Indian Nuclear Attack Submarine (Project 77) - Updates & Discussions

[Parthu]

@Gautam @Ashwin

Ok, so appraently we're indeed going for a SSN with VLS as per the source. He only mentions LACMs though (Nirbhay/ITCM), no AShM.

Just as well, if we're getting a 190MWt reactor, we might as well onboard additional mission sets i.e. long range land-attack.

No info regarding numbers but I personally don't expect too many on a 6k ton boat...maybe in the region of 12-16 missiles, triple- or quad-packed in 4 tubes. Enough to strike a specific target from a survivable platform on short notice but no sustained volleys like a true SSGN a-la converted Ohio or Virginia Block-5.

If we want an SSGN in that league, we're gonna have to wait till S5-class completely takes over the deterrence role and then convert the Arihant Stretch into SSGNs with 5-6 Nirbhay per tube for a total of 40-48 LACMs.

Oh, and no specifics regarding NEP but says that should be the way to go considering the timeframe in question.

Personally, with around 60MWe on tap, I think we can safely assume that the 35MWe motive setup (Pumpjet-NEP) who's diagrams we've seen will become a reality on the SSNs. If not in the first 2, then definitely in the next 4.

 

[randomradio]

Probably not appropriate to share the DMs here but word from a well-established source who reported on N-sub program for over a decade is this:

The bit about the SSN having 190MWt reactor is correct. However, 10k ton displacement figure is wrong - it's closer to 6k tons.

Now, this is my further analysis based on what he said:

So it would seem BARC has indeed fully absorbed the production-engineering knowledge of the OK-650B PWR that our Akula crews trained on. There were hints all the way back in 2018 that a land-based version of the CLWR-B2 reactor (Indianized OK-650) was under some stage of construction and/or limited operation by that time itself:

View attachment 37213

^^ From BARC publication:

http://www.barc.gov.in/presentations/fddir18.pdf

Secondly, the bit about it being around 6k tons leads me to believe that we need to entertain the possibility of an entirely new hull design at this point. Because Arihant itself is believed to be 6k tons (the Stretch variant probably 7k) and with the missile silo section removed there's no way an SSN design based around the same bulkheads would also displace the same amount.

I think we cannot rule out that our SSN is going to be Barracuda/Suffren-sized. There are other offline sources saying that the French have indeed parted with the hull design of the Barracuda itself (all those visits to Naval Group by Indian Navy officials probably weren't for nothing), just withholding the reactor tech. But that's not an obstacle because our HEU-based program is incompatible with their LEU ecosystem anyway. However this would also entail us having to relearn a lot of stuff wrt hull-forging as we'd be going from Soviet-style double-hull to Western-style single-hull construction.

We'll see if that indeed turns out to be the case.

Either way, with a 190MWt reactor (meaning a total possible electrical output of around ~60MWe assuming 33% efficiency) on a 6k ton boat, expect an SSN that is P-O-W-E-R-F-U-L. Will run circles around any existing Chinese N boat, plus with lots of power on tap to operate some truly powerful next-gen sensors. A real hunter-killer.

Oh, and there's no confirmation from that source regarding pumpjet status, at least for the first 2. Fingers crossed.

Fingers crossed about NEP as well (didn't ask him about that though).

P.S.

There are also people saying we'll be going for a 150MWt reactor for SSN. If that turns out to be true, it would probably mean it's still the same CLWR-B2 reactor (because I sincerely don't think B1 can be scaled that high), just in a lower state of tune so to speak. A reduced output like this would probably have to be a result of the SSN's hull not having enough space for the kind of shielding or heat-exchanging capacity that the reactor would require for the full 190MW thermal output. It probably serves to know that the K15 reactor France uses on Suffren is also 150MWt.

The S5-class SSBN would however have all the space it needs for full 190MWt. Again, we'll see how it goes.

@Ashwin @Gautam

Our reactors are not Indianized Russian reactors. That would break every single rule in the rulebook created by NSG. And it would have been reported by multiple countries and nuclear watchdogs in the West, if that were the case.

India did not have access to either Chakra I or Chakra II's reactors, both were operated by Russian sailors. It was only at the end of Chakra II's lifecycle that Indian sailors were allowed to operate some parts of the reactor as part of training under Russian supervision. And no, BARC didn't get designs of their reactors either, they only received Russian consultancy and some parts outside the purview of NSG. Although the consultancy received was quite a bit more significant than normal.

Russia is not stupid enough to break the rules of NSG. They didn't do that even for MTCR. As mentioned before, other countries would have protested it. Russia's already making a fuss about AUKUS, talking about bringing the deal under IAEA, never mind the fact that the Australians will not have access to any part of the reactor.

As for SSN displacement, I think 6000T is too less for a 190 MWth reactor. Virginia B5's 7.5k T would make more sense.

 

[Parthu]

Our reactors are not Indianized Russian reactors. That would break every single rule in the rulebook created by NSG. And it would have been reported by multiple countries and nuclear watchdogs in the West, if that were the case.

India did not have access to either Chakra I or Chakra II's reactors, both were operated by Russian sailors. It was only at the end of Chakra II's lifecycle that Indian sailors were allowed to operate some parts of the reactor as part of training under Russian supervision. And no, BARC didn't get designs of their reactors either, they only received Russian consultancy and some parts outside the purview of NSG. Although the consultancy received was quite a bit more significant than normal.

Russia is not stupid enough to break the rules of NSG. They didn't do that even for MTCR. As mentioned before, other countries would have protested it. Russia's already making a fuss about AUKUS, talking about bringing the deal under IAEA, never mind the fact that the Australians will not have access to any part of the reactor.

As for SSN displacement, I think 6000T is too less for a 190 MWth reactor. Virginia B5's 7.5k T would make more sense.

I'm afraid this is a space where we're probably never going to see any public disclosure so everyone is free to believe whatever they want.

However, if we go with the notion that our CLWRs are fully Indian designs with no Russian analogues, then quite a lot has to be chalked up to coincedence.

Like, our two reactors corresponding almost perfectly to the rated output of the ones onboard Russian subs of the specific type we took on lease (Charlie's VM4 is 70-90MWt and Nerpa's OK650B is 190MWt. Our B1 is 83MWt and B2 is 190MWt).

Or how the level of fuel enrichment our reactors have is also the same as what Russian marine PWRs typically work with (~40% enriched).

If a certain agreement was secret, then secret it shall remain. Eventhough it may be technically illegal. End of the day, there was no IAEA representative onboard Chakra-I or -II to verify what was actually happening. Only crew vetted by GRU.

Whether anyone in the West would have opposed this would be dependent on what their calculus was wrt containment of China. India was always a non-P5 nuclear power not signatory to NPT. Any agreement surrounding our status as an operator of either nuclear weapons or nuclear powered platforms would have to be either ad-hoc or under the table anyway.

 

[darkflame]

Our reactors are not Indianized Russian reactors. That would break every single rule in the rulebook created by NSG. And it would have been reported by multiple countries and nuclear watchdogs in the West, if that were the case.

India did not have access to either Chakra I or Chakra II's reactors, both were operated by Russian sailors. It was only at the end of Chakra II's lifecycle that Indian sailors were allowed to operate some parts of the reactor as part of training under Russian supervision. And no, BARC didn't get designs of their reactors either, they only received Russian consultancy and some parts outside the purview of NSG. Although the consultancy received was quite a bit more significant than normal.

Russia is not stupid enough to break the rules of NSG. They didn't do that even for MTCR. As mentioned before, other countries would have protested it. Russia's already making a fuss about AUKUS, talking about bringing the deal under IAEA, never mind the fact that the Australians will not have access to any part of the reactor.

As for SSN displacement, I think 6000T is too less for a 190 MWth reactor. Virginia B5's 7.5k T would make more sense.

Well an article from federation of American scientists from 1990s says India got detailed designs of the Charlie class submarine and it's reactor from Russia
The Indian Strategic Nuclear Submarine Project An Open Literature Analysis
From paragraph 41
"has also been reported that the Russian submarine-design bureau Rubin is cooperating in developing the nuclear submarine's 190 MW PWR. Russian engineers have been working with DRDO on the design since 1991"
From paragraph 31
"Two different type of reactors would have also been considered. The water-cooled water-moderated reactor (PWR) was designed by BARC and is believed based on Soviet design information obtained form the leased submarine. Some information is known about Soviet reactor design. Naval reactor cores have been described as having 248-252 fuel assemblies depending upon type of reactor. There may be up to a few tens of fuel rods per assembly"

 

[randomradio]

I'm afraid this is a space where we're probably never going to see any public disclosure so everyone is free to believe whatever they want.

However, if we go with the notion that our CLWRs are fully Indian designs with no Russian analogues, then quite a lot has to be chalked up to coincedence.

Like, our two reactors corresponding almost perfectly to the rated output of the ones onboard Russian subs of the specific type we took on lease (Charlie's VM4 is 70-90MWt and Nerpa's OK650B is 190MWt. Our B1 is 83MWt and B2 is 190MWt).

Or how the level of fuel enrichment our reactors have is also the same as what Russian marine PWRs typically work with (~40% enriched).

If a certain agreement was secret, then secret it shall remain. Eventhough it may be technically illegal. End of the day, there was no IAEA representative onboard Chakra-I or -II to verify what was actually happening. Only crew vetted by GRU.

Whether anyone in the West would have opposed this would be dependent on what their calculus was wrt containment of China. India was always a non-P5 nuclear power not signatory to NPT. Any agreement surrounding our status as an operator of either nuclear weapons or nuclear powered platforms would have to be either ad-hoc or under the table anyway.

There's a lot of standardization when it comes to reactor designs. We seem to have standardized around Soviet tools and equipment that were transferrable without raising eyebrows, along with the nuclear sub designs of the time. We didn't try to do anything original back then, just the god ol' tried and tested. We are probably the same today.

40% enrichment is simply the most convenient level of purity to use. It's also meant to demonstrate to the world that we do not want insane amounts of weapons grade materials. If we used weapons grade, then other countries will not be able to estimate how much fissile material we are making for bombs. It's an unnecessary escalation. And LEU is sh!t. The French are stuck with it due to their own restrictions.

Russia to date has not done anything serious that goes against NSG. Transfer of reactors and their designs was possible in the 50s, 60s and 70s before NSG was fully established, which helped Pakistan and Israel to establish their own programs. Even if we claim the West turned the other way in the late 80s, impossible during the time, the Chinese and Turks would have protested. Plus India was a very weak state back then. Our 5-sub Chakra lease was canceled at the behest of the US, never mind the impossibility of any transfer of reactor tech.

And this IAEA wasn't there stuff doesn't work. All these guys spy on each other way too much. They always find people willing to speak, especially after all this time.

Plus ToT of a reactor in the 90s and a prototype set up in 2002 is an impossible timeframe. It would take a decade just to understand and then build and test individual parts before starting our own program. Their program for sub reactors began in the 70s. Quite a few of our modern reactors today date back to the 70s and 80s, including FBR and AHWR. So a 20-25 year design, prototyping and production process before beginning Arihant in 1997 makes more sense. It's proven by the fact that BARC said they need 20 years to design and build a reactor for ships.

Lastly, our nuclear capabilities are one of the best in the world. BARC works on cutting edge stuff at the same level as other nuclear powers.

 

[Gautam]

Unfortunately, no.

Check out this document though:

https://lynceans.org/wp-content/uploads/2015/09/Part-3_Russia-60-yrs-of-marine-nuc-power.pdf
There's no cutaway of OK650 but there are diagrams of a few other Afrikantov designs that might be related. You might find what you're looking for.

Thanks, guys, for the photos & link. This is what I was looking for:

Having a natural circulation type primary coolant loop allows the subs to have a higher silent speed. This is a necessity for modern SSNs.

 

[randomradio]

Well an article from federation of American scientists from 1990s says India got detailed designs of the Charlie class submarine and it's reactor from Russia
The Indian Strategic Nuclear Submarine Project An Open Literature Analysis
From paragraph 41
"has also been reported that the Russian submarine-design bureau Rubin is cooperating in developing the nuclear submarine's 190 MW PWR. Russian engineers have been working with DRDO on the design since 1991"
From paragraph 31
"Two different type of reactors would have also been considered. The water-cooled water-moderated reactor (PWR) was designed by BARC and is believed based on Soviet design information obtained form the leased submarine. Some information is known about Soviet reactor design. Naval reactor cores have been described as having 248-252 fuel assemblies depending upon type of reactor. There may be up to a few tens of fuel rods per assembly"

These were speculations pushed by civvie analysts of the time. "Oh, we know India can't do it, so the Russians helped." You see the same attitude by the same people in the West in pretty much every sector today, especially aerospace programs. A lot of you have the same anti-China bias towards Chinese tech.

Even your article says transferring reactor designs would violate NPT.
The initial design strategy was to copy a leased Russian nuclear submarine (Charlie II) using an Indian built nuclear reactor for propulsion. The Russians are said to have provided detailed drawing of the leased submarine minus the reactor design (providing reactor design details would have been a violation of the NPT).

And then funny how problems were found, as is the case in any development program, versus if the Russians have simply handed the design over.
The PWR failed tests at Kalpakkam in November and December 1995. The failures were believed to be caused by "several integration and fabrication problems" that have yet to be solved.

In June of 1996 it was reported that the program suffered further setbacks following additional failed tests of the reactor. Problems in fabricating the containment vessel have also occurred.

Anyway, as per my previous post, the timeframe doesn't match. The Charlie deal to beginning construction of a prototype is too short. In fact, with a 2002 finish date, the reactor should have begun construction right after the SU fell, perhaps even before that. Then we notice that problems showed up during tests in 1995, that would mean there was quite a bit of redesigning and rebuilding before success was guaranteed and that followed the official launch of the Arihant program in 1997.

Did we use a Russian reactor from the outset? Zero chance.
Did we use Russian tech and consultancy to improve our own design? Very likely.

At the level both the CIA and KGB/SVR had penetrated the Indian govt, the most unlikely event would have been transfer of ridiculously critical technologies from the Russians.

Furthermore, there's also the impossibility to having achieved Akula-class noise levels with an obsolete VM-4 reactor from the Charlie class, there's a 2 generation difference. And the impossibility of Russia having transferred OK-650 family designs considering they are using them right now, and will continue doing so for a very long time. This, when the Russians do not want to transfer AL-31FP tech simply 'cause they are also using the engine.

Both logic and common sense indicate we are using indigenously developed designs.

 

[Parthu]

@Gautam

Regarding upcoming sonar tech, some stuff I found on another forum. Not sure if this was posted here before:

All in all, it appears we're pursuing a conformal bow array for future boats. Not the old cylindrical type as on current Arihant, and not spherical as on Seawolf/earlier Virginia blocks.

Among new-age SSNs, the Astute comes to mind as one that has a conformal bow array:

And considering that we've been working on planar arrays, I think we can safely assume that flank-array sonars will be there on our SSN as well. Especially now that we've gotten a taste for the advantages that the increased FoV of a flank array brings thanks to Scorpene.

 

[mamiam23]

Thanks, guys, for the photos & link. This is what I was looking for:
View attachment 37224
Having a natural circulation type primary coolant loop allows the subs to have a higher silent speed. This is a necessity for modern SSNs.

Somewhere I read that American SSNs completely eliminated the need for Natural Circulation because their Pumps got silent enough. Is it true?

 

[Gautam]

Somewhere I read that American SSNs completely eliminated the need for Natural Circulation because their Pumps got silent enough. Is it true?

No clue.

 

[South block]

Somewhere I read that American SSNs completely eliminated the need for Natural Circulation because their Pumps got silent enough. Is it true?

It's true.... One of the reason why modern Western & Russian Nuclear Subs are very quite even at higher speeds.

 

[mamiam23]

It's true.... One of the reason why modern Western & Russian Nuclear Subs are very quite even at higher speeds.

So what would we be having? Natural Circulation upto some x-Knots or completely Pumps only with no natural cooling?

 

[South block]

So what would we be having? Natural Circulation upto some x-Knots or completely Pumps only with no natural cooling?

Both with Natural Circulation upto X Nots & than pumps.

 

[mamiam23]

Both with Natural Circulation upto X Nots & than pumps.

Yeah, It would be unwise to go Only pumps on our first version. Would need lot of refinements and maybe in later batch we can switch to complete pumps only.

 

[South block]

Yeah, It would be unwise to go Only pumps on our first version. Would need lot of refinements and maybe in later batch we can switch to complete pumps only.

OK 650 reactors coolant system operates on Natural circulation.... Pumps are only needed when going faster.....Ours Reactor is based on OK 650 only...... Latest Russian Yasen-M is said to be very quite even at higher speeds 28 Knots + & this when it's still using screw & no pump-jet thanks to new fourth generation KTP-6 Monoblock reactor which does not have separate steam generators.

A distinctive feature of the new type of reactor was the integral monoblock arrangement of devices in which the reactor and its first cooling circuit are mounted in a single housing. This solution allows to exclude large pipelines from the PPU design (their maximum diameter was reduced from 675 for OK-650 to 40 mm for connecting pipelines for KTP-6) and, thereby, facilitates the natural circulation of the coolant in all operating modes. The latter is one of the key criteria for the low noise of the entire boat, eliminating the need for continuous operation of the main circulation pumps and reducing the reactor's energy consumption by its own needs by an order of magnitude, thereby giving a higher overall efficiency. Monoblock PPU is much more compact than the previous generation, easier to maintain, more secure and reliable.

 

[YoungWolf]

I got a few questions (apologise if it's a bit silly): what kind of rudder design is our SSN rumoured to sport, X-stern or cross-form (like Virginia/Yasen)? Also, pumpjet or the usual 7-blade propeller? Is our CLWR 190MWth reactor a 2nd gen or 3rd gen?

 

[Parthu]

I got a few questions (apologise if it's a bit silly): what kind of rudder design is our SSN rumoured to sport, X-stern or cross-form (like Virginia/Yasen)?

Unknown. There's no official graphics to go with and rudder design is too specific a detail for anyone outside the program to know about at this point.

Also, pumpjet or the usual 7-blade propeller?

Also unknown. The best source I have says there's no word on that - but expects pumpjet given the timeline we're looking at. Personally, I adopt a low risk approach wrt what I believe. I believe wel'll go with a regular screw at least for the first 2 boats. That way, if it indeed turns out to be the case, I won't be disappointed. But if it ends up with pumpjet from the start, it'll be a pleasant surprise for me.

Win-win.

Is our CLWR 190MWth reactor a 2nd gen or 3rd gen?

If you go with the notion that it's based on/inspired by the OK-650B, then it'll be 3rd gen at the very least.

But again, considering the fact we've already operationalized a "Gen-3+" reactor like the IPHWR-700, I think one can be forgiven for expecting to have certain features ahead of the base Gen-3 standard on the CLWR-B2.

 

[mamiam23]

Unknown. There's no official graphics to go with and rudder design is too specific a detail for anyone outside the program to know about at this point.



Also unknown. The best source I have says there's no word on that - but expects pumpjet given the timeline we're looking at. Personally, I adopt a low risk approach wrt what I believe. I believe wel'll go with a regular screw at least for the first 2 boats. That way, if it indeed turns out to be the case, I won't be disappointed. But if it ends up with pumpjet from the start, it'll be a pleasant surprise for me.

Win-win.



If you go with the notion that it's based on/inspired by the OK-650B, then it'll be 3rd gen at the very least.

But again, considering the fact we've already operationalized a "Gen-3+" reactor like the IPHWR-700, I think one can be forgiven for expecting to have certain features ahead of the base Gen-3 standard on the CLWR-B2.

Eh. That land based Generation designation is not same as Naval Reactors. Naval Reactors have their Gen tags based on Silence.

 

[Parthu]

Eh. That land based Generation designation is not same as Naval Reactors. Naval Reactors have their Gen tags based on Silence.

Yeah but that's unique to each country. Russians consider the Akula's 650B as a 3rd gen in their parlance.

The US counterpart to the Akula (LA-class) had S6G which in their parlance was 6th gen.

Even though they both had broadly comparable feature sets.

Assuming we adopted the same parlance as the Russians, our B2 would certainly be ahead by atleast a few notches simply because it's been so long since 650B came out.

The Russian generation parlance more closely matches the one for civilian reactors so "Gen-3+" in the context is probably apt.

 

[_Anonymous_]