Part 3: Slew of Developments in the Indian Nuclear Submarine Program: First Two SSNs Funded

On the 9th of October 2024, The Cabinet Committee on Security (CCS), the apex decision-making body of the Indian Government regarding all Military matters, has officially granted its final seal of approval to the Indian Navy's nuclear attack submarine program, now designated as Project-77 (previously known as Project-75A).

A sum of Rs. 40,000 crores (equivalent to about US$4.8 Billion) has been allocated toward the construction and acquisition of the first two boats out of a planned total of six.

Artistic impression of the Indian Navy's SSN by Nilanjan Das of the India Today magazine (not representative of actual design)
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Veteran journalist Sandeep Unnithan who has reported on the Indian nuclear submarine program for over a decade has stated that the P77-class SSNs would incorporate a 190MWth reactor which would represent a generational leap over the 83-100MWth PWRs of the Arihant-class. Sandeep Unnithan can be safely assumed as having sources inside the program or at least being a 'designated' individual through which the Government and/or the Navy publicizes developments. Of note is the fact that Mr. Unnithan (then working for India Today magazine) was the first journalist who reported that the 3rd and 4th Arihant-class boats will be larger than the first two, years before the S4 boat first appeared in public. Satellite images from late 2021 vindicated him.

The new 190MWth reactor, known as CLWR-B2 is likely based on or at least built along the same lines as the Russian OK-650B that powers the Akula II-class SSN that India took on lease between 2012-2021. It would also be prudent to estimate that the CLWR-B1 that powers the Arihant-class was derived from the VM-4 reactor family that powered the Charlie-class SSGN that India leased between 1988-1991. However, any help or guidance from Russian agencies (whether in design itself or at least in the design-validation phase) is unlikely to ever be publicized by either side due to obvious reasons, such as eliciting nuclear proliferation concerns.

On both these reactors, it's likely a great deal of redesign and redevelopment was involved in order to bring them up to modern standards of the time - as well as getting them to work optimally in the warm-water conditions of the Indian Ocean as opposed to the freezing waters of Russia's operating environments. They're still likely to use the same level of reactor fuel enrichment as most Russian marine PWRs (~45% enriched HEU). However, I think it can be safe to assume that the new reactor will differ from its baseline Russian design (presumed by me to be OK-650B) to a significantly greater degree than the Arihants' reactors difference from the VM-4.

With around ~60MWe of total electrical power (assuming a 33% efficiency on a 190MWth thermal output), the P77 SSN would be well-placed to incorporate the 35MW Nuclear-Electric Propulsion (NEP) setup. This would involve a silent electric motor replacing the noisy reduction gearing used in older submarines. This is also known as Turbo-Electric Drive, known to have been in the works for the Indian Navy. Assuming this setup is indeed intended for the SSN project, it can be a reason as to why a significantly higher degree of redesign may have been necessary for the CLWR-B2's power delivery system - especially the secondary loop setup - as the OK-650B was not originally meant to work with NEP.

Above is a publicly-available Expression of Interest (EoI) document (sourced via the Twitter handle of strategicfront.org) calling for industry to develop a 35MW Electric Drive solution for future submarines of the Indian Navy.
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For comparison, the French Navy's Barracuda/Suffren-class SSN uses a 20MW NEP setup fed by a 150MWth LEU reactor to drive its pumpjet propulsor. Notably, the setup on Barracuda-class is only designed to use the nuclear-electric solution up to a certain speed (let's say 20-25 knots) for relatively silent transit. Beyond 25 knots the submarine has to rely on its backup conventional propulsion that is understandably more noisy - in order to attain higher speeds (up to a maximum of 30 knots I would assume).

The Expression of Interest (EoI) documentation above also calls for the Indian NEP setup to drive the submarine to a maximum speed of 25 knots. It's likely that the P77 would also have to fall back on a conventional setup to go faster (again, let's say it can do a maximum of 30 knots or more). Either way, even without the NEP, this reactor should put the P77 in a very good place in terms of speed and performance when going up against any given opponent SSN, such as the new Type-093B of the Chinese PLA Navy. Actually, the P77 is very likely to enjoy an advantage in those regards against the Chinese boats - barring any considerable improvement the PLAN manages to make in the decade-plus it would take for the P77 to arrive.

Also worthy of note is the fact that, at least according to the the EoI document above, the nuclear-electric setup being pursued by the Indian Navy clearly calls for the P77's NEP to drive a pumpjet propulsor. Is that enough reason to assume the P77 will have a pumpjet? We'll see.

Example of a turbo-electric generator manufactured by India's state-owned BHEL corporation for commercial applications. BHEL is very likely to be the contractor responsible for building any NEP solution for future submarines.
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This same reactor and NEP propulsion setup are also likely to drive India's upcoming "S5" class of next-gen SSBNs. The S5s will be much larger, believed to displace between 13,000-14,000 tonnes, with 12 or more vertical launch silos. The S5s will perform a very different mission (deterrence). Hence S5 reactors will have to cater for different SSBN power delivery needs  (smooth and gradual acceleration) compared to the rapid stop-starts of SSN operations.

Based on reports from official DRDO publications (pictured below) it's evident that R&D work on both conformal bow-array sonars as well as planar-arrays (ostensibly used for flank-array setups) is/has been ongoing in India for several years. It's difficult to say which R&D program might or might not find a real-world application on upcoming submarine programs. I think it can be safely said that there's at least a determination in the Indian Navy to advance past the older cylindrical-array sonar setup used in the bow of the current generation of Indian nuclear boats. Among SSNs that are currently being built, the Astute-class comes to mind as one that has a conformal bow array.

Screen-grabs from the DRDO's official 'Technology Focus' publication, detailing some R&D work on next-generation sonar solutions.
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While there's no official word on this, I would estimate using a 190MWth reactor, there would be enough power on tap for the P77 SSN to incorporate additional mission sets beyond pure hunter-killer duties. This could include carrying a pack of vertically-launched Land-Attack Cruise Missiles (LACMs) like the Nirbhay. It remains to be seen what the configuration of the P77 SSN class will be. I would estimate its surfaced displacement to be somewhere between 5,000 and 7,000 tons. P77s will likely be larger than the 5,300 tonne French Barracuda/Suffren-class but possibly smaller than the Royal Navy's 7,400 tonne Astute class and the US Navy's 7,900 tonne Virginia-class (Blocks I-IV).

I personally do not believe in the reports in some sections of media (like this article from the Times of India (TOI)) that says the SSNs will displace 10,000 tons. Such a displacement would make P77s similar to submerged Improved Akulas. I think the TOI reporter in question either misinterpreted the information brief given to him, or the brief itself was a deliberate attempt at misdirection. Either way, I think we'd do well to believe that the P77 would incorporate an entirely new hull design compared to the Arihant - as I believe that the Arihant-class's internal bulkheads would probably be too small to accommodate the 190MW reactor compartment.

All that said, I think we can expect that the first P77 will be commissioned in the mid-late 2030s. This is assuming the construction starts in 2025, with a build time of between 8 and 10 years followed by sea trials. Much would also depend on how much technology being rapidly iterated over the Arihant-class finds application on the P77.

It's worth noting that even going by what's known so far, every single Arihant-class boat appears to be significantly different from the last owing to continuous technology insertion i.e. improved reactor and hull extension. It is also possible the upcoming S4* might turn out having a pumpjet. This is if a decision were taken to de-risk the P77's and S5's next-gen propulsion setup by testing the pumpjet on S4*.

It's also possible that the eventual requirement will be extended beyond the six P77s currently sought, to twelve, as I previously theorized. This is keeping in mind the construction of a new large, higher capacity, dry-dock at SBC (refer the satellite image in Part-2 of this series). It is very likely that at some point within the end of the 2020s, the Indian Navy could have both the new SSNs and S5-class SSBNs under construction at the same time, They might also be delivered simultaneously over a period of time in the 2030s. Unfortunately, being a strategic program (for carrying nuclear weapons) the funding modes for the S5-class boats will be secret. None of the public reporting such as cabinet approvals or funding details applied to the P77s will likely apply to the S5s.

The upcoming part (probably the last) of this SubMatts series will cover a few updates regarding some ancillary programs that support India's nuclear submarine effort without being directly a part of it.