Author : Aditya Bhan

Expert Speak India Matters
Published on Aug 30, 2022
The Indian Navy must revisit the fundamental question of whether it wants the newest air-independent propulsion architecture or the newest propulsion technology.
Project-75I Submarine Acquisition: Should the Indian Navy Relax Air-Independent Propulsion Requirement?

With Russia pulling out of the race for building six state-of-the-art diesel-electric submarines for the Indian Navy under the Project-75 (India) or P-75I programme, five of six original equipment manufacturers (OEM) that were in contention have now pulled out. Although the only remaining vendor—a South Korean OEM—does have a proven fuel cell air-independent propulsion (AIP) system, a stated requirement under the programme, the single-vendor situation has understandably led to uncertainty over the fate of India’s ambitious submarine acquisition programme.

A German OEM, also possessing a demonstrated fuel cell AIP architecture, was earlier a frontrunner under P-75I but withdrew from the programme last year. The OEM cited as unfeasible clauses relating to indigenous content and nearly unlimited liability on the foreign technology partner.

The indigenous AIP is still under development on a test bed and is unlikely to be installed on P-75I vessels, given the Indian Navy’s insistence on a proven architecture for this class.

While it could be tempting to argue a case in favour of utilising indigenously developed fuel cell AIP in P-75I submarines, these are more likely to be installed in the preceding Kalvari-class submarines once ready. The indigenous AIP is still under development on a test bed and is unlikely to be installed on P-75I vessels, given the Indian Navy’s insistence on a proven architecture for this class.

Russia’s Exit

While announcing its decision to pull out of the programme, Russia pointed out that no naval force possesses the kind of submarines sought by the Indian Navy, and the vessels have to consequently be designed and constructed from inception. “The Swedish were the first one to pull out of the project, then Germany, and now France. We are also not participating,” said the deputy-director general of the Russian OEM while speaking at the Army 2022 defence exhibition in Moscow. Underscoring the Russian OEM’s 120-year long history of designing ships and submarines, he stated that the greatest difficulty always lies in constructing the first vessel, and this would be impossible to complete within the short time period specified in the programme’s request for proposal (RFP).

The senior Russian official added that “The key requirement (in the RFP) is that submarines have to be constructed in India. If timelines are not met, the penalty is very high. From the very beginning we have been saying it is not possible to make the first submarine in such a short time. This concern was not considered and an RFP was issued. And hence Russia informed the Indian Navy about its unwillingness to participate.” He also stated that many systems to be integrated with the submarines, including AIP and propulsion motors, are yet to be manufactured or tested in India, further rendering the stipulated timelines prohibitive.

The Case for AIP

The AIP requirement is deemed critical by the Indian Navy because it would grant its conventionally powered submarines increased underwater endurance. The technology would enable these diesel-electric submarines to stay submerged for over a fortnight, compared to two-to-three days for current conventional submarines. In fact, the Indian Navy’s regional rival—the Pakistan Navy—also operates three AIP-installed French-origin Agosta 90B submarines and is going to be supplied with eight AIP-equipped Type 039 submarines by China, beginning in the later part of this decade.

The closed-cycle steam turbine-based French MESMA AIP system on the Pakistan Navy’s Agosta 90B submarines.

Commodore Anil Jai Singh (Retd.), Vice President of the India Maritime Foundation, stresses the need for AIP in operations and during war, especially in dense anti-submarine warfare environments. The former Indian Navy officer has emphasised in the past the need to guarantee that each foreign OEM participating in the tender offers a proven AIP. According to the former submariner, “The P-75I submarines are unlikely to enter service before the early 2030s, by which time technology would have advanced even further and the AIP-lead acid battery combination would have been superseded by the AIP–lithium-ion battery combination which would provide additional capability to the submarines.”

Drawbacks

Despite the afore-discussed ability to enable submarines to remain submerged for longer durations, there are also significant pitfalls of using AIP systems. The length of the submarine has to be increased to insert the AIP module which, in turn, makes the vessel heavier and markedly slower.

Further, refuelling of the AIP system can only be conducted in a specific facility at the home port. This implies that unlike air intakes, AIP systems cannot be charged at sea once discharged, thereby severely limiting the operational range and profile of the submarines largely to coastal defence.

Again, all AIP architectures other than those using fuel cells feature many moving parts which produce noise, and thereby, compromise the submarine’s stealth. Consider, for instance, the closed-cycle steam turbine-based French MESMA AIP system on the Pakistan Navy’s Agosta 90B submarines. This architecture enables faster underwater speeds but at the cost of lower efficiency, faster rate of oxygen consumption, and high systemic complexity.

For that matter, even more recent AIP architectures utilising Sterling cycle engines, such as the Soryu class of Japan and the Yuan class of China, grant submarines with submergence capacity only comparable to lithium-ion batteries. Although fuel cell AIP offers better submergence than Sterling engines, the high power output of lithium-ion batteries allow submarines to travel underwater for extended durations at faster speeds, a critical ability for avoiding retaliatory strikes after attacking surface targets.

The above exhortation naturally entails that the technology avoids obsolescence for at least the next two decades, which limits it to fuel cell-based solutions of which only two proven options are available globally.

While the tendencies of lithium-ion batteries to “run away”, overcook themselves, and catch fire would be a nightmarish concern on a submarine packed with hundreds of batteries in close proximity, Japan has made significant investment in ensuring greater protection and dependability. This has been achieved through utilisation of upgraded battery-cell matrices featuring hardened drivers, stabilised chemicals, as well as automatic fire extinguishers. it only seems reasonable to expect technical features of lithium-ion propulsion to improve in future.

Moreover, while fuel cell AIP possesses many virtues, it is highly costly to purchase and sustain compared to AIP architectures like the Sterling engine. For instance, Sterling engines feature lower refuelling costs than fuel cells because of the easy obtainability of diesel.

Finally, proven fuel cell AIP systems are available with only two OEMs of which one has exited the P-75I competition.  The only remaining OEM is also highly unlikely to be able to meet the infeasible terms of the Indian Navy’s submarine tender.

The Way Forward

From the Indian Navy’s insistence on an AIP architecture, it appears that extended submergence durations are deemed more critical than the ability to quickly escape on detection post firing at enemy combatants. Moreover, the above exhortation naturally entails that the technology avoids obsolescence for at least the next two decades, which limits it to fuel cell-based solutions of which only two proven options are available globally. This has led to a single-vendor situation.

The Indian Navy must, therefore, revisit the fundamental question of whether it wants the newest AIP architecture or the newest propulsion technology, especially in light of the recent advancements and the immense potential of lithium-ion battery-based propulsion technology. In the answer to this question may lie the fate of the P-75I programme.

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Author

Aditya Bhan

Aditya Bhan

Dr. Aditya Bhan is a Fellow at ORF. He is passionate about conducting research at the intersection of geopolitics national security technology and economics. Aditya has ...

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