09III/09IV (093/094) Nuclear Submarine Thread

[Blitzo]

Why's that? The submarine's internals obviously went through extensive redesign to fit 24 VLS tubes, why wouldn't the pressure hull have been widened? Wasn't the reason it was narrow to begin with a reflection of China's poor metallurgical capabilities at the time of the original 09III?

Because changing the maximum pressure hull diameter of a submarine is like changing the maximum beam of a surface ship.
It is the equivalent of designing a whole new class of submarine.


I chose my words very carefully in that post -- specifically that the maximum pressure hull diameter of 09IIIB probably isn't different from prior 09III/As.

I did not say that there was no significant rearrangement of the 09IIIB's internals compared to prior 09III/As, and I also didn't say that there wasn't a possibility that they could've changed the overall pressure hull geometry in a way that may have provided more internal volume without changing maximum pressure hull diameter (in fact both of these I consider to be very likely and plausible, respectively, in enabling 09IIIB having more internal pressure hull volume), which would have contributed to both having more space for insulation, subsystems and of course adding the VLS.
I also didn't say that the PRC today didn't have the ability to design or develop a submarine with a larger pressure hull (in fact, I expect 09V to have a pressure hull diameter of 12m, much larger than the pressure hull diameter of 09III family).

I believe 09IIIB's internal pressure hull volume is being used more efficiently than that on 09III/A due to miniaturization of subsystems and further improvements of automation (reduced crewing), and there is also a possibility that the maximum internal pressure hull volume is increased relative to 09III/A if its pressure hull geometry was modified (e.g.: a more consistent cylindrical pressure hull of its preexisting maximum pressure hull diameter, rather than perhaps a preexisting pressure hull geometry that was more "tapered" on its bow and aft).
But changing/increasing the maximum pressure hull diameter of the submarine to be a "hybrid hull" submarine? That's a huge step and basically you're designing and building a clean sheet new class of submarine.


Now, it is technically possible that 09IIIB is such a major deviation from the prior 09III/A that it might be a "hybrid" hull submarine (i.e.: single hull in some parts of the hull while double hull in large portions of the aft and bow) -- that would be even more extreme than the relationship from 054A to 054B... one where the class/type family they are part of is essentially only in name rather than hullform, as a "hybrid hull" 09IIIB would very much be a whole new submarine class relative to prior 09III/As.

If 09IIIB had anything as drastic as being a "hybrid hull" compared to 09III/A, I strongly suspect that also would have come through via the grapevine along with the other preceding rumours we've had of 09IIIB back in the late 2010s or even some of the rumours we have come to know about 09V.

 

[ZeEa5KPul]

Because changing the maximum pressure hull diameter of a submarine is like changing the maximum beam of a surface ship.
It is the equivalent of designing a whole new class of submarine.

I didn't know the change was that radical. To be clear, I also chose my words carefully. It's not my position that the 09IIIB is a single/hybrid hull submarine; that would likely have leaked in years prior (although the fact that the J-36 has 3 engines was kept secret until a couple of weeks before the reveal, and the interior dimensions of a submarine are far easier to keep secret).

My speculation is that given interior volume is so important for rafting, insulation, and so forth, the maximum diameter of the pressure hull might have been expanded from the commonly thrown around 9m to 9.5m or 10m, while keeping the same 11m outer hull diameter by changing the geometry and position of the ballast tanks and other components between the inner and outer hulls. Not that the 09IIIB was redesigned from a double to a single/hybrid hull.

 

[Blitzo]

I didn't know the change was that radical. To be clear, I also chose my words carefully. It's not my position that the 09IIIB is a single/hybrid hull submarine; that would likely have leaked in years prior (although the fact that the J-36 has 3 engines was kept secret until a couple of weeks before the reveal, and the interior dimensions of a submarine are far easier to keep secret).

My speculation is that given interior volume is so important for rafting, insulation, and so forth, the maximum diameter of the pressure hull might have been expanded from the commonly thrown around 9m to 9.5m or 10m, while keeping the same 11m outer hull diameter by changing the geometry and position of the ballast tanks and other components between the inner and outer hulls. Not that the 09IIIB was redesigned from a double to a single/hybrid hull.

Maximum pressure hull diameter should be seen as one of the most "difficult" things to change for any given submarine class.

As for the idea of "what if they tweaked the maximum pressure hull diameter just a little bit to increase it a smidge" --- sure, increasing it by half a meter in overall maximum diameter would likely be easier than increasing it by say, 2 whole meters. But it's still a whole new maximal cross section for a submarine for arguably one of the most if not the most difficult part of a submarine to change.


I've already offered a somewhat more viable way of increasing interior volume, which is by keeping the same maximal pressure hull diameter inside, but by extending it out a bit more compared to previous 09III/A to be more "uniform" (aka less "tapered"), while keeping the outer hydrodynamic hull the same in terms of overall dimensions.
Depicted very simply below.

Putting it another way, why even entertain the idea of 09IIIB increasing its maximal pressure hull diameter relative to 09III/A, considering how vital and difficult to change that aspect is for a submarine class, when there are more viable ways to increase internal pressure hull volume?

Edit:
If I were to try and make a list of potential improvements and advancements that 09IIIB has over 09III/A, the idea of having a maximal, larger pressure hull diameter, would be something that I'd actively leave off my list, because it is difficult to substantiate, and because of how vital it is to a submarine being of a given "class".
I would need a rather firm rumour base to offer it as an idea. Without that, the overall argument would be stronger by simply ignoring such a possibility.

 

[Iron Man]

The actual thing to figure is why all the contortions over gutting and redesigning the innards when they could have just added a section with the missile tubes. The only thing I can think off is the previous displacement was already at the upper end of the displacement range the reactor was able to handle. But then I remember the 094....

 

[Blitzo]

The actual thing to figure is why all the contortions over gutting and redesigning the innards when they could have just added a section with the missile tubes. The only thing I can think off is the previous displacement was already at the upper end of the displacement range the reactor was able to handle. But then I remember the 094....

There's a few reasonable ways in which they could have added the VLS cells into the 09IIIB while keeping the same overall external submarine length, one of which like you said is adding a pressure hull plug in with missile tubes and overall extending the pressure hull length while keeping the overall submarine length the same.

The discussion (see edit below) about redesigning the innards and the pressure hull geometry relates to not just answering the question about the VLS tubes, but also about the total available pressure hull volume which determines the volume available for sound dampening systems and thus affects the overall ability to further quieten the vessel on top of other means of quietening it that 09IIIB is likely to enjoy relative to 09III/As.

Edit: specifically, the discussion between Zeak and I

 

[Iron Man]

The discussion about redesigning the innards and the pressure hull geometry relates to not just answering the question about the VLS tubes, but also about the total available pressure hull volume which determines the volume available for sound dampening systems and thus affects the overall ability to further quieten the vessel on top of other means of quietening it that 09IIIB is likely to enjoy relative to 09III/As.

What does that mean? You can always increase the total available pressure hull volume by increasing the length of the boat, e.g. by adding a new section. Virginia did this, Seawolf did this, and maybe even the 092 and 094 did this. I'm not sure how this relates to the question of why the PLAN did not actually choose the most simple and obvious solution.

 

[Blitzo]

What does that mean? You can always increase the total available pressure hull volume by increasing the length of the boat, e.g. by adding a new section. Virginia did this, Seawolf did this, and maybe even the 092 and 094 did this. I'm not sure how this relates to the question of why the PLAN did not actually choose the most simple and obvious solution.

You asked why there were "contortions" about the internals of the vessel, which made it sound like you didn't understand why Zeak and I were focusing so much on the internals of the 09IIIB.
I am explaining that the discussion was about the ways in which they could have improved the performance of the boat (particularly acoustic quietening) in context of how it seems 09IIIB has kept the same overall length and dimensions as the preceding 09III/As.


Yes, they could always increase the pressure hull volume by lengthening it, but they didn't do that, so instead we are talking about what they could have done internally.

 

[Iron Man]

You asked why there were "contortions" about the internals of the vessel, which made it sound like you didn't understand why Zeak and I were focusing so much on the internals of the 09IIIB.
I am explaining that the discussion was about the ways in which they could have improved the performance of the boat (particularly acoustic quietening) in context of how it seems 09IIIB has kept the same overall length and dimensions as the preceding 09III/As.


Yes, they could always increase the pressure hull volume by lengthening it, but they didn't do that, so instead we are talking about what they could have done internally.

The contortions is in reference to what the PLAN must have done to get a large set of launch tubes into a sub with expanding its volume instead of just... expanding its volume.

 

[Blitzo]

The contortions is in reference to what the PLAN must have done to get a large set of launch tubes into a sub with expanding its volume instead of just... expanding its volume.

Fair, I can see the meaning of the post now.


To address the question, I have a few ideas, which I considered back in 2020-21 when the suspected model of the 09IIIB first came out and it looked like it was not much longer than a usual 09III/A:
- Lengthening the overall hull itself (thus increasing its overall tonnage) does offer certain drawbacks, in terms of hydrodynamic/kinetic performance of a submarine. It is possible that lengthening it would have adversely affected the performance beyond the target requirements the PLAN wanted for 09IIIB, in context of the reactor/propulsion train they were able to put into it.
- They didn't need to actually lengthen the hull for the VLS alone, because new technologies had emerged at that point anyway which were more miniaturized and allowed for more automation (a smaller crew requirement), which would allow them to install the VLS tubes in the same hull length, thus avoiding the drawbacks of lengthening the overall hull.
- In terms of sound dampening, I am not sure to what extent lengthening the pressure hull (and overall hull) offers benefits versus expanding its continuous cross sectional pressure hull diameter (or having a larger maximal pressure hull diameter overall, which would be basically a new class of submarine). A longer submarine of the same pressure hull geometry/proportions should allow internal systems to be placed more longitudinally "spaced out" which can then offer more cross sectional area to put in sound dampening measures per given length -- but that goes back into the question of whether the drawbacks of a longer/heavier submarine is deemed a worthwhile trade. OTOH, a submarine of the same length but with greater internal continuous pressure hull diameter would offer more pressure hull volume without increasing the submarine's overall displacement as much.

 

[Jason_]

Maximum pressure hull diameter should be seen as one of the most "difficult" things to change for any given submarine class.

As for the idea of "what if they tweaked the maximum pressure hull diameter just a little bit to increase it a smidge" --- sure, increasing it by half a meter in overall maximum diameter would likely be easier than increasing it by say, 2 whole meters. But it's still a whole new maximal cross section for a submarine for arguably one of the most if not the most difficult part of a submarine to change.


I've already offered a somewhat more viable way of increasing interior volume, which is by keeping the same maximal pressure hull diameter inside, but by extending it out a bit more compared to previous 09III/A to be more "uniform" (aka less "tapered"), while keeping the outer hydrodynamic hull the same in terms of overall dimensions.
Depicted very simply below.

Putting it another way, why even entertain the idea of 09IIIB increasing its maximal pressure hull diameter relative to 09III/A, considering how vital and difficult to change that aspect is for a submarine class, when there are more viable ways to increase internal pressure hull volume?

Edit:
If I were to try and make a list of potential improvements and advancements that 09IIIB has over 09III/A, the idea of having a maximal, larger pressure hull diameter, would be something that I'd actively leave off my list, because it is difficult to substantiate, and because of how vital it is to a submarine being of a given "class".
I would need a rather firm rumour base to offer it as an idea. Without that, the overall argument would be stronger by simply ignoring such a possibility.



View attachment 146769

Submarines pressure hulls are not tapered like this. You need a hemisphere capping each end of a cylinder. You also cannot easily use the space outside the pressure hull because they contain important things like sonar, ballast tanks, etc.