The Indian Navy is on the verge of finalising contract negotiations with the German firm ThyssenKrupp Marine Systems (TKMS) for the construction of six next-generation conventional submarines under the Project 75(I) or P-75(I) program.

This strategic initiative aims to significantly strengthen India's undersea warfare capabilities with submarines equipped with advanced Air Independent Propulsion (AIP) technology, allowing these vessels to remain submerged for up to three weeks, thereby enhancing stealth and endurance.

The project, estimated to cost between ₹70,000 crore to potentially ₹100,000 crore (approximately $8.3 billion to $12 billion), represents a major leap in indigenous manufacturing through the Make in India initiative, with significant technology transfer and local content build-up targeted as part of the production process at Mazagon Dock Shipbuilders Limited (MDL) in Mumbai.

The contract talks, expected to conclude within six to eight months as per the latest Defence Ministry timeline, follow the rejection of competing bids such as the L&T-Navantia alliance, primarily due to non-fulfilment of the AIP criteria. MDL is collaborating with TKMS, whose submarine design is believed to be an advanced customised variant based on the German Type 214 class, featuring a longer hull and improved acoustic stealth designed to meet Indian Navy requirements.

This marks the second time Indian submarines are of German origin, reflecting the Navy's confidence in TKMS's expertise. Production is slated to commence within three years of contract signing, with the first submarine delivery projected around 2032-33, approximately seven years after deal closure.

The P-75(I) project is not only a force multiplier for the Indian Navy but also a critical element of the country’s long-term strategic posture in the Indo-Pacific region, particularly to counter growing naval challenges posed by China and Pakistan.

The acquisition complements parallel indigenous efforts in nuclear-powered submarines spearheaded by the private sector and the Submarine Building Centre. The program additionally foresees a follow-on order for three more P-75(I) submarines, potentially replacing the older Scorpène-class vessels, which lack AIP capability and are based on an older design generation.

The deal embodies a broader vision to ensure future operational readiness through advanced stealth, endurance, and localised production, bolstering India’s maritime security and defence industrial base in the coming decades.

The Cabinet Committee on Security (CCS) clearance in August 2025 has paved way for these critical contract negotiations to officially begin by the end of August 2025 and is expected to finalise the deal within six months thereafter. This contract is among the largest for conventional submarines globally in recent years and is integral to India’s defence modernisation efforts.

AIP Integration And Operational Endurance

The integration of Air Independent Propulsion (AIP) technology significantly enhances submarines' operational endurance by allowing them to remain submerged for much longer periods compared to conventional diesel-electric submarines.

Typically, diesel-electric submarines must frequently surface or snorkel to recharge their batteries using atmospheric oxygen, limiting underwater endurance to only a few days.

AIP systems enable submarines to generate electricity underwater without needing atmospheric oxygen, extending submerged endurance from a few days to potentially up to two weeks or more, depending on the system and mission profile.

This prolonged underwater endurance reduces the submarine's need to surface or snorkel, which dramatically lowers the risk of detection from enemy sensors, thereby increasing stealth capabilities.

AIP systems, most commonly based on fuel cells, produce silent power that drives the electric propulsion system more quietly and efficiently than diesel engines, further reducing acoustic signatures.

Operationally, this allows submarines to execute longer surveillance, patrol, and combat missions with enhanced tactical flexibility and survivability in hostile maritime environments.

For example, the Indian Navy's Kalvari-class submarines fitted with DRDO's indigenous fuel cell-based AIP will see their underwater endurance increase from a few days to almost two weeks, translating into sustained stealth and operational effectiveness in complex maritime theatres.

The extension from days to weeks is a transformative force multiplier, bridging some of the endurance gaps between conventional submarines and nuclear-powered submarines without requiring nuclear propulsion. This extended endurance also supports a wider range of mission profiles, including anti-submarine warfare and special operations, making AIP integration a critical advancement for modern conventional submarine fleets.

AIP integration boosts operational endurance by three to five times or more, resulting in significantly enhanced stealth, mission duration, and tactical options for conventional submarines. This technology marks a pivotal evolution in submarine capabilities, especially for navies focused on maintaining a credible underwater deterrence with non-nuclear.

IDN (With Agency Inputs)