After teething troubles, including a crippling accident, India’s nuclear submarine programme — the country’s costliest defence project, monitored directly by National Security Advisor, Ajit Doval — has made big strides in recent years. In October 2018, the wraps of secrecy around the programme were uncovered for the first time when India acknowledged that INS Arihant, its first SSBN — a nuclear-powered submarine equipped with nuclear-tipped ballistic missiles — had completed its first deterrence patrol. In 2017, INS Arighat, the second of Arihant-class boats, had been quietly launched.

With the Arihant-class project now working at assembly-line pace, the programme has got a new vertical — SSNs or nuclear-powered boats armed with conventional missiles. A new report reveals that the government has granted Rs 100 crore for the initial phase of development of these submarines — a phase that may stretch beyond 2025.

India plans to build six SSNs with a displacement capacity of 6,000 tonnes. The government gave a go ahead for the 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 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 boats. The nuclear reactor being developed for the SSNs will also be more powerful than the one on the Arihant-class submarines.

SSNs — given that they are powered by a nuclear reactor — can travel almost indefinitely underwater, like SSBNs. At the same time, they are easier to operate in comparison with SSBNs as they are armed with conventional weapons. When deployed, submarines need to remain in touch with the Command and Control Centre to receive orders for launch, if and when required. This is a critical requirement especially in the case of a nuclear-armed submarine (SSBN), like INS Arihant, which needs approval from the Nuclear Command Authority to launch a nuclear-tipped missile.

According to the news report, a scale model of the SSNs will soon be fabricated and tested for design flaws. The leasing of an Akula-2 SSN from Russia for a ten-year period in a $3 billion deal earlier this year is also likely to come handy for the development of the new type and and also for training the crew that will operate it.

Although the effort behind the projects is indigenous with 60 per cent of the components for the Arihant-class being sourced from local manufacturers, the Navy has benefited from a close design-and-technical cooperation with Russia.

Work on SSNs will continue as the Navy inducts Arihant-class boats. The Arighat, in an advanced stage of trials, is likely to enter service with the Indian Navy around 2020. The next two units of the Arihant-class boats, identified as S4 and S4 'star' for now, are also under construction at the Ship Building Centre in Visakhapatnam.

These two boats will displace at least 1,000 tonnes more than the 6,000 tonne INS Arihant. The two units will be capable of carrying eight 3,500 km range K-4 Submarine Launched Ballistic Missile (SLBM) while INS Arihant can carry only four of these. The first Arihant-class boat is currently equipped with a dozen 750 km range K-15 Sagarika SLBM. While the K-15 has entered service, K-4 is still being tested.