First Two S-5 SSBNs Under Construction, and a Comment on India's Nuclear Submarine-Building Capacity

In an article written mainly about the S4* (the fourth & final Arihant-class boat) sailing out for sea trials, Chakra News has reported that the first two boats (out of a reported four-boat order) of the “S5”-class nuclear-powered ballistic missile submarines (SSBNs) are already under construction for the Indian Navy as of late 2025.

It serves to know that Chakra News was co-founded by Sandeep Unnithan, the veteran journalist who is the go-to media authority on India’s nuclear submarine program, with well-placed sources inside the program, as I have previously noted on SubMatts.

Provisional sketch of the S-5 class SSBN (based on an older iteration of the hydrodynamic testing models). Courtesy H.I. Sutton of Covert Shores.
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While writing about India authorizing the construction of the first two boats (out of a planned six-boat requirement) under its nuclear-powered attack submarine (SSN) program known as Project-77, I had made the assumption that due to the nature of the SSBN program, which involves carrying nuclear weapons as a standard mission, seen together with India’s status as a non-signatory to the Nuclear Non-Proliferation Treaty (NPT), the progress of the S-5 program will not be subject to the same level of media access and will therefore be harder to keep track of. I was previously of the opinion that progress on the S-5 program is likely to be in a more advanced stage than the P-77 SSN program.

Both these assumptions turned out to be correct. We never heard about the funding being granted for commencing the S-5’s build program, or when the build had actually started. Also, it becomes clear that the S-5 program is now in a much more advanced stage than the P-77 SSN.

So what is the S-5?

To refresh everyone’s memory, the “S-5” is a class of four SSBNs planned to succeed the Arihant-class (inclusive of the Arihant Stretch sub-class) in the all-important role of serving India's equivalent of what the UK would refer to as Continuous At-Sea Deterrence (CASD), by ensuring a credible Nuclear Second-Strike capability. As such, the S-5 can be regarded as the second generation of Indian SSBNs.

The S-5 is widely reported (including by Mr. Unnithan) as displacing around 13,500 tons surfaced (so around ~16,000 tons submerged), about the same as the Royal Navy’s Vanguard-class SSBNs, and more than twice as much as the first-generation Arihant-class. The S-5’s deterrence mission is expected to be served by no less than 12 missile tubes carried behind the sail/conning tower, as opposed to 4 tubes on the Arihant-class (SSBN hulls S2 and S3) and 8 tubes on the Arihant Stretch variant (SSBN hulls S4 and S4*). These 12 tubes are expected to house the upcoming K-5 and/or K-6 submarine-launched ballistic missiles (SLBMs) with MIRV'ed nuclear warheads. I’ll be writing more about developments in that missile program later.

An example of an older (c. 2018-19) hydrodynamic model of the S-5 SSBN. Image sourced via the website of Manjira Machine Builders Pvt. Ltd, a private defence contractor involved in the process.
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While I had previously speculated, based on Mr. Unnithan’s reporting, that both the P-77 SSN & S-5 SSBN will be powered by the same CLWR-B2 Pressurized Water Reactor (PWR), it has now been confirmed by the Times of India, quoting an unnamed BARC scientist, that both these classes of submarines will indeed share the same reactor model.

While previous reportage on the CLWR-B2 PWR quotes it as having an output of 190 MWth (MegaWatt Thermal), the Times of India report linked above describes it as being 200 MW (an editorial oversight by the newspaper means they erroneously write it as MWe (MegaWatt Electric) instead of MWth, 200 MWe would translate into 650-700 MWth which is obviously not attainable for a submarine-based reactor given the size & weight limitations of onboard heat-exchanging & primary/secondary loop equipment).

It's unclear whether the 190 MWth figure was just rounded off to 200 MWth by the BARC source or if we are indeed looking at a slightly improved/uprated output for the final configuration. Either way, an output of 190-200 MWth would make the upcoming Indian submarines very much comparable in terms of ‘power on tap’ with most contemporary American/Russian submarines like the Virginia, Ohio, Yasen or Borei-classes, all of which have reactor outputs in the 190-220 MWth range, which translates into an electrical output of between 50-60 MWe depending on efficiency of the electrical system’s design and materials.

This electrical output will likely drive a 35 MW Nuclear-Electric Propulsion setup (also known as a Turbo-Electric Drive, where the noisy mechanical reduction gearbox is replaced with a silent electric motor serving as transmission), which I had also written about in my article dealing with the SSN program. This NEP/TED setup, much like the 190-200 MWth PWR, will likely be utilized across both submarine classes (assuming it does end up getting implemented), and just like the reactor, it will likely be ‘tuned’ to support each class’s unique power-delivery requirements.

An example of a newer (c. 2023-24) hydrodynamic model of what is presumed to be the S-5 SSBN. This is a cropped image with AI-based resolution upscaling, enhanced sharpness, contrast and colour-correction. The original, uncropped image can be found here.
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With a maximum of around 35 MWe going to the submarines' motive/propulsion needs (though the propulsion won't generally be using 35 MWe all the time), it would still leave about 15-25 MWe on the table to serve other electrical purposes (for powering Sensors, Life Support Systems, Combat Management Systems, the boats' own Integrated Platform-Management System, etc.) even while the submarine is in a high-speed transit.

For comparison, the French Navy (Marine Nationale)'s Barracuda/Suffren-class SSN uses a 20 MWe nuclear-electric propulsion system (consisting of 2 x 10MWe turbo-generators) while the Triomphant-class SSBN is believed to use a 30.5 MWe system. Assuming the French K15 reactor (150 MWth) and secondary systems, shared by both Suffren & Triomphant classes, have a similar ~30% efficiency ratio (providing about 45 MWe of total electrical power), the French boats would also be left with a similar amount of power on the table (15-25 MWe) for non-propulsion needs. Note that, as stated earlier, just because an electric motor is of a certain power rating doesn't necessarily mean it will use that much all the time. The full rated power of the propulsive motor will likely only be used when the submarines are in high-speed transits.

A further note would be that, while at least the Suffren-class only uses its electric motors for transit up to a certain unspecified speed (switching to conventional reduction gearing for speeds beyond that, as mentioned in my previous article), it's not known how the Indian boats are configured for higher-speed transits. It's also not known if the 35 MWe setup is only for the S-5 SSBN while the P-77 SSN will get a smaller motor rated for less power or if the same motor with the same power rating will be shared by both classes, which I think is unlikely though much will depend on how big the P-77 SSN turns out to be, which is information that's not yet public knowledge though some informed sources put it at around the 6,000 tons (surfaced) figure while others say it will be 10,000 tons.

On topic, the first S-5 SSBN is expected to be commissioned into active service at some point in the mid-2030s. All four boats under this class could be in service by the late-2030s or possibly the early 2040s.

New Dry-Dock

A new, large dry dock that was being constructed at the Ship-Building Centre (SBC) right outside the city of Vizag on the eastern coast of India appears to be either complete or close to completion. The new dock, which I wrote about earlier, is situated beside the smaller, but longer, older one (which built the Arihant-class) and is part of the same SBC complex, dedicated for the construction of nuclear-powered submarines for the Indian Navy.

The large northern structure (with blue roof) is the new dry dock. The smaller southern structure (with 'L&T Heavy Engineering' pin on top) is the older dry dock, where the Arihant-class was built. Image via Google Maps.
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The new dry dock, as per some quick Google Earth-based map measurements done by me, is around 64 meters wider than BAE System’s Devonshire Dock Hall at Barrow-in-Furness, which is notably capable of simultaneously fitting out three Astute-class hulls, side by side. That makes the new Indian dock nearly about the same length as the one in England (253m compared to 268m), but over TWICE as wide (128m compared to BAE’s 63m-wide facility). It's also about 30 meters wider than General Dynamics Electric Boat's final assembly building at Groton, Connecticut. A dock this large could enable the SBC complex to build at least three, if not four, large nuclear submarine hulls side by side under one roof, if needed.

Three Astute-class SSNs of the UK Royal Navy, seen under various stages of construction inside BAE's Devonshire Dock Hall at Barrow-in-Furness, northern England. BAE Systems image, sourced via Navy Lookout.
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This capacity, especially when seen combined with the older, longer (358m) dry dock (which is known to be capable of simultaneously building at least two Arihant-class boats, one behind the other), would imply that the SBC complex as a whole would ultimately be capable of simultaneously building at least 5-6 nuclear boats, under various stages of fitting out, at any given time. This capacity would be greatly necessary should the Indian government decide to expand the required number of SSNs in the future from six to at least twelve, as I had previously advocated for.

A clear view of the SBC complex, just outside the city of Vizag, south-eastern India. Image sourced via Twitter/X.
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On the topic at hand, the fact that the first two S-5s are already under construction would imply that the older dock (which has already been freed up as of late 2025 when the last Arihant-class boat sailed out for sea trials) would be utilized for their final assembly, while the new dock would exclusively cater to the P-77 SSN program. However, it’s also possible that commencement of S-5’s build program only implies that module fabrication of the boats has started at places like L&T’s Hazira facility (which also built modules for the Arihant-class) located on the western coast just outside Surat, a city of 7 million people located approximately 300 km north of Mumbai, from where they are shipped for final assembly to SBC on the eastern coast.

A presentation believed to show CAD images of L&T's Hazira module-fabrication facility, located in the western State of Gujarat. Real images of the interior of this facility have never been seen. This picture is also sourced via Twitter/X.
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This is a process similar to how the US builds modules for the Columbia-class SSBN at a Newport News facility in Virginia and then ships them to GDEB's aforementioned facilities in Connecticut on a barge for final assembly, a distance of some 600+ kms along the US east coast.

In this case, it could mean that final assembly of the S-5s could happen at either dry dock, old or new. That remains to be seen.

The stern section of a Columbia-class SSBN of the US Navy being transported on a barge toward the final assembly site. Image via General Dynamics Electric Boat.
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End of article. Stay tuned for more, this time regarding developments in the aforementioned K-5 SLBM program.

16 or more Columbias due to Russian AND rising China Threats

Thanks Anonymous for your 5/10/2026 11:33 AM comment. 

More Than 12 Columbias?

Given rising threats from Russian and Chinese nuclear submarine fleets the US should strongly consider building more than the 12 scheduled Columbia-class SSBNs. More than 12 might already be a top secret intention.

-  For the US that will be 12 scheduled Columbias to construct until ~ 2043. In addition the US may well build 4 or more additional Columbias to achieve parity with an enlarged combination of new high quality threats (SSBNs and SSNs) from Russia and now also China. The China threat was not fully considered when the US was settling on Columbia production numbers in the 2010s. 

So potential threats to the US include:

    =   12 x Russian Borei SSBNs already built/building and 12 x Yasen SSNs built/building/planned

    =   China has not yet revealed its plans in nuclear submarine quality and quantity. However to build a global blue water nuclear submarine force China may want qualitive and quantitative parity with Russia and must also consider 4 to 6 x future Indian S5 SSBNs and up to 6 x Indian Project 77 SSNs as threats. 

     =   China has the shipbuilding capacity to design and high rate build 12+ x Type 096 SSBNs each with at least 16 x JL-3 or JL-4 SLBMs and 12+ x Type 095 SSNs.

Australia's AUKUS Needs?

Directly competing with the Columbia build is the Virginia SSN build and Virginia  maintenance programs. Indirectly, 3 to 5 Virginias earmarked for Australia under AUKUS, exacerbates problems with the Columbia build. 

More broadly all of Australia's real or imagined SSN allies (US, UK and France) are fully committed with current SSN construction. For example the Virginia program will reduce its construction drumbeat rate from 1.15 to 0.8 standard Virginias per year due to 1 Columbia per year being built from 2029. UK - final Astute(s) for UK Navy only, then straight to 15-20 years of Dreadnought SSBN production. France - final Suffrens for the French Navy only, then 20 years of SNLE-3G/newly named L'Invincible class SSBN production. All this prevents any spare SSN construction capacity for the Royal Australian Navy (RAN). That is unless South Korea's formidable SSN production potential kicks in to save Australia. 

France is also building/planning 3-5 non-Suffren, non-SSBN designs namely 4 x Orkas for the Netherlands, 1 x Brazilian Álvaro Alberto SSN, and perhaps 2 classes of small Scorpenes for Indonesia and the Philippines.  

I'll write further on nuclear submarine considerations of the UK, France and Australia around May 19, 2026.

Possible influences on India's future S5 SSBNs

A comment following Gessler's fine April 25, 2026 article is: 

As well as Kilo square sail characteristics influencing the Arihants, Russia's Delta SSBNs (with similar square sails side on) and hump back would influenced India's  Arihant designs. 

What INS Arihant (and Arighaat) may look like. Note square sail, planes on sail and hump back (Artwork courtesy H I Sutton at Covert Shores).
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I theorise that Russia has suffered so much financially from Ukraine war sanctions and higher tri-service defence spending that Russia may have traded accelerated SSBN and SSN design secrets to India. Unlike China (1969) India has no record of fighting Russia. So little risk for Russia that its defence tech exports to India would be used against Russia.

In return guaranteed Indian purchases of Russian oil and gas and joint energy projects have been considerable.

Its possible the now 30 year old Russian Borei/Borey SSBN design features will influence India's future full size S5 SSBNs. Also design features of the French and now German SSKs sold to India will influence India's S5 SSBNs.

 

Possible Borei/Borey SSBN design (Artwork courtesy Mike1979 Russia - Own work at Wikipedia (right sidebar).
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Overt and covert intelligence gathering (proud professions) about current UK, US, Chinese and French SSBN programs, would also influence India's S5 designs.

See previous Submarine Matters articles on the S5s HERE.

Trump Picks Well Qualified Ambassador to Australia

Pete Comment

Australia often has to put up with US Ambassadors who are shopping mall developers, golfing buddies and, most importantly, donors to US presidential campaigns.

Now Trump has shocked all by picking someone more than qualified.

Articles

Australian Associated Press (AAP) via the Canberra Times reports https://www.canberratimes.com.au/story/9234452/trump-reveals-long-awaited-pick-for-top-australia-post/ [link is behind a Paywall] April 28, 2026:

"Trump has announced his pick for the next American ambassador to Australia more than a year after [Trump's] return to the White House.

Former Virginia congressman David ["Dave"] Brat was nominated for the ambassador role, which has been vacant since 2024...

The ambassador position is yet to be finalised as the appointment needs to be ratified by the US Senate...

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Wikipedia https://en.wikipedia.org/wiki/Dave_Brat reveals Dave Brat is unusually well qualified, given: 

"Brat earned a B.A. in business administration from Hope College in 1986, a master's degree in divinity (M.Div.) from Princeton Theological Seminary in 1990 and a Ph.D. in economics from American University in 1995.^[11][12][13]

Academic career

After working for Arthur Andersen and as a consultant for the World Bank,^[14] Brat joined the faculty of Randolph–Macon College in 1996^[12] as an economics professor.^[15] For six years, Brat chaired the college's department of ethics and business.^[12] At Randolph-Macon, Brat taught courses including "Britain in the International Economy", "International Economic Development", and "Business Ethics".^[16]

From 2010 to 2012, Brat headed Randolph-Macon's BB&T Moral Foundations of Capitalism program. Endowed by the BB&T Corporation, the program was one of 60 similar programs devoted to the study of capitalism and morality in philosophy and economics departments at U.S. universities.^{[17][18][19][20]}

In 2006, Brat was appointed by Virginia governor Tim Kaine to the Governor's advisory board of Economists. He has also served on the board of directors of the Richmond Metropolitan Authority, and on the advisory board of the Virginia Public Access Project.^{[20][better source needed]}

In January 2019, following his defeat in the 2018 congressional election, Brat was named dean of the Liberty University School of Business.^[21] In May 2023, Brat became Vice Provost for Engagement and Public Relations at Liberty.^[22]"

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India Commissions 3rd SSBN 'INS Aridhaman'

On 4 April 2026, the Times of India reported that Defence Minister Rajnath Singh, alongside Chief of Naval Staff Admiral Dinesh K. Tripathi, had attended the commissioning ceremony of INS Aridhaman, which is the third of the Indian Navy’s Arihant-class nuclear-powered ballistic missile submarines (SSBNs).

In keeping with the tight lid on press releases regarding the SSBN program, not a single image has so far made it to the press from the event itself.

Annotated 3D model of an Arihant Stretch-class SSBN. Sourced via Reddit.
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As written on SubMatts earlier, the INS Aridhaman, also known by its hull number ‘S4’ (and presumed pennant number SSBN-82) is the first of the ‘Arihant Stretch’ sub-class, which has 8 missile launch-tubes and is estimated to be about 130 meters long as opposed to the first two boats which were about 110 meters long and only had 4 missile tubes. The displacement figures are also estimated to have gone up from about 6,000 tons surfaced (possibly ~8,000 tons submerged) to around 7,000 tons surfaced (and ~9,000 tons submerged) on the Stretch.

While the S4 boat, just like the previous two, retains the flexibility to carry either a single K-4 intermediate-range submarine-launched ballistic missile (SLBM) per launch tube or up to 3 x K-15 short-range SLBMs in a triple-packed configuration in each tube (for a total of either 8 x K-4s or up to 24 x K-15s, or any combination in between), it is my opinion that both S3 and S4 would only carry the K-4 SLBMs, due to reasons I mentioned in a previous article of mine.

The Fourth (and presumed last) boat, only known so far by its hull number ‘S4*’ (pronounced S4 Star) and widely anticipated to be named INS Arisudan, is also a ‘Stretched’ boat.

Comparison of Arihant & Arihant Stretch sub-class. Artwork by H.I. Sutton of Covert Shores.
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I had previously written about the launch ceremony of the S4* which had happened in October 2024. I had speculated then, based on reasoning mentioned within that article, that the Fourth boat could be commissioned by 2028 or thereabout, which would then mark the end of the Arihant-class build program.

It is widely believed that every Arihant/Arihant Stretch-class boat since the S3 (INS Arighaat) has an 'improved' Pressurized Water Reactor or PWR, which I had designated as the 'CLWR-B1v2' in the absence of any official literature on what the improved variant should be called. It's not known for sure as to what all went into the improved reactor and how it differs from the base variant that powered the first-of-class INS Arihant (hull S2).

1. Anzac Day songs 2. My Grandfather at Gallipoli

 Two songs by Eric Bogle, in Remembrance:

Greenfields of France (also called No Man's Land and Willie McBride)

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The Band Played Waltzing Matilda (above) also by Eric Bogle, which is more to do with Gallipoli and the repatriation of a crippled Digger.

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My Grandfather, Staff Sergeant Leo Coates (above standing) in 1915. He worked at the 1st Australian "Stationary" Hospital (but still a field hospital). This was situated at Mudros, on the Mediterranean island of Lemnos, near Gallipoli. Here Leo's doing an X-ray - looking for a bullet in a wounded Anzac's leg. (The photo was donated by the Royal Australasian College of Surgeons - Photo courtesy oof the Australian War Memorial Archive).

Leo then shifted to Gallipoli later in 1915, where the field hospital was shelled by the Turks - because the Turks knew the Aussies were hiding ammunition in some of the hospital tents!  

Leo Coates was involved in early mobile X-ray machine development. Then, after he returned to Australia, he helped develop and operate permanent veterans' hospital X-ray machines.