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See:
h t t p://www.navyleague.org/seapower/aip_alternative.htm
The four main types of AIP are:
1) Stirling engine. This is the Swedish AIP option. It burns diesel and liquid oxygen and acts via a closed cycle piston engine which uses an inert gas such as helium. The gas is alternately heated and cooled and the movement of gas is used to power a piston, which is used to run a motor to charge batteries. Stirling AIP has been to sea in the Swedish Nacken and Gotland class submarines.
2) Closed cycle diesel. This uses a supply of liquid oxygen and an inert gas such as argon. The argon is mixed with the oxygen to make artificial air. This is then used as an oxidizer to run the submarine's normal diesels under water. The argon is recovered at the end of the process to mix with more liquid oxygen. I think the Russians and Germans have worked on this type of AIP.
3) MESMA is a French steam turbine based AIP. A fuel (diesel or ethanol) and an oxidizer (liquid oxygen) are burnt to make steam to power a fairly normal steam turbine.
4) Fuel cell. This consumes oxygen and hydrogen and produces water and electricity. The Germans have developed an operational fuel cell AIP on the type 212 and 214 submarines. I think the Russians have also developed fuel cells for submarine AIP.
Of these options, the closed cycle diesel and the Stirling engine involve running a piston engine. So that they might generate noise. The MESMA runs a steam turbine. So it would probably generate as much noise as a nuclear submarine, though the collant pumps might generate more noise on a nuclear submarine. A fuel cell has no moving parts. So it should be fairly quiet.
Note that the original AIP, the German Walter turbine from WWII, is not on the list. This involved running highly volatile and corrosive hydrogen peroxide fuel over a catalyst. The peroxide broke down into water and oxygen and released large amounts of energy. Because of the energy, the water was in the form of steam. Because of the oxygen generated, a fuel, such as diesel could also be injected to cause further combustion. The result of both these combustions was used to drive a turbine. This type of AIP propulsion was experimented with by the Germans in WWII, and both the Russians and British after WWII but was considered dangerous due to the corrosive and explosive nature of the fuel.
Artificial Air But Tangible Improvements
Key Data
Crew
42 (including 6 officers)
Dimensions
Length
78m
Beam
8m
Draught
7m
Displacement
3,050t (surfaced)
3,350t (dived)
Performance
Speed
Surfaced - 10kt
Snorting - 10kt
Dived - 20kt
Range
At 10kt surfaced - 11,500 miles
At 10kt snorting - 9,000 miles
At 4kt dived - 400 miles
Weapon Systems
Surface-to-Surface Missile
Sub Harpoon
Torpedoes
6 x 533mm tubes for Harpoon and Gould mk 48 torpedoes - total of 22 carried
Mines
Up to 44 (in place of torpedoes)
Combat Data System
Rockwell Australia combat system, being replaced with Ratheon CCS mk 2
Countermeasures
ESM
EDO ES-5600 ESM, ARGO AR-740
Decoys
Strachan and Henshaw SSDE
Radar
Kelvin Hughes I-band navigation radar
Sonar
Thales Underwater Systems Scylla bow sonar
Thales underwater Systems Kariwara or Namara towed array
Periscopes
Thales optronics CK043 search and CH093 attack periscopes
Propulsion
Engines
3 x Hedemora / Garden Island type V18B/14 diesel engines, 1,475kW each
Generators
3 x Jeumont Schneider 440V generators, 1,400kW each
Motors
1 x main motor, 5,250kW
1 x Mactaggart Scott DM 43006 hydraulic motor for emergency propulsion
Increased submerged enduranceThe Kockums Stirling AIP system considerably increases the submerged endurance.
The systems offers an alternative to battery power, which in turn means less frequent requirements for noisy battery recharging, with the diesel generators.
Instead of a number of days, a Stirling AIP submarine can extend the time submerged to weeks and thus outperform any other conventional submarine with regard to that key capability - submerged endurance.
Outstanding advantagesThe main feature of the Kockums air independent propulsion (AIP) system is the use of Stirling engines burning pure oxygen and diesel fuel in a pressurized combustion chamber.
The combustion pressure is higher than the surrounding seawater pressure, thereby allowing the exha