Recent report by ThePrint indicate that India’s first Scorpene submarine INS Kalvari, which was commissioned in 2017, will undergo a scheduled normal refit this year but is unlikely to get an Air Independent Propulsion System (AIP) as was planned.

INS Kalvari, the first of India's Scorpene submarines, commissioned in 2017, is scheduled for a normal refit in the second half of this year; however, the refit is unlikely to include the planned Air Independent Propulsion (AIP) system due to developmental delays. The original plan intended for the 5th and 6th Scorpene submarines to be fitted with the AIP system during construction, while earlier submarines would receive it during their refits. Due to delays in the AIP development, the 5th and 6th boats were also commissioned without it.

The integration of the DRDO-built Air Independent Propulsion (AIP) system on the INS Kalvari is scheduled to begin during its refit in 2024. The Ministry of Defence (MoD) and France’s Naval Group have an agreement for this integration.

The AIP system enhances a submarine's ability to remain submerged for extended periods without surfacing, reducing the need for frequent snorkelling to recharge batteries. Trials of a land-based prototype AIP system demonstrated an endurance of 14 days in endurance mode and two days in max power mode.

Integrating the AIP system involves cutting the submarine hull in half to insert the AIP sections, which will then be welded back together. This process will increase the submarine's length and weight, requiring further testing.

The energy modules (EMs) comprising fuel cells produce the required power, along with onboard hydrogen generation. The technology of this indigenous AIP system is unique – it generates hydrogen on demand, thereby obviating the need for carrying hydrogen onboard which is a major safety concern for a submarine.

Larsen & Toubro (L&T) and Thermax will manufacture the AIP, with the French Naval Group as the lead integrator. A steel-cutting ceremony for the DRDO-developed AIP system took place at L&T's Hazira facility in December.

INS Kalvari, the first of six Scorpene-class submarines, was commissioned into the Indian Navy in December 2017. It was built under a $3.5 billion deal with the French Naval Group, with Naval Group providing technology transfer and partnership to Mazagon Dock Shipbuilders Limited (MDL).

Following successful integration on the INS Kalvari, the AIP system may be fitted on five more Kalvari-class submarines during their major refits.

There are advanced talks for a deal where the Indian Navy would acquire three additional Kalvari-class submarines that will be larger and more advanced than the initial six. MDL has submitted a techno-commercial bid promising at least 60% indigenous content in these new submarines.

INS Kalvari is likely to undergo its normal refit at the Naval Dockyard Mumbai instead of Mazagon Docks Limited (MDL), the company that originally manufactured the submarines with the French firm Naval Group (formerly known as DCNS). The Navy is favouring its own dockyard to keep costs down.

ThePrint