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

I believe USN was wrong about noise level 093 (worse than Victor III), not sure whether it was intentional or lack of analysis. It is almost impossible the China would accept it if it was worse than victor III (commissioned in 1967), China is already very very advanced, in computer, engineering, manufacturing, material, etc and also China has produced the most advanced CNC machines in the world, so it doesn't make sense at all

antiterror13 said:

I believe USN was wrong about noise level 093 (worse than Victor III), not sure whether it was intentional or lack of analysis. It is almost impossible the China would accept it if it was worse than victor III (commissioned in 1967), China is already very very advanced, in computer, engineering, manufacturing, material, etc and also China has produced the most advanced CNC machines in the world, so it doesn't make sense at all

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I do not believe they are that far off.

There's more to it than simply having the machinery.

If it represented an increase over what they had before...they probably accepted it, and then found that they could do a lot better.

They were clearly (IMHO) not that happy with it as they quickly came out with a modification and built the rest of them to the modified standard.

Now they are moving on to the Type 095, which I am sure will represent another significant step forward.

The US did not get where it is today in SSN design in a short time. It took decades and numerous different classes and many submarine builds. The Chinese are trying to catch up...and they are closing the gap much faster than that gap developed in the first place.

Jeff, I think it's pointless to argue with someone who writes that some of the brightest minds in US who probably catch quantum mechanics in a second and work for US as experts are a level below some folk on Internet forum and that they don't know their work.

Some things are worth discussion here but surely not this one.

antiterror13 said:

... China is already very very advanced, in computer, engineering, manufacturing, material, etc and also China has produced the most advanced CNC machines in the world, so it doesn't make sense at all

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While China's computing technology would arguably make not much of a difference and its CNC machines were among the most advanced in the world, the same could not be said about engine design and materials technology. China has always been a few steps behind.

Hence Jeff's quote is reasonable.

Jeff Head said:

If it represented an increase over what they had before...they probably accepted it, and then found that they could do a lot better.

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Characteristics and origins of submarine generated sound is a function of four things :
(a) Machinery noise generated by machine vibration within the hull;
(b) Propeller noise generated by cavitation of the moving propeller blades;
(c) Propeller noise generated by the fluctuating thrust force as the propeller blades rotate through the asymmetric wake; and
(d) Hydrodynamic noise generated by turbulent flow past the surface of the submarine
(source :Strategic antisubmarine warfare and naval strategy by Tom Stefanick)

In my view, it has very little to do with how advanced you are in CNC machines.

What about materials science?

The original Type 093s were designed in the mid 1990s, and Chinese metallurgy wasn't very good then. All the computerized CNC machines in the world won't do you any good once the reactor machinery and crankshaft start wearing down, deforming (even at the microscopic level) and making a lot of noise.

The Type 093 might have been very quiet at first, but if you run at a high speeds for a while, the wear and tear will show*. The ONI chart didn't say at what speeds those subs were running at, incidentally.

*Sure, you probably could keep wear and tear on the machinery by never/rarely running the Type 093 SSN at low speeds (less than ten knots?) but that at the point, you might as well use that money to buy two AIP equipped SSKs.

novice question, so apologys in advanced:

What about the nuclear reactors themselves in PRC SSN/SSBN? I've read on the www that one of the main reasons for Seawolf, Virginia, Astute class subs being so quiet are the reactor designs. The Russians have also managed to reduces noise close to Seawolf/Virginia class SSN for the 1st time with the Yasen class, but the not the Borei class since it still uses older components. Borei-II class will rectify this.

So how advanced are the PRC reactor tech compared to the above mentioned?

I don't think China' reactor tech (for Subs) is as goog as the THE ... perhaps 2 generations behind the US and 1 generation behind the Russia. But I have no doubt China will catch up very quickly.

Machinery is the primary source of noise at low speeds. Machines have parts and the moving parts generate noise by their vibration. Machines are mounted and coupled to the hull and by default the noise gets propagated out to the sea. The main machinery noise source is from the gear- turbine unit and the main circulation pumps in the primary loop in the reactor cooling system. Specific solution is in using turbine electric drive and natural cooling augmented by pumps in the cooling loop to provide high flow rates during emergencies. General sound dampeners include using vibration mounts, suspended racks, flexible connectors, absorbing foams and whatever means that come through experience and ingenuity.

The other main source of noise is propeller cavitation which can come from the blade surface, propeller hub and the blade tips with the most problematic being blade-surface cavitation. The nature of propeller cavitation is its wideband character of its noise due to the superposition of many short pulses generated by collapsing air bubbles. The cavitation fluctuates each time a blade moves past a stabilizer resulting in tonal frequencies. The propeller cavitation tonals are most pronounced near the onset of cavitation and is at the most detectable state outside of machinery noise. Modern submarines with larger propellers and slowly turning propellers are less likely to cavitate. It is speculated that the Seawolf running at tactical speed is more silent than a Los Angeles moored at pierside.

Brumby said:

In my view, it has very little to do with how advanced you are in CNC machines.

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I don't think so. The submarines of the soviets become much more silent in the 80ies of the last centuary, because they got advanced CNC machines from Toshiba and Kongsberg (Toshiba-Kongsberg scandal) to make the propellers.