S4 & S4*: 24 × K15SLBM (750 km or 470 mi range) or 8 × K-4 SLBM (3,500 km or 2,200 mi range)
6 × 21" (533 mm) torpedo tubes – est 30 charges (torpedoes, cruise missiles or mines)
The Arihant class (Sanskrit, for Slayer of Enemies) is a class of nuclear-poweredballistic missile submarines being built for the Indian Navy. They were developed under the ₹90,000 crore (US$13 billion) Advanced Technology Vessel (ATV) project to design and build nuclear-powered submarines. The vessels are classified as Strategic Strike Nuclear Submarines by India.
The Arihant-class submarines are nuclear powered ballistic missile submarines built under the Advanced Technology Vessel (ATV) project. They will be the first nuclear submarines designed and built by India. The submarines are 112 m (367 ft) long with a beam of 11 m (36 ft), a draught of 10 m (33 ft), displacement of 6,000 tonnes (5,900 long tons; 6,600 short tons) and a diving depth of 300 m (980 ft). The complement is about 95, including officers and sailors. The boats are powered by a single seven blade propeller powered by an 83 MW (111,000 hp) pressurised water reactor and can achieve a maximum speed of 12–15 knots (22–28 km/h) when surfaced and 24 knots (44 km/h) when submerged.
The submarines have four launch tubes in their hump and can carry up to twelve K-15 Sagarika missiles with one warhead each (with a range of 750 km or 470 mi) or four K-4 missiles (with a range of 3,500 km or 2,200 mi). The third and fourth submarines will have a larger configuration, carrying twenty-four K-15 Sagarika or eight K-4 missiles. The Indian Navy will train on INS Chakra, an Akula-class submarine leased from Russia in 2012.
The submarines are powered by a pressurised water reactor with highly enriched uranium fuel. The miniaturized version of the reactor was designed and built by the Bhabha Atomic Research Centre (BARC) at the Indira Gandhi Centre for Atomic Research (IGCAR) in Kalpakkam. It included a 42-metre (138 ft) section of the submarine's pressure hull containing the shielding tank with water and the reactor, a control room, as well as an auxiliary control room for monitoring safety parameters. The prototype reactor became critical on 11 November 2003 and was declared operational on 22 September 2006. Successful operation of the prototype for three years enabled the production version of the reactor for Arihant. The reactor subsystems were tested at the Machinery Test Center in Visakhapatnam. Facilities for loading and replacing the fuel cores of the naval reactors in berthed submarines were also established.The prototype 83 MW light water reactor that was installed at Kalpakkam by BARC is codenamed S1 and is used to train nuclear submariners.
In 2007, then finance minister P. Chidambaram, who was a member of the political committee which monitors the ATV programme, questioned the huge amount of money being spent on submarines with just 4 missile launch tubes. Hence the ATV project team tweaked the Arihant design by adding a 10-metre-long section for four more K-4 SLBMs to be integrated into the boat codenamed S4. After it became evident that the larger S5 class of SSBNs will take more time to develop, an additional unit, codenamed S4*, was sanctioned in 2012 to ensure that the production line doesn’t go idle.
The detailed engineering of the design was implemented at Larsen & Toubro's submarine design centre at their Hazira shipbuilding facility.Tata Power SED built the control systems for the submarine. The steam turbines and associated systems integrated with the reactor were supplied by Walchandnagar Industries. The lead vessel underwent a long and extensive process of testing after its launch in July 2009. The propulsion and power systems were tested with high-pressure steam trials followed by harbor-acceptance trials that included submersion tests by flooding its ballast tanks and controlled dives to limited depths. INS Arihant's reactor went critical for the first time on 10 August 2013. On 13 December 2014, the submarine set off for its extensive sea trials.
Ships in class
Conceptual drawing of INS Arihant
Four boats of this class are planned. The first boat of the class, INS Arihant, was commissioned in August 2016. The first four vessels are expected to be commissioned by 2023. In December 2014, the work on a second nuclear reactor began and the second boat, INS Arighat is being prepared for sea trials. The final two ships S4 and S4* in the class will be larger displacing over 1,000 tonnes more than the Arihant and have 8 missile launch tubes to carry up to 8 K4 and a more powerful pressurized water reactor than INS Arihant. A larger follow on class to the arihant class, designated the codename S5, is also planned. Three boats of this class are planned to be built. These new boats will be capable of carrying 12 to 16 long range ballistic missiles. The first submarine was commissioned into the Indian Navy in August 2016.