India Navy Nuclear Submarines (SSBN & SSN)

4 Boomers before 2030. With capacity for 24 K4/5 SLBM. Hopefully we have 500kt bombs to go with it.

Nilgiri said:

https://twitter.com/i/web/status/2024687599743574242

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It's commissioning today!


The 3rd Arihant-class nuclear-powered ballistic missile submarine (hull S4, pennant SSBN-82).

The S4 marks the advent of the "Arihant-Stretch" sub-class. Biggest outwardly visible change being the expansion of missile launch cells from 4 to 8.

Gessler said:

It's commissioning today!

https://twitter.com/i/web/status/2039925045779439821

The 3rd Arihant-class nuclear-powered ballistic missile submarine (hull S4, pennant SSBN-82).

The S4 marks the advent of the "Arihant-Stretch" sub-class. Biggest outwardly visible change being the expansion of missile launch cells from 4 to 8.

View attachment 79812

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So S5 construction also has started according to this report.

An AI-upscaled, enhanced version of an old photo of the INS Arihant from over a decade ago:



Original image source:



Also, a cool new AI-generated artwork from LiveFist of the Arihant Stretch:



It seems to have been prompted using real images like this of the S3/Arighaat (but with the missile compartment increased in length to reflect the S4's configuration):



On that note, found some nice 3D models of the Arihant online, though there are some mistakes like the tailfin design (compare with real photo above):

dronie said:

So S5 construction also has started according to this report.

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An earlier report by Sandeep Unnithan's Chakra News (Sandeep is the most reliable source on the nuclear submarine program) revealed that the first TWO boats of the S5 class were under construction, not just one:

"The ATVP has already begun construction of the first two units of the S5 SSBNs, which at 13,500 tons are twice the size of the Arihant-class submarines. The first S5 will enter service in the early 2030s. A total of four S5 SSBNs will be acquired by the late 2030s."


My comment on that:

Good article from the IISS (International Institute for Strategic Studies), credit to Joseph Dempsey & Karl Dewey:


There's lots of interesting satellite images (via Vantor) and information, here's some excerpts:

"On 3 April 2026, the Indian Navy commissioned INS Aridhaman (S4), its third nuclear-powered ballistic missile submarine (SSBN), at Visakhapatnam on the Bay of Bengal.

Despite widespread reporting by local media, there was no official confirmation, with New Delhi remaining secretive about its growing SSBN capabilities. Nonetheless, satellite imagery analysis by the IISS corroborates reporting, with imagery from 5 April showing an SSBN – almost certainly INS Aridhaman – with maritime signal flags strung along its hull. Known as ‘dressing overall’, the practice is reserved for special celebratory events."



"Assessments regarding the status of India’s naval deterrence are mixed. Indian authorities credit their SSBNs as having undertaken ‘deterrence missions’ – with the lead boat Arihant completing a first patrol in late 2018. However, their growing fleet is not yet fully operational in a commonly understood Continuous At-Sea Deterrent (CASD) role, with imagery from January 2026 showing all four hulls alongside at Visakhapatnam."



"Though a continuous patrolling cycle is theoretically possible with three boats rotating between patrol, repair, and training, this leaves little redundancy or flexibility, especially considering that each stage is likely to vary in duration. Commissioning S4*, potentially in 2027, will ease operational pressures and allow at least one boat to be continuously on patrol. In conjunction, the other SSBNs can progress through repair and training cycles while the fourth boat remains in reserve, in case of operational or technical issues.

As such, only once all four Arihant-class boats are commissioned will India have the foundations for a robust nuclear triad, though purists may go further and insist that, because of the seeming capability differences between the Arihant class’s two batches, Indian strategists may need to wait for the S5s to enter service before the navy has an undeniably robust CASD. In addition to the boats themselves, other factors, such as India’s evolving submarine-launched ballistic missile (SLBM) capability and growing Very Low Frequency (VLF) communications systems, are also key to a survivable second-strike capability."



"Visakhapatnam has been home to India’s SSBNs for several decades, with the four Arihant-class boats all constructed, fitted out and operating within close proximity. Housing an SSBN base within a wider congested port complex may pose operational and physical security challenges, with mobile floating shelters providing limited concealment and little in the way of protection.

However, over at least the last 15 years, work has been slowly progressing on a more remote and secure home, some 50 km south of Visakhapatnam. While the new naval base, known as INS Varsha, is expected to host other elements of the Indian Navy’s Eastern Naval Command’s growing fleet of surface combatants, it is expected principally to serve as a nuclear submarine support facility for India’s SSBN fleet. In addition to the existing fleet, INS Varsha seems prepared to accommodate India’s next generation of SSBNs, with two S5 SSBNs already under construction at Visakhapatnam, according to local media."



"Information on the secretive base remains sparse, but one element that is increasingly apparent from satellite imagery is the widely reported construction of an underground submarine facility, with two large tunnel entrances visible. Recent imagery indicates water within the tunnels, suggesting completion of the waterway, and a logical next step would be to remove the cofferdams used to hold back the water during construction. Though the layout of the facility is not clear beyond these two – presumed linked – water entrances, some 1.5 km apart, it is also ringed by over a dozen apparent road-access tunnel entrances, indicating the potential for a much vaster underground support complex for SSBN operations."

"While housing the facility underground provides additional natural protection for berthed submarines and infrastructure, it also aids in the concealment of deployed numbers from space surveillance. There are numerous precedents for underground submarine basing, and this is a feature of China’s People’s Liberation Army Navy base at Hainan Island."

Outlook​

"The commissioning of India’s third SSBN is an indisputable milestone in the country’s ambitions to establish a credible minimum deterrence, with the additional boat marking a further step towards enhanced survivability and a credible second-strike capability. That said, India’s vision of credible minimum deterrence remains a work in progress, as the country begins to implement CASD, finalises basing at INS Varsha and rolls out planned VLF communications systems for the Indian Ocean region. Yet, even with these limitations, India is planning for its next generation of capabilities, as the country makes slow but deliberate progress in its nuclear deterrence."

Based on the most recent reliable information, the size & shape of the Project-77 SSN program becomes clearer:

What is confirmed by reliable sources so far:

• It will indeed displace around 10,000T (one figure quoted by an older source states a very specific 9,800T figure). So very much in the league of Russia's Yasen, China's future Type-095 & upcoming AUKUS boats, and significantly bigger than UK's Astute, France's Suffren or the earlier blocks of US' Virginia-class boats.
• It will be powered by a 190-200 megawatt PWR known as CLWR-B2. A shore-based prototype of which is known to have been in existence at least as of 2018.
• It will have VLS capability. Described as having "close to a dozen" VLS cells of the 'large' variety, so would be capable of launching likes of BrahMos/future Scramjet-based Hypersonics & possible ASBMs.

What has not been confirmed so far:

• Whether it will be a single-hulled or double-hulled design.
• Whether it will have an X-form rudder or conventional rudder/tail planes.
• Whether Nuclear-Electric Propulsion (NEP), aka Turbo-Electric Drive will be implemented or not.
• Whether the boat will have a Pump-Jet Propulsor (PJP) or not. The PJP & NEP might be tied to each other, and will have implications on whether we follow the Russian doctrine of speed over stealth or if we choose to go with Western doctrine. This is the most interesting part to look forward to as Pumpjet & NEP is pretty much guaranteed to find application on the S-5 SSBN program, which is in a much more advanced stage than the SSN (first 2 boats already in construction). So we know that whether we put it on the SSN or not will come down to doctrinal choices.

What has not been confirmed, but is extremely likely nevertheless:

• It will make use of conformal sonars. Especially a Conformal Bow Array (CBA) along with flank arrays integrated into the hull. Provision of towed array will anyway be there.

Gessler said:

So apparently, NSTL is testing this design, lack of a missile hump implies this is an SSN:

View attachment 58976

It does not necessarily mean that the upcoming Project-75A/76 SSN will have a pumpjet, or that this is indeed the indigenous SSN design (could just be a case-study of a generic modern SSN boat). But it's definitely interesting.

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Gessler said:

Based on the most recent reliable information, the size & shape of the Project-77 SSN program becomes clearer:

What is confirmed by reliable sources so far:

• It will indeed displace around 10,000T (one figure quoted by an older source states a very specific 9,800T figure). So very much in the league of Russia's Yasen, China's future Type-095 & upcoming AUKUS boats, and significantly bigger than UK's Astute, France's Suffren or the earlier blocks of US' Virginia-class boats.
• It will be powered by a 190-200 megawatt PWR known as CLWR-B2. A shore-based prototype of which is known to have been in existence at least as of 2018.
• It will have VLS capability. Described as having "close to a dozen" VLS cells of the 'large' variety, so would be capable of launching likes of BrahMos/future Scramjet-based Hypersonics & possible ASBMs.

What has not been confirmed so far:

• Whether it will be a single-hulled or double-hulled design.
• Whether it will have an X-form rudder or conventional rudder/tail planes.
• Whether Nuclear-Electric Propulsion (NEP), aka Turbo-Electric Drive will be implemented or not.
• Whether the boat will have a Pump-Jet Propulsor (PJP) or not. The PJP & NEP might be tied to each other, and will have implications on whether we follow the Russian doctrine of speed over stealth or if we choose to go with Western doctrine. This is the most interesting part to look forward to as Pumpjet & NEP is pretty much guaranteed to find application on the S-5 SSBN program, which is in a much more advanced stage than the SSN (first 2 boats already in construction). So we know that whether we put it on the SSN or not will come down to doctrinal choices.

What has not been confirmed, but is extremely likely nevertheless:

• It will make use of conformal sonars. Especially a Conformal Bow Array (CBA) along with flank arrays integrated into the hull. Provision of towed array will anyway be there.

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Knowing what we know now (confirmation of ~10K tons, VLS & what not), I think it might be worth it to take a second look at this design that NSTL was testing a while ago:





Overall configuration appears to be quite similar to the Virginia-class (sail-forward design, crossform rudder, pumpjet).

Fourth and Final Arihant class SSBN S5 Arisudan expected to be commissioned this year or early next year.

24 K4/K5 or 72 K15 missile capacity

Rajendra Chola said:

Fourth and Final Arihant class SSBN S5 Arisudan expected to be commissioned this year or early next year.

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2028 is more likely. The fourth boat started sea trials only in December 2025, a minimum of 2 years is a given. So late 2027/early 2028 completion of trials. Commissioning a few months afterward so mid-2028.

Rajendra Chola said:

24 K4/K5 or 72 K15 missile capacity

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Lol, no.

It'll be a Stretched boat, same as the 3rd one (Aridhaman), so either 8 K4 or 24 K15 maximum.

K5 physically cannot fit any Arihant-class boat, it's diameter is too huge (at 2.4m, it's almost twice as big as K4's 1.3m).

Only the future S5-class SSBNs can carry the K5/K6.

Gessler said:

2028 is more likely. The fourth boat started sea trials only in December 2025, a minimum of 2 years is a given. So late 2027/early 2028 completion of trials. Commissioning a few months afterward so mid-2028.



Lol, no.

It'll be a Stretched boat, same as the 3rd one (Aridhaman), so either 8 K4 or 24 K15 maximum.

K5 physically cannot fit any Arihant-class boat, it's diameter is too huge (at 2.4m, it's almost twice as big as K4's 1.3m).

Only the future S5-class SSBNs can carry the K5/K6.

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I mentioned the capacity of all 4 SSBN or INs strategic weapons capability. Not for Arisudan.

I am not sure regarding commissioning cos after INS Arihant & Aridhaman other subs commissioning went quite faster.

Rajendra Chola said:

I mentioned the capacity of all 4 SSBN or INs strategic weapons capability. Not for Arisudan.

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Ah, ok.

But all 4 subs will not be available at the same time though, only 1 or at best 2 will be in a ready-to-launch state at any given time.

Rajendra Chola said:

I am not sure regarding commissioning cos after INS Arihant & Aridhaman other subs commissioning went quite faster.

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The build rate does get faster as you make more boats, but there's no shortcuts in Sea Acceptance Trials (SATs).

The Arihant-class is pretty unique in a way because so far, every boat was significantly different from the last*. This does not usually happen on other SSBN classes but we have to use these boats to prove a lot of techs & implement constant, iterative improvements if we want to catch up with China by the time we commission S-5 class & P-77 SSNs.

*Arihant was the first-ever nuclear submarine we ever built so a lot of unknowns all around, not just with the construction itself but with all the component suppliers for the boat + the reactor. Arighat took a lot more time than a typical 2nd-of-class should because it brought an improved reactor configuration online and that was essentially like building an all-new class cuz N-subs are pretty much "built around the reactor"...you change the reactor, you have a change a whole lot of things (they say the new reactor came online with 3rd boat but I don't buy it. The timeline only makes sense if it came with 2nd boat). Aridhaman was the first 'stretched' variant with an additional 4-missile plug compartment and we had to go back to the drawing board to recertify the hull for a different CoG/CoM. Arisudan is supposed to be a simple repeat of Aridhaman but that's to be seen. I won't be surprised if it turns out we've plonked a pumpjet on the 4th boat to de-risk future developments.

That said, all boats have taken 2-3 years in SATs, regardless of new reactor or not, so indeed there are no shortcuts there. Minimum 2 years would be my guess.

We'll see.

Gessler said:

Ah, ok.

But all 4 subs will not be available at the same time though, only 1 or at best 2 will be in a ready-to-launch state at any given time.



The build rate does get faster as you make more boats, but there's no shortcuts in Sea Acceptance Trials (SATs).

The Arihant-class is pretty unique in a way because so far, every boat was significantly different from the last*. This does not usually happen on other SSBN classes but we have to use these boats to prove a lot of techs & implement constant, iterative improvements if we want to catch up with China by the time we commission S-5 class & P-77 SSNs.

*Arihant was the first-ever nuclear submarine we ever built so a lot of unknowns all around, not just with the construction itself but with all the component suppliers for the boat + the reactor. Arighat took a lot more time than a typical 2nd-of-class should because it brought an improved reactor configuration online and that was essentially like building an all-new class cuz N-subs are pretty much "built around the reactor"...you change the reactor, you have a change a whole lot of things (they say the new reactor came online with 3rd boat but I don't buy it. The timeline only makes sense if it came with 2nd boat). Aridhaman was the first 'stretched' variant with an additional 4-missile plug compartment and we had to go back to the drawing board to recertify the hull for a different CoG/CoM. Arisudan is supposed to be a simple repeat of Aridhaman but that's to be seen. I won't be surprised if it turns out we've plonked a pumpjet on the 4th boat to de-risk future developments.

That said, all boats have taken 2-3 years in SATs, regardless of new reactor or not, so indeed there are no shortcuts there. Minimum 2 years would be my guess.

We'll see.

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Again, dates arent being shared when they started sea trials generally. But even by Indian standards, SSBN induction has been quite faster.