# Kalvari-class submarine (2015)

The Kalvari-class submarines (lit. 'Tiger shark'), formally classified as the Project-75 submarines (P-75), is a class of diesel-electric attack submarines operated by the Indian Navy (IN). Built by a syndicate of French and Indian shipyards, namely, Naval Group and Mazagon Dock Limited (MDL) respectively, the class is an export derivative of the French-origin Scorpène-class submarine, originally designed by Naval Group.
A namesake of the former Foxtrot-class submarines that the IN operated between 1967 and 2010, the class was originally planned in the late-1990s as an initial phase of a 30-year long naval rearmament roadmap to replace the IN's conventional submarine fleet, namely the Sindhughosh and Shishumar-class submarines. India's Ministry of Defence (MoD) placed an order of six submarines in 2005, at a cost of ₹23,562 crore (equivalent to ₹800 billion or US$9.3 billion in 2023). The last of the first batch of submarines entered service on 15 January 2025. A repeat order for another batch of 3 submarines is to be placed in February 2025 at a cost of ₹38,000 crore (US$4.4 billion).
First introduced to operational service in 2017, the submarines are currently operated by the IN for a variety of missions, namely, littoral surveillance, intelligence gathering, anti-submarine warfare, anti-surface warfare and minelaying operations.

## History
### Origins

In 1997, the Cabinet Committee on Security (CCS), the highest-decision making body of India's Ministry of Defence (MoD), approved a proposal for the purchase of two Type 209/1500 attack submarines (SSK) for the Indian Navy (IN), at a then-estimated cost of ₹700 crore (equivalent to ₹36 billion or US$410 million in 2023). The two examples of the design, originally conceived by the German-based Howaldtswerke-Deutsche Werft, were proposed to be built at Mazagon Dock Shipbuilders (MDL), located in Mumbai, with the assistance of a foreign naval firm in a corroborative role.
In accordance with the scheme, the IN and MDL approached several naval enterprises for assistance; however, the French-based Thomson-CSF (TCSF) was the only firm willing to participate. Two years later, in 1999, the MoD approved a two-phase plan to build 24 submarines over a 30-year period. For the first phase, which called for the construction of SSKs at MDL, two options were proposed: the former option recommending the construction of the Type 209/1500 at MDL with the assistance of TCSF; the latter option recommending the construction of SSKs based on the newer Scorpène submarine design, conceived by the French-based Armaris (later DCNS, now Naval Group).
Ultimately, the IN chose the latter, reasoning that the Scorpène, which had been offered with a provision of technology transfer (TOT), was more advanced than the Type 209/1500. Another reason for choosing the Scorpène design was because of the IN’s interest in acquiring submarine-launched missiles. At the time, the French-designed Exocet, the US-designed Harpoon and the Russian-designed Kalibr were the only such missiles that were commercially obtainable; however, the Harpoon was unavailable to the IN and the Kalibr was incompatible with the Type 209/1500's torpedo tubes. This led to the Exocet being preferred and subsequently, the Scorpène design. It was also thought that the Scorpène design won the deal because of its capability to fire Exocet anti-ship missiles and an agreement on the air-independent propulsion (AIP).

### Orders

Batch-I: On 6 October 2005, India signed a series of contracts for transfer of technology to construct six submarines at MDL with Armaris, along with the supply of SM39 Exocet missiles manufactured by MBDA. DCN International was designated as the prime contractor in partnership with Navantia. Armaris was responsible for supply of combat systems and technical advisors for construction of submarines at MDL. Valued at a then-total cost of €2.4 billion, the deal included a 30% offset clause and a delivery timeline wherein the six ordered units were to be delivered between 2012 and 2017.
Batch-II: On 10 July 2023, plans for the acquisition of three additional submarines was formally proposed to the Ministry of Defence along with the proposal for the procurement of 26 Rafale M aircraft. On 13 July 2023, Defence Acquisition Council (DAC), headed by the Defence Minisiter Rajnath Singh, of India granted the Acceptance of Necessity (AoN) for the procurement of both 3 Kalvari-class submarines and 26 Rafale M F4 variant aircraft for the Indian Navy.
In December 2023, MDL submitted a bid to construct the three submarines, equipped with higher measures of indigenously-developed technology along with an AIP module for enhanced underwater endurance. By June 2024, the price negotiation for acquiring 3 additional submarines were in advanced stages. Three submarines would have more than 60% of indigenous content. The entire upgraded combat management system for the Batch II submarines will be indigenously developed by Bharat Electronics Limited. The first submarine shall be delivered after six years of contract signing.
As of 13 January 2025, the deal worth ₹38,000 crore (US$4.4 billion) will be cleared by the Cabinet Committee on Security by late January or early February while the same would be concluded during the visit of the Indian Prime Minister Narendra Modi to France on 11 and 12 February.
On 9 February 2025, it was reported that the high costs for the three P-75 (Additional) submarines were because of their relatively larger size, similar to Riachuelo-class submarine for the Brazilian Navy, and a higher indigenous content of 60% which is twice of that for the initial batch of submarines. Also, the cost negotiations had been completed at a final cost of around ₹36,000 crore (US$4.2 billion) and does not include the cost of air-independent propulsion system.

## Construction
### Batch-I construction timeline

2006-07: The steel cutting for the first submarine, the Kalvari, commenced on 14 December 2006, with its hull construction beginning on 23 May 2007. However, work stalled when public disclosures revealed that the 2005 agreement had omitted the procurement of specific components, including engines, generator and raw materials. The issue prompted the MoD to establish a public entity, the Mazagaon Procured Materials (MPM), to directly procure the aforementioned materials. Protracted negotiations between the MoD and DCNS for the components lead to the additional sanctioning of ₹4,764 crore by the CCS, which further delayed the project by two years.
2011: The project suffered another setback following a breach and flooding at MDL's dockyard in which components, including sections of the already fabricated hull of at least one of the six units, were submerged under seawater; however, the incident was dismissed by the IN as a "minor obstacle".
2015: The project suffered further delays when Navantia exits the project. After eight years in construction, Kalvari was finally launched in October 2015 and commenced sea trials a year later, on 1 May 2016.
2016: In June, initial plans to purchase ninety-eight Black Shark torpedoes from the Italian-based munitions manufacturer Whitehead Alenia Sistemi Subacquei (WASS) were cancelled in response to corruption allegations against WASS's sister company, AgustaWestland. Although alternatives, such as the SeaHake torpedoes from Germany's Atlas Elektronik and the F21 torpedoes France's Naval Group were considered, the MoD resorted to installing its existing inventory of older AEG SUT 264 torpedoes on the submarines as a stopgap measure.
2017-19: The second unit, the Khanderi, was launched in January 2017, which was soon followed by the commissioning of Kalvari in December 2017. The third and fourth units, the Karanj and the Vela respectively, were launched between January 2018 and May 2019, while Khanderi was commissioned in September 2019.
2020-21: The fifth unit, the Vagir, was launched in November 2020, while Karanj and Vela were commissioned between March and November 2021, respectively.
2022-23: The sixth and final unit of the class, the Vagsheer, was launched in April 2022, which was soon followed by the commissioning of Vagir in January 2023. The same month, India's Naval Materials Research Laboratory (NMRL) and Naval Group reached an agreement to integrate NMRL's locally-developed AIP technology into the six submarines. Vagsheer commenced its first sea sortie in May 2023, with delivery scheduled for early 2024. On 22 June, Larsen & Toubro signed a contract with DRDO for the construction of two units of AIP system modules for the Kalvari class.
2024: The Defence Acquisition Council (DAC) granted an Acceptance of Necessity (AoN) in February 2024 for the purchase of forty-eight heavyweight torpedoes for the submarines under a global tender as a stopgap measure until an indigenous option, supposedly a submarine-launched version of Varunastra torpedo, becomes available. On 14 September, the Indian Navy commissioned the Kalvari Submarine Escape Training Facility, Vinetra, at INS Satavahana, Visakhapatnam to train personnel in escape procedures during a distress situation. The facility was constructed by Larsen & Toubro and is equipped with a five-metre (16 ft) escape tower integrated with an adjacent diving basin. On 30 December, the Indian Ministry of Defence signed two contracts with Mazagon Dock Limited (MDL) and Naval Group, France for upgrades related to the Kalvari-class submarines. The first contract, the one signed with MDL [worth ₹1,990 crore (US$230 million)], is for the construction and integration of AIP Plug into Batch 1 submarines, while the second contract signed with Naval Group [worth ₹877 crore (US$100 million)] is for the integration of indigenous Electronic Heavy Weight Torpedo (EHWT) systems.
2025: The last of the Batch 1 submarines, INS Vagsheer, commissioned on 15 January. Expected integration of DRDO AIP modules on Kalvari the first submarine.

## Design
### Hull

The Kalvari class is capable of offensive operations across the entire spectrum of naval warfare including anti-surface warfare, anti-submarine warfare, intelligence gathering, mine laying and area surveillance. They have a length of 67.5 m (221 ft 5 in), height of 12.3 m (40 ft 4 in), overall beam of 6.2 m (20 ft 4 in) and a draught of 5.8 m (19 ft 0 in). They can reach a top speed of 20 knots (37 km/h; 23 mph) when submerged and a maximum speed of 11 knots (20 km/h; 13 mph) when surfaced. Each submarine has a complement of 8 officers and 35 sailors.
The hull, fin and hydroplanes are designed for minimum underwater resistance and all equipment inside the pressure hull is mounted on shock absorbing cradles for enhanced stealth. Special steel was used in its construction which has high tensile strength, capable of withstanding high yield stress and hydro-static force. Each submarine has 60 km (37 mi) of cabling and 11 km (6.8 mi) of piping.
The class displaces 1,615 tonnes (1,589 long tons) when surfaced and 1,775 t (1,747 long tons) when submerged.

### Propulsion

The submarine is powered by two 1,250 kW MAN diesel engines, which are complemented 360 battery cells (750 kg, 1,650 lb each) that powers a Permanently Magnetised Propulsion Motor for extremely-silent underwater operation, thus allowing it have an operational range of around 6,500 nautical miles (12,000 km; 7,500 mi) at 8 knots (15 km/h; 9.2 mph) when surfaced.

#### AIP module

The six Batch-I submarines are expected to retro-fitted with an indigenously developed AIP modules during their respective mid-life refits, starting with Kalvari in September 2025. The retrofitting will add-on the AIP section in the middle of the submarine increasing the length and displacement of the submarines. The three Batch-II submarines, in turn, will be equipped with the AIP modules during the construction with technological oversight from Naval Group. The system provides an enhanced submerged endurance of about 14 days to 21 days over 48 hours endurance of conventional non-AIP submarines.
Development: In March 2021, the land-based prototype (LBP) of the system was tested. As per a release, "The plant was operated in endurance mode and max power mode as per the user requirements". It is primarily designed by Naval Materials Research Laboratory (NMRL). Larsen & Toubro os the development and production partner of this project. L&T has received the technology transfer approval for production from the Defence Ministry in 2021. On 22 June 2023, L&T and DRDO signed a contract to manufacture two units of Air Independent Propulsion (AIP) System Modules. The manufacturing, integration and factory acceptance trials of the Energy Modules (EMs) will be conducted at L&T’s AM Naik Heavy Engineering Complex at Surat. The EMs will be delivered for integration into the AIP Plug followed by integration into the first submarine. The AIP module, which is being manufactured as of 2024, will undergo testing in AIP Integration and Testing facility, inaugurated in July the same year. A shore-based prototype has undergone extensive trials and has been demonstrated to the Navy. Suman Roy Choudhury is the programme director, AIP, NMRL. On 30 December 2024, Mazagon Dock received a contract, worth ₹1,990 crore (US$230 million), for the fabrication of AIP Plug and its integration into the submarines.
Design: The Engine Modules are the core component of the AIP system. The modules are composed of phosphoric acid fuel cells (PAFC) and the on-board Hydrogen generation system. The hydrogen generation system excludes the need of hydrogen storage and the by-product is non-polluted water which is to be released into the oceans.

### Armament

This class is equipped with six 533 mm (21 in) weapon launching tubes. A total of 18 weapons can be carried with a combination of heavyweight German-origin SUT torpedo and SM39 Exocet anti-ship missiles. In place of torpedoes and missiles, 30 mines can be carried.
On 30 December 2024, the Naval Group was contracted to integrate DRDO developed EHWT Takshak on the submarines.

### Sensors

The class is also fitted with mobile C303/S anti-torpedo decoys for self-defence. The weapon systems and sensors are integrated with Submarine Tactical Integrated Combat System (SUBTICS). It has a sonar system is capable of Low Frequency Analysis and Ranging (LOFAR) enabling long range detection and classification.

## Operational history

In June 2023, Vagir was deployed on an extended patrol in the Indian Ocean. As a part of the deployment, the submarine reached Colombo, Sri Lanka, on 19 June 2023. Then, it covered nearly 7,000 kilometres (4,300 mi) to reach Fremantle, Australia, on 20 August 2023. This was the first time that a submarine of this class was on a long-range deployment.
On 24 March 2024, a Kalvari-class submarine reached Campbell Bay, the southernmost port of India in the Nicobar Islands, for the first time.
Three of these submarines were deployed alongside the aircraft carrier INS Vikrant along with seven frontline warships and three other submarines (Shishumar class and Sindhughosh classes) on 7 November 2024. The operations included carrier operations of MiG-29K aircraft, missile firing drills, submarine manoeuvres and flypasts by 30 aircraft demonstrated to the President of India Droupadi Murmu who was present on board Vikrant.
In an incident on 22 November 2024, a submarine of the Kalvari class collided with a fishing boat about 70 nautical miles (130 km; 81 mi) off the coast of Goa. The Navy rescued 11 fishermen before their boat sank. Two fishermen were reported missing, with the Navy and Coast Guard deploying various ships to locate them.

## Ships of the class

| Name | Pennant | Yard | Builder | Launched | Commissioned | Homeport | Status |
| Batch-I ||||||||
| Kalvari | S21 | 11875 | Mazagon Dock Limited | 27 October 2015 | 14 December 2017 | | Active |
| Khanderi | S22 | 11876 | Mazagon Dock Limited | 12 January 2017 | 28 September 2019 | Mumbai | Active |
| Karanj | S23 | 11877 | Mazagon Dock Limited | 31 January 2018 | 10 March 2021 | Karwar | Active |
| Vela | S24 | 11878 | Mazagon Dock Limited | 6 May 2019 | 25 November 2021 | | Active |
| Vagir | S25 | 11879 | Mazagon Dock Limited | 12 November 2020 | 23 January 2023 | Mumbai | Active |
| Vagsheer | S26 | 11880 | Mazagon Dock Limited | 20 April 2022 | 15 January 2025 | | Active |
| Batch-II ||||||||
| TBD | | | Mazagon Dock Limited | | | | To be ordered |
| TBD | | | Mazagon Dock Limited | | | | To be ordered |
| TBD | | | Mazagon Dock Limited | | | | To be ordered |

## Gallery

* A Kalvari-class submarine up close during an exercise
* A trio of Kalvari-class submarines during an exercise
* A Kalvari-class and Shishumar-class submarine during an exercise
* Khanderi at sea
* Vela during sea trials
* Vagir