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An Elektroboot ("electric boat" in German) was a submarine designed to operate entirely submerged, rather than as submersibles that could submerge as a temporary means to escape detection or launch an attack. [1]
Even before the Second World War the rocket designer Hellmuth Walter had been advocating the use of hydrogen peroxide (known as perhydrol) as a fuel. His engines were to become famous for their use in rocket-powered aircraft—notably the Me 163 Komet —but most of his early efforts were spent on systems for submarine propulsion.
In these cases the hydrogen peroxide was reduced chemically and the resulting gases used to spin a turbine at about 20,000 rpm, which was then geared to a propeller. This allowed the submarine to run underwater at all times, as there was no need for air to run the engines. The system also used up tremendous amounts of fuel, and any boat based on the design would either have to be huge or have limited range.
Thus the system saw only limited development even though a prototype was running in 1940. But when problems with the existing U-boat designs became evident in 1942, the work was stepped up. Eventually two engineers identified a solution to the problem. [2]
Instead of running the submarine entirely on the perhydrol, they used it just for bursts of speed. Most of the operations would then be carried out as with a normal boat, using a diesel engine to charge batteries. However while a conventional design would use the diesel as the primary engine and the batteries for short periods of underwater power, in this case the boat would run almost all the time on batteries in a low-speed cruise, turning on the perhydrol during attacks. The diesel was now dedicated entirely to charging the batteries, which it needed only three hours to do. [3]
The perhydrol design suffered from several design flaws which were not fixed before the end of the war. As an intermediate solution, the perhydrol propulsion system was dropped in favour of a conventional diesel/electric solution, but retaining the streamlined hull-shape. The battery capacity was increased significantly along with fuel stores, and the boat was designed to operate underwater for long periods. [4]
The result was the "Elektroboot" series, the Type XXI U-boat and a short range Type XXIII U-boat, finalized in January 1943 but with production only commencing in 1944–1945. When under water, the Type XXI managed to run at 17 knots (31 km/h; 20 mph), which was faster than a Type VII running full out on the surface and almost as fast as the ships attacking her. After the war, tests carried out by the United States Navy on two captured Type XXIs showed they could outrun some ASW ships by going in the direction of heavy seas. (The US Navy's first nuclear-powered submarine, USS Nautilus (SSN-571), used a modified Type XXI hull shape.) For most of the trip it ran silently underwater on batteries, surfacing only at night, and then only to snorkel depth. Weapons were likewise upgraded, with automated systems allowing the torpedo tubes to be reloaded in less than a quarter of the time, firing homing torpedoes that would attack on their own. Even the interior was improved: it was much larger and fitted with showers and a meat refrigerator for long patrols.
The design was to be produced in two versions, primarily the Type XXI, and lesser numbers of the smaller Type XXIII. Both were much larger and more difficult to build than the existing designs, the Type XXI taking some 18 months. Mass production of the new type did not really get started until 1944 and subsequently only one combat patrol was carried out by a Type XXI before the war ended. This patrol is considered controversial. According to some sources,[ which? ] the U-2511 did not make any contact with the enemy. Another version suggests that the U-boat did make contact with HMS Norfolk of the Royal Navy, but did not fire as the captain had already received orders of surrender. A number of boats were commissioned into Allied navies after the war for research purposes, and one into the Bundesmarine of post-war Germany.
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. The term is an anglicised version of the German word U-Boot, a shortening of Unterseeboot, though the German term refers to any submarine. Austro-Hungarian Navy submarines were also known as U-boats.
Type XXI submarines were a class of German diesel–electric Elektroboot 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.
German Type XXIII submarines were the first so-called elektroboote to become operational. They were small coastal submarines designed to operate in the shallow waters of the North Sea, Black Sea and Mediterranean Sea, where larger Type XXI electric boats were at risk in World War II. They were so small they could carry only two torpedoes, which had to be loaded externally. As with their far larger sisters—the Type XXI—they were able to remain submerged almost all of the time and were faster than conventional U-boats, due to the improved streamlining of their shape, batteries with larger capacity and the snorkel, which allowed the diesel engines to be used while submerged. The Type XXI and XXIII U-boats revolutionized post-war submarine design. Nearly a thousand Type XXIII boats were projected towards the close of World War II, but most of these were either cancelled, scrapped incomplete, or only projected.
An attack submarine or hunter-killer submarine is a submarine specifically designed for the purpose of attacking and sinking other submarines, surface combatants and merchant vessels. In the Soviet and Russian navies they were and are called "multi-purpose submarines". They are also used to protect friendly surface combatants and missile submarines. Some attack subs are also armed with cruise missiles, increasing the scope of their potential missions to include land targets.
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Tench-class submarines were a type of submarine built for the United States Navy (USN) between 1944 and 1951. They were an improvement over the Gato and Balao classes, only about 35 to 40 tons larger, but more strongly built and with a slightly improved internal layout. One of the ballast tanks was converted to carry fuel, increasing range from 11,000 nautical miles to 16,000 nautical miles. This improvement was also made on some boats of the previous two classes. Further improvements were made beginning with SS-435, which are sometimes referred to as the Corsair class. Initial plans called for 80 to be built, but 51 were cancelled in 1944 and 1945 when it became apparent that they would not be needed to defeat Japan. The remaining 29 were commissioned between October 1944 (Tench) and February 1951 (Grenadier). The last submarine of the Tench class, as well as the last submarine which served during World War II, remaining in service with the U.S. Navy was USS Tigrone (AGSS-419) which was decommissioned on 27 June 1975.
The Tang-class submarines were the first submarines designed and built by the United States Navy after WWII. They incorporated the best features of the high-speed German Type XXI U-boat and the venerable U.S. Navy fleet submarine. The Tang-class, with the fleet submarines converted under the Greater Underwater Propulsion Power (GUPPY) program, had much higher submerged performance than their predecessors, but were quickly surpassed by the nuclear-propelled submarines that entered service beginning in 1954. Six units in total were built.
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Air-independent propulsion (AIP), or air-independent power, is any marine propulsion technology that allows a non-nuclear submarine to operate without access to atmospheric oxygen. AIP can augment or replace the diesel-electric propulsion system of non-nuclear vessels.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
The history of the submarine goes back to antiquity. Humanity has employed a variety of methods to travel underwater for exploration, recreation, research and significantly, warfare. While early attempts, such as those by Alexander the Great, were rudimentary, the advent of new propulsion systems, fuels, and sonar, propelled an increase in submarine technology. The introduction of the diesel engine, then the nuclear submarine, saw great expansion in submarine use – and specifically military use – during World War I, World War II, and the Cold War. The Second World War use of the U-Boat by the Kriegsmarine against the Royal Navy and commercial shipping, and the Cold War's use of submarines by the United States and Russia, helped solidify the submarine's place in popular culture. The latter conflicts also saw an increasing role for the military submarine as a tool of subterfuge, hidden warfare, and nuclear deterrent. The military use of submarines continues to this day, predominantly by North Korea, China, the United States and Russia.
Seehund, also known as Type XXVII, was a midget submarine built by Nazi Germany during World War II. Designed in 1944 and operated by two-man crews, it was used by the Kriegsmarine during the closing months of the war, sinking nine merchant vessels and damaging an additional three, while losing 35 boats, mostly attributed to bad weather. The French Navy used four captured boats after the war until 1953.
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A teardrop hull is a submarine hull design which emphasizes submerged performance over surfaced performance. It was somewhat commonly used in the early stages of submarine development, but was gradually abandoned in the early 20th century in favour of designs optimized for high performance on the surface as a result of changes in operational doctrine. Although naval doctrine changed, design practices remained until the later parts of World War II when the German Kriegsmarine suffered ever-growing losses of submarines in the Battle of the Atlantic.
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