Kalvari-class submarine (2015)

The Kalvari-class submarines, formally classified as the Project-75 submarines (P-75), is a class of diesel-electric attack submarines operated by the Indian Navy (IN). Currently being constructed 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-class and Shishumar-class submarines. India's Ministry of Defence (MoD) ordered an introductory batch of six submarines in 2005, at an initially-estimated cost of inr 130000000000; of the ordered six, five are currently in operational service. In addition to the first batch, a proposal for the purchase of three more submarines was approved in 2023, at an estimated cost of inr 360000000000.

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.

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 INR ₹700 crore. The two examples of the design, originally conceived by the German-based Howaldtswerke-Deutsche Werft, were proposed to be built at Mazagon Dock Shipbuilders Limited (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.

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, the MoD's Defence Procurement Board (DPB) greenlighted the acquisition of three additional submarines, which was further cleared the Defence Acquisition Council (DAC) three days later, on 13 July.

In December 2023, MDL submitted a bid of over inr 200000000000 to construct the three submarines, equipped with higher measures of indigenously-developed technology along with an air-independent propulsion (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 and were expected to cost around inr 350000000000. It is expected that the price negotiations will start by July-August and the final deal of Batch 2 of the submarines will be signed by year end.

Batch-I construction timeline
2006-07: The steel cutting for the first submarine, the Kalvari, commences on 14 December 2006, with its hull construction beginning on 23 May 2007. However, work stalls when public disclosures reveal that the 2005 agreement had omitted the procurement of specific components, including engines, generator and raw materials. The issue prompts 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 delays the project by two years.

2011: The project suffers 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, are submerged under seawater; however, the incident is dismissed by the IN as a "minor obstacle".



2015: The project suffers further delays when Navantia exits the project. After eight years in construction, Kalvari is finally launched in October 2015 and commences 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) was 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 resorts to install its existing inventory of older AEG SUT 264 torpedoes on the submarines as a stopgap measure.

2017-19: The second unit, the Khanderi, is launched in January 2017, which is soon followed by the commissioning of Kalvari in December 2017. The third and fourth units, the Karanj and the Vela respectively, are launched between January 2018 and May 2019, while Khanderi is commissioned in September 2019.

2020-21: The fifth unit, the Vagir, is launched in November 2020, while Karanj and Vela are commissioned between March and November 2021, respectively.

2022-23: The sixth and final unit of the class, the Vagsheer, is launched in April 2022, which is soon followed by the commissioning of Vagir in January 2023. The same month, India's Naval Materials Research Laboratory (NMRL) and Naval Group reach an agreement to integrate NMRL's locally-developed AIP technology on the six submarines. Vagsheer commences its maiden sea sortie in May 2023, with delivery scheduled for early-2024.

2024: The Defence Acquisition Council (DAC) grants 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.

2025: Expected integration of DRDO AIP modules on INS Kalvari the first submarine.

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. It has a length of 67.5 m, height of 12.3 m, overall beam of 6.2 m and a draught of 5.8 m. It can reach a top speed of 20 kn when submerged and a maximum speed of 11 kn when surfaced.

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 of cabling and 11 km of piping.

The class displaces 1615 tonnes when surfaced and 1775 tonnes when submerged.

Propulsion


The submarine is powered by two 1,250kW MAN diesel engines, which are complemented 360 battery cells (750 kg each) that powers a Permanently Magnetised Propulsion Motor for extremely-silent underwater operation, thus allowing it have an operational range of around 6500 nmi at 8 kn when surfaced.

In addition to surfaced operations, the six submarines will be equipped with fuel-cell air-independent propulsion (AIP) modules for extended endurance during submerged operations. The modules, which have been originally designed by India's Naval Materials Research Laboratory (NMRL), are powered by ruggedized phosphoric acid fuel cells (PAFC). They will provide an enhanced submerged endurance of estimated 14 days to the submarines. As of 2024, the AIP module is being manufactured in L&T's AM Naik Heavy Engineering Complex in Hazira, Gujarat. After manufacturing, the module will undergo testing in AIP Integration and Testing facility which was inaugurated in July 2024.

The six Batch-I submarines are expected to retro-fitted with the AIP modules during their respective mid-life refits, the first of which begins in September 2025, while the three Batch-II submarines that yet to be purchased will be equipped with the AIP modules during the construction phase with technological oversight from Naval Group.

Armament
This class is equipped with six 533 mm torpedo tubes for a combination of 18 heavyweight wire-guided German-made Surface and Underwater Target (SUT) torpedoes and SM39 Exocet anti-ship missiles or 30 mines in place of both.

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. Each submarine has a complement of 8 officers and 35 sailors.

Operational history
In June 2023, INS 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 to reach Fremantle, Australia on 20 August 2023. This is the first time that a submarine of this class was on a long-range deployment.

On 24 March 2024, a Kalvari class submarine reached, the Campbell Bay, the southernmost port of India in the Nicobar Islands, for the first time.