts were kept to a minimum and given a streamlined shape. As a result, compared to the previous large submarines of the IXD/42 series, the Admiralty coefficient, which characterizes the hydrodynamic qualities of the ship, for submerged boats of the XXI series increased by more than 3 times (156 versus 49).

The increase in underwater speed required an increase in the stability of the submarine in the vertical plane. For this purpose, horizontal stabilizers were introduced into the stern tail. The applied stern empennage scheme turned out to be very successful. In the post-war period, it became widespread and was used on a number of diesel and then first-generation nuclear submarines.

Hydrodynamic perfection had a beneficial effect on the ship's underwater noise. As shown by post-war tests conducted by the US Navy, the noise of the XXI series boats when moving under the main electric motors at a speed of 15 knots was equivalent to the noise of American submarines traveling at a speed of 8 knots. When moving at a speed of 5.5 knots under the electric creeping motors, the noise of the German submarine was comparable to the noise of American boats at the slowest speed (about 2 knots). In low-noise mode, the XXI series boats were several times superior in the range of mutual hydroacoustic detection to the destroyers guarding the convoys.

Special measures were envisaged to significantly improve the habitability of new submarines. Realizing that during long-term cruising, the combat effectiveness of a submarine largely depends on the physical condition and well-being of the crew, the designers used such new items as air conditioning and a water desalination plant. The system of “warm” beds was eliminated, and each submariner received his own individual sleeping place. Favorable conditions were created for the crew's service and rest.

Traditionally, German designers paid great attention to ergonomic factors - the convenience of the crew, the most effective combat use of technical equipment. The degree of thoughtfulness of these “details” characterizes this example. The flywheels on the valves of ship systems, depending on the purpose, had their own shape, different from others (for example, the flywheels of the valves on the lines going overboard had handles with a ball fitting). Such a seemingly trifle allowed submariners in an emergency situation, even in complete darkness, to act unerringly, by touch controlling the valves and shutting off or activating the necessary systems.

Before the end of World War II, German industry in 1944-1945. transferred 121 submarines of the XXI series to the fleet. However, only one of them, on April 30, 1945, went out on its first combat campaign. This is explained by the fact that after the submarine left the factory, 3 months of testing were envisaged, and then another 6-month course of combat training. Even the agony of the last months of the war could not break this rule.

Everything that remained after Operation Deadlight was divided between the USA, USSR and England. The UK's share of the 8 boats of the XXI series included U-25I8 and U-3017. Soon after, Great Britain transferred the U-25I8 to France. The boat was manned by a French crew and was part of the French fleet under the name "Roland Morillot" until 1968.

In November 1945 The British brought submarines to Liepaja to be transferred to the Soviet Union. Among them were four submarines of the XXI series: U-2529, U-3035, U-3041 and U-3515. All of them became part of the Baltic Fleet and served there as combat submarines until 1955. After this, the boats were used as blockers (U-3515), floating charging stations (U-2529 and U-3035) and experimental submarines (U-3041). In 1958-1959 all electric boats, except U-3515, were scrapped. U-35I5 was used as a training station until 1972, thus existing for 27 years.

In addition to these boats, our troops captured 20 unfinished submarines of the XXI series and a significant number of blocks prepared for assembling boats in Danzig at the Schichau shipyard. Summer 1945 submarines with numbers from U-3538 to U-3557 were launched and transferred to the USSR. They were supposed to be completed according to Project 614 using domestically produced components instead of the missing equipment. But under pressure from former allies, the Soviet leadership abandoned these plans. U-3538 - U-3540, which were in the greatest state of readiness, were sunk in August 1947 in the Baltic Sea 20 miles northwest of the Ristna lighthouse. The remaining boats in 1947-1948. sent for disassembly.

The Americans took U-2513 and U-3008 for study. They also conducted a thorough study of the trophies in Key West, Florida. U-3008 was decommissioned in 1947, and the equipment from the boat was used to repair U-2513. In July 1949 U-2513 was removed from the American fleet. For some time, both boats were laid up and then used as targets for testing naval weapons. U-2513 was sunk in October 1951, and U-3008 by July 1954.

In 1957 In the Flensburg area, the Germans raised the sunken submarine XXI series U-2540. The Kiel shipyard Howaldtswerke took on the task of restoring it to its original form. But in the fall of 1958. it was decided to convert the U-2540 into an experimental submarine for testing new equipment. Converted for new purposes, U-2540 entered service with the Bundesmarine in September 1960, under the name "Wal" (type 241). In 1984 a boat called "Wilhelm Bauer" was installed in the Museum of German Navigation in Bremenhaven (near Bremen). There she remains today.

Three more Type XXI boats, U-2505, U-3004 and U-3506, were considered missing, but were discovered in 1987 in the blown up Hamburg bunker Elbe II. All three boats are in poor technical condition. U-3506 was crushed and damaged by fallen concrete floor beams.

15.09.2009


U-21: the hidden threat
Text: Margarita Safonova

German U-type submarines made a real world revolution in naval combat tactics. The story began in 1906. It was then that the first submarine of this type, U-1, was launched. However, success did not come immediately. Most submarine models were imperfect, and the opportunity to check all the shortcomings was only in practice. U-9 and other models were powered by kerosene engines, U-15 was easily sunk by the British, and only U-21 became the first submarine in world history to sink a cruiser.

Technical characteristics of the underwater “monster”

The submarine U21 belonged to the Sh 9 series and, together with two other boats of the same project - U20 and U22 - was built in Danzig. The boat was launched on February 8, 1913. Instead of the kerosene engines previously used on all German submarines, the U21, like the rest of the boats in the series, was equipped with diesel engines mass-produced by the German industry. Submarines of the U19 series took an active part in the First World War.

A country:Germany
Launch date: February 8, 1913
Crew:35
Displacement:surface – 650 t, submerged – 837 t
Dimensions64.2x6.1x3.5
Weapons:four 500 mm torpedo tubes, one 88 mm deck gun
Power point: twin-shaft, diesel-electric, 1700/1200 hp.
Speed:when on the surface - 15.4 knots, when underwater - 8.1 knots



Captain Otto Herzing

In history, this name is mentioned much less often than the name of Herzing's namesake Otto Weddingen. However, we must not forget that it was the commander of U-21, Lieutenant Commander Otto Herzing, who was the first to achieve success. On September 5, 1914, the German submarine U-21 under his command destroyed the English armored cruiser Pathfinder.

Despite the fact that U-21 was rocking heavily due to the storm, the torpedo hit the small cruiser under the forward funnel. The bow of the ship exploded, engulfed in flames, the stern rose out of the water, the stricken ship tilted and sank in 4 minutes, plunging nose-first along with a crew of 259 people.

From the memoirs of U-21 captain Otto Herzing:

“My partner was looking through the periscope, and I stood there holding my breath. The propellers of the military giant were directly above us. And we moved almost by touch.

Torpedoes! Fire! - I screamed, and my heart almost jumped out of my chest.

There was a terrible explosion, a huge black cloud of smoke appeared on the surface of the sea. I saw that the torpedo had hit its target, and since we were directly under the ship, the likelihood of a double disaster was almost inevitable. It was reckless, I agree, but I had to take the risk.

Full speed ahead! - I commanded and we dived as deep and swam as fast as possible. A crazy maneuver saved us. When I dared to look through the periscope, we were already far from the crash site." (Report by German Captain Herzing dated May 25, 1915.)

Herzing's shot opened a new page in the history of naval warfare. And U-21 was lucky enough to turn this page. Now surface ships (both military and commercial) no longer feel invulnerable to attacks from under water.

This drawing shows a cross-section of one of the 380 German submarines that served in the First World War. Shown here is the U-21 model. U21 sank on 22 February 1919 in the North Sea during a voyage from Germany to Great Britain.

Statistics
In total, during the First World War, 600 submarines of the warring states sank 55 large warships (battleships and cruisers), 105 destroyers, and 33 submarines.

During World War II, Germany built 1,157 submarines until 1945. German submariners sank 2,603 ​​Allied warships and transport vessels with a total displacement of 13.5 million tons. As a result, 70 thousand military sailors and 30 thousand sailors of the Allied merchant fleet died.

During the Second World War, 789 German submarines were destroyed (according to Anglo-American data) or 651 (according to German data).

Submarines of the XXI series

Historical data

Power plant

Armament

Submarines of the XXI series are German diesel-electric submarines built in 1943-1945. These submarines became the first diesel-electric submarines designed primarily for underwater navigation, in contrast to previous projects of “diving” boats.

General information

The main advantages of these ships were:

  • High capacity rechargeable batteries;
  • Powerful underwater motors;
  • Availability of low-noise creeping electric motors;
  • TA reloading system;
  • Improved body contours.

Thanks to them, these submarines had a significant impact on the post-war development of the navies of all major states.

History of creation

Prerequisites for creation

The main task of the German Navy after the outbreak of World War II was the destruction of transport ships and the protection of convoys in the Atlantic, which threatened the supply of raw materials to Great Britain from the colonies, vital to British industry. In order to continue the fight, Great Britain had to receive more than a million tons of raw materials and various products per week. In Western historiography, the Battle of the Atlantic is considered the longest continuous campaign of WWII.

September 1939 - May 1940. In 1939, the German submarine fleet was small. Of the 57 diesel-electric submarines available for combat operations, a significant proportion of the II series boats had low seaworthiness and autonomy and were suitable only for coastal operations. However, the submariners quickly scored several major victories - on 09/17/39 U-29 sank HMS Courageous, and a month later Gunther Prien penetrated Scapa Flow and sank HMS Royal Oak. Submarine activity then declined due to the winter of 1939-1940, as well as the invasion of Norway and problems with magnetic fuses for torpedoes, which were not resolved until March 1941.

June 1940 - February 1941. Due to the fall of France, Germany gained direct access to the Atlantic, and the Royal Navy was forced to operate over a larger area. Between June and October, over 270 Allied merchant ships were sunk. The British began to assemble larger convoys, and the Germans began to use "wolf pack" tactics, where several submarines attacked a convoy at night on the surface, coordinating their actions by radio.

March - May 1941. Beginning in October 1940, the British began to receive more escort ships, and permanent escort groups were created. In the spring of 1941, this tactic began to bear fruit: U-47, U-99 and U-100 were sunk. Dönitz lost three of his leading aces (Prien, Kretschmer and Schepke), and in April 1941 he moved the wolf packs further west to attack the convoys before the escorts could join.

June - December 1941. In June 1941, the British decided to cover convoys all the way across the Atlantic, dividing the ocean into zones of responsibility. Cooperation increased between Great Britain and the United States, which realized the danger of the Kriegsmarine's actions in the Atlantic. In the spring and summer, hacking Enigma and using radio interception made it possible to reduce the losses of merchant ships by 2/3.

January - June 1942. After the United States entered the war, Series IX submarines were sent to the shores of the United States, where the submarines were weak and disorganized. After them, submarines of the VII series were sent, receiving supplies from boats of the XIV series - the so-called. "cash cows" Starting in May, a convoy system was introduced off the US coast, and the number of attacks decreased. However, due to the effectiveness of the submarines, Dönitz receives the title of grand admiral and carte blanche to use them.

July 1942 - February 1943. In mid-1942, the main actions were again transferred to the central Atlantic, however, due to the increase in the number of anti-submarine ships, the use of radars, aircraft and Yozh bombers, boat losses were increasing. The Kriegsmarine switched to the four-rotor Enigma, but by December 1942 it was hacked again, and losses of merchant ships were greatly reduced.

March - May 1943. By March 1943, there were so many submarines in the Atlantic that it was extremely difficult for the convoy to pass undetected, but in March and April 27 submarines were lost, and in May - 34. Dönitz was forced to curtail all operations in the North Atlantic.

Design and construction

In November 1942, Karl Dönitz called a meeting at his Paris headquarters to discuss ways to regain the initiative in submarine warfare. The meeting, which was attended by officers from the submarine fleet headquarters, engineers from shipyards and experts from the design department of the naval command from Berlin, was an important moment in the development of submarines. The primary issue was the development of Professor Helmut Walter's project to create a submarine from PSTU. The prototype was shown to Erich Roeder in February 1942, but he showed little interest, despite Dönitz's intervention.

By November 1942, there was still too much of a gap between the small experimental ship and the full-fledged version. One of the biggest problems was hydrogen peroxide, a concentrated volatile fuel that Walther's engine consumed at a tremendous rate. Walter designed the boat's double hull in the shape of a figure eight. The crew and equipment would occupy the upper part, and the lower part would be occupied by a huge fuel tank. However, despite all efforts, it was impossible to count on the construction of such a boat in the near future.

The solution was found by one of the specialists from the design bureau of G. Walter, G. Heep, and an officer from the design department of the Navy Command, H. Elfken. It was proposed to develop a project with a traditional diesel-electric installation based on the XVIII series submarines, designated XXI series. Preliminary calculations were completed by January 1943, the results of which promised outstanding performance characteristics: an “electric boat” with a displacement of 1600 tons could go underwater for 90 minutes at 18 knots, or 10 hours at 12 knots, as well as 60 hours at 5 knots in sneaking mode. The new submarine could not only navigate the Bay of Biscay underwater, but also reach the main convoy routes undetected.

In April 1943, Grand Admiral Dönitz, in a conversation with Armament Minister Albert Speer, stated:

Sketch and working drawings were ready by June 19, 1943, and the first boats were supposed to be received by November 1944 from the Deschimag AG Weser shipyard, and from other shipyards not earlier than the spring of 1945. The time required for the crews to master the submarines delayed military operations new submarines in the Battle of the Atlantic in 1946, which did not suit the naval officers. To speed up the construction process as much as possible, Minister of Armaments Albert Speer entrusted the leadership to the general director of the Magirus Werke automobile plant, O. Merker.

Having understood the technology of building submarines, Merker came to the conclusion that it was necessary and possible to switch to the methods of large-scale production that were familiar to him, similar to those used in mechanical engineering and the automotive industry. The entire submarine was divided into 9 sections, assembled by different companies independently of each other. Each company produced no more than four types of blocks, which ensured the constancy of the required resources supplied by 33 enterprises. The completed hull sections, each weighing no more than 200 tons, were sent to the assembly shipyards of Blohm & Voss (Hamburg), Deschimag AG Weser (Bremen) and Schichau (Danzig), where they were joined by welding.

Division of submarines of the XXI series into sections. The robust housing is shown in bold lines.

Hull sections:

  1. Feed, steering mechanisms and working accessories;
  2. Electric motor compartment;
  3. Diesel compartment;
  4. Aft living compartment;
  5. Central post and galley;
  6. Bow living compartment;
  7. Racks of spare torpedoes;
  8. Bow torpedo compartment;
  9. Fencing of retractable devices.

Despite the optimistic statements of the manufacturers, at first it was not possible to achieve the required accuracy in the manufacture of the sections; the sections required finishing at the shipyards. As a result, it was decided to use the first 6 boats from each shipyard as training ones. This can be explained by the complexity and secrecy of the project, the lack of experience in coordinating various enterprises, and disruptions in the work of industry due to Allied air raids.

Due to high secrecy and a small amount of time, numerous mistakes were made during the design of the submarine. By September 1944, more than 150 changes had to be made to the design of the boats. For example, the speed of a boat under a snorkel was limited to 6 knots.

Major problems with the original project:

  • Water absorption by diesel engines through the gas exhaust system during reversal of propulsion electric motors;
  • Transfer of power to the armatures of the main electric motors when running under diesel engines;
  • Inability to develop the full power of diesel engines under the snorkel;
  • High noise level of compressors;
  • Increased vibration of the snorkel and periscopes at speeds above 10 knots;
  • Uneven discharge and charge of battery groups;
  • Insufficiently efficient hydrogen afterburning system;

It was also not possible to provide the required protection of the submarine from magnetic mines due to an excessive increase in the magnetic field of the main motor when moving at high speeds. Despite the creation of a full-scale model, a number of layout miscalculations were revealed. For example, there was no access to service compressors and a number of auxiliary mechanisms of the power plant. At the same time, high-pressure air cylinders that did not require maintenance were freely accessible. Air pockets appeared in the drainage system pipeline due to improper installation. New anti-aircraft artillery installations, a complex and extensive hydraulic system, and other mechanisms and devices required painstaking fine-tuning. A serious drawback was the inability to use turbocharging of diesel engines. On the XXI series boats, it was supposed to use compressors to pre-compress the air entering the engine cylinders, but due to miscalculations in design and construction, this turned out to be impossible. The power of each engine was reduced from 2000 to 1200 hp, surface speed dropped to 14.6 knots, and battery charging time increased. It is reliably known that U-2518 was the only one of all the XXI series submarines captured by the British that had turbocharged diesel engines installed.

The boats were launched for high-speed tests only at the end of 1944. Deep-sea tests were carried out in the Norwegian fiords only in 1945, in the last months and days of the war. Their significance was determined by the lack of reliable calculation methods for the area of ​​the strong hull, which had the shape of a figure eight. Tests of U2511, which plunged to 160 m in March 1945, showed that the “eight” successfully withstood the load. At the same time, it turned out to be necessary, due to local strength conditions, to reinforce a number of structures and, in particular, the torpedo-loading hatch. After completing these works, the submarine U2506 sank to a depth of 220 m without any problems, exceeding the design test depth by 10%.

According to calculations, the construction of each submarine should have taken 266 thousand man-hours, but this value turned out to be underestimated - in December 1944 the labor intensity averaged 332,500 man-hours. The average cost of one submarine was 4.6 million Reichsmarks. The launch of the first boat of the XXI series took place in Danzig only on April 19. The desire to make a gift for A. Hitler's 55th birthday prompted the shipyard management to launch the submarine U3501 with an insufficient degree of readiness. Completion was delayed, and U3501 was transferred to the fleet only on July 29, 1944.

On September 11, 1944, American units reached the western border of Germany, directly threatening the industry of the Ruhr. A counterattack in the Ardennes would push them back and reduce the threat, so priority shifted to tank production. The number of submarines delivered to the fleet reached its peak (28 units) in December, and by the end of the year, 62 submarines were handed over to the fleet, all with significant defects and not ready for combat, instead of 233 according to the original plan.

On January 12, 1945, US troops in Strasbourg captured 20 aft sections, which had nothing to replace, and 1/3 of the required number of batteries was also missing. In February 1945, all efforts were ordered to be transferred to completing the most completed ships, and on March 24, the order for all boats whose construction had not yet begun was canceled. On March 27, in Gdansk, the Soviet army captured 88 separate sections. The last boat of the XXI series was launched on April 20, a week before the capture of the AG Weser shipyard by British units. Before the end of the war, the British captured another 28 more or less completed boats on the stocks.

In total, before the end of the war, the Germans built and delivered 119 submarines from three shipyards:

  • “Blohm & Voss” - U2501 - U2762 - 48 pcs.;
  • "Deschimag AG Weser" - U3001 - U3295 - 41 pcs.;
  • "Schichau" - U3501 - U3695 - 30 pcs.

Description of design

Frame

The XXI series submarines had a double-hull design with a durable hull, which was divided into 7 compartments. In the German fleet, the compartments were numbered from the stern:

  1. Aft compartment - hydraulic cylinders for rudder drives, high-pressure air cylinders and a ship's workshop;
  2. Electric motor compartment - main electric motors, creeping electric motors, electrical panels and control panels;
  3. Diesel compartment - diesel engines, gearboxes, large-sized snorkel locks and exhaust pipes;
  4. Aft living compartment - living and living quarters for the crew, aft battery pit;
  5. Central compartment - central post, retractable devices, galley, high pressure cylinders, replacement tanks;
  6. Bow living compartment - officers' living quarters, infirmary, bow battery pit;
  7. Bow torpedo compartment - torpedo tubes, racks of spare torpedoes, compensation tank.

The shape of the durable hull is cylindrical, in the area of ​​the living compartments it is in the form of an inverted number 8. The length of this section is about 40% of the length of the durable hull. The upper cylinder of the pressure hull has a diameter of 5300 mm with a maximum plating thickness of 26 mm. The lower part, which is not truly circular except at the two outermost compartments and ends at the engine compartments, has 18mm thick plating. At the intersection of the upper and lower segments, heavy transverse beams run across the hull, on which lies the 18 mm thick deck flooring. Almost along the entire length of the hull, the frames are external, with the exception of the ends of the strong hull, where the gaps between the hulls are reduced to a minimum. In these places, the frames are made internal, of reduced size (160x7 versus 220x11), the spacing is also reduced from 800 mm to 400.

The material of the strong hull, end bulkheads and frames is St52KM steel. The working depth of immersion was 135 meters, the maximum depth was 200 meters, and the depth of destruction of the hull was 330 meters. The safety factors for the ultimate and destructive depths were 1.5 and 2.5, respectively. Intercompartment bulkheads were designed for a depth of 50 m with a safety factor of 1.5.

The following openings were provided in the robust housing:

  • hole for access to auxiliary equipment of the diesel compartment;
  • one hole for access to the rear battery;
  • two holes for access to the front battery;
  • lower deckhouse hatch;
  • two holes for periscopes;
  • torpedo loading hatch.

The lightweight body covered the durable one along its entire length. Between the hulls there were bow and stern ballast tanks, 5 main ballast tanks, 7 fuel tanks and freely flooded space on the sides.

Power point

The submarine's power plant consisted of two six-cylinder diesel engines, two main electric motors, two creeping electric motors of lower power and 6 battery groups of 62 cells each.

Two six-cylinder diesel engines MAN M6V 40/46 were previously installed on the U27 submarine (VIIA series). The M6V was a non-reversible four-stroke engine with a cylinder diameter of 400 mm. The engine weight to power ratio was 14.4 kg/hp. Since the electric motor armatures and gearbox gears also rotated under the diesel engines during running mode, the useful power on the shaft was only 88% of the engine power. To increase the power of diesel engines, turbocharging had to be used. With its help, the engines developed power up to 2x2000 hp, allowing a speed of 15.4 knots over water. Without turbocharging, power dropped to 2x1200 hp, and speed - to 14.6 knots. A significant problem was the drop in diesel power when driving under a snorkel. The cross-sectional areas of the two snorkel pipes limited the possibility of air supply to 43%, and exhaust gas removal to 55% of the surface. The speed of movement when charging batteries with both diesel engines did not exceed 6 knots, which did not allow catching up with the convoy after the batteries were discharged.

The snorkel on the XXI series submarine was proposed by Walter in a letter to Dönitz on May 19, 1943. Extremely important from the point of view of practical application was his idea, according to which, when the valves are closed with sea water for up to 1 minute, the diesel engine can use air from the submarine compartments. This leads to pressure surges of up to 200 millibars inside the compartments and the danger of exhaust gas breakthrough with subsequent poisoning of the crew. Using a motor, the snorkel could be raised in 2.7 minutes and removed in 1.5. For emergencies, provision was made for manual control.

Movement under the snorkel allowed movement at depths of up to 16 m, charging batteries, largely unnoticed. Thus, U-977 and U-978 (series VIIC) spent 66 and 69 days under water, respectively. Since the fall of 1944, the periscope head or snorkel mast could be seen by an Allied aircraft with a radar with a wavelength of 0.1-0.5 m, and since March 1945, an APS-20 aircraft radar (wavelength 10.5 cm) could notice a snorkel from a distance of 20 km. As a countermeasure, several protective coatings have been developed that reduce the detection range by up to 65% depending on the frequency range.

The battery consisted of 2x (3x62) = 372 AFA 44 MAL cells weighing 620 kg, the total mass of the battery was 236 tons. Dividing the battery into three parts on each side made it possible to safely reduce the voltage for the creep motors from 360 to 120 V, but the armatures of the main electric motors they were powered only by 360 V. One of the problems was a strong voltage drop in the cables between the battery and the motor, the battery was discharged after 80 minutes of full speed movement instead of the calculated 100 minutes. The capacity of each battery cell ranged from 6267 to 12150 Ampere-hours, depending on the current and discharge time.

Recharging the batteries on the left or right side was carried out only sequentially; charging the batteries independently was impossible. 3 hours of snorkeling at a speed of 5 knots per day was considered sufficient to maintain the battery charge between 60 and 90%. Due to the diesel power of 2x1050 hp. in battery charging mode, charging the battery from 10 to 90% took 6.2 hours, and from 90 to 100% - an additional 2.4 hours.

Engine 2GU 365/30

2 GU 365/30 machines from Siemens were used as the main electric motors. They had a mass of 10.33 tons each and a power of 2500 hp. However, the initially calculated maximum speed of 18 knots turned out to be impossible to achieve due to a decrease in power due to a drop in network voltage. On November 8, 1944, at the measured mile, U-3506 showed a speed of 15.93 knots. After reducing the scuppers by 2/3 and closing the holes in the upper deck and bridge, the speed increased to 17.2 knots. As a result, reducing the scuppers by 1/3 of the original value allowed the U-3507 to reach a speed of 16.5 knots. for 50 minutes, and the highest speed is 16.8 knots. - for 20 min.

GV 323/28 from Siemens was used as creeping engines, developing a power of 113 hp. At the measured mile, U-3506 moved at a maximum speed of 6.1 knots.

After the war, two submarines (U-2513 and U-3008) received by the United States were carefully examined. Test results showed that at creeping speed the boat could not be heard further than 220 m, while merchant ships were detected at a distance of up to 13 km. At a speed of 5.5 knots. The XXI series submarine made as much noise as the quietest American submarines at a speed of 2 knots, and at a depth of over 150 m the boat was not detected by passive methods even at maximum creep speed. At 15 knots the submarine made as much noise as the American ones at 8 knots, and at 10 knots. - like American ones at 6 knots.

Armament

Section of the XXI series submarine. Torpedo racks shown.

In the bow torpedo compartment there were 6 533 mm caliber torpedo tubes. The torpedo tubes were steel, tubular type, capable of launching torpedoes from a depth of up to 50 meters. The torpedoes were pushed out by compressed air; for bubble-free firing, the torpedoes were tilted 2° down. Spare torpedoes were stored on racks, three torpedoes for the upper tubes, and 2 for each of the lower ones. The submarines were equipped with an electromechanical fast-loading device, which consisted of charging carts moving on rails and made it possible to fire a second salvo after the first salvo in 5-15 minutes when loading torpedoes from the cells closest to the TA, or after 15-19 minutes otherwise. Another torpedo was located under the deck flooring.

It was also assumed that it would be possible to use 12 or 18 mines transported inside the TA, which would reduce the supply of torpedoes to 14 units. However, by the end of the war the mine-laying system had not been completed, so no boats used them.

The artillery armament included 2 twin Flak C/38 anti-aircraft guns, installed in two turrets, which had light armor 17 mm thick, in the wheelhouse fence. The ammunition load was 3450 shells.

Radioelectronic and navigation equipment

The radio equipment generally corresponded to the equipment of the IXC series submarines, but was distinguished by the absence of a long-wave transmitter:

  • long-range shortwave transmitter Telefunken T200 FK39 (power 200 W at frequency 3-23 MHz);
  • short-wave long-range transmitter Lorenz Lo40 K39A (power 40 W at frequency 3-16.5 MHz);
  • receiver with retractable directional antenna and direction finder for the Telefunken T8 K44 “Cologne” shortwave receiver (1.5-25 MHz) or T9 K39 (1.5-3 MHz);
  • long-wave receiver Telefunken T3Pl Lä38 (frequencies 15-33 kHz and 70-1.260 kHz);
  • Lorenz LoUK39 10 transceiver with a power of 10 W on VHF (41.55 - 45.75 MHz) for communication between nearby boats;
  • FuMO 65 radar (pulse power 40 kW, frequency 556 MHz) for aircraft warning at a distance of up to 30 km;
  • Enigma encryption machine with four rotors (planned with five).

The FuMO 65 radar could be used on the surface, the range accuracy was ±10% of the measured value, and the bearing accuracy was ±1.5°-2°. Detection radii were small due to the low altitude of the radar: a destroyer was detected from 4-5 km, a transport ship from 6-10 km, aircraft from 9 to 40 km. In addition, in the sector 18°-50° the radar was obscured by the night periscope.

The hydroacoustic passive detection station "GHG-Anlage", the antenna of which consisted of 144 hydrophones and was located under the nose tip in a fairing ("balcony"), under favorable conditions, detected single targets at a distance of up to 20 km, and group targets up to 100 km, with average accuracy 1°, minimum - 1.5°.

The Nibelung sonar made it possible to determine the direction, distance and approximate speed of a target using several pulses. The power was 4.4 kW and the frequency was 15 kHz, with a pulse length of 20 ms. Magnetostrictive emitters were used for transmission; the receiver and transmitter were located on the front of the wheelhouse fence. The viewing sector was about 110°, and the system could rotate 150° in both directions. The received echo signals were processed by an analog computer, and the firing data was entered directly into the torpedoes. The Doppler effect was used to measure the relative speed of the target, and the direction to the target was calculated from the phase difference. Depending on water conditions, the target detection range ranged from two to four nautical miles with an error of 2%, with a maximum error in determining the direction to the target of 1.5°.

The periscopes of all German submarines were manufactured by Zeiss and were the strong point of these boats. Initially, the submarine was supposed to have a periscope with an optical length of 9 m. However, tests showed that at a speed of 6-7 knots, due to vibrations, it was completely impossible to observe the target. Thus, a StaSR C/2 periscope with an optical length of 7.5 m was installed on most of the submarines, allowing observation at speeds of up to 8.5 knots.

Habitability

The crew of the XXI series submarine consisted of 58 people: 6 officers, 19 foremen and 33 sailors. The boat's living quarters occupied the upper part of the 4th and 6th compartments. The submariners' berths were located on 47 beds: 24 in the aft living compartment, and the commander's and chief engineer's cabins, 4 officer's berths and 19 petty officers' berths in the forward living compartment. At the same time, the living quarters were, as far as possible, freed from the passage of crew members engaged in their duties. UV lamps were installed to replace sunlight.

The air volume of the submarine was about 900 m³. Without air renewal with a crew of 60 people, in 11.3 hours the concentration of carbon dioxide increased from 0.03% to 1.5%. Over 27 hours, the oxygen content dropped from 21% to 17%.

To maintain air quality at the proper level, there were two air regeneration systems designed for 19 - 22 days. The oxygen supply was contained in 30 50 liter cylinders under a pressure of 150 atm. In addition, the submarine had 25 cartridges with chemically bound oxygen, which released 1.5 m³ of oxygen in 50 minutes. The entire supply of oxygen on the boat was designed for 150 hours of continuous stay under water.

These boats were the first to have a hot shower. In addition to this, the boat had 3 sinks in the bow and 2 toilets (one in the bow, the other in the stern).

The galley was equipped with an electric stove, two sinks, a water boiler, and a refrigerator.

Service history

The first submarines took a very long time to arrive in the Baltic Sea due to delays in crew training.

U-2510 and U-2518 spotted the C-13 on January 30, 1945, several hours before the Wilhelm Gustloff's attack, but did not attack due to poor visibility. U-2506, U-2511, U-2519, U-3007 and U-3008 later passed the sinking ship, but were ordered to proceed west without rendering assistance.

The first boat of the XXI series to Norway was U-2511, where it arrived on March 23, 1945. On April 17-18, while moving to Bergen, U-2511 met with the British submarine "Tapir", which sank U-486 VIIC series on April 12, but not began to attack. 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 1 May, off the east coast of Great Britain, moving at periscope depth, she encountered a group of British submarine hunters, but thanks to effective navigational aids and her speed advantage, she managed to evade them. On May 4, the order was given to end the submarine war, and U-2511 set off on a reverse course. In the Faroe Islands area, she met with a group of British ships, including the heavy cruiser Norfolk and several destroyers. The boat, moving on sneaking engines, entered a position to attack the cruiser, but the commander did not give the order to open fire, and U-2511 disappeared, remaining unnoticed by the British.

In addition to U-2511, U-3008, passing through the Skagerrak Strait off the coast of Norway, attempted to attack an unidentified large British ship, but, like U-2511, abandoned its intentions. About a dozen more boats of type XXI, which were trying to leave for Norway these days, were sunk in the Baltic straits by anti-Hitler coalition aircraft.

U-3008 during testing in the USA

France
U-2518 became the French submarine Roland Morillot. She served during the Suez Crisis in 1956, and until 1967. It was cut in 1969.

USSR
Four Type XXI boats were transferred to the Soviet Union after the Potsdam Agreement. These were U-3515, U-2529, U-3035, and U-3041, which entered service with the Navy as the B-27, B-28, B-29, and B-30. These four submarines served until 1957-1958, then became training submarines, and the B-27s were scrapped only in 1973.

Great Britain
U-3017 was commissioned into the Royal Navy as HMS N41. She was used for testing before dismantling in November 1949.

USA
The US Navy received U-2513 and U-3008 for testing and operation in the Atlantic. In November 1946, President Harry Truman became the first American president to dive in a submarine. U-2513 was sunk as a target in 1951, U-3008 was dismantled in 1956.

U-2540, raised in 1957, named Wilhelm Bauer and serving as a prototype vessel, has been a museum in Bremenshafen since 1984.

Three more Type XXI boats (U-2505, U-3004 and U-3506), considered missing, were discovered in 1987 in the blown up Hamburg bunker Elbe II. All three boats were in poor technical condition; in the 1950s, American troops partially removed diesel engines and electric motors from the boats. U-3506 was crushed and damaged by fallen concrete floor beams. That same year, the remains of the Elbe II were demolished and buried, along with three boats, for the construction of port facilities.

Images

Exterior drawing of the XXI series submarine