On August 29, India’s defense minister presided over the commissioning ceremony of S3 Arighat, the country’s second-ever home-built nuclear-powered submarine. The nuclear-armed sub is a manifestation of India’s progress toward deploying a diversified “triad” of of air, sea, and land-based nukes. At the same time, the U.S. and its allies are seeking deeper military cooperation with the Indian Navy due to mutual tensions with Beijing. So, the overall goal is to provide round-the-clock sea-based nuclear deterrence—especially against China.
Arighat, which translates to “slayer of enemies,” and the preceding Arihant submarine, which the new ship is based on, are initial stepping stones in the Indian Navy’s ambitious program to build a fleet of nuclear-powered submarines loaded with nuclear-armed ballistic missiles.
Rather than hunting enemy ships, ballistic missile submarines (also known as “boomers” or SSBNs) lurk quietly in hiding. They await a signal transmitted from national leadership via very-high-frequency radio before releasing a volley of nuclear ballistic missiles on distant targets.
Because India has experienced long-running—and sometimes deadly—border disputes in the Himalayas dating back to a 1962 war with China, INS Varsha, a base shrouded in secrecy on India’s east coast, will harbor the fleet of ballistic missile submarines meant to specifically deter China.
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Nuclear reactors allow the subs to remain underwater for weeks or months (50 days in the case of Arihant) unlike conventionally powered submarines, which must risk detection every few days to surface or snorkel to recharge batteries. This means active boomer submarines are relatively immune to surprise attack unless individually detected and tailed by adversary submarines.
At 6,000 tons of displacement, India’s “pocket boomers” remain significantly smaller than the boomers of other navies, and have much shorter-range ballistic missiles, reflecting the challenges of simultaneously developing, testing, and scaling these technologies.
Indeed, while Arighat was launched in 2017, she only began sea trials in 2022, and her commissioning ceremony came three years later than planned. Media outlets in the 2010s claimed Arighat would boast a more powerful nuclear reactor and twice as many nuclear missiles as Arihant. But Arighat retains the same 83-megawatt-class CLWR-B1 pressurized water reactor and offensive payload of four medium-range K-4 missiles in vertical launch tubes.
Some reports state the alternate payload of 12 short-range K-15 missiles (three per tube) remains unchanged, while others assert it’s somehow increased.
Undoubtedly there are major upgrades to reliability and efficiency for regular operational use, as the preceding Arihant is viewed more as a tech demonstrator/training vessel. Reports also suggest Arighat received improved acoustic dampening for stealth.
Otherwise, Arighant shares Arihant’s double-hulled configuration, with an outer titanium shell wrapped around the main hull with its seven primary compartments. Other common features include three 533-millimeter tubes carrying wire-guided torpedoes for self-defense and two auxiliary and one retractable emergency thruster. The ovoid-shape of the class is relatively aquadynamic compared to other boomers with boxy, protruding missile compartments.
Tech transfers from Russia aided India’s development of Arihant, including the leasing of two Russian Akula-class nuclear-powered submarines renamed Chakra I and II. Arihant’s external design appears to have been strongly inspired by Russia’s Kilo-class diesel-electric submarines also operated by India. However, internal systems such as radar, combat, and torpedo-defense systems were sourced domestically or from British, French, and Israeli companies.
At the moment, China has more nuclear delivery systems able to reach targets across India than India has that can reach central or eastern China. That includes six beefier Type-094 boomers with longer-range JL-2 or 3 missiles.
And beside the border skirmishes, China is the chief ally of India’s main rival, Pakistan, and its Pacific-based navy increasingly patrols the Indian Ocean, complemented by a Chinese base in Djibouti to India’s west.
Even with the addition of Arighat, India’s sea-based deterrence remains immature. At minimum, three boomers are needed to ensure at least one of India’s subs is at sea 365 days a year. Even then, more are preferred to hedge against maintenance or combat casualties, and to release larger missiles salvoes more likely to overwhelm defenses.
Most importantly, Arighat’s K-15 missiles have a range of 466 miles—meaning they can’t reach significant targets on Chinese soil from the Indian Ocean. Even to attack inland targets in neighboring Pakistan, an Indian submarine would have to approach dangerously close to coastal defenses.
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Underwater test launch of a K-series SLBM missile in 2016 in the Bay of Bengal.
That said, the four 12-meter-long K-4 intermediate-range missiles the subs carry are more practical, able to fly 2,500 miles to threaten high-value targets in China. The 19-ton K-4 has been test-fired six times from submerged pontoon launchers (with only one outright failure in 2017), and once by Arihant in 2016 while shallowly submerged.
So, to achieve the holy grail of credible, continuous, at-sea deterrence, the Indian Navy needs more, bigger submarines armed with a larger number of missiles that fly further. And India’s nuclear-armed submarine roadmap is moving in just that direction.
The slightly larger and improved submarine S4 Aridaman—measuring 125 meters long and weighing 7,700 tons—is scheduled for delivery next year, with one or two similar but improved S4* subs to follow.
The S4-series submarines double capacity to eight medium-range missiles and support the improved K-5 missile, which can travel up to 3,100 miles, allowing boomers to hide over a wider expanse of the Indian Ocean while still threatening key targets.
Next year, India should also begin building the first of four huge 15,000-ton S5 boomers capable of carrying 12–16 longer-range K-6 missiles (still notional) with multiple, independently targetable nuclear warheads, technology India first tested in March.
The Indian Navy is also procuring two or three 7,000-ton nuclear-powered attack submarines for India, scheduled for delivery around 2032, that could help protect India’s boomer subs and aircraft carriers from Chinese attack submarines venturing into the Indian Ocean.
The greatest hurdle lies in developing a 190-megawatt-class reactor to support bigger and faster submarines while remaining sufficiently compact, safe, and quiet. India’s Bahba Atomic Research Center in Mumbai drew up a design for such a reactor in 2018, but hasn’t yet built a land-based prototype.
If India’s S4 and S5 submarine programs proceed as scheduled, the shortcomings of India’s undersea nuclear deterrence may rapidly shore up—unless affected by the same delays impacting Arighat.
It’s worth noting both India and China have a No-First Strike doctrine, meaning their nuclear forces supposedly would only be unleashed in retaliation against a nuclear attack. So if both stick to doctrines (which substantively affects training and organization of nuclear forces) they should never go nuclear.
However, national leaders can and do change their minds about nuclear arms policies, and trust is generally lacking between military rivals. For now, one can only hope India’s effort to reduce the current imbalance in nuclear capabilities will make nuclear war between the world’s two most populous countries even more unthinkable—not less.
Sébastien Roblin has written on the technical, historical, and political aspects of international security and conflict for publications including 19FortyFive, The National Interest, MSNBC, Forbes.com, Inside Unmanned Systems and War is Boring. He holds a Master’s degree from Georgetown University and served with the Peace Corps in China. You can follow his articles on Twitter.
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