Yuan Class AIP & Kilo Submarine Thread

[tphuang]

Continuing the discussion of what China's future conventional fleet looks like. Shilao's podcast recently mentioned that when 039B production slowed down, people were speculating whether the next submarine would be much smaller or be using mini nuclear reactor. But with 039C, it looks like they just continued with incrementally improving Yuan class.

Imo, there is some real issues with the existing Yuan class. To start off, it has the constraint of a submarine that was first launched 18 years ago. Back then, AIP section with Stirling engine was probably the most logical solution to the endurance problem that conventional subs have. But with Stirling, you have something that is inherently producing noise and probably can't be perfectly isolated. It is true that Soryu also use Stirling, but it has a larger pressure hull that can install raft needed to more significantly isolate AIP section. Secondly, Stirling itself does not generate enough power to allow Yuan class to be going faster than 4 knots. That presents significant restrictions on how you can operate the submarine. At the same time, lead acid battery no longer makes sense for China at a time when lithium ion battery types have made so much advancement. While there has been posters on Winton Lithium battery, I really don't think it's on any of the 039Bs, because S26T export did not mention Lithium ion battery installation at all. So, I assume that all of 039A/B are using lead acid battery with AIP.

The mystery is around 039C. Here is why I was surprised that they continued to build submarine around the same hull as 039B

1) A lot of 039B's data were made public with S26T export. So now, USN would know exactly the endurance of 039B's AIP system and lead acid battery. It would also know the depth at which 039B can operate with its AIP system. We know the dimensions of 039B. We even know its pressure hull is 10m shorter than its overall length. There is huge advantage for USN/JMSDF ASW team to know how far a 039B can go while submerged.
2) There was a 4 to 5 year gap between the last 039B and first 039C launching. That's quite long when considering that the first Yuan was launched before the last Song was launched. On top of that, 039C was launched 4 years after 039B numbers were already declassified. What did they spend those years developing?
3) China normally does not mark something available for export and declassify its performance data for its front line platform. In J-10C's case, it was not made available in air shows until around the time J-20 was ready to join service. As of now, we see no conventional submarine version of J-20 anywhere.
4) What happened to the mini-nuke version of 039C? I would be very surprised if 039C can host a mini-nuke and associated equipments without some stretching.
5) Yuan submarine was a nice design for early 2000s. But we are now almost 20 years later. With the experience that they have, are they unable to create something with larger pressure hull?

This is my theory. 039C has different battery/engine than 039B. Given the declassification of 039B AIP system, 039C would need to have different top speed, endurance and cruising performance metrics. I think they were originally intending to install a mini-nuke, but the development of Lithium ion batteries surprised everyone. As such, they can get all the performance they need out of LIB vs installing a weak nuclear reactor that would need to be isolated. Just think about all the room dedicated to nuclear reactor or AIP engine (+ associated noise isolation structures) that can now be used as battery storage or enlarged combat room or berthing anything else. A 039C that uses purely LIB would have significant differences endurance/speed performance compared to 039B.

It is also possible that 039C is a testing platform for LIB like the last 2 Soryu class submarines. As such, it will continue to have Stirling AIP engine. For me, that would be a huge disappointment. However, that may be the path PLAN is taking if it is looking to immediately add more deep ocean diesel subs. We've seen additional 052D/054A orders in the short term to build up numbers for a near/medium term conflict. In that case, 039C change would be more modest and they are likely to also be planning a new conventional sub.

Another possibility is a combination of fuel cell AIP + LIB. since they are also among the world leaders in hydrogen fuel cells, this would not be a bad idea. I think it is more likely that 039C is trialing out with a modern LIB (maybe based on LFP technology for safety) and modern high efficiency electric train that can achieve long range by itself. For example, a 400t LFP battery using the current technology (150 wh/kg at pack level) would be able to store 60 MWh of energy with minimal degradation, faster charging and able to be used down to 0% before charging. if traveling at 6 to 8 knots require 200 kw/h of energy, that battery pack would last 300 hours (12.5 days). That's not too far behind 2.5 days with LAB + 2 weeks or so on Stirling AIP. It also makes more sense to have a radar deflecting sail if you can charge more quickly (which is the case with LIB).

So, the entire Yuan series is quite good for deeper water operation. They have those long flank arrays that function better in deeper vs littoral waters. What's replacing Song in the shallower water?

I think that will have to be the new small subs we have seen. A single hull design similar in size to Type 206 but with a good sized LIB pack can stay in littoral waters for days. With noisier surroundings, it would be a lot harder for them to get detected by incoming ships. In the coastal waters and water around Spratley/Paracel and Ryuku islands, they could be quite the menace. I think they will be quieter than Song class. With much longer endurance, they also will be less vulnerable to getting spotted by P-3Cs while surfacing to recharge.

I think they also badly need something to replace Kilo/Yuan subs for deeper waters. As I said earlier, I don't believe 039C to be the ultimate solution for PLAN. They need something with larger pressure hull and larger battery pack to take advantage of the latest LIB technology and possibly carry VLS installation. They'd be able to have the latest/quietest/most efficient electric motors fitted with latest rafting technology they have. It would have the latest sonar/communication technology that China has and can control AUV/UUVs in the water. That would be something quite effective in the much of Philippine Sea and SCS.

 

[FairAndUnbiased]

Continuing the discussion of what China's future conventional fleet looks like. Shilao's podcast recently mentioned that when 039B production slowed down, people were speculating whether the next submarine would be much smaller or be using mini nuclear reactor. But with 039C, it looks like they just continued with incrementally improving Yuan class.

Imo, there is some real issues with the existing Yuan class. To start off, it has the constraint of a submarine that was first launched 18 years ago. Back then, AIP section with Stirling engine was probably the most logical solution to the endurance problem that conventional subs have. But with Stirling, you have something that is inherently producing noise and probably can't be perfectly isolated. It is true that Soryu also use Stirling, but it has a larger pressure hull that can install raft needed to more significantly isolate AIP section. Secondly, Stirling itself does not generate enough power to allow Yuan class to be going faster than 4 knots. That presents significant restrictions on how you can operate the submarine. At the same time, lead acid battery no longer makes sense for China at a time when lithium ion battery types have made so much advancement. While there has been posters on Winton Lithium battery, I really don't think it's on any of the 039Bs, because S26T export did not mention Lithium ion battery installation at all. So, I assume that all of 039A/B are using lead acid battery with AIP.

The mystery is around 039C. Here is why I was surprised that they continued to build submarine around the same hull as 039B

1) A lot of 039B's data were made public with S26T export. So now, USN would know exactly the endurance of 039B's AIP system and lead acid battery. It would also know the depth at which 039B can operate with its AIP system. We know the dimensions of 039B. We even know its pressure hull is 10m shorter than its overall length. There is huge advantage for USN/JMSDF ASW team to know how far a 039B can go while submerged.
2) There was a 4 to 5 year gap between the last 039B and first 039C launching. That's quite long when considering that the first Yuan was launched before the last Song was launched. On top of that, 039C was launched 4 years after 039B numbers were already declassified. What did they spend those years developing?
3) China normally does not mark something available for export and declassify its performance data for its front line platform. In J-10C's case, it was not made available in air shows until around the time J-20 was ready to join service. As of now, we see no conventional submarine version of J-20 anywhere.
4) What happened to the mini-nuke version of 039C? I would be very surprised if 039C can host a mini-nuke and associated equipments without some stretching.
5) Yuan submarine was a nice design for early 2000s. But we are now almost 20 years later. With the experience that they have, are they unable to create something with larger pressure hull?

This is my theory. 039C has different battery/engine than 039B. Given the declassification of 039B AIP system, 039C would need to have different top speed, endurance and cruising performance metrics. I think they were originally intending to install a mini-nuke, but the development of Lithium ion batteries surprised everyone. As such, they can get all the performance they need out of LIB vs installing a weak nuclear reactor that would need to be isolated. Just think about all the room dedicated to nuclear reactor or AIP engine (+ associated noise isolation structures) that can now be used as battery storage or enlarged combat room or berthing anything else. A 039C that uses purely LIB would have significant differences endurance/speed performance compared to 039B.

It is also possible that 039C is a testing platform for LIB like the last 2 Soryu class submarines. As such, it will continue to have Stirling AIP engine. For me, that would be a huge disappointment. However, that may be the path PLAN is taking if it is looking to immediately add more deep ocean diesel subs. We've seen additional 052D/054A orders in the short term to build up numbers for a near/medium term conflict. In that case, 039C change would be more modest and they are likely to also be planning a new conventional sub.

Another possibility is a combination of fuel cell AIP + LIB. since they are also among the world leaders in hydrogen fuel cells, this would not be a bad idea. I think it is more likely that 039C is trialing out with a modern LIB (maybe based on LFP technology for safety) and modern high efficiency electric train that can achieve long range by itself. For example, a 400t LFP battery using the current technology (150 wh/kg at pack level) would be able to store 60 MWh of energy with minimal degradation, faster charging and able to be used down to 0% before charging. if traveling at 6 to 8 knots require 200 kw/h of energy, that battery pack would last 300 hours (12.5 days). That's not too far behind 2.5 days with LAB + 2 weeks or so on Stirling AIP. It also makes more sense to have a radar deflecting sail if you can charge more quickly (which is the case with LIB).

So, the entire Yuan series is quite good for deeper water operation. They have those long flank arrays that function better in deeper vs littoral waters. What's replacing Song in the shallower water?

I think that will have to be the new small subs we have seen. A single hull design similar in size to Type 206 but with a good sized LIB pack can stay in littoral waters for days. With noisier surroundings, it would be a lot harder for them to get detected by incoming ships. In the coastal waters and water around Spratley/Paracel and Ryuku islands, they could be quite the menace. I think they will be quieter than Song class. With much longer endurance, they also will be less vulnerable to getting spotted by P-3Cs while surfacing to recharge.

I think they also badly need something to replace Kilo/Yuan subs for deeper waters. As I said earlier, I don't believe 039C to be the ultimate solution for PLAN. They need something with larger pressure hull and larger battery pack to take advantage of the latest LIB technology and possibly carry VLS installation. They'd be able to have the latest/quietest/most efficient electric motors fitted with latest rafting technology they have. It would have the latest sonar/communication technology that China has and can control AUV/UUVs in the water. That would be something quite effective in the much of Philippine Sea and SCS.

Stirling has negligible noise, since it has no detonation like a diesel or ICE, no boiling water like a steam turbine and if built in a diaphragm configuration is also linear bearing free, and thus would only have a rotary transmission for running the generator. With sufficient lubrication in the gearbox, the rotary transmission is also silent.

You don't need as much damping if the engine doesn't make noise. Just listen to how quiet even a hybrid car is much less a full electric, you barely hear the engine and most noise is wheel to road friction. And that's an ICE engine with detonation.

 

[tphuang]

Stirling has negligible noise, since it has no detonation like a diesel or ICE, no boiling water like a steam turbine and if built in a diaphragm configuration is also linear bearing free, and thus would only have a rotary transmission for running the generator. With sufficient lubrication in the gearbox, the rotary transmission is also silent.

You don't need as much damping if the engine doesn't make noise. Just listen to how quiet even a hybrid car is much less a full electric, you barely hear the engine and most noise is wheel to road friction. And that's an ICE engine with detonation.

Based on what I heard from my sources, they definitely do have noise and completely isolating those noise against low frequency sonar in deep water is not a given.

Yes, hybrid cars are quiet, but the engine in question would be a lot larger and deep sea water transmits sound really well.

I don't see why you would want to keep Stirling AIP when there are clearly better technology available now.

 

[Andy1974]

Continuing the discussion of what China's future conventional fleet looks like. Shilao's podcast recently mentioned that when 039B production slowed down, people were speculating whether the next submarine would be much smaller or be using mini nuclear reactor. But with 039C, it looks like they just continued with incrementally improving Yuan class.

Imo, there is some real issues with the existing Yuan class. To start off, it has the constraint of a submarine that was first launched 18 years ago. Back then, AIP section with Stirling engine was probably the most logical solution to the endurance problem that conventional subs have. But with Stirling, you have something that is inherently producing noise and probably can't be perfectly isolated. It is true that Soryu also use Stirling, but it has a larger pressure hull that can install raft needed to more significantly isolate AIP section. Secondly, Stirling itself does not generate enough power to allow Yuan class to be going faster than 4 knots. That presents significant restrictions on how you can operate the submarine. At the same time, lead acid battery no longer makes sense for China at a time when lithium ion battery types have made so much advancement. While there has been posters on Winton Lithium battery, I really don't think it's on any of the 039Bs, because S26T export did not mention Lithium ion battery installation at all. So, I assume that all of 039A/B are using lead acid battery with AIP.

The mystery is around 039C. Here is why I was surprised that they continued to build submarine around the same hull as 039B

1) A lot of 039B's data were made public with S26T export. So now, USN would know exactly the endurance of 039B's AIP system and lead acid battery. It would also know the depth at which 039B can operate with its AIP system. We know the dimensions of 039B. We even know its pressure hull is 10m shorter than its overall length. There is huge advantage for USN/JMSDF ASW team to know how far a 039B can go while submerged.
2) There was a 4 to 5 year gap between the last 039B and first 039C launching. That's quite long when considering that the first Yuan was launched before the last Song was launched. On top of that, 039C was launched 4 years after 039B numbers were already declassified. What did they spend those years developing?
3) China normally does not mark something available for export and declassify its performance data for its front line platform. In J-10C's case, it was not made available in air shows until around the time J-20 was ready to join service. As of now, we see no conventional submarine version of J-20 anywhere.
4) What happened to the mini-nuke version of 039C? I would be very surprised if 039C can host a mini-nuke and associated equipments without some stretching.
5) Yuan submarine was a nice design for early 2000s. But we are now almost 20 years later. With the experience that they have, are they unable to create something with larger pressure hull?

This is my theory. 039C has different battery/engine than 039B. Given the declassification of 039B AIP system, 039C would need to have different top speed, endurance and cruising performance metrics. I think they were originally intending to install a mini-nuke, but the development of Lithium ion batteries surprised everyone. As such, they can get all the performance they need out of LIB vs installing a weak nuclear reactor that would need to be isolated. Just think about all the room dedicated to nuclear reactor or AIP engine (+ associated noise isolation structures) that can now be used as battery storage or enlarged combat room or berthing anything else. A 039C that uses purely LIB would have significant differences endurance/speed performance compared to 039B.

It is also possible that 039C is a testing platform for LIB like the last 2 Soryu class submarines. As such, it will continue to have Stirling AIP engine. For me, that would be a huge disappointment. However, that may be the path PLAN is taking if it is looking to immediately add more deep ocean diesel subs. We've seen additional 052D/054A orders in the short term to build up numbers for a near/medium term conflict. In that case, 039C change would be more modest and they are likely to also be planning a new conventional sub.

Another possibility is a combination of fuel cell AIP + LIB. since they are also among the world leaders in hydrogen fuel cells, this would not be a bad idea. I think it is more likely that 039C is trialing out with a modern LIB (maybe based on LFP technology for safety) and modern high efficiency electric train that can achieve long range by itself. For example, a 400t LFP battery using the current technology (150 wh/kg at pack level) would be able to store 60 MWh of energy with minimal degradation, faster charging and able to be used down to 0% before charging. if traveling at 6 to 8 knots require 200 kw/h of energy, that battery pack would last 300 hours (12.5 days). That's not too far behind 2.5 days with LAB + 2 weeks or so on Stirling AIP. It also makes more sense to have a radar deflecting sail if you can charge more quickly (which is the case with LIB).

So, the entire Yuan series is quite good for deeper water operation. They have those long flank arrays that function better in deeper vs littoral waters. What's replacing Song in the shallower water?

I think that will have to be the new small subs we have seen. A single hull design similar in size to Type 206 but with a good sized LIB pack can stay in littoral waters for days. With noisier surroundings, it would be a lot harder for them to get detected by incoming ships. In the coastal waters and water around Spratley/Paracel and Ryuku islands, they could be quite the menace. I think they will be quieter than Song class. With much longer endurance, they also will be less vulnerable to getting spotted by P-3Cs while surfacing to recharge.

I think they also badly need something to replace Kilo/Yuan subs for deeper waters. As I said earlier, I don't believe 039C to be the ultimate solution for PLAN. They need something with larger pressure hull and larger battery pack to take advantage of the latest LIB technology and possibly carry VLS installation. They'd be able to have the latest/quietest/most efficient electric motors fitted with latest rafting technology they have. It would have the latest sonar/communication technology that China has and can control AUV/UUVs in the water. That would be something quite effective in the much of Philippine Sea and SCS.

now add to this the ability to recharge at any floating windmill while submerged and you have submarine dominance.

 

[taxiya]

Another possibility is a combination of fuel cell AIP + LIB. since they are also among the world leaders in hydrogen fuel cells, this would not be a bad idea. I think it is more likely that 039C is trialing out with a modern LIB (maybe based on LFP technology for safety) and modern high efficiency electric train that can achieve long range by itself. For example, a 400t LFP battery using the current technology (150 wh/kg at pack level) would be able to store 60 MWh of energy with minimal degradation, faster charging and able to be used down to 0% before charging. if traveling at 6 to 8 knots require 200 kw/h of energy, that battery pack would last 300 hours (12.5 days). That's not too far behind 2.5 days with LAB + 2 weeks or so on Stirling AIP. It also makes more sense to have a radar deflecting sail if you can charge more quickly (which is the case with LIB).

I am not sure if any LIB has the kind of specific energy (Wh/kg) anywhere close to stirling engine.

I think

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is showing figures accurate enough to make a rough judgement.

Diesel fuel is 12,667 Wh/kg. Stirling Engine's efficiency is about 40%. That gives 5066.8 Wh/kg mechanical energy which translates to 4813 Wh/g electricity energy. Sirling engine itself is a extra dead weight that pure battery based sub don't have.

LIB is 100 to 243 Wh/kg (wiki). The highest 243 is only 5% (243/4813) of what diesel can provide. LFP of 150wh/kg is only 3%.

The stirling engine used by Gotland class is only 600kg per unit. If I am not mistaken, there are two, in total 1.2 tonne. That is almost neglect-able considering the vast advantage of specific energy of diesel fuel.

It is the same problem that EV is facing, short of range/endurance.

I agree with your point to replace stirling engine if there is a better alternative. But so far IMO the only better solution is still small nuclear reactor. It's only limit is the crew/food/ammunition, not fuel. It's power output is also much larger than any conventional sub. All other subs run on battery under water. Stirling engine can drive the sub without going through the battery but under very low speed. Battery run hot in high power rating which can burn. LFP is much safer than other Li-On, but only to a point. Higher temperature also means lot of energy is wasted as heat. Nuclear power has no such limitation.

 

[taxiya]

now add to this the ability to recharge at any floating windmill while submerged and you have submarine dominance.

I am sure you are just kidding.

 

[tphuang]

I am not sure if any LIB has the kind of specific energy (Wh/kg) anywhere close to stirling engine.

I think

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is showing figures accurate enough to make a rough judgement.

Diesel fuel is 12,667 Wh/kg. Stirling Engine's efficiency is about 40%. That gives 5066.8 Wh/kg mechanical energy which translates to 4813 Wh/g electricity energy. Sirling engine itself is a extra dead weight that pure battery based sub don't have.

LIB is 100 to 243 Wh/kg (wiki). The highest 243 is only 5% (243/4813) of what diesel can provide. LFP of 150wh/kg is only 3%.

The stirling engine used by Gotland class is only 600kg per unit. If I am not mistaken, there are two, in total 1.2 tonne. That is almost neglect-able considering the vast advantage of specific energy of diesel fuel.

It is the same problem that EV is facing, short of range/endurance.

I agree with your point to replace stirling engine if there is a better alternative. But so far IMO the only better solution is still small nuclear reactor. It's only limit is the crew/food/ammunition, not fuel. It's power output is also much larger than any conventional sub. All other subs run on battery under water. Stirling engine can drive the sub without going through the battery but under very low speed. Battery run hot in high power rating which can burn. LFP is much safer than other Li-On, but only to a point. Higher temperature also means lot of energy is wasted as heat. Nuclear power has no such limitation.

Keep in mind that LAB itself is quite heavy. The Lithium ion battery would be replace the LAB as well as the weight of Stirling engine and associated equipment. With Stirling engine, you will need to install a very large raft to isolate the noise. You also have the additional machinery associated with Stirling.

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In the Stirling cycle, the fuel is continuously burned, whereas, in a diesel engine, the combustion is an explosive, noise-generating process. In fact, the motive machinery associated with the Stirling revealed itself to be much noisier than the combustion. Thus, Kockums’ engineers had to ensure that all machinery mounts were placed on rafts to reduce detectable vibration through the hull.

With mini-nuke, you are going to be dealing with the same issues of all the equipment associated with nuclear to electricity generation + safety structures and rafting built around. And worst of all, China has huge problems with noise level in its nuclear subs. There won't be any more quiet mode since you can't just turn off a reactor. I never understood the logic of mini-nukes in diesel subs. If subs can't be quiet, it doesn't matter how long their endurance is. Stealth is always the most important consideration in subs.

We have seen LFP blade battery by BYD that can continue to function after getting crushed by 50t trucks and punctured by nails. The CTB structure in Seal is is so strong that it can handle stress level that rivals Porsche Taycan. BYD has achieved 90% efficiency in its batteries. There should be no more doubt over this technology. If you want to try SSB, you could get even higher energy density, but may require more material to prevent possible fire.

If we look at Taigei, they were able to fit

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640 LIB modules with each weighing 770kg -> about 500t of battery. That's a lot.

500t of battery at 150wh/kg (at pack level) is about 75 MWh. That would support 375 hours -> 15.6 days of endurance 200 wh per hour. I'm not saying they will be able to install that much battery, but Winston ad was advertising 330t of battery. I don't think 400t of LIB on a sub as large as 039C is unreasonable.

 

[Andy1974]

I am sure you are just kidding.

only a little..

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[taxiya]

only a little..

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It is good idea for civilian usage. But for military, I highly doubt. Submarine does not want any enemy to know where it is, where it may be at, where it is likely going. Wind-farm is the stopover, gather point that is well known. Secondly, how far out from the coast are you going to and can you possibly put the wind-farm? As far as the operation area of the sub which is along the sea lanes? If they are close to the shore, then why not just go back to port?

 

[Andy1974]

It is good idea for civilian usage. But for military, I highly doubt. Submarine does not want any enemy to know where it is, where it may be at, where it is likely going. Wind-farm is the stopover, gather point that is well known. Secondly, how far out from the coast are you going to and can you possibly put the wind-farm? As far as the operation area of the sub which is along the sea lanes? If they are close to the shore, then why not just go back to port?

yes I agree that it will be civilian use cases that perpetuate offshore charging infrastructure, but I also think it will be very widespread, even in the deep oceans.

I am not sure if windfarms are the best way to do it, probably not, but I do know that the latest ones can withstand typhoons and thus be placed anywhere in the pacific, in their thousands. I do also think there are plenty of other energy sources that battery submarines can use.

I did adapt this idea from my original one, which is to use nuclear powered subs to recharge purely battery powered ones, but I think China will just develop and basically colonize the oceans with their planned marine economy blueprints, and so the infrastructure can be built by the private sector and the PLAN can just use it, which is nice civil-military fusion.