Project 75 Kalvari Class SSK: News & Discussion

[Rakesh]

Starting this thread, because we do not have a dedicated thread on the topic.

[Rakesh]

Indian Navy's first AIP-equipped submarine to be ready by year-end
https://www.business-standard.com/exter ... 080_1.html
06 March 2026

Between December 2017 and January 2025, six Kalvari-class conventional diesel-electric attack submarines were commissioned into service.

[Rakesh]

Three additional Kalvari Class (Project 75AS - Advanced Scorpene) boats still on the menu

https://x.com/sougat18/status/2031615318519583107?s=20 ---> Major Planned Shipbuilding Programs of the Indian Navy

[ashthor]

Once the german sub are contracted, 3 more french ones will come and P76 will get approved.
Just like the AF and Naval Rafale's. If you do this...i will do this. Ek haat le, Ek haat de.

[Rakesh]

Once the german sub are contracted, 3 more french ones will come and P76 will get approved.
Just like the AF and Naval Rafale's. If you do this...i will do this. Ek haat le, Ek haat de.

Bingo! Well said. That is the game plan now...

[Rakesh]

AIP System To Make Kalvari Class Subs Deadlier

By 2026, INS Khanderi will be retrofitted with India’s indigenously developed Air-Independent Propulsion (AIP) system, enhancing underwater endurance. All six Kalvari-class submarines will eventually receive the DRDO-developed fuel-cell-based AIP, which has passed extensive shore trials. Installation will occur during refits at Mazagon Dock, with sea trials slated for 2027 and completion by 2028. Using phosphoric acid fuel-cell technology, the system enables submarines to remain submerged for weeks, boosting stealth and sustainability, marking a milestone in India’s domestic defence innovation.

[Rakesh]

https://x.com/cezamne/status/2031694450154521054?s=20 ---> India’s DRDO (Defence Research & Development Organization) is reportedly poised to deliver its indigenously developed Air Independent Propulsion (AIP) plug-in time for integration with INS Khanderi during its scheduled refit in 2026–27. INS Khanderi is the second Kalvari Class (Project-75, Scorpene) submarine inducted into the Indian Navy (IN). It was commissioned on 28 September 2019. The Indian Navy inducted six Kalvari Class submarines under Project-75 between 2017 and 2024. Originally, it was planned to integrate DRDO-developed AIP plugs — designed to facilitate extended submerged endurance — into all Kalvari Class boats. However, the DRDO plug was not ready in time for installation on the first boat, INS Kalvari. The AIP modules, also called Energy Modules (EMs), are integrated into the AIP plug, which is then retrofitted into the submarine during refit. The refit will also include equipping the boat to launch DRDO-developed heavyweight torpedoes.

[Rakesh]

https://x.com/VinodDX9/status/2030508837007220923?s=20 ---> So INS Khanderi will get two major upgrades:

1) NMRL AIP (manufactured by L&T, ToT)

2) NSTL EWHT (Electric/Electronic Heavy Weight Torpedo)

[VinodTK]

Tracking P-75 Story Of Indian Navy

The discussion also explores:

• Why submarine-building skills are so critical—and so hard to retain

• The role of indigenisation and Indian MSMEs

• How Air Independent Propulsion (AIP) could change underwater warfare

• Plans for next-generation submarines and deeper strike capabilities

• India’s growing push towards self-reliance in defence

As India looks to expand its submarine fleet and strengthen naval capabilities, this conversation offers key insights into the future of undersea warfare.

[Rakesh]

Fuel Cell Air-Independent Propulsion for Submarines
https://www.thedefencematrix.in/fuel-ce ... submarines
30 March 2026

[Rakesh]

https://x.com/NetramDefence/status/2041 ... 39716?s=20 ---> Defence Research & Development Organisation is preparing to begin trials of the indigenous ‘Takshak’ electric heavyweight torpedo (EHWT) on Kalvari Class submarines by late 2026.

- Testing plan: Harbour-based dry & wet trials first, followed by live-fire testing by 2027
- Launch system: “Swim-out” mechanism designed to reduce acoustic signature during launch
- Guidance: RLG-based inertial navigation with GPS/NavIC support and fibre-optic wire guidance (autonomous mode if wire breaks)
- Performance: Estimated ~40 km range and ~ 400 m operational depth
- Integration: ₹877 crore contract with Naval Group for compatibility with SUBTICS on Kalvari Class submarines

[Rakesh]

Takshak Torpedo Integration Gains Momentum, Trials on Scorpene Submarine Soon
https://bharatshakti.in/takshak-torpedo ... rine-soon/
07 April 2026

[Rakesh]

https://x.com/NetramDefence/status/2041 ... 39716?s=20 ---> Defence Research & Development Organisation is preparing to begin trials of the indigenous ‘Takshak’ electric heavyweight torpedo (EHWT) on Kalvari Class submarines by late 2026.

- Launch system: “Swim-out” mechanism designed to reduce acoustic signature during launch

U212 (from Germany) uses a water ram expulsion system to fire torpedoes. Designed to maximize stealth by avoiding the acoustic signature created by compressed air. Takshak uses a similar concept and will be a game changer for the Indian Navy in undersea warfare.

The Project 75I series of boats (a customized variant of U212CD for India) will also feature a water ram expulsion system.

[Manish_P]

U212 (from Germany) uses a water ram expulsion system to fire torpedoes. Designed to maximize stealth by avoiding the acoustic signature created by compressed air. Takshak uses a similar concept and will be a game changer for the Indian Navy in undersea warfare.

Admiral sir, just a wild thought- any possibility of exploring a bottom located recessed Torpedo magazine bay? The Bay just opens and the torpedo drops like a dumb bomb and at a safe depth engages it's motor. Sort of like a F-22 bay for AAMs.

I guess it's a solution looking for a problem

[Rakesh]

I guess it's a solution looking for a problem

Nice One!

[Rakesh]

https://x.com/vinayak_kh56506/status/20 ... 46692?s=20 ---> India has 6 top tier stealth submarines named Kalvari Class.

All 6 have 1 thing in common - CFF Fluid.

The fluid systems in stealth submarine must be silent to avoid acoustic detection. CFF is the only Indian company authorised to manufacture & service for KALVARI class Submarines:

- Critical fluid control systems
- Weapon handling systems

This comes via Technology Transfer from Coyard (France) and these systems are standardised across the fleet. Plus CFF is one of the very few players in India that can work with exotic materials like Titanium and Inconel to meet these stealth standards.

[Rakesh]

The first official confirmation from Naval Group, about the three additional Scorpene Class (known as Project 75AS - Advanced Scorpene) for the Indian Navy. It is my hope that the previous six submarines of the class are retrofitted to the same standard during a future MLU program. Below tweet is from Naval Group India.

https://x.com/navalgroup_IN/status/2044 ... 30093?s=20 ---> Advancing India’s Underwater Edge. Building on the success of the Kalvari Class submarines, the additional submarines built on latest Scorpene design represents continuity, capability enhancement and strategic partnership. Developed in collaboration with @navalgroup, additional Scorpene submarines can bring together:

Proven platforms
Advanced Technologies
Increased Industrial Cooperation

Naval Group is proud to continue supporting India’s vision of a future-ready and self-reliant submarine force.