India’s program to retrofit its Scorpene (Kalvari-class) submarines with air independent propulsion (AIP) systems, aimed at boosting stealth and operational underwater endurance, has suffered significant delays and missed milestones, reported Rajat Pandit of TOI.

The domestically developed fuel cell-based AIP system—led by DRDO’s Naval Materials Research Lab (NMRL) with L&T as a key industry partner—remains unavailable for operational integration.

As a result, the first Scorpene, INS Kalvari, will complete its current maintenance refit without the planned AIP upgrade and the system might only be ready for installation aboard the second Scorpene, INS Khanderi, during its scheduled refit in mid-2026.

The original AIP project, sanctioned in 2014 at an initial cost of ₹270 crore, was supposed to be completed by June 2017. However, it has faced recurring delays due to inability to meet operational readiness and technical maturity requirements, with the land-based prototype only recently achieving a certain level of maturity. Such retrofits require a complex “Jumboisation” process: the submarine hull is cut, the AIP plug inserted, and then the structure is reassembled with precision to restore full operational capability.

AIPs are critical because conventional diesel-electric submarines must surface or snorkel every few days to recharge batteries, risking detection. With AIP, submarines can remain submerged for up to two weeks, greatly enhancing stealth and survivability.

This is particularly urgent because Pakistan is in the process of inducting eight Yuan/Hangor-class AIP-equipped submarines from China, representing a substantial leap in regional capability. In contrast, India currently operates six French-origin Scorpene-class, seven outdated Russian Kilo-class, and four German HDW submarines, along with two operational nuclear ballistic missile submarines (SSBNs).

The repeated delays have also impacted future plans. The agreement for integrating the indigenous AIP system into the current Scorpene fleet—with crucial technical assistance from the French Naval Group—was only signed in July 2025. Meanwhile, larger contracts to build three additional Scorpene and six new-generation submarines under Project-75 India (P-75I), meant to have AIP and advanced missile capabilities, remains to be finalised. This reflects broader issues with India’s submarine procurement: structural inefficiencies, shifting strategic priorities, tender complications, and technological delays.

The Indian Navy’s pursuit of AIP-ready platforms is also complicated by their insistence on field-proven technology and concerns about over-promising from R&D agencies, resulting in drawn-out acquisition timelines and strategic vulnerabilities. Major international contenders for P-75I have balked, citing onerous indigenous partnership requirements, and the project timeline continues to slip.

The critical delays to the Scorpene AIP retrofit stem from technical hurdles with indigenous AIP development, requirements for operationally proven systems, complex retrofit logistics, and procurement process inefficiencies.

These delays are exacerbating India’s submarine fleet modernization gap at a time when both Pakistan and China are rapidly upgrading their undersea warfare capabilities, making the timely completion of the AIP project and broader submarine modernization essential for India’s naval security posture.

Based On TOI Report