An Assessment Of Different Submarines Powered By AIP System That Indian Navy Has To Choose From


The Project 75I-class submarine is a follow-on of the Project 75 Kalvari-class submarine for the Indian navy. Under this project, the Indian Navy intends to acquire 6 diesel-electric submarines, which will also feature advanced Air Independent Propulsion (AIP) systems to enable them to stay submerged for longer duration and substantially increase their operational range.

The six new submarines for the P-75I project is the next phase of the same submarine project and will be worth over $ 11.10 billion.

India is poised to select a partner for co-development of Air-Independent-Propusion System based Submarines. Even the Scorpene class submarines will be retrofitted to AIP system. So it would be interesting to look at the options available to Indian Navy.


Sweden was the first to develop Gotland class submarines that use AIP-based system. They use sterling cycle based AIP system. A Gotland class submarine got the world in awe of AIP system when in a naval exercise it was reported to have locked on an American Nuclear Submarine without giving out its location. The tongues were set wagging that Nuclear Submarines were afterall not the only ultimate weapon when it came to sea-warfare.
Gotland class submarine has a displacement of 1599 tonnes. Speed when submerged is 37km/h and Surface speed is 20km/h. It carries 4 torpedo tubes for 533 mm torpedos, 2 for 400 mm torpedoes and in addition carries 48 externally mounted mines.
China is developing sterling cycle based AIP system with the help of Sweden for its submarines. Moreover Indian scientists believe that their own Phosphoric Acid Fuel Cell (PAFC) based AIP system is more advanced than Sterling cycle, so India is not very keen on this



SAAB A-26 :

Saab’s A26 submarine has a proven modular design and silent long-endurance. A26 uses the latest stealth technology and advanced tactical communication to allow submarines to integrate their communications with those of other defence forces. Operational flexibility, together with a comprehensive weapons suite, enables it to carry out a wide variety of missions like Maritime security operations, Intelligence operations, Covert mine countermeasure operations, Special operations by carrying, deploying and retrieving special forces along with equipment and underwater vehicles, Underwater work, Anti-submarine & anti-surface warfare, Mine-laying in covert mode.

The A26 submarines fair very well on paper, but not even a single A26 submarines has been commissioned till date. These submarines are not time proven as others in the category.

Saab’s A-26 is still under development and has delayed many times. It is not in service in any nation’s navy, not even in Swedish Navy. Buying of A-26 will be a bad gamble by the Indian Navy.



It employs more expensive and complicated to refuel Siemens Proton Exchange Membrane (PEM) compressed hydrogen fuel cells based AIP system. But it gives greater power output. There are fewer moving parts that give out lesser noise and hence it is more stealthy to accoustics-based sonars of the rival. Hull of 212A is made of non-magnetic materials. Hence it cannot be detected by Magnetic anomaly detectors. The softer hull means its operational depth is 200 metres.
212A has a displacement of 1800 tonnes. It can achieve an under-water speed of 37km/h though sustainable speed using AIP system is 14.5 km/h. Range of this submarine is 15000 km at speed of 15km/h. Endurance is 30 days. German submarine’s X-shaped rudder allows it to operate in waters as shallow as 17 metres. So advantage vis-a-vis India is that such submarines can alight naval commandos like Marcos close to the shore for swifter missions.
Armaments include 13 torpeodes of 533mm specification that can be fired from 6 torpedo tubes. Connected to the submarine by a fibre optic cable means they can have more than 1 take on the target. Torpedos have a range of 50km. In addition, it can carry 24 mines.
German Navy is also at an advanced stage of developing IDAS fibre-optic missiles that can be fired from four-cell magazines in the torpedo tubes. Based on IRIS-T air to air missiles they can shoot down aircrafts or even surface ships 20 km away.



Naval Group’s Scorpene submarines are designed for all types of mission, such as surface vessel warfare, anti-submarine warfare, long-range strikes, special operations or intelligence gathering.

With 14 Scorpenes sold to various nations including India, the Naval Group are looking to extend the sale by bagging Project 75I.
Scorpene are may be the runner-up in the Project 75I. Scorpenes are amongst most advanced submarines. But since India already has ordered 6 of them, India might wanted to buy some other variety than Scorpenes. The Scorpene data leak in 2016, may also keep Indians away from future Scorpenes order.




While Process to initiate Project 75I tender was started in 2014, Navy is yet to select an Indian shipyard nor any foreign original equipment manufacturer has been selected for the program to move forward. Due to delays in implementing Strategic partnership (SP) model and due to long cumbersome procurement procedure adopted to execute the project, many in Indian Navy fear that Project 75I too will face delays of 4-6 years like its predecessor Project-75 program derailing India’s 30-Year Submarine Building Plan for induction of 24 submarines in a phased manner completely.

With China making rapid increase in its footprint in Indian ocean , Recent reports hint that Navy and Government of India are considering a proposal floated by defence PSU to use Kalvari class submarine as a template to develop a new class of submarine which will replace imported content in the submarine with local alternatives sourced from Nuclear Arihant class project.

Kalvari+ will feature DRDO developed Air-independent propulsion (AIP) system and will also incorporate Vertical launch system (VLS) to launch Submarine launched Cruise missiles (SLCM) like BrahMos and Nirbhay. Kalvari+ will have stretched midsection to accommodate VLS due to which submarine will have higher displacement and will also have improved operational range.

Kalvari+ will have higher indigenized content and will have locally developed submarine Sonar suite, periscope and other sub-systems which India can source from Arihant class project. Kalvari+ not only will reduce timeline required to manufacture this six submarines for Indian navy but it also will help Public and Private sector companies to be better prepared to gain experience and expertise before India can initiate Project-76 which is to be executed after Project 75I.



Russia in 2004 launched 2800 tonne Amur class submarine Sanket-Petersburg (B-585) that uses Oxygen/Hydrogen fuel cells giving it an endurance of 45 days.Test depth is 300 metres. 2 more are under construction. .
Russia is offering Amur-1650 to export markets like China and India in different configurations with displacement of 550 tonnes to 1850 tonnes and with different weapon systems. Amur that had a displacement of 970 tonnes had a range of 5600 km. Speed of Amur is 39 km/h when submerged and 18.5 km/h when on surface.
For armaments, Amur-1650 has 6 torpedo tubes that can fire up to 18 torpedoes of 533 mm specification or tube-launched anti-submarine and anti-ship missiles. Club-S, submarine launched cruise missiles can be fired from standard torpedo tubes. Club-S carries 400 kg warhead and can strike land and naval targets 300 km away.
Something, that shall be of importance to the readers is that Sanket-Petersburg (B-585) was rejected by Russian Navy in 2012 for having been able to produce only half the required power. In 2016, it carried out a missile test successfully. Upto what level Russia has been able to rectify the shortfalls must be kept in consideration before taking a call.




Finally we reach to a class of submarine that in my view is most powerful and Indian navy should possess. This French submarine uses Pump jet propulsion instead of propeller technology making it quieter. It combines a rotor and stator, within a duct to significantly reduce the level of radiated noise through the effects of wake harmonization and avoidance of cavitation. X- rudder further helps in this regard.
Displacement is 4700 tonnes when surfaced, when submerged may reach 5300 tonnes. Speed is 37km/h when submerged and 26 km/h on surface. Endurance at sea is 90 days. Range is 29000 km at 18.5 km/h. A very powerful sonar suite is made by reliable Thales. Operational depth is 300 metres. Under-water endurance is 21 days.
It will be capable of launching Under-water Unmanned Vehicles (UUVs) and UAVs. SMX Ocean will be equipped with 34 weapons of 5 different types including torpedoes, mines, anti-ship missiles and cruise missiles. Vertical launchers will be included. It completely realises the concept of 4D warfare.



Indian scientists themselves have developed capabilities to keep submarines submerged for 14 days. So for shallow waters we can even plan out completely indigenous smaller submarines. Australia is going for Short-fin Barracudas submarines because it doesn’t have the wherewithal to make nuclear submarines. India might begin with indigenous AIP-based submarines in the range of 1800 tonnes displacement for Project 75I. Submarines of Short-fin Barracuda class might be rather part of Project 76. It remains to be seen whether DRDO develops its own capabilities by then or eventually seeks foreign collaboration. But planning for even the same has to start from now. Because if we will start construction of a 4700 tonne submarine say by 2021, the first submarine will roll out by 2030.


Facebook Comments

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *


Adblock Detected

Please consider supporting us by disabling your ad blocker