In this episode of Cut the Clutter, ThePrint Editor-in-Chief Shekhar Gupta explains India’s commissioning of its third nuclear-powered ballistic missile submarine. He breaks down the role of SSBNs in India’s nuclear triad, the logic of deterrence, and the technological and strategic challenge of building these submarines. He also places India’s programme in a wider global context, including comparisons with China and other nuclear powers.
Here’s the full transcript, edited for clarity:
Trump has been yo-yoing between profanities and peacemaking, from ‘I will come and destroy everything’ and ‘I believe I will leave no weapon unused’ to ‘we are about to make peace’. And that has given us a day’s break from what is going on in the Gulf war.
We can therefore focus on something that has happened domestically: India commissioning its third nuclear weapons submarine, an SSBN.
Once again, I had explained it in episode 1512. There are two kinds of nuclear submarines: SSN and SSBN.
SSN is a Submersible Ship Nuclear that is a nuclear submarine that carries conventional weapons. That is the kind of submarine that the US used to sink IRIS Dena in the Indian Ocean. That was USS Charlotte, which is an SSN. The other category is SSBN.
SSBN stands for a Submersible Ship Ballistic Nuclear. So SSN is a submarine that runs on a nuclear reactor but does not carry nuclear weapons. SSBN also runs on a nuclear reactor but it carries nuclear ballistic missiles. That is the difference.
India started moving into the SSBN area much before it started planning to build SSNs, and the third of those has just been commissioned, INS Aridhaman.
This series is named as follows: Ari means enemy, or dushman. The first was Arihant, the second was Arighat, the third is Aridhaman. All mean the same thing—destroyer of the enemy.
The fourth one is in the works. I think it will be out in another year or year and a half, and then a fifth in this series. Once these five come, then India will have a truly credible triad.
A nuclear triad is essential to deterrence. You do not make nuclear weapons for using. No country that makes nuclear weapons ever hopes to use them. Deterrence means: if you use nuclear weapons against me, I will use 10 times as many and I will deter you. But the other side might say it knows where your nuclear weapons are, because after all there are satellites, electronic intelligence and human intelligence. Most countries will know many of the locations of the other side’s nuclear weapons and missiles.
That is why you distribute your nuclear weapons or strategic deterrent in three places, or in three dimensions.
One is gravity-drop bombs—like the Hiroshima bomb. You can sling them under a big fighter aircraft. A Rafale or Mirage 2000 or Sukhoi-30 MKI can carry it. But increasingly the value and use of gravity bombs is going down, because that means an aircraft has to go very deep into adversary territory. You are not going to drop a nuclear weapon 100 kilometres away from your border, or 10 kilometres away. The more advanced nations are able to have air-launched missiles, nuclear-tipped air-launched missiles that carry nuclear warheads. India still does not have them. I presume that is something in the works. Pakistan does not have that either. I do not know what they are doing, but I know for sure that on our side the Integrated Guided Missile Development Programme is looking at something like this too, in partnership with the Strategic Forces Command.
The second dimension is land. India has plenty of land-based missiles. All of India’s ballistic missiles are nuclear-capable, though not all have been given nuclear warheads.
Prithvi can go up to 350 kilometres, which covers most of Pakistan if that is India’s target. Then we have various iterations of Agni 1, 2, 3, 4 and 5, now credibly going up to about 5,000 kilometres. God forbid if it ever has to be used, it can cover almost all of China from some place deep inside India. However, it would still be either on a launcher that can be tracked, or underground, or wherever these things are kept, and satellites and movements are also being used to strengthen our land-based deterrent.
India has also experimented with train-based missile-launch capability, which means a launcher can travel on a train from one place to another, making it much tougher for an adversary to take it out. What will an adversary usually do if it thinks India may use nuclear weapons, particularly because India has a publicly stated no-first-use doctrine.
India says it will never use nuclear weapons or weapons of mass destruction against anybody first. But if somebody uses any nuclear weapon or any weapon of mass destruction—biological, chemical, nuclear, whatever—against India, then the response will be massive, disproportionate and totally destructive. That is why any adversary in this case—the usual suspect would be Pakistan, because they talk about nuclear weapons loosely quite often, particularly tactical nuclear weapons, and think that if they use one tactical nuclear weapon they can get away with it—may be tempted to take out all of India’s nuclear weapons on the ground and then say, “air I can manage”. In any case, who goes that far inside somebody’s airspace to drop a nuclear weapon? That era is gone.
To prevent that, and to cover for that most unlikely possibility, you need a third dimension.
That third dimension is not on water. You can put nuclear launchers on ships, but ships are easy to find and track, difficult to hide and do not move very fast. Surface ships carrying nuclear weapons are not your third dimension. It has to be something deep underwater and able to stay deep underwater for a very long time, with a proper protocol for when to launch. That is why countries that want to build a triad need a nuclear-powered submarine that also carries nuclear weapons.
Why nuclear-powered? Why not put these on a conventional submarine? Because a conventional submarine has limitations on how long it can remain underwater.
After some time, it has to come up to snorkel to get more oxygen and recharge its batteries. Some of the newer submarines with air-independent propulsion can stay underwater longer, but still not long enough. They will come out at some point, and some satellite or some surveillance will pick them up and start plotting them. An SSBN, on the other hand, runs on a nuclear reactor.
India’s current SSBN, Aridhaman, runs on an 83-megawatt compact light-water reactor. It uses uranium, but not uranium enriched to the degree where it can become a weapon. The reactor is not the weapon. Where that uranium comes from, do not ask me. India has sufficient output of uranium of its own from those nuclear installations which have been declared military under the Indo-US nuclear deal. These military facilities are not subject to the UN/IAEA safeguards. That means inspectors of the International Atomic Energy Agency do not come to these installations. Most of our other power plants, where we import uranium, are subject to IAEA safeguards. Those are the civil nuclear installations.
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What does an SSBN do? An SSBN can sit underwater for months together. In fact, it can sit underwater indefinitely because it is the same fuel being used. It needs a lot of water for cooling, but that water is recirculated. The time it can spend underwater is only limited by two things: first, the amount of food and provisions it can carry; and second, simple human endurance, because staying underwater is very challenging. Submariners have among the toughest jobs in the world. Even in a conventional submarine it is very tough because spaces are limited. It is cramped. You are underwater for a long time. But in this case, for an SSBN, you are underwater for months at a time.
The second thing to remember is that an SSBN, counterintuitively, is less quiet. It makes more acoustic noise—not noise that you and I hear, but noise for sensors to pick up — simply because it circulates coolant inside, and that makes a bit of a racket. That is why countries will not send their SSBN too far away from them. Also, an SSBN in India’s context does not have to go too far. It does not have to go and sit deep inside the Pacific somewhere. It can be somewhere in the Bay of Bengal or maybe the other side of the Indian Ocean, south of the Indian coast, and still cover most of the territory of India’s interest.
The message is that you cannot be sure. You may try what you want. You may think you have the best intelligence, that somebody’s satellites are telling you what is where. But there will always be something. You will always have to cater to the possibility—or maybe inevitability—that there will be something hanging somewhere underwater that will then carry out devastating retribution on you.
For this to be credible, you have to have two or three of these boats underwater at any point in time. These need frequent servicing, maintenance, and the human beings inside the submarines also need recovery time after being away for long periods on long voyages underwater. So if you have three, you cannot have all three in the water all the time. Once you have five, you can be reasonably confident that at least three will be operationally deployed. Even if you had three, maybe one or two would be operationally deployed, but once you have five you can have about three, and that is when your deterrence triad becomes more complete.
Once that is done, India is not stopping there. After that, India plans to bring the next series, which will be bigger, with bigger reactors and perhaps more weapons as well. That said, once we understand the basics, I will tell you about these submarines. The submarine we talked about last time was INS Arighat, which was a 6,000-ton displacement submarine. Displacement is the weight of water displaced once a vessel goes into water, which means the weight of the vessel plus everything inside it—personnel, missiles, food, water, everything. The larger the displacement, the bigger the boat.
The latest one, Aridhaman, is 7,000 tonnes, so it is a bit bigger than the last one. It is also bigger in size. The last one was 101.6 metres. This one is about 124 or 125 metres. The width, or what in naval language would be called the beam, is 11 metres. In both cases, the basic difference between the two is the weaponry they carry. Our two submarines already in the water, Arihant and Arighat, carry missiles or missile tubes—four missile tubes. These carry K-15 missiles, with a range of 750 kilometres.
India has tested the K-4 missile. That missile has been tested from a submerged platform, not from a submarine but from a submerged platform. The K-4 missile can reach 3,500 kilometres. This new submarine, Aridhaman, also has more displacement. It is heavier. It carries eight missile tubes. Its two older sisters carried four missile tubes each. Aridhaman carries eight missile tubes. It can carry both K-15 missiles and K-4 missiles as well by this time, because Indian engineering is getting better and many private companies are also working on this project.
Larsen and Toubro is working on it. In fact, when you go to Larsen and Toubro’s headquarters in Mumbai, one of the things they have displayed with pride is a model of one of these Arihant-class boats, as they are called. Larsen and Toubro has worked on this. Tata Power Systems has worked on this. They have made control systems. Walchandnagar has worked with high-tech defence work for a very long time. It has built steam turbines for this project, and a lot of other organisations are putting their capabilities into it.
With the improvements taking place as each new version comes out, the reactor is also becoming quieter. So the acoustic signature of Aridhaman is lower than Arighat’s. And the presumption is that as the next boats come, and heavier boats come, bigger boats come, they will be even more sophisticated. Just to understand the size issue: the Chinese boats, the Chinese have six boats in what is called the Jin class, or JL-3s.
They have a displacement or tonnage of 13,000. So they are about twice as big as Indian SSBNs. But you know what? In this business, in the deterrent business, Dr Subramaniam and General Sundarji used to say, “more is not needed when less is enough”. Which means as long as you have the ability to deliver one, two, three, four accurate hits on an adversary, and do so credibly, that gives you deterrence. It is not just that you have to keep piling up more and more weapons. The nature of nuclear weapons is that once you start with them, you cannot say, “I have two bombs, that is enough.” You have to look at deterrence and go into the second dimension and the third dimension.
India started thinking of a nuclear weapons submarine in 1974 itself, when Pokhran-I took place, although Mrs Gandhi’s government called it a peaceful nuclear explosion. At that point, India set up a project in its defence research group called Project 932. You might even find some stories I probably did about this, either for the Indian Express earlier, before 1983, or in India Today magazine. I am sure there are a couple like that. Project 932 then came to be named the Advanced Technology Vehicle. That was also something that was spoken about in hush-hush tones. Nobody knew any details. In any case, those who knew did not talk about it.
It was George Fernandes, as India’s defence minister, who first made this public formally in 1998 in Parliament. He said that India was working on its nuclear triad by building a submarine capacity. That was after India formally became a nuclear weapons power. With all of this, India became formally a nuclear power in 1998. India made a public disclosure that it was working on an ATV, as it was then called.
From then until the launch of the first SSBN, it took more than 10 years. It was in 2009 that Arihant was launched. In 2016 it was commissioned quietly. It took seven years. The current one, the latest one, Aridhaman, was launched in 2021. It was scheduled to be launched last year, but now it has taken five years. What was seven years has now become five. I suspect the next one will come out even earlier, because India is mastering this technology and engineering.
Even with the launch of this one, there was no ceremony — nothing. It was quietly launched in Vizag. All we saw was a cryptic, or maybe not so cryptic, tweet by Raksha Mantri Rajnath Singh that said, “it’s not words but power”, in single quotes, and that Aridhaman was now working.
शब्द नहीं शक्ति है, ‘अरिदमन’!
— Rajnath Singh (@rajnathsingh) April 3, 2026
How significant is this? First of all, to build a nuclear reactor for a submarine is very complicated, and to build a nuclear submarine takes time. Even a conventional one takes time. Australia signed the AUKUS agreement with the UK and America; both have been building nuclear submarines for a very long time. The first SSN under this joint arrangement will not come out before 2032. That is almost 7-8 years for the first one to come out. It is complicated.
India focused so far only on the technology of building SSBNs because that was essential for the triad to be credible. That has made India only the sixth country in the world to have this ability. The other five are the usual suspects: the P5, the permanent five in the UN Security Council—the US, France, Britain, China and Russia.
As we speak, India is still some distance away from building its own SSN. In fact, two SSN boats have been approved. They have been budgeted for. Work has started. But these boats, SSN—nuclear-powered but not carrying nuclear weapons—are likely to come out only between 2036 and 2037. That is how complicated this engineering is.
India, by the way, has experience in operating SSNs. Those were leased by the Indian Navy. The first one was from the Soviet Union, the second from Russia. The first was a Charlie-class. The second was an Akula-class called INS Chakra. A third one is due, but delayed, maybe because of production delays in Russia, and that will also be an Akula-class.
A key difference needs to be understood. These submarines that India leased earlier, and the ones that come in as SSNs, are all operated by the Indian Navy. But SSBNs do not fall under the Indian Navy. SSBNs are part of your nuclear assets, your strategic assets. They fall under the Strategic Forces Command. And even the budget for these does not come from the defence budget. It comes from a separately allocated budget for the Strategic Forces Command.