Chinese Submarines - are they noisy?

[gambit]

I'm not a submarine expert. But, is the following story fabricated? If not, how "noisy" could it have been?

The uninvited guest: Chinese sub pops up in middle of U.S. Navy exercise, leaving military chiefs red-faced | Daily Mail Online

Nobody in the submarine community take that tale seriously.

But here is my take on it...

First...A sub's maximum depth is secret, even published figures are taken to be estimated, not true. But while this figure may not be true, at least it give those outside the community a reasonable gauge to compare to other vessels from other navies, as such comparisons are inevitable. So if a sub's true depth, one of many capabilities, is secret, why should its ability to trail a target while producing as little noise as possible, whether the target is surface or sub-surface, be any less secret? It is NOT any less secret.

Second...If a sub's noise level is measurable and tactically useful in anyway is equally a secret as its true maximum depth, why should anyone reveal it with such a stupid stunt? A war is when all capabilities of a military is either revealed and/or new capabilities that were secret finally exposed and exposed by wartime necessities. So why would anyone revealed to a potential adversary what his underwater warfighting capabilities will be in the event of a real war? If the order to reveal came from above, whoever gave that order should be removed from office and executed for foolishness. If the act was locally motivated, then the sub's captain and all his officers should be executed for stupidity, then the enlisted crew members demoted one rank down, at least two years added to their enlistment contract, and dispersed throughout the fleet.

The reality behind this event is too boring.

The Song-class subs top submerged speed is estimated 22 kts but under wartime conditions this speed is most likely will never be used to 'stalk' any surface enemy combatants for the simple fact that the sub would give itself away via a variety of noises, notably from engine and hull (skin) friction. The higher the speed, the higher the noise. Any Song-class sub foolish enough to do this will be torp-ed by the carrier's sub escort. Further, if these surface combatants are under full steam, as in under wartime conditions, the fleet will actually outrun this Song-class sub.

Diesel/battery subs do not stalk. Such a sub will lie in wait or drift with the current if the current will take him to where he wants to be, or he may be under minimal propulsion to get where he wants to be. Where this event took place, an area between Japan and Taiwan, the average depth is 350 meters. Factor in safety margin, this would be at the Song-class sub's maximum estimated depth. Contrary to comic books portrayal, subs do not rest -- LITERALLY -- on the bottom. The noise generated by sand, rocks, and who knows what against the hull will be greater than flow friction noise. When a sub is 'at bottom' it mean the sub is at neutral buoyancy 'hovering' above the sea bottom, providing this depth is within the sub's maximum depth safety margin.

It takes a lot of 3D underwater real estate to maneuver a sub. A sub cannot 'turn on a dime', as how Americans say about things agile and nimble. Even so, the word 'hover' is used casually. Diving officers do not like to 'hover' their boats. While submerged, a sub is pretty much constantly moving through the water. It changes depth the same way an aircraft changes altitude -- through planes that operate like an aircraft's ailerons. If the sub stop its propulsion, it does not mean the sub is not moving. Underwater currents will keep it moving and the planes can still be used to change depth. So when a diving officer say his boat is 'hovering' he means the boat is not changing depth, not that the boat is literally stationary.

Oddities of Physics | Modern Mechanix

Can a submarine remain stationary at any desired level?

The answer is that it cannot, unless a slight headway is maintained or water is admitted to and discharged from the trimming tanks. A submarine cannot find a state of hydrostatic equilibrium or a point at which all pressures are equal.

Keywords are 'a slight headway' and 'or water is admitted', meaning either from propulsion or from moving with currents, and from pumping/purging water in/out of the ballast tanks, which would give the sub away immediately to any adversary listening. Flooding a ballast tank is noisy enough, but blowing air into a ballast tank to displace water is a thousand times noisier.

The Song-class sub is about 75 meters in length.

The Right Submarine for Lurking in the Littorals | U.S. Naval Institute

High maneuverability is also critical in shallow and confined waters. All submarines sailing at less than 165 feet need to have excellent depth control. 11 There a submarine can maneuver in a water column of only two to three ship lengths. 12 At periscope depth, it has to operate around a keel depth of 50 to 65 feet, depending on the sea state and periscope and mast extension.

The highlighted is important.

If this Chinese Song-class sub, with its estimated maximum depth rating of 300 meters, was lying in wait for the Kitty Hawk and her escorts, most likely the sub was 'hovering' at (best) 200 meters depth with 100 meters as safety margin.

Remember: A water column of only two to three ship length.

So for a vessel length of 75 meters, 100 meters as a safety or maneuvering margin is being extremely tight and for this discussion, extremely generous to the crew's ability at depth control. But if assume the norm, that mean the Chinese sub was 'hovering' at around 150 meters depth.

And if the sub was lying in wait, it mean she was not under propulsion but is adrift with the current and this is where it gets dangerous for the sub when there is an American carrier battle group running at flank speed that is greater than the sub is capable of doing. She probably guessed correctly that there would be at least one American sub lurking around. Since this is peace time, she is not allowed to do anything but if she does nothing, the odds of collision or being tossed about even more by currents induced from the surface increases as the fleet nears. So for the safety of the crew, the Chinese sub captain have only one option: Make himself known.

You are free to believe anything you want. As far as the American submariners are concerned, they have no problems with the Chinese believe that story. In fact, they want more and more Chinese believe that story.

 

[PoKeMon]

Not sure if they are really noisy on decibel level

But they do make lot of noise on PDF.

 

[Beast]

Not sure if they are really noisy on decibel level

But they do make lot of noise on PDF.

You just demonstrate as one.

 

[PoKeMon]

You just demonstrate as one.

Ofcourse

 

[gambit]

I made the above opinion about the Kitty Hawk and the Chinese sub in an old post. I saved the text and the link to that post. I have always suspected that my posts that technically debunked Chinese claims were under risks. That old post no longer exist. Good thing I saved the text.

 

[longlong]

I made the above opinion about the Kitty Hawk and the Chinese sub in an old post. I saved the text and the link to that post. I have always suspected that my posts that technically debunked Chinese claims were under risks. That old post no longer exist. Good thing I saved the text.

4 Apr, 2015, Royal Navy nuclear submarine hit Russian submarine while tracking it which they claimed to be floating ice.
Don't judge the submarines you totally don't know.

 

[DoTell]

gambit, you basically just speculated that the Chinese sub was waiting deep down in the ocean, and submerged itself when the U.S. carried sailed on top. But how did the Chinese know the U.S. carrier was going to go there? Suppose they knew the location, how did they figure out the time? How did the Chinese know when the carrier group was on top of them and it was time to show up? They must have the capability to remotely detect the carrier presence without themselves being found first. No?

As you stated, it is big deal to do a stunt like this. If failed, many lives could be lost, not to mention secrets revealed. Unless the Chinese commander who gave the order is a total idiot, he had to have a very high degree of confidence in his sub's capability. Which leads us to a more logical explanation: the Chinese sub has the capability and it did dodge detection fair and square. And, the U.S. capability is not as high and foolproof as one believed. Yes, such an explanation is hard to accept. But unfortunately for you this seems to be a very logical one. You can keep that arrogance and laugh it off. Like you implied, we all can believe whatever we want to believe. Cheers.

 

[BigDaddyWatch]

I think we need to seperate nuclear attack subs (SSN) and diesel electric subs (SSK). China's current generations of nuclear subs are indeed loud like the Type 092 (Xia), Type 091 (Han), Type 093 (Shang) and even the Type 094 (Jin). But SSK is a different story as China has much more experience building them and they are quieter to begin with. China's Wuhan shipyard have been pumping out Type 041 (Yuan) like crazy over the past few years and has already build 3 different upgraded variants. And there is a new generation of SSN coming up like the Type 093G and further down the road the Type 095. Those will be much quieter than the previous generations of SSN's.

 

[SipahSalar]

I have always suspected that my posts that technically debunked Chinese claims were under risks. That old post no longer exist. Good thing I saved the text.

China hacking skills?

 

[Rain]

Yes they

Are they still extremely noisy?

are, for example you can hear the noise created by those submarine here in south Asia even they have not started their engine yet.

Are they still extremely noisy?

Yes they are, for example you can hear the noise created by those submarine here in south Asia even they have not started their engine yet.

 

[xuxu1457]

One thing is :Japan, US forces in Japan has more than 130 P3, P1 and P8 anti-submarine aircrafts and put anti-submarine net on sea nere China, but can't stop China's submarine cruise on Pacific Ocean, and some times several KM nere US's carrier， that can say many info;
And another hand, India bought several P8 and think these can stop China or other countries submarine in so big Indian Ocean, that's completely impossible，130 such aircraft can't do this on small Northeast Asia sea area, not to say so big Indian Ocean with only 8 P8

 

[xunzi]

gambit, you basically just speculated that the Chinese sub was waiting deep down in the ocean, and submerged itself when the U.S. carried sailed on top. But how did the Chinese know the U.S. carrier was going to go there? Suppose they knew the location, how did they figure out the time? How did the Chinese know when the carrier group was on top of them and it was time to show up? They must have the capability to remotely detect the carrier presence without themselves being found first. No?

As you stated, it is big deal to do a stunt like this. If failed, many lives could be lost, not to mention secrets revealed. Unless the Chinese commander who gave the order is a total idiot, he had to have a very high degree of confidence in his sub's capability. Which leads us to a more logical explanation: the Chinese sub has the capability and it did dodge detection fair and square. And, the U.S. capability is not as high and foolproof as one believed. Yes, such an explanation is hard to accept. But unfortunately for you this seems to be a very logical one. You can keep that arrogance and laugh it off. Like you implied, we all can believe whatever we want to believe. Cheers.

Don't listen that American big mouth gambit. The French submarine SUNK a US carrier in a war game. That just demonstrate how vulnerable US detection can be if they face with an enemy sub. And French sub is a notch below us as far as I"m concern.

 

[Beast]

Don't listen that American big mouth gambit. The French submarine SUNK a US carrier in a war game. That just demonstrate how vulnerable US detection can be if they face with an enemy sub. And French sub is a notch below us as far as I"m concern.

Not only that. Chile has demonstarted too that their sub sunk a carrier in the exercise just few years ago.

 

[Keel]

One thing is :Japan, US forces in Japan has more than 130 P3, P1 and P8 anti-submarine aircrafts and put anti-submarine net on sea nere China, but can't stop China's submarine cruise on Pacific Ocean, and some times several KM nere US's carrier， that can say many info;
And another hand, India bought several P8 and think these can stop China or other countries submarine in so big Indian Ocean, that's completely impossible，130 such aircraft can't do this on small Northeast Asia sea area, not to say so big Indian Ocean with only 8 P8

Hmm no they claimed they have spotted our presence at least 22 times in this report on Apr 07, 2013
But there is no way to know how many sorties we have conducted into the area all together out of the so called "at least 22 contacts"

"Citing subsurface contact data shared by US forces, the document said at least 22 contacts were recorded with vessels suspected to be Chinese attack submarines patrolling outside Beijing’s territorial waters last year.
China's submarines in Indian Ocean worry Indian Navy "

I believe USN is doing the monitoring jobs with the Indian navy most likely from the extensions their base at Diego Garcia and some of the Indian controlled outlying islands in the ocean like Adaman Isle and Nicobar Isle and the Malacca Strait or even via satellites through the form of Non-Acoustic Anti-Submarine Warfare (NAASW)

But they have failed to notice our presence before we docked at Sri Lankan port - so close to the Indian shores

China says nothing unusual in submarine docking at Lanka port | Zee News

Quartz snuff bottle with internal handpainting

 

[GoGetIt]

I'm sure 039A is quieter than Kilo 636M