India's top secret nuclear submarine project reached another decadal milestone last month with the launch of a second ballistic missile submarine, the Arighat . On November 19, Union defence minister Nirmala Sitharaman cracked the auspicious coconut on the fin of the submarine in the drydock of the Ship Building Centre (SBC) in Visakhapatnam in a low-key ceremony. Following this, the SBC's drydock was flooded and the submarine quietly floated out. It will be at least another three years before the navy commissions the Arighat.

The event skipped the high-profile public ceremony of the Arihant's launch in 2009 even as the four-decade Advanced Technology Vessel (ATV) project to field a series of ballistic missile firing nuclear submarines is now moving at a furious assembly-line pace.

Two new units, the S4 and S4 'star', displacing over 1,000 tonnes more than the Arihant class will move into the SBC drydock vacated by the two Arihant class submarines. These submarines, fitted with eight ballistic missiles or twice the Arihant's missile load, will be launched by 2020 and 2022. An official says the Arighat launch has more to do with creating more work space within the cramped SBC for assembling the S4 and S4*. The ATV project is India's costliest defence project. The programme to build four SSBNs (hull classification symbol for a nuclear-powered, ballistic missile-carrying submarine) is India's largest defence programme, estimated at Rs 90,000 crore. Each of these nuclear-powered sharks costs upwards of Rs 4,000 crore, not counting the infrastructure created by the Bhabha Atomic Research Centre (BARC) to build their nuclear powered reactors and the Defence Research and Development Organisation's (DRDO) submarine launched ballistic missiles (SLBMs).

The project's pan-India spread-headquartered in New Delhi, hull fabrication facility in Gujarat, missile development in Hyderabad, nuclear reactor in Tamil Nadu and final assembly in Visakhapatnam-is the biggest Make in India industrial ecosystem-nearly 60 per cent of the submarine's components are indigenous. It is also the cornerstone of Indo-Russian strategic cooperation; top officials admit the project would not have been possible without extensive Russian design and technical assistance. Ahead of the submarine arm's golden jubilee on December 8, the ATV programme has nearly doubled in size with a Rs 60,000 crore project to build six indigenous nuclear-powered attack submarines (SSNs).

"It has kicked off, " navy chief Admiral Sunil Lanba told the media about the SSN project on December 1. "It is a classified project? the process has started." Design work for the indigenous SSNs displacing around 6,000 tonnes is under way at a newly constructed submarine design centre in Gurgaon. SSNs are armed with conventional cruise missiles and torpedoes but powered by nuclear reactors which give it excellent underwater speed and endurance.

The navy has opened up talks for the lease of another Akula-class submarine from Russia for over $2 billion, to replace the existing INS Chakra when it is returned in 2022 after the end of its lease. (The Chakra is currently non-operational after an incident last August). Meanwhile, final design work is under way on a new series of 13,500-tonne ballistic missile submarines. Called the 'S-5', it will be twice the weight of the Arihant class SSBNs and armed with 12 nuclear-tipped missiles. Earlier this year, the DRDO flagged off its K-6 SLBM project, a missile with an ICBM-like range of 6,000 km. The first phase of Project Varsha, a nuclear submarine base, will be completed by 2022. The base will house India's SSBN fleet in concrete pens blasted out of the hills at Rambilli 50 km south of Visakhapatnam, reportedly at a cost of Rs 30,000 .

THE THIRD LEG OF THE TRIAD

A nuclear engine allows a submarine to travel almost indefinitely underwater. They don't have to surface to recharge their batteries like conventional diesel-electric submarines (SSKs) and they move faster underwater because they avoid surface wave resistance.

The Arighat, like the Arihant, is a ballistic missile submarine or a boomer because it carries nuclear-tipped missiles and forms the third leg of a triad of air, land and sea-based nuclear weapon carrying platforms, enunciated in India's draft nuclear doctrine after the May 1998 Pokharan-2 nuclear tests. When India observes the 20th anniversary of the tests five months from now, it will have a modest sea-based deterrent with one SSBN in service and a second soon to join it.

"The triad becomes effective when you have a submarine operational at all times. In our case, a triad is operational only part of the time-when the Arihant sails out to sea," says strategic analyst Bharat Karnad. When an Indian SSBN sails out of Visakhapatnam and into the Bay of Bengal, it can virtually disappear for months, remaining underwater, its endurance limited only by the endurance of its crew, communicating only through extremely low frequency (ELF) antennae which it trails in the water. While bombers, mobile missile launchers, missile trains and ground-based launchers can be tracked, nuclear submarines are virtually undetectable. This is what makes them the most precious asset of the nuclear triad.

Submarines thus become an important component of India's 'no first use' policy for nuclear weapons because they act as guarantors of 'assured retaliation' or a second-strike, preventing any surprise first-strike by a nuclear-armed adversary. They are vital at a time when China's PLA Rocket Forces can target any point on the Indian mainland with nuclear tipped missiles and India has fewer retaliatory options.

The Arihant has so far been equipped with 12 B-05 SLBMs which have a range of 750 km-which means a distant transit to an adversary's shores. A 3,500-km range missile, the 'K-4' is still in trials-the DRDO is to conduct a fourth test of the missile sometime in December, from a specially designed submersible pontoon launcher in the Bay of Bengal. Final tests of the K-4 from the Arihant are due in the Bay of Bengal in the near future. These are to be followed by tests of a K-5 missile, a 5,000-km SLBM, a project started in 2015. The 'K series' missiles are all named after former president A.P.J. Abdul Kalam. The K-4 and K-5, each of which can carry a two-tonne warhead will give the triad a longer, more robust leg.

Information about the ATV project is meagre. It operates directly under the supervision of national security advisor Ajit Doval and is now wrapped in deep levels of secrecy. A navy proposal for a high-profile launch of the Arighat where the PM and cabinet ministers would be present was overruled by the PMO. Security around the project is the heaviest for any publicly known military facility (the navy recently cited security concerns to acquire a public road passing near the SBC in Visakhapatnam).

Naval top brass are chary of even discussing the project either in public or in private. "That (the ATV) is a classified project... I'm not going to take any questions on that," navy chief Admiral Sunil Lanba told the media a press conference on December 1, a marked departure from a predecessor who claimed, rather disingenously in 2010, of the INS Arihant undertaking 'a deterrent patrol by 2012'. The Arihant was inducted into service in August last year after weapon trials but continues to undertake extensive trials but without a prolonged sea deployment. An actual deterrent patrol-where a nuclear-missile armed submarine goes into its operational area armed with nuclear warheads-is thought to be further away.

The launch of the Arighat comes amidst fast-changing geopolitical developments. The Chinese navy has deployed and initiated the fastest submarine expansion of any navy since the end of the Cold War with an operational undersea force of 63 vessels-5 SSNs, 4 SSBNs and 54 SSKs.

It recently sold a class of eight conventionally powered diesel-electric submarines to Pakistan, at least some of which are likely to be fitted with nuclear-tipped missiles.

"Sea-based deterrents are going to become more important as time passes, especially for a country with a no-first use policy," says strategic analyst Rear Admiral Raja Menon (retired). "The location of your nuclear weapons becomes known and even a half per cent knowledge of your existing weapon sites each year could add up to something substantial over the years, thus degrading your deterrent."

THE HUNTER-KILLERS

A solitary two-month patrol by a Chinese submarine in late 2013 came as a rude wake-up call for India's security establishment. Chinas most advanced SSN, a Shang class, sailed out from its bastion in Hainan island on December 13, 2013 and returned after a two-month 'anti-piracy' patrol in the Indian Ocean, on February 12, 2014. R&AW assessments termed the deployment 'seriously aggravated India's security concerns'. The ATV headquarters soon dusted out plans for building a series of six indigenous SSNs, shelved by the government over a decade ago due to budgetary constraints. Plans called for a series of submarines capable of speeds of over 25 knots and diving to 500 metres.

SSNs are like multi-role fighter jets, ferocious underwater predators. The navy's INS Chakra, for instance, can run underwater at speeds of close to 30 knots, more than twice the speed of conventional diesel-electric submarines, stalk and hunt warships and attack shore targets.

But like fighter jets, their performance lies in their propulsion plant, in this case a high output nuclear reactor which can cope with the tremendous bursts of sustained speed without degrading reactor output. And this is where the Indian Navy and BARC are said to be staring at a technological abyss. An 83 MW SSBN reactor like that of the Arihant, is essentially meant for slow, steady operation, using it onboard an SSN would call for more frequent refuelling cycles.

One solution believed to be under contemplation is for BARC to design a twin-reactor configuration for the SSN to meet its increased power demands. Another solution currently being explored would be to get foreign design assistance and leapfrog from India's second generation reactor technology to fourth gen.

DREAMS OF A BEHEMOTH

The ATV headquarters building in New Delhi's cantonment area has a rather unusual name: 'Akanksha' or desire. Since its start in the 1970s, the nuclear submarine project has been a dream-never constrained by finance, only by technology.

BARC's prototype 83 MW light water reactor at Kalpakkam, the S-1, used to train nuclear submariners. BARC's prototype 83 MW light water reactor at Kalpakkam, the S-1, used to train nuclear submariners.

There's a reason for the modest size of the Arihant class submarines and why they are called 'baby boomers'. When the Pokharan-2 nuclear tests announced India's entry as a nuclear weapons power, the Arihant class were meant to be SSNs. Post the tests, they were converted into SSBNs-DRDO inserted a plug with four short-ranged ballistic missiles. The design got another tweak a decade ago after an intervention from then finance minister P. Chidambaram who was on the political committee which monitors the classified programme. The minister questioned the billions being spent on a boat launching just four nuclear tipped missiles. The ATV project team came back with an 'Arihant-stretch'-an additional 10-metre-long plug for four K-4 SLBMs to be integrated into the S-4, then on the design board. The plug would increase the weight of the submarine by nearly 1,000 tonnes without significantly altering its performance. An additional unit, the S-4* was sanctioned in 2012 when it became clear that the S-5 would take a longer development cycle and would result in the ATV line being idle.

Plans for building a new series of strategic nuclear submarines had begun over a decade ago when the missile payload and reactor capacity constraints of the Arihant class submarines became evident.

In 2006, a high-level committee under Dr R. Chidambaram, principal scientific advisor to the government of India, assessed India's ability to design and construct a class of three new SSBNs the 'S5', to be fielded beginning in 2021. It budgeted Rs 10,000 crore, to be divided among BARC, DRDO and the ATV project headquarters, to begin the project by 2015. The project continued in the development stage and an indication of a possible long lead construction time began when the government sanctioned a fourth unit around five years ago (squeezed between the two projects as the 4*) to keep the nuclear submarine line employed. (S-1 being the shore-based pressurised water reactor at the DAE facility in Kalpakkam, iterations of which are on the Arihant class.)

The S-5 is the true-blue SSBN on par with those fielded by the five permanent members of the UN Security Council.

Plans drawn up over a decade ago called for an SSBN of 13,500 tonnes, a behemoth displacing nearly the weight of India's first aircraft carrier the INS Vikrant and armed with 12 SLBMs with ranges of 6,000 km and with multiple independently targetable re-entry vehicle (MIRV) capability.

In February this year, the DRDO's Hyderabad-based Advanced Naval Systems began a fourth separate SLBM project-the K-6 missile. This three-stage solid-fuel missile with a 6,000 km range is said to be completely different from the K-4 and K-5. It will carry MIRVs and will be ready for induction in less than a decade. These new missiles, over 12 metres tall and over 2 metres in diameter, will carry a three-tonne warhead. The K-6 will ensure that the future Indian SSBN's bastion area will be within the Bay of Bengal, from where it can target all its potential adversaries. A former head of India's Strategic Forces Command hinted at this in a 2014 think tank event in Washington when he said that India's sea-based deterrent would eventually "be secured in havens, waters we are pretty sure of, by virtue of the range of the missiles. We will be operating in a pool in our own maritime backyard." From the safety of its depths, Indian SSBNs would be able to target all its potential adversaries with its 6,000-km range ballistic missiles (SLBMs).

The SSBN fleet is based on the east coast for reasons of geography-the Indian continental shelf dips sharply into the abyssal Bengal fan. A submarine can dive and be concealed just 2 nautical miles from harbor (a submarine on the west coast can dive only after sailing out for 80 nautical miles).

The S-5 is on the drawing board but the project team has already started ordering its ancillary equipment. A new dockyard is being created at the SBC and sources say the project will have an indigenous component of over 80 per cent when they are built a decade from now.

Yet, as is the case with the indigenous SSN, the main challenge in building the S-5 lies in its propulsion plant-a 190-MW nuclear plant- says an official familiar with the project. Development work has started on this new plant will have thrice the output of the Arihant's 83 MW reactor which uses Highly Enriched Uranium (HEU). A former BARC official and part of the Reactor Projects Division which built the Arihant's reactor is confident the 83 MW can be scaled up. "One of the biggest challenges in a naval reactor is compacting it to fit a confined space. Since the new platform (S-5) will have a bigger volume and displacement, upscaling the present reactor should be no problem."- Without a breakthrough in propulsion technology, India's sea-based deterrent will continue to be a modest one.