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Has the Indian Navy’s AIP Riddle Been Solved?

Extended underwater operations is a niche capability that every naval force aspires to acquire. For the Indian Navy which sees itself as the predominant and so far unrivalled maritime force in the Indian Ocean region such a capability was increasingly being questioned given the numbers and state of its submarines. There appears to be some light at the end of the tunnel now.

On the day the Indian Navy commissioned INS Vagir, fifth in the Scorpene or Kalvari series of submarines, India’s Ministry of Defence announced that Fuel Cell-based Air Independent Propulsion (AIP) system of DRDO’s Naval Materials Research Laboratory (NMRL) will soon be fitted onboard INS Kalvari.

INS Kalvari is first of the submarines of the series by the same name also referred to as the Scorpene class the French name is due for a refit and the AIP is expected to be fitted in this process.

Advantages of AIP

As per the Ministry of Defence press release, “AIP has a force multiplier effect on lethality of a diesel electric submarine as it enhances the submerged endurance by several folds. It has merits in performance compared to other technologies and is unique as the hydrogen is generated onboard”.

It is well known that diesel electric submarines have limited underwater endurance, particularly at high speed. When they come up for operating their diesel engines by snorkelling they can be detected.

Use of nuclear power is one option but that is expensive and has attendant problems of nuclear waste disposal.

The AIP is a cheaper option that allows a submarine to run its electric motor and other electrical systems without using the batteries. Thus the submarine does not have to surface to recharge batteries.

Development by DRDO

AIP technology has been successfully developed by Naval Material Research Laboratory [NMRL] with the support of Indian industry partners and is said to have reached the stage of maturity for industrialisation.

“It is an non-nuclear alternative. While one incorporates a phosphoric acid fuel cell (PAFC), another has a polymer electrolyte fuel cell. It provides longer endurance under submerged conditions by supplementing the lead acid batteries,” a DRDO official was quoted by the Hindu Businessline in 2017.

The official also provides alternative technologies being used by other countries to include, “Germany has PEMFC (Proton Exchange Membrane Fuel Cells) technology which is in use by many countries, while Russia's AFC is a diesel reformer, at prototype level. Similarly, France and Spain's PEMFC (Polymer Electrolyte Membrane Fuel Cells) is a diesel reformer at prototype level. DRDO, on the other hand, has a PAFC Borohydride, an advanced prototype”

Present Initiative

An agreement was signed between senior officials of NMRL and Naval Group France in Mumbai on January 23, 2023 to extend cooperation to enter into the detailed design phase for integration of indigenous AIP in the Kalvari class submarines.

As part of the agreement, Naval Group France will certify the AIP design for integration in the submarines. This comes even as land-based prototype of the NMRL’s AIP has already been tested successfully.

Future Roadmap

As a part of its undersea warfare capabilities, the Indian Navy’s quest for fielding 24 -30 submarines in multiple configurations is expected to continue in the long term.

This could fructify into conventional non nuclear powered submarines through AIP or other advance technology in the future and nuclear powered ones.

The success of integration of AIP in the Kalvari class would be a precursor to inducting the same in the next generation submarines the 75 I series which could be six in number.

When successfully executed the Navy will have strengthened its underwater capabilities substantially which if the programmes are sustained consistently by 2050 or so.

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