Indian nuclear submarines

[Haldilal]

so are they building another one for ssn??

bec 83MW will be insufficient

Ya'll Nibbiars S5 is a new design with powerful reactor don't make wrong assumptions. SSN class will probabaly have the same reactors. And for referrence see the SSN around the world which shares the similar reactors with the SSBN counterparts.

 

[THESIS THORON]

Ya'll Nibbiars S5 is a new design with powerful reactor don't make wrong assumptions. SSN class will probabaly have the same reactors. And for referred see the SSN around the world which shares the similar reactors with the SSBN counterparts.

then it would be damm fast due to huge power available

 

[Haldilal]

then it would be damm fast due to huge power available

Ya'll Nibbiars SSN are faster than the SSK and eaily above 35 Knots top speed if the 7,000 tons displacement is considered.

 

[Gessler]

Yes likely.
But the reactor which is in officially public domain; CLWR-B2 (190 MW) is for S5 class SSBN. We don't know about others.

Only submarine PWR projects being pursued are B1 and B2.

If there's a 3rd model, it has never been heard of or mentioned in any official document AFAIK. If it does exist, chances are it could be a somewhat enhanced version of B1 - with output pushed to approx 100MWt and maybe fuel also enriched to a slightly higher grade (45% overall compared to 40% overall).

But its unclear how much further the VM-4 base design can be pushed within safe limits. There's a reason why Soviets never pushed it past 90MWt and whenever the VM series was used on attack subs, it was always in pairs and never single.

• If we choose speed over stealth (Soviet thought process), only the B2 makes sense. Alternative would be designing a complex with 2 x B1 PWRs, which could take lot of time, might as well spend that time going with single B2 instead - especially if we already have OK650 design on hand.

• If we choose stealth over speed (Western thought process), either out of doctrine or compulsion (like B2 can't be ready in time and we need SSNs ASAP or something like that), then a B1 may be sufficient.

But if we choose B1 and half-a$$ the stealth aspect (no pumpjet, no NEP, no advanced forging of outer hull etc.), then in the next decade, we could be in SERIOUS trouble.

Note that this doesn't mean Russian subs aren't silent or Western subs can't run fast. It is however, a general tendency of submarine design. RUS realized early on that Western sonar had the advantage and that they used to keep eyes on Soviet subs 24x7 while Soviets were lucky if they managed to find a US boat once. So they learnt to play the hand they were dealt, prioritizing fast movements. While NATO built on the advantage they had, they would do anything to not get caught in first place.

Simply put - Russian boats: faster than they are quieter. Western boats: Quieter than they are faster.

If we choose B1 for SSN, our doctrine may be forced to go a hybrid way. Adopting the Western doctrine of stealth over speed, but with a Russian-style double-hulled boat and Russian-style reactor design.

 

[THESIS THORON]

Only submarine PWR projects being pursued are B1 and B2.

View attachment 113376

If there's a 3rd model, it has never been heard of or mentioned in any official document AFAIK. If it does exist, chances are it could be a somewhat enhanced version of B1 - with output pushed to approx 100MWt and maybe fuel also enriched to a slightly higher grade (45% overall compared to 40% overall).

But its unclear how much further the VM-4 base design can be pushed within safe limits. There's a reason why Soviets never pushed it past 90MWt and whenever the VM series was used on attack subs, it was always in pairs and never single.

• If we choose speed over stealth (Soviet thought process), only the B2 makes sense. Alternative would be designing a complex with 2 x B1 PWRs, which could take lot of time, might as well spend that time going with single B2 instead - especially if we already have OK650 design on hand.

• If we choose stealth over speed (Western thought process), either out of doctrine or compulsion (like B2 can't be ready in time and we need SSNs ASAP or something like that), then a B1 may be sufficient.

But if we choose B1 and half-a$$ the stealth aspect (no pumpjet, no NEP, no advanced forging of outer hull etc.), then in the next decade, we could be in SERIOUS trouble.

Note that this doesn't mean Russian subs aren't silent or Western subs can't run fast. It is however, a general tendency of submarine design. RUS realized early on that Western sonar had the advantage and that they used to keep eyes on Soviet subs 24x7 while Soviets were lucky if they managed to find a US boat once. So they learnt to play the hand they were dealt, prioritizing fast movements. While NATO built on the advantage they had, they would do anything to not get caught in first place.

Simply put - Russian boats: faster than they are quieter. Western boats: Quieter than they are faster.

If we choose B1 for SSN, our doctrine may be forced to go a hybrid way. Adopting the Western doctrine of stealth over speed, but with a Russian-style double-hulled boat and Russian-style reactor design.

But the 2 B1 will be too big and heavy especially considering B1 a gen behind B2. It might also reduce the stealth due to B1 being more noisier.

Refueling 2 B1 will be the worst nightmare for in and would also inc down time significantly.

 

[Gessler]

But the 2 B1 will be too big and heavy especially considering B1 a gen behind B2. It might also reduce the stealth due to B1 being more noisier.

Refueling 2 B1 will be the worst nightmare for in and would also inc down time significantly.

Already said that we'd go with 2 x B1 only if speed is prioritized over stealth AND for whatever reason the B2 design is deemed unworkable.

 

[gearedcombustor]

Already said that we'd go with 2 x B1 only if speed is prioritized over stealth AND for whatever reason the B2 design is deemed unworkable.

No PWR type naval reactor can reach efficiencies above 25%. It's theoretically not possible. Even civil reactors with water/heavy water coolant can only reach efficiencies of max 30%. Going above 30% requires using Sodium/Lead as coolant. Going above 40 requires Gas cooled reactors.

Even Ultra Super Critical Coal power plants with Full Speed multi stage turbines with steam super heat temperatures at 600 deg C struggle to reach 45% efficiency.

To increase efficiency you need to increase coolant output temperatures. Due to void physics you cannot allow steam boiloff to occur within the flux space of the reactor, for PWR's boiloff doesn't occur at all before the steam generator due to pressures and they can only operate with coolant output temp of 320 deg C. For PHWR, boiloff can occur at tube outlet but not too much.

Due to all this issues, nuclear reactor turbines can only be inefficient half speed turbines. No reactor uses full speed turbines common in thermal coal/gas/oil power plants.

This situation gets worse in naval reactors as the number of turbines stages that can be crammed in, the size of the steam generator heat exchange area gets much worse

All in all - all PWR type naval reactors only have efficiencies less than 25%. Civil PWRs reach 30%. Fast breeders with sodium coolant at 590 deg C reach 40%.

Your claim on twitter that USN subs have 45% efficiency is inaccurate

 

[gearedcombustor]

No PWR type naval reactor can reach efficiencies above 25%. It's theoretically not possible. Even civil reactors with water/heavy water coolant can only reach efficiencies of max 30%. Going above 30% requires using Sodium/Lead as coolant. Going above 40 requires Gas cooled reactors.

Even Ultra Super Critical Coal power plants with Full Speed multi stage turbines with steam super heat temperatures at 600 deg C struggle to reach 45% efficiency.

To increase efficiency you need to increase coolant output temperatures. Due to void physics you cannot allow steam boiloff to occur within the flux space of the reactor, for PWR's boiloff doesn't occur at all before the steam generator due to pressures and they can only operate with coolant output temp of 320 deg C. For PHWR, boiloff can occur at tube outlet but not too much.

Due to all this issues, nuclear reactor turbines can only be inefficient half speed turbines. No reactor uses full speed turbines common in thermal coal/gas/oil power plants.

This situation gets worse in naval reactors as the number of turbines stages that can be crammed in, the size of the steam generator heat exchange area gets much worse

All in all - all PWR type naval reactors only have efficiencies less than 25%. Civil PWRs reach 30%. Fast breeders with sodium coolant at 590 deg C reach 40%.

Your claim on twitter that USN subs have 45% efficiency is inaccurate

For reactors, you can't increase output temperatures due to pressure metallurgical and void issues. You cannot allow water to convert to steam within the Reactor flux area(where the fission happens) as the voids generated will be devoid of the moderator(water) and will increase the reactivity and turn into Chernobyl. To avoid this you need to keep water at high pressures - due to metallurgical and manufacturing reasons the current max pressure seen in reactors is around 16 MPa. The high pressure water instead is flown through a steam generator where the heat is transferred to low pressure water which converts to steam and then turns the turbine.



There is another type of reactor called the Boiling water reactor where boiloff happens above the reactor head space but the steam temperature here is very low and inefficient.



The sodium/lead cooled reactors have high efficiencies but still cannot exceed coal. The Soviets built lead cooled fast breeder Alfa-class subs but couldn't continue the design due to serious operability and maintenance issues.

There are reactor designs like https://en.m.wikipedia.org/wiki/High-temperature_gas_reactor HTRs that have outlet temperatures of 1000 deg C to have high efficiencies but there are serious maintenance issues preventing them from being operationalised. Molten salt reactors are targeting 1400 deg C but metallurgical issues are preventing them from being built. HTRs and MSBRs won't be suitable for naval use anyway as they are only practical if used to manufacture hydrogen which is later converted to electricity

 

[Gessler]

No PWR type naval reactor can reach efficiencies above 25%. It's theoretically not possible. Even civil reactors with water/heavy water coolant can only reach efficiencies of max 30%. Going above 30% requires using Sodium/Lead as coolant. Going above 40 requires Gas cooled reactors.

Even Ultra Super Critical Coal power plants with Full Speed multi stage turbines with steam super heat temperatures at 600 deg C struggle to reach 45% efficiency.

To increase efficiency you need to increase coolant output temperatures. Due to void physics you cannot allow steam boiloff to occur within the flux space of the reactor, for PWR's boiloff doesn't occur at all before the steam generator due to pressures and they can only operate with coolant output temp of 320 deg C. For PHWR, boiloff can occur at tube outlet but not too much.

Due to all this issues, nuclear reactor turbines can only be inefficient half speed turbines. No reactor uses full speed turbines common in thermal coal/gas/oil power plants.

This situation gets worse in naval reactors as the number of turbines stages that can be crammed in, the size of the steam generator heat exchange area gets much worse

All in all - all PWR type naval reactors only have efficiencies less than 25%. Civil PWRs reach 30%. Fast breeders with sodium coolant at 590 deg C reach 40%.

Your claim on twitter that USN subs have 45% efficiency is inaccurate

Agreed - should have been based around higher power density of >95% HEU as opposed to LEU.

 

[gearedcombustor]

Agreed - should have been based around higher power density of >95% HEU as opposed to LEU.

Yes Power density is the right word. Efficiency doesn't change - HEU or LEU or even 100% U235 or Pu or any fuel won't change this fact. Fuel enrichment is used to enhance the maximum allowable fuel burnup not the thermal efficiency.

LEU/HEU generally contains U238 which produces Plutonium while U235 fission produces most of the energy. The maximum permissible limit of side reactions like Plutonium, Neptunium being generated through the neutron absorption by U238 is the Maximum allowable fuel burnup. Exceeding the burnup will cause increase in uncharacterised fission reactions that will melt the fuel rods or create too much radioactivity that exceeds shielding limits or damages the RPV. Moving from LEU to HEU allows you to reduce these unnecessary side reactions and allows you to increase your Maximum fuel burnup before you need to refuel.

Humans only extract small percentage of the fission energy from U235 due to these limits. HEU raises that limit but doesn't change the transient energy release for the chain reaction as long as the core doesn't go supercritical. Raising transient energy release will require increasing neutron flux i.e the rate of the chain reaction which means you will go Chernobyl/Hiroshima beyond a limit. The flux limit is the same even if it HEU or LEU.

Enrichment only affects your burnup not the per atom heat generation.

Enrichment doesn't affect thermal efficiency.

Enrichment doesn't affect the coolant's reactor outlet temperature. It's only a function of pressure and coolant void coefficient.

i.e. enrichment only affects your refueling frequency not your efficiency

 

[gearedcombustor]

Yes Power density is the right word. Efficiency doesn't change - HEU or LEU or even 100% U235 or Pu or any fuel won't change this fact. Fuel enrichment is used to enhance the maximum allowable fuel burnup not the thermal efficiency.

LEU/HEU generally contains U238 which produces Plutonium while U235 fission produces most of the energy. The maximum permissible limit of side reactions like Plutonium, Neptunium being generated through the neutron absorption by U238 is the Maximum allowable fuel burnup. Exceeding the burnup will cause increase in uncharacterised fission reactions that will melt the fuel rods or create too much radioactivity that exceeds shielding limits or damages the RPV. Moving from LEU to HEU allows you to reduce these unnecessary side reactions and allows you to increase your Maximum fuel burnup before you need to refuel.

Humans only extract small percentage of the fission energy from U235 due to these limits. HEU raises that limit but doesn't change the transient energy release for the chain reaction as long as the core doesn't go supercritical. Raising transient energy release will require increasing neutron flux i.e the rate of the chain reaction which means you will go Chernobyl/Hiroshima beyond a limit. The flux limit is the same even if it HEU or LEU.

Enrichment only affects your burnup not the per atom heat generation.

Enrichment doesn't affect thermal efficiency.

Enrichment doesn't affect the coolant's reactor outlet temperature. It's only a function of pressure and coolant void coefficient.

i.e. enrichment only affects your refueling frequency not your efficiency

Power density affects the size of your reactor and control systems. Going too high on your power density is not recommended either - This will require very miniaturised and very sensitive control rods but there is still a lower limit on the reactor vessel size as you cannot put the fuel rods too close to avoid going critical at idle.



The American reactors are still probably the same size as the Russian ones as at such high 90%s enrichment you will have to fill the reactor with dummy rods to avoid localised criticality and have fast flowing coolant to quickly take away heat so the fuel rods won't melt. The lesser enrichment reactors are much safer.



Balancing safety with your refueling frequency also becomes important.



Such dreams of high power density might even give ideas to bring back the lead cooled fast reactors like the Alfa. Sodium Fast breeders are too flammable for mil application.

 

[Aniruddha Mulay]

Guys, I wanted a clarification, as you all know, INS Chakra(K-152) has been returned to Russia.
So is it a temporary return where a Russian shipyard to rectify all the issues plauging the boat or a permanent return where the sub will be repaired and put into active Russian Navy service.
It does not make sense that India having paid close to $900 million(i.e. 60% cost of the original price) for just 9 years of Indian Navy service for the Akula class sub.

 

[THESIS THORON]

Guys, I wanted a clarification, as you all know, INS Chakra(K-152) has been returned to Russia.
So is it a temporary return where a Russian shipyard to rectify all the issues plauging the boat or a permanent return where the sub will be repaired and put into active Russian Navy service.
It does not make sense that India having paid close to $900 million(i.e. 60% cost of the original price) for just 9 years of Indian Navy service for the Akula class sub.

imo the chakra 2 will not return.

 

[Gessler]

Guys, I wanted a clarification, as you all know, INS Chakra(K-152) has been returned to Russia.
So is it a temporary return where a Russian shipyard to rectify all the issues plauging the boat or a permanent return where the sub will be repaired and put into active Russian Navy service.
It does not make sense that India having paid close to $900 million(i.e. 60% cost of the original price) for just 9 years of Indian Navy service for the Akula class sub.

There's no indication of the Nerpa returning.

If you think the $900 mil was high - what about the $3.3 billion we're spending on the new lease (expected to be inducted around 2025).

There's more to it though. The deals aren't just about leasing SSNs to India - they're about financing the refit/repair (or in some cases, completing the construction of partly-built submarines), using them for a period to get training & other jobs, then giving them back to Russia - where they can do a minor refit and continuing using them to their end of life.

The Russian nuclear fast attack submarine fleet is expanding for the first time in post-Soviet era, and we are directly financing a portion of that.

However, we have to assume that the new deal (3.3 bn one, presumably for the Bratsk) entails more than the submarine itself - I'm more than willing to bet this deal includes the designs & engineering models for the OK-650B PWR as well. Plus the contract for sending personnel to help us build our own comparable PWR.

You can't put a price on that - especially as its a single-vendor situation. Absolutely no-one else in the world would let us (let alone help us) do this.

 

[THESIS THORON]

However, we have to assume that the new deal (3.3 bn one, presumably for the Bratsk) entails more than the submarine itself - I'm more than willing to bet this deal includes the designs & engineering models for the OK-650B PWR as well. Plus the contract for sending personnel to help us build our own comparable PWR.

BRATSK is first gen akula, do you think that it will be upgraded to the akula i or u standards ??

 

[Gessler]

BRATSK is first gen akula, do you think that it will be upgraded to the akula i or u standards ??

Who knows - far as I know, the original plan was to repair and "modernize" the Bratsk (a process still happening and unlikely to end before ~2025). What exactly this modernization entails, nobody knows.

 

[ShukantC]

If we are still in the design phase of the SSN's, I really hope the designers incorporate an angled hull rather than the old cigar shape that we are so used to seeing on submarines. Apparently it has a lot of advantages for stealth against the active sonars which apparently are making a comeback in subsurface warfare.

I had come across the below article about the new Type 212CD for the German/Norwegian navies by H.I Sutton who happens to be one of the best open source intelligence on submarines and the like.

Radical New Stealth Submarine, Type-212CD, Will Be Much Larger - Naval News

Submarines rely on stealth to maintain the element of surprise and escape threats. For decades this has focused on reducing the noise emitted by the submarine. A resurgence of using active sonar to locate submarines now means that new stealth measures may be required. German submarine builder...

www.navalnews.com

 

[THESIS THORON]

If we are still in the design phase of the SSN's, I really hope the designers incorporate an angled hull rather than the old cigar shape that we are so used to seeing on submarines. Apparently it has a lot of advantages for stealth against the active sonars which apparently are making a comeback in subsurface warfare.

I had come across the below article about the new Type 212CD for the German/Norwegian navies by H.I Sutton who happens to be one of the best open source intelligence on submarines and the like.

Radical New Stealth Submarine, Type-212CD, Will Be Much Larger - Naval News

Submarines rely on stealth to maintain the element of surprise and escape threats. For decades this has focused on reducing the noise emitted by the submarine. A resurgence of using active sonar to locate submarines now means that new stealth measures may be required. German submarine builder...

www.navalnews.com

you are right, but our first goal is to make ssn which is quiter than upcoming chinki's ssn.

 

[Gessler]

If we are still in the design phase of the SSN's, I really hope the designers incorporate an angled hull rather than the old cigar shape that we are so used to seeing on submarines. Apparently it has a lot of advantages for stealth against the active sonars which apparently are making a comeback in subsurface warfare.

I had come across the below article about the new Type 212CD for the German/Norwegian navies by H.I Sutton who happens to be one of the best open source intelligence on submarines and the like.

Radical New Stealth Submarine, Type-212CD, Will Be Much Larger - Naval News

Submarines rely on stealth to maintain the element of surprise and escape threats. For decades this has focused on reducing the noise emitted by the submarine. A resurgence of using active sonar to locate submarines now means that new stealth measures may be required. German submarine builder...

www.navalnews.com

I doubt we have the expertise (or the time to build the expertise) with regard to specialized hull forging at this point. Our priorities are likely to be dominated by timelines primarily.

Any such undertaking is highly risky.

Even speaking of distant future, there is a middle road to take with regard to active stealth. Like the Astute, which has angled bow but rest of the shape is conventional, can be a route to take:

That said, it doesn't seem to be a universal approach. The French Barracuda/Suffren, designed much after the Astute was frozen, does not care about such designs.

Neither does the future Columbia-class SSBN of US.

I remain skeptical of the utility of active stealth shaping for a nuclear-powered submarine. May have more utility for a diesel boat that might choose to stay put at choke points/littoral waters expecting to be constantly pinged by surface ships. But a nuke sub in the deep seas? Utility is likely reduced as they would not be facing active sonar as often as a diesel boat may have to.

The primary threat for SSNs comes from other SSNs - which would use active pinging very conservatively so as not to give away their own position.

A FAR MORE critical importance should be accorded to PASSIVE STEALTH i.e. making less noise.

EDIT:

As a P.S. let me say that such angled hulls designed for active stealth are hugely sub-optimal when it comes to being truly hydrodynamic. The same powerplant will have to work harder to push such a hull through water, which in turn may end up making more noise.

Doesn't matter for an Ambush predator like SSK, but for a hunter-killer like SSN, that is a serious problem.

 

[MonaLazy]

the designs & engineering models for the OK-650B PWR

Didn't we already get access to OK-650B in Chakra 2/Nerpa?

Chakra 3 may be OK-650V incorporating improvements in reactor design of the Yasen class or hoping against hope 4th gen KPM-6 of the Yasen-M ($3.3B is a lot of money more than INS Vikramaditya & is the only possible pointer in this direction)?

However, according to https://media.nti.org/pdfs/Replacing_HEU_in_Naval_Reactors_Report_FINAL.pdf Chakra -3 "was supposed to include elements of the newer Yasen class SSGN".

Is it reasonable to assume the following improvements of the Yasen are headed our way?

• Spherical bow sonar array, as is the US practice, replacing the cylindrical arrangement in MGK-501 Skat-MS of Chakra 2.
• Conformal flank arrays in sonar suite
• retractable towed array sonar
• new 4th gen nuke plant with partial electric drive (for low speeds)? Plus the reactor has 25-30 year core life- so no refueling for the life of sub
• 8x large diameter (for varied weapons load) VLS tubes located aft of sail
  • 3x sub launched Brahmos per VLS tube
  • 5x 3M-54 Klub cruise missile per VLS tube for land attack, anti ship & anti sub
• crew size of about 90, high automation
• test depth of 600m substantially more than any US SSN
• Yasen is the quietest Russian sub till date

Whatever we get in the 2025 lease will get into our own SSNs operational by 2030-5 and Russians have already started work on 5th gen SSNs circa December 2014- all pointers to 4th gen Yasen class technology being shared with India.

Source- https://lynceans.org/wp-content/uploads/2015/09/Part-3_Russia-60-yrs-of-marine-nuc-power.pdf