Internal oxygen supply
History
In 1867 Narcís Monturiol i Estarriol successfully developed an early form of anaerobic air independent propulsion. In 1908 the Imperial Russian Navy launched the Pochtovy submarine which used a gasoline engine fed with compressed air and exhausted under water.
During World War II the German firm Walter experimented with submarines that used concentrated hydrogen peroxide as their source of oxygen underwater. These used steam turbines, employing steam heated by burning diesel fuel in the steam/oxygen atmosphere created by the decomposition of hydrogen peroxide by a potassium permanganate catalyst.
Several experimental boats were produced, and one, U-1407, which had been scuttled at the end of the war, was salvaged and recommissioned into the Royal Navy as HMS Meteorite. The British built two improved models in the late 1950s, HMS Explorer, and HMS Excalibur.
The Soviet Union also experimented with the technology and one experimental boat was built. Hydrogen peroxide was eventually abandoned since it is highly reactive when in contact with various metals, is volatile, and submarines had a high rate of consumption. Both the British and the Soviets, the only countries known to be experimenting with it, abandoned it when the United States developed a nuclear reactor small enough for submarine propulsion.
It was retained for propelling torpedoes by the British and the Soviet Union, although hastily abandoned by the former following the HMS Sidon tragedy. Both this and the loss of the Russian Submarine Kursk were due to accidents involving hydrogen peroxide propelled torpedoes.
[edit] Closed cycle diesel engines
This technology uses a submarine diesel engine which can be operated conventionally on the surface, but which can also be provided with oxidant, usually stored as liquid oxygen, when submerged. Since the metal of an engine will burn in pure oxygen, the oxygen is usually diluted with recycled exhaust gas. As there is no exhaust gas upon starting, argon is used.
During World War II the Kriegsmarine experimented with such a system as an alternative to the Walter peroxide system, including a variant of the Type XXVIIB Seehund midget submarine, the "Klein U-boot". It was powered by a 95 hp Diesel engine of a type commonly used by the Kriegmarine and which was available in large numbers, supplied with oxygen from a tank in the boat's keel holding 1,250 litres at 4 atm (410 kPa). It was thought likely that the boat would have a maximum submerged speed of 12 kn (22 km/h; 14 mph) and a range of 70 mi (110 km), or 150 mi (240 km) at 7 kn (13 km/h; 8.1 mph).
The German work was subsequently expanded upon by the Soviet Union who invested heavily in this technology, developing the small 650 ton Quebec-class submarine of which thirty were built between 1953 and 1956. These had three diesel enginestwo were conventional and one was closed cycle using liquid oxygen.
In the Soviet system, called a "single propulsion system", oxygen was added after the exhaust gases had been filtered through a lime-based chemical absorbent. The submarine could also run its diesel using a snorkel. The Quebec had three engines: a 32D 900 bhp diesel on the centre shaft and two M-50P 700 bhp diesels on the outer shafts. In addition a 100 hp "creep" motor was coupled to the centre shaft. The boat could be run at slow speed using the centreline diesel only.[2]
Because liquid oxygen cannot be stored for any great length of time these boats could not operate far from a base. It was also a dangerous system; at least seven submarines suffered explosions, and one of these, M-256, sank following an explosion and fire. They were sometimes nicknamed cigarette lighters. The last was scrapped in the early 1970s.
The German Navy's former Type 205 submarine U1 was fitted with an experimental 3000 horsepower (2.2 MW) unit.
[edit] Closed cycle steam turbines
The French MESMA (Module d'Energie Sous-Marine Autonome) system is being offered by the French shipyard DCNS. MESMA is available for the Agosta 90B and Scorpène class submarines. It is essentially a modified version of their nuclear propulsion system with heat being generated by ethanol and oxygen. A conventional steam turbine power plant powered by steam generated from the combustion of ethanol (grain alcohol) and stored oxygen at a pressure of 60 atmospheres. This pressure-firing allows exhaust carbon dioxide to be expelled overboard at any depth without an exhaust compressor.
Each MESMA system costs around $5060 million. As installed on the Scorpène, it requires adding a new 8.3 meter (27 foot), 305 tonne hull section to the submarine, and results in a submarine able to operate for greater than 21 days underwater, depending on variables like speed, etc.[3][4]
An article in Undersea Warfare Magazine notes that: although MESMA can provide higher output power than the other alternatives, its inherent efficiency is the lowest of the four AIP candidates, and its rate of oxygen consumption is correspondingly higher.[5]
[edit] Stirling cycle engines
The Swedish shipbuilder Kockums has constructed three Gotland class submarines for the Swedish Navy which are fitted with an auxiliary Stirling engine which uses liquid oxygen and diesel fuel to drive 75 kilowatt generators for either propulsion or charging batteries. The AIP endurance of the 1,500 tonne boats is around 14 days at five knots (9 km/h).
Kockums has also delivered Stirling engines to Japan. The new Japanese submarines will all be equipped with Stirling engines. The first submarine, Sōryū, in the class was launched on 5 December 2007 and were delivered to the navy in March 2009.
[edit] Fuel cells
Type 212 submarine with fuel cell propulsion of the German Navy in dock
Siemens has developed a 30-50 kilowatt fuel cell unit. Nine of these units are incorporated into Howaldtswerke Deutsche Werft AG's 1,830t submarine U31, lead ship for the Type 212A class of the German Navy. The other boats of this class and HDW's AIP equipped export submarines (Type 209 mod and Type 214) use two 120 kW modules, also from Siemens.[6]
After the success of Howaldtswerke Deutsche Werft AG's in its export activities, several builders have developed their own fuel-cell auxiliary units for submarines but until today[clarification needed] no other shipyard has a contract for a submarine so equipped.
[edit] Nuclear power
Nuclear reactors have been used for 50 years to power submarines, the first being USS Nautilus. The United States, France, the United Kingdom, Russia, the People's Republic of China, and India are the only countries known to operate nuclear powered submarines. Five of these six countries also have permanent seats on the United Nations Security Council and are the only countries allowed to possess nuclear weapons according to the Nuclear Non-Proliferation Treaty. India has only in 2009 completed construction of its first domestically built nuclear submarine. India in the past has leased a Charlie class nuclear powered submarine from Russia and plans to acquire two used Akula class submarines which would be used for training purposes. Brazil is also known to research nuclear propulsion for submarine use. However, Air Independent Propulsion is a term normally used in the context of improving the performance of conventionally propelled submarines.
There have nevertheless been suggestions for a reactor as an auxiliary power supply, which does fall into the normal definition of AIP. For example, there has been a proposal to use a small 200 kilowatt reactor for auxiliary power (styled a "nuclear battery") to improve the under-ice capability of Canadian submarines.
