India’s conventional submarine programme is increasingly being shaped around two parallel requirements: acquiring a new generation of long-endurance boats while preventing the existing submarine-production ecosystem from losing momentum. The proposed ₹80,000-crore-plus Project-75(I) programme with Germany’s Thyssenkrupp Marine Systems (TKMS) addresses the first requirement, while a possible 3-boat follow-on order for the Kalvari class would address the second.
Defence Secretary Rajesh Kumar Singh has described the P-75(I) negotiations as being in their final stages, placing the programme in the broader context of India’s effort to expand underwater capability. The two programmes should not therefore be viewed as competing purchases. They represent different time horizons: P-75(I) is the long-cycle capability jump; additional Kalvari submarines are the near-term fleet and industrial bridge.
The Impending CCS Clearance: Navigating the Final Laps of the MDL–TKMS Deal
Project-75(I) has taken years to reach its present stage because the programme combines submarine acquisition with substantial technology transfer and indigenous construction requirements.
Under the proposed arrangement, Mazagon Dock Shipbuilders Limited (MDL) would construct six submarines in India with TKMS as the foreign technology partner. The programme is designed around a strategic partnership model rather than a conventional off-the-shelf purchase, making commercial negotiations, technology-transfer provisions and Indian-content requirements particularly significant.
The final approval process also needs to be distinguished from the negotiations themselves. Completion of commercial negotiations does not automatically constitute a contract award; the proposal still has to pass the government's financial and approval mechanisms before the Cabinet Committee on Security (CCS) provides the final sanction.
That distinction matters because the P-75(I) construction timeline remains long even after approval. A new submarine design, production tooling, technology absorption and supplier qualification mean that the first boat cannot enter service immediately after the contract is signed. The programme is consequently a long-term fleet-replacement mechanism, not an immediate answer to submarine-force attrition.
Countering the Hangor Threat: The Urgent Force-Level Math in the IOR
The operational case for accelerating India's submarine programme is closely connected to the changing underwater balance in the Indian Ocean Region.
Pakistan is acquiring eight Hangor-class submarines based on the Chinese Type 039B design, with construction divided between China and Pakistan. These boats are intended to provide Pakistan with a modern conventional submarine force featuring air-independent propulsion and greater submerged endurance.
India, meanwhile, has to manage an ageing conventional fleet alongside the newer Kalvari-class submarines. The Sindhughosh and Shishumar classes represent earlier generations of submarine technology, and ageing hulls inevitably create availability constraints through refits, maintenance and eventual retirement.
The strategic problem is therefore one of available hulls rather than headline fleet size. A submarine undergoing major refit is not available for patrol, while a boat approaching the end of its service life cannot be treated as equivalent to a newly commissioned platform.
P-75(I) addresses this long-term deficit, but its delivery schedule means that India cannot rely on it alone. A supplementary Kalvari order would provide additional hulls sooner while sustaining the industrial base required to construct them.
Fleet Matrix: Project-75(I) vs Follow-On Kalvari
| Parameter | Project-75(I) — 6 Submarines | Follow-On Kalvari — 3 Additional Boats |
|---|---|---|
| Estimated Outlay | ~₹80,000 crore-plus, subject to final contract | Public estimates vary; final cost requires formal approval |
| Foreign OEM Partner | Thyssenkrupp Marine Systems (TKMS), Germany | Naval Group, France |
| Indian Shipbuilder | Mazagon Dock Shipbuilders Limited | Mazagon Dock Shipbuilders Limited |
| Submarine Category | Larger ocean-going conventional submarine | Kalvari/Scorpene-class conventional attack submarine |
| AIP | New-build fuel-cell AIP architecture | Indigenous DRDO AIP planned for integration/retrofit |
| Primary Function | Long-term fleet modernisation and extended submerged endurance | Nearer-term fleet reinforcement and industrial continuity |
The Technology Delta: TKMS Fuel-Cell AIP vs Indigenous Kalvari AIP
Air-independent propulsion is central to the distinction between conventional submarines and their operational endurance.
The P-75(I) requirement is intended to deliver submarines with an advanced AIP system integrated into the platform from the outset. TKMS has extensive experience with fuel-cell AIP, including its Type 214 family. Fuel-cell systems allow submarines to generate electricity without relying continuously on atmospheric oxygen, substantially extending submerged endurance compared with conventional battery-only operations.
The Kalvari programme represents a different technology pathway. India is developing a DRDO fuel-cell-based AIP system intended for installation on the Scorpene/Kalvari class. The system is based on phosphoric-acid fuel-cell technology and is intended to be retrofitted to existing submarines during major refit cycles.
This creates an important industrial advantage: India can use the Kalvari fleet to introduce indigenous AIP technology progressively while P-75(I) brings a more advanced foreign-developed AIP architecture into a new submarine class.
The two approaches therefore serve complementary purposes. One prioritises new-build long-endurance capability; the other provides a pathway for increasing the submerged endurance of an established Indian submarine fleet.
The 3-Boat Scorpene Option: Preventing Mazagon Dock’s Submarine Assembly Line from Going Cold
The proposed three-boat Kalvari follow-on has an industrial rationale that extends beyond simply adding three submarines.
MDL has developed specialised submarine construction expertise through the existing Scorpene programme, including hull fabrication, systems integration, testing and the coordination of a domestic supplier network. If there is a prolonged gap between completion of the existing Kalvari programme and the start of P-75(I) production, some of that capability could become underutilised.
This is the classic submarine-line hibernation problem. Unlike conventional shipbuilding, submarine construction depends heavily on specialised skills and tightly controlled manufacturing processes. Rebuilding an experienced workforce after a prolonged production gap can itself introduce delays.
An additional three-boat order could therefore function as a bridge between programmes. It would allow MDL to retain specialised capacity while P-75(I) moves through technology transfer, design adaptation and production preparation.
The trade-off is cost. Ordering additional Scorpenes while simultaneously funding P-75(I) creates a substantial near-term financial requirement. The justification consequently rests on fleet availability and industrial continuity rather than simply increasing the number of submarines on paper.
India’s dual-track approach is ultimately an exercise in time management. Project-75(I) is intended to provide the next major step in conventional submarine capability, but its construction cycle means the first boats will arrive only years after contractual approval. Additional Kalvari submarines could narrow that interim gap while preserving MDL’s specialised production workforce and supplier network.
The larger strategic issue is therefore not whether India needs one programme or the other. It is whether the Navy can maintain sufficient available submarine hulls throughout the transition between generations.
A successful strategy would connect the two programmes rather than treat them as isolated acquisitions: Kalvari follow-ons sustain near-term numbers and industrial continuity, indigenous AIP upgrades improve the existing fleet, and P-75(I) establishes the next-generation conventional submarine capability.
.jpg)
0 Comments