Navy is looking to acquire six new submarines with Air Independent Propulsion technology, which allows vessels to stay underwater for longer periods

The Navy’s insistence on a proven Air Independent Propulsion (AIP) system for its submarine acquisition program—Project 75 India, or P-75(I)—has become the focal point for the two frontrunners, Germany and Spain.

German submarine maker ThyssenKrupp Marine Systems (TKMS)—which is in talks with an American private equity firm for selling its submarine arm with a German state-run bank enjoying minority blocking rights—has tied up with India’s state-run Mazagon Dock Shipbuilders Ltd (MDL) to bid for the project.

On the other hand, Spanish submarine manufacturer Navantia has partnered with Indian private company Larsen & Toubro (L&T).

Both the German and Spanish governments have now stepped in to push for their companies as the Navy is in the final stages of finalising the AIP system’s field evaluation trials (FET).

The main point of contention is the AIP. Under P-75(I), the Navy will procure six new conventional diesel-electric submarines with AIP technology that allows the vessels to operate underwater for longer periods instead of surfacing every two or three days to recharge their batteries.

However, this is where the project—first envisaged in 1998 and cleared as part of a 30-year submarine-building plan that ends in 2030—gets into tricky waters.

AIP Evaluations

Sources in the defence establishment stated that neither company, during the FET, was able to present a proven AIP of the size and capacity the Navy had mentioned in its request for proposal (RFP) documents.

While Navantia’s AIP parameters come closest to the Navy’s requirements, its first submarine with the technology will only be out in 2026, a fact the Indian authorities knew from the beginning.

Navantia showcased its AIP using a mix of land and onboard systems for the FET, but it is up to the Navy to decide if it considers this proven, even though the system has undergone over 50,000 hours of testing and has been selected by the Spanish Navy.

The AIP showcased by TKMS was smaller than the Navy wanted. This is because the AIP is fitted on board the Type 214 submarines, which are smaller than the ones required by the Navy and hence need a smaller pack of the AIP system.

Sources said this means TKMS will have to develop a bigger AIP system. The fuel cell batteries on board the German submarines are manufactured by a different firm and TKMS has offered its own for the Indian contract, which means the battery performance will have to be tested again, sources said.

“Both the companies don’t meet the complete requirements as sought by the Indian Navy in the RFP but both are good and can deliver. The Spanish would be a faster one since they already have the larger S-80 class and were inducted into the Spanish Navy and will undergo minor design tweaks. TKMS will have to design the submarine completely,” a source said.

Sources said the Navy had insisted on proven AIP technology because it feared the Defence Research and Development Organisation (DRDO) would say it could offer the systems it was developing indigenously, which would delay the program further.

India is building six Scorpene-class submarines, with the fifth and sixth to have an indigenous AIP system, but both have missed their deadlines.

The plan was then tweaked for the first Scorpene-class submarine coming into refit next year to be integrated with an AIP system. However, it is not certain because trials are still on, sources said.

Navantia uses the latest-generation Bio Ethanol Stealth Technology for its AIP with bioethanol as a fuel, making it both environmentally friendly and easy to refuel as bioethanol is easily available across the world.

Bioethanol’s availability makes it easy to refuel an AIP plant at any port without needing specialised hydrogen refuelling systems, unlike previous generation AIP plants offered by TKMS, which require handling of pure hydrogen.

Navantia’s AIP plant is also relatively safer as hydrogen is produced on demand and not stored on board, unlike the other technology where hydrogen is stored and carried in the form of metal hydrides.

Navantia’s AIP plant has been cleared by the Spanish Navy for installation on board its third S-80 class submarine, thereby demonstrating the technological readiness of the system.

Price Discovery Could Be Key

While both TKMS and Navantia have bid for the project, the Germans will have to design a completely new submarine for the Navy, whereas the Spanish are offering the latest S-80 class of submarines, inducted into their Navy in 2023.

The S-80 class is among the latest conventional submarines in the world. With a displacement of close to 3,000 tonnes and a hull diameter of 7.2 metres, it is almost identical to the Indian Navy’s specifications, it is learnt.

Given the size and space, the submarine packs a staggering level of automation, enabling the entire submarine to be operated by a significantly smaller crew strength than smaller submarines.

Sources in the Indian defence establishment admitted that the S-80 class would require minimal redesign for the programme, unlike the other platforms in the fray, as its design and specifications were closest to P75(I) requirements.

Sources said the FET was undertaken after the bids by the German and Spanish companies were technically cleared by the Navy.

It is learnt that the Spanish submarine maker argued with the Navy and the Indian defence ministry that there should be a price discovery, meaning that the bids of both firms should be opened up rather than just going by the FET.

The Chequered Past of The P-75(I)

The project was first envisaged in 1998 and is part of the Navy’s 30-year submarine-building plan to build 24 submarines by 2030.

However, only six submarines have been built so far under Project 75.

The P-75(I) program is being pursued under the strategic partnership (SP) model, which aims to encourage broader participation by the private sector, in addition to defence PSUs and the Ordnance Factory Board (OFB), in the manufacture of defence platforms and equipment such as aircraft, submarines, helicopters and armoured vehicles.

And this is where the problem lies, private industry sources say.

In the submarine project, the frontrunner is the state-run MDL, which has tied up with TKMS, and not a private firm for which the strategic partnership was envisaged. L&T had initially tied up with TKMS to bid for the project.

Other foreign contenders dropped out of the race because of the Navy’s strict conditions.

Swedish group Saab and Russia’s Rosoboronexport Rubin Design Bureau pulled out as they were both against foreign partners being liable for any delays or accidents even though the contract was with the Indian entity.

Even TKMS was not keen on the project initially but changed its mind after the German government came in to back the project and the Navy diluted some of the contentious provisions.

The French dropped out because they did not have a proven AIP system. The South Koreans did have one but stayed out of the bidding process because the Daewoo shipyard was undergoing an acquisition process.

(With Input From Agencies)