India Quietly Launched Third Nuclear-Powered Ballistic Missile Submarine In November This Year: Report

India quietly launched its third ballistic missile submarine (SSBN) S-4, the latest in the Arihant-class of nuclear-powered boats, a report by Chris Biggers of the United Kingdom-based Janes Defence Weekly has said, citing the latest satellite imagery from Planet Labs.

The S-4 was launched on 23 November at the Submarine Building Center (SBC) in Visakhapatnam, the Janes report said. Government sources, however, have refused to comment on the development so far.

Satellite imagery has confirmed the reports of the S-4 being slightly larger than INS Arihant and Arighat, India's other SSBNs. The length of the boat could have been increased to make space for additional tubes for nuclear-tipped ballistic missiles. While INS Arihant, India's first SSBN and the lead boat of the class, has four vertical-launch missile tubes, the S-4 is reported to have at least eight tubes for nuclear missiles.

As a result, S-4 will be able to carry eight K-4 Submarine Launched Ballistic Missiles (SLBMs) and 24 K-15 SLBMs, reportedly twice of what INS Arihant can carry. K-4 and K-15 missiles have ranges of around 3,500 kilometres 750 kilometres, respectively. While the current status of the K-4 missile project remains unknown, the addition of the missile to India's nukes delivery arsenal will allow India's SSBNs in the Bay of Bengal to target major population and production centres in China.

For a credible at-sea deterrence, a country’s SSBNs must be capable of, among other things, targeting the population and industrial centres of the adversary. In India’s case, this means that India’s SSBNs must be capable of holding at risk large cities not only in Pakistan but also in the Chinese mainland, most preferably those located in its eastern coastal belt.

The increase in size over INS Arihant means that the S-4 also has a higher displacement. While the former displace 6,000 tonnes, the latter is reported to have a displacement of 7,000 tonnes.

While the S-4 has been launched, work on the next boat in the class, S-4*, continues at SBC. Arighat, the second of the Arihant-class boats, had been quietly launched in 2017 by the then defence minister Nirmala Sitharaman. The Arighat was to be commissioned into service late last year but the outbreak of the Covid-19 pandemic derailed the plan. INS Arihant was commissioned into service in 2016 and completed its first 20-day long deterrent patrol in November 2018.

India is also working on SSNs or nuclear-powered submarines which are armed with missiles with conventional warheads. The programme involves the design and construction of six SSNs, each displacing around 6,000 tonnes.

SSNs will make the Indian Navy’s submarine arm stealthier. Unlike diesel-electric (or conventional) submarines, SSNs can remain underwater almost indefinitely. A diesel-electric submarine has to snorkel frequently to recharge its batteries which power its propellers. The process of snorkelling involves travelling just below the surface of the water with the submarine’s periscope and generator exhaust pipe above the surface.

Submarines have to come to ‘periscope depth’ and extend the snort mast above the waterline so as to ingest the air needed for running noisy diesel generators to charge their batteries. Snorkelling significantly increases the risk of detection.

SSNs, powered by nuclear reactors, can remain submerged for months — their endurance is limited only by the crew's food supply and weapons expenditures.

Unlike nuclear-powered ballistic missile submarines (SSBNs), SSNs don’t carry nuclear-tipped ballistic missiles. These boats are equipped with long-range anti-ship and land-attack cruise missiles and torpedoes.

The government gave the go-ahead for the SSN project in 2015. Design work had begun at the Gurgaon-based Submarine Design Centre sometime around 2017 and considerable progress has been made since. The design is likely to be finalised in the next two years and the fabrication of the hull will begin after that.

The Hyderabad-based, state-owned Mishra Dhatu Nigam, has been asked to develop an indigenous special alloy for the hull of the submarine to allow it to dive much deeper than the Arihant-class SSBNs.

The reactor being developed for the SSN project would be a vast improvement over the one used on Arihant class boats. It is believed to have an output of around 190 MW, a major upgrade over the 83 MW reactor on Arihant-class SSBNs.

India is also working on a new series of SSBNs, which will be a marked improvement over the Arihant-class. The designing work for this new series, as Sandeep Unnithan reported in India Today back in 2017, is also currently underway.

Identified as S-5, this new type of submarine will have a displacement of 13,500 tonnes, which is twice that of the Arihant-class boats, and will be capable of carrying 12 long-range nuclear-tipped missiles.

In total, India is working on three nuclear submarine projects — Arihant-class SSBNs, six 6,000 tonnes SSNs, and the 13,500 tonne S-5 class SSBNs.