INS Arihant India's indigenous Nuclear submarine~ A preview

Arihant, India's first indigenously built nuclear submarine, cost $2.9bn. It was jointly developed by the Indian Navy, Bhabha Atomic Research Centre (BARC) and Defence Research and Development Organisation (DRDO) at the naval dockyard in Visakhapatnam. Russian designers assisted in building the vessel.

Other companies involved in the development of the submarine are Tata Power, a division of Tata Group and Larsen & Toubro (L&T), a technology, engineering, construction and manufacturing company.

Arihant has been developed as part of the military modernisation programme undertaken by India. The Indian Navy has a fleet of 16 diesel-electric submarines bought from Russia and Germany. However, the diesel electric submarines cannot stay under water for an extended period.

Conventional diesel-electric submarines have to ascend to the surface each day to eject carbon dioxide produced by the generator. Nuclear-powered submarines, on the other hand, can stay under water for long durations without being detected. Arihant is expected to enhance the Indian Navy's capability of delivering nuclear weapons from all terrains.

Arihant design

Arihant's design is based on the Russian Akula-1 Class submarine. It weighs 6,000t. At a length of 110m and breadth of 11m, Arihant is the longest in the Indian Navy's fleet of submarines and can accommodate a crew of 95. It can reach a speed of 12kt-15kt on surface and up to 24kt when submerged.

Arihant is able to stay under water for long periods undetected due to the nuclear-powered 80MW pressurised water reactor (PWR). The PWR was developed by the Bhabha Atomic Research Centre with assistance from a Russian design team.

The submarine's exterior is uneven and the hull is placed on a mat covered with tiles. The tiles help in absorbing sound waves and provide stealth capability to the submarine. Compared to conventional submarines, the conning tower of Arihant is situated near the bow instead of the centre.

The central part of the submarine's body consists of the outer hull and an inner pressurised hull. The starboard side consists of two rectangular vents that draw in water when the submarine submerges into sea.

The Indian Navy and the DRDO together designed the submarine. Once the design was finalised detailed engineering was implemented at L&T's submarine design centre using 3D modelling and product data management software.

Tata Power designed the control systems for the submarine while Walchandnagar Industries, designed parts of the steam turbine.

Arihant armament

Arihant will be capable of carrying all types of missiles and will have underwater ballistic missile launch capability. It will carry 12 K-15 SLBMs that can be launched even under ice caps.

the K-15 missiles are 10.4m long and have a diameter of 1m. The 6.3t missiles can carry a 5t nuclear warhead targeted 750km away. The K-15 missiles, however, will be replaced later by the 3,500km range K-4missiles.

Apart from the K-15s, the submarine will carry a range of anti-ship and land-attack cruise missiles and torpedoes.

Submarine propulsion

A significant progress in the development of Arihant took place when the land-based pressurised water reactor became operational in 2004 at the Indira Gandhi Centre for Atomic Research in Kalpakkam, Chennai. Following this, miniaturisation of the land-based PWR had to be carried out to enable it to fit into a confined space in the submarine. The reactor consists of 13 fuel assemblies each having 348 fuel pins.

Several companies supplied components of the reactor. High grade steel supplied by Heavy Engineering Corporation, Ranchi was used to build the reactor vessel. The steam generator was provided by Bharat Heavy Electricals Limited (BHEL); and Audco India, Chennai built the pressure valves.

The PWR consists of a huge pressure hull, a tank containing water and a reactor. It also consists of a pressure vessel built from unique steel, a control room as well as an auxiliary control room.

The propulsion plant housing the reactor is 42m long and 8m in diameter. The complete propulsion plant along with the primary, secondary, electrical and propulsion systems occupy half of the submarine. To reduce the weight of the plant, light water and enriched uranium was used as opposed to non-enriched uranium used in land-based reactors.

Control and communication systems

Arihant is fitted with a combination of two sonar systems – Ushus and Panchendriya. Ushus is state-of-the-art sonar meant for Kilo Class submarines. Panchendriya is a unified submarine sonar and tactical control system, which includes all types of sonar (passive, surveillance, ranging, intercept and active). It also features an underwater communications system.