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

[Janiz]

China is now one of the world's top producers to such advanced tooling.

Can you name any company which produces those tools used to make Chinese subs props?

 

[tidalwave]

when are they going to produce a 170meters long SSBN?

 

[coolieno99]

I remember ... I think in 1980s ... Toshiba secretly sold high tech CNC machine to USSR, so Soviets was able to produce much better propellers for the subs

The Soviets were able to produce advance propellers using conventional toolings, but the Toshiba CNC machines allow them to mass produce the advance propellers at a much higher rate.

 

[Hendrik_2000]

Chinese subs have been using the most advanced prop designs for at least 2 decades. They are a bit slow on moving to pumpjets, but that's a very react addition to even western subs, and hopefully they are introduced with the 095s.

As mentioned, the Soviet shortcoming wasn't with design, but at her application. And was only solved by buying high precision multi-axis computer controlled milling tools from Japan. China is now one of the world's top producers to such advanced tooling.

By all accounts, modern Chinese SSKs are world class, so they certainly know how to make a quiet sub.

The problem with their nuclear subs is almost certainly reactor related, since that's the only meaningful difference between SSKs and SSNs.

With China fast becoming the world leading civilian nuclear reactor producing nation, that bottleneck should be broken soon, if it hasn't been already.

Yup They do indeed built high efficiency propeller . The problem with propeller is cavitation. the small bubble that implode and as they implode they create noise that can be picked up. The faster the propeller rotate the more tendency there is to cavitate. That is why the propeller rotate slowly But if there is too much losses it can't propelled the craft. That is why you need high efficiency propeller. The math of propeller design is old technology widely available in open literature. The problem is making it . Because you need 5 or even 7 axis CNC .
At one time US and Japan is the world leader in CNC machine design. And ITAR forbid china to buy it on the open market.

Well what you do .Built your own of course.

The irony is now China is the world leading CNC machine producer. and whittle down their competition in the west.

And for those of you who look down on China or Chinese know how on Submarine quieting I find this article on active noise cancelling technology Read it ,it is informative Notice the author name are Chinese who went to work in Australia.

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[schenkus]

The problem with their nuclear subs is almost certainly reactor related, since that's the only meaningful difference between SSKs and SSNs.

There is another difference that might be relevant: the typical operating speed of SSKs is much lower.

We know that SSKs operating at a very low speed are almost silent, but do we know about the noise level of chinese (or other nations) SSKs at higher speeds (15 - 20kn) ?

If chinese SSKs have relatively high noise levels at higher speeds this would not be a big problem if they are generally operated at low speeds close to the chinese coast, but it would indicate that building silent and fast submarines is still a problem.

 

[Skywatcher]

Well, since the original Type 093 was designed in the mid 1990s, they'd have to make do with the state of Chinese metallurgy.

They might be able to precisely machine a very silent reactor, but if the materials aren't up to snuff, your reactor won't stay silent for very long, especially at high speed operations.

Given improvements in Chinese metallurgy since then, the new 093 SSNs are likely more quite.

 

[plawolf]

There is another difference that might be relevant: the typical operating speed of SSKs is much lower.

We know that SSKs operating at a very low speed are almost silent, but do we know about the noise level of chinese (or other nations) SSKs at higher speeds (15 - 20kn) ?

If chinese SSKs have relatively high noise levels at higher speeds this would not be a big problem if they are generally operated at low speeds close to the chinese coast, but it would indicate that building silent and fast submarines is still a problem.

Actually, I have considered that, but dismissed it as a valid possibility.

Increasing noise with speed is actually mostly an engine and hydrodynamics issue, that is largely moot for SSNs.

We commonly associate higher speeds with higher noise from our daily experience with car engines. But nuclear subs are far more like electric cars rather than traditional fossil fuel cars.

With electric cars, noise level does not increase much, if at all, with speed increases up to a point. The lion share of increases noise from higher speeds in traditional cars comes from the engine. For an SSN, engine output is pretty much a constant no matter how fast they are going because of the nature of their nuclear reactors.

Comparatively speaking, it's child's play to design a hydrodynamic shape that produces minimal noise increases when operating at your typical max range speed figures for SSNs of 20-30kts.

 

[schenkus]

Comparatively speaking, it's child's play to design a hydrodynamic shape that produces minimal noise increases when operating at your typical max range speed figures for SSNs of 20-30kts.

I always thought that increasing the speed has a big influence on the noise level of a submarine.

A quick search lead me to a very interesting looking article from the mid 90s:

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If we believe this article flow noise becomes very important at higher speeds.

 

[asif iqbal]

We commonly associate higher speeds with higher noise from our daily experience with car engines. But nuclear subs are far more like electric cars rather than traditional fossil fuel cars.

With electric cars, noise level does not increase much, if at all, with speed increases up to a point. The lion share of increases noise from higher speeds in traditional cars comes from the engine. For an SSN, engine output is pretty much a constant no matter how fast they are going because of the nature of their nuclear reactors.

Comparatively speaking, it's child's play to design a hydrodynamic shape that produces minimal noise increases when operating at your typical max range speed figures for SSNs of 20-30kts.

SSN are not like electric cars they are basically run on steam

Nuclear reactor produces heat the heat boils water and steam turns the turbine which runs the propeller

More steam means more speed and everything has to work harder like the heat exchangers, propellers and coolers etc all make more noise

With SSK the noise is Diesel engine

 

[Air Force Brat]

I always thought that increasing the speed has a big influence on the noise level of a submarine.

A quick search lead me to a very interesting looking article from the mid 90s:

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If we believe this article flow noise becomes very important at higher speeds.

Quite Right Schenkus, you're the man on the money here son, when you increase the speed of the boat, you are displacing a lot of water in a hurry, and that makes turbulence, and turbulent flow is "noisy", trust me, fluid dynamics are sisters, whether hydrodynamics or aerodynamics, the science is the same, and it does not change the rules for "certain players", the rules are the same for both teams!