Gessler: Future Indian SSNs & SSBNs: Comment 1.

Following India's 6 Future Alpha SSNs - SSBN Protectors of April 7, 2021 Gessler made some learned and extensive comments on April 9, 2021. Pete has added some comments in [...] brackets. Here is the first of 3 Gessler instalments:

“@Pete. I'm sceptical about the figures of India’s future indigenous Project 75 Alpha SSN tonnage/displacement floating around in the media. I suspect those displacement figures (not only mentioned by Hindustan Times but many others as well) are from the same erroneous sources that also claimed that the S-3 boat (INS Arighat) the sister of S-2 (INS Arihant) would be considerably bigger and carry 8 missile silos. 

The photo in question, showing INS Arihant and Arighant, at right, berthed alongside each other and the pier. (Photo reproduced from idrw . com December 18, 2020.)
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But satellite images (like this) of the Ship Building Centre (SBC) harbour at Visakhapatnam (Visak, most commonly pronounced & spelled Vizag) prove that both of the Arihant-class INS Arihant and INS Arighat are the same eg. Arihant class displacement 6,000 tonnes (surfaced, confirmed), length (116m) and size (Beam 11m, Draught 15m), and carry the same number of missile tubes, ie. 4. [See "Future of Indian Navy - Nuclear Submarines"]

Now don't get me wrong - I still am inclined to believe the 4th nuclear boat to be built by SBC (known in the media as the S-4* or S-4 Star) [see "Ships in class"] would indeed be considerably bigger than the Arihant-class, satellite images of a new submarine dockyard shelter constructed at Vizag which is up to 40m longer than Arihant's shelter substantiate the theory that a new, bigger boat is around the corner - and it definitely can't be the S-5 yet. So it has to be the rumoured S-4* SSBN, with perhaps 8 silos.

Nuclear expert Hans M. Kristensen's observation of the same summarized in his tweet, though he speculates this to be intended for the S-4 itself (3rd nuclear boat), not the S-4*. Personally, I would think all three Arihant-class SSBNs will be of the same dimensions, it would not make any sense to have the last boat in class to be substantially different than the others.

The S-4* on the other hand might make sense as both a test platform for new, larger equipment that may eventually find use on the still larger S-5 class down the line, once the systems mature after at-sea testing on this boat. The Arihants would have to be at sea (or in refit), delivering on the deterrence role, you can't ask them to come off their vitally important duties to function as test platforms for new stuff - the S-4* might make a lot of sense in that respect. 

Another reason to be sceptical about the Alpha's displacement figures would be that pretty much all available sources (unless I'm misremembering) quote the Arihant-class boats' surfaced displacement as approx. 6,000 tonnes. 

So if the Alpha indeed turns out to 'Arihant without silos' then there's no way it'll also be 6,000 tonnes surfaced. The Alphas will have to be 5,000 tonnes [surfaced], but even that is speculation.

So personally I'll hold my horses for now regarding the displacement figures."

[For comparison see the 6,000 tonne (likely submerged) 100m long, Brazilian future SSN Alvaro Alberto (SNB or SN-BR). Implicitly its displacement may also be around 5,000 tonnes surfaced.] 

On Saturday April 17 Gessler's 2nd informative Comment will appear.