China's Type 093 SSN has acoustic signature of 110 decibels

Discussion in 'China' started by Martian, Sep 1, 2015.

  1. Martian

    Martian Respected Member Senior Member

    Joined:
    Sep 25, 2009
    Messages:
    1,348
    Likes Received:
    266
    Location:
    Boston
    China's Type 093 SSN has acoustic signature of 110 decibels

    https://www.usnwc.edu/getattachment...ture-Nuclear-Submarine-Force_NWCR_2007-01.pdf (p. 67)

    [​IMG]
    ----------

    American Innovation: China's Anti Access Strategy: Submarine Force - Part I

    [​IMG]

    China's Type 093 Shang nuclear submarine has an acoustic signature of 110 decibels. This is approximately the same acoustic emission as an American Los Angeles submarine. It makes sense that both submarines have the same decibel level. Both were designed on supercomputers, built with precise five-axis CNC machine tools, and have a seven-bladed asymmetric propeller.

    The Seawolf and Virginia class nuclear attack submarines are substantially quieter than the Type 093 Shang (and Los Angeles class), because they have a shrouded propeller.

    The Kilo is quieter than the SSBNs and the Shang, because the Kilo is a small diesel-electric submarine. A smaller submarine requires a smaller propeller that generates less cavitation. A diesel-electric submarine also lacks a noise-generating compressor pump for a nuclear power plant. The disadvantage of a diesel-electric submarine is that a shrouded propeller is too heavy and would drain the batteries.

    China's Type 094 Jin-class SSBN is ten decibels noisier than a Russian Akula-class submarine, because the hump on the Type 094 disrupts the water flow. By eliminating the hump, the Type 094 SSBN can be as silent as an Akula. By adding a shrouded propeller design, the Type 094 can be quieter than an Akula.

    Ocean background noise - 90 decibels
    Seawolf-class - 95 decibels (has shrouded propeller)
    Virginia-class - 95 decibels (has shrouded propeller)
    636 Kilo class - 105 decibels (smaller propeller, lacks coolant pump for a nuclear submarine)
    Akula-class - 110 decibels (lacks shrouded propeller)
    Type 093 - 110 decibels (lacks shrouded propeller)
    Type 094 - 120 decibels (has hump, lacks shrouded propeller)
     
  2.  
  3. Martian

    Martian Respected Member Senior Member

    Joined:
    Sep 25, 2009
    Messages:
    1,348
    Likes Received:
    266
    Location:
    Boston
    Shrouded propeller and Curtiss-Wright coolant pumps mean 95-100 decibel Chinese nuclear submarines

    China's Type 093 Shang-class nuclear attack submarine has an acoustic signature of 110 decibels.

    There are two important upgrades that will drive future Chinese nuclear attack submarines into the 95-100 decibel range.

    I have already mentioned the shrouded propeller design. Obviously, the propeller generates more cavitation at higher propeller speeds. This problem is significantly reduced by enclosing the propeller in a ducted fan.

    The other major noise-generator is the nuclear reactor coolant pump. China can reverse-engineer the latest American advanced Curtiss-Wright nuclear reactor pumps for the AP1000 nuclear reactor.

    China's original Type 093 nuclear attack submarine was built between 1998-2012. This means China was using Chinese technology to build its coolant pump for the submarine's nuclear reactor.

    [​IMG]
    "The coin with the words, 'Commemorating the construction of the first nuclear-powered Type 093 submarine,' followed by the date. (Internet photo)"

    However, Curtiss-Wright shipped highly-advanced coolant pumps for the AP1000 to China in 2012. There is also a technology-transfer agreement between Curtiss-Wright and China.

    China Wants ‘Made in China’ Nuclear Reactors - WSJ

    [​IMG]

    The only question is whether China has reverse-engineered the Curtiss-Wright coolant pumps and adapted them for use in new Chinese nuclear submarines.

    Obama’s quiet nuclear deal with China raises proliferation concerns - The Washington Post

    [​IMG]

    In conclusion, if China has implemented a shrouded propeller and Curtiss-Wright technology for coolant pumps then Chinese nuclear submarines should be in the 95 to 100 decibel range.
     
  4. blueblood

    blueblood Senior Member Senior Member

    Joined:
    Jan 28, 2011
    Messages:
    1,871
    Likes Received:
    1,429
  5. Martian

    Martian Respected Member Senior Member

    Joined:
    Sep 25, 2009
    Messages:
    1,348
    Likes Received:
    266
    Location:
    Boston
    Road to 95 decibels

    If the Type 093G has a shrouded propeller design, that alone should bring the noise level down to the 105 decibel range.

    Here's my best estimate.

    Shang: 110 decibels.
    -5 decibels for shrouded propeller
    -5 decibels for advanced nuclear reactor coolant pump
    -5 decibels for all other minor improvements combined
    ---------------------------------------------------------------------------------
    95 decibels (equivalent to Virginia class)

    90 decibels is ocean background noise. There really isn't much room for improvement beyond 95 decibels.

    [​IMG]
    China's "Huludao Shipyard has completed the construction of three Type 093G nuclear-powered attack submarines" with a Vertical Launch System (VLS).
     
    Last edited: Sep 1, 2015
  6. blueblood

    blueblood Senior Member Senior Member

    Joined:
    Jan 28, 2011
    Messages:
    1,871
    Likes Received:
    1,429
  7. warrior monk

    warrior monk Regular Member

    Joined:
    Nov 24, 2014
    Messages:
    590
    Likes Received:
    731
    Location:
    Odisha
    @Martian
    Few questions about China's nuclear subs.
    What kind of reactor does China use in 093 and the 095 subs ??
    093 probably uses double reactor which may be a cause of additional acoustic signature . Using LEU will make it less efficient than HEU PWRs and nobody other than USN uses HEU so that is a concern.
    If China has achieved 110 db SL then well and good but at what speed ?? it is still 100 times higher than Virginia class .
    What is the refueling rate of Chinese SSNs and SSBNs ??
    What kind of hull does China use single or double hulled ??
    Does China use anechoic tiles for low SL level ??
    Turbines and reduction gears can be an additional source of signature how many Turbines and reduction gears does China use in its newest boomers ??


    Small observations shrouded propeller does reduce SL but penalizes efficiency because of the shroud . I have read somewhere that India's newest boomer will not have a coolant pump but will have natural circulation for reducing the SL though the report could be wrong as the newest boomer is not yet revealed.
     
    Last edited: Sep 3, 2015
    blueblood likes this.
  8. Martian

    Martian Respected Member Senior Member

    Joined:
    Sep 25, 2009
    Messages:
    1,348
    Likes Received:
    266
    Location:
    Boston
    Type 093 Shang SSN has a normal speed of 30 knots

    At zero knot, the propeller is not moving. The only major sound source for an SSN is the coolant pump for the nuclear reactor. The sound generated by water flowing over the submarine hull drops to zero.

    At zero knot, the Shang should be 95 decibels (e.g. 90 decibels background + 5 decibels for coolant pump).

    At normal operating speed, the Shang moves all the way up to 110 decibels (e.g. 90 decibels background + 5 decibels for coolant pump + 5 decibels for propeller + 5 decibels for moving shaft and gears + 5 decibels for water-hull interface noise).

    Shang range: 95 decibels (not moving) to 110 decibels (at normal speed)

    As the Shang increases speed, the noise from the propeller increases. The coolant pump may increase activity to keep the nuclear reactor within normal temperature. The noise from the mechanical parts (ie. shafts and gears) will increase too. Finally, the noise from the water-submarine hull interface increases as well.

    The difference is 30 knots. The decibel difference is 15 decibels. Assuming a linear relationship, a rough guess looks like the following.

    Shang (not moving): 95 decibels
    Shang (10 knots): 100 decibels
    Shang (20 knots): 105 decibels
    Shang (30 knots): 110 decibels

    Note: "A change in power by a factor of 10 is a 10 dB change."
    Also, a knot is 1.15 miles per hour.

    This means a Shang traveling at 30 knots should be ten times louder compared to a speed of 10 knots.
    ----------

    At zero knot, a diesel-electric submarine is basically at the level of background ocean noise (or 90 decibels). There is no major SSK sound source when it's not moving.
     
  9. Martian

    Martian Respected Member Senior Member

    Joined:
    Sep 25, 2009
    Messages:
    1,348
    Likes Received:
    266
    Location:
    Boston
    Type 095 SSN will feature two expected upgrades to Type 093 Shang SSN

    1. We expect China to move from "shaft seal pumps" to "canned motor reactor coolant pumps."

    2. If they haven't already, we expect China to adopt a "digital instrumentation and control (I&C) system."

    3. We might see a ducted fan to shroud the propeller.

    http://www.uscc.gov/sites/default/files/8.13.08Mladineo.pdf (p. 3)

    [​IMG]
     
  10. blueblood

    blueblood Senior Member Senior Member

    Joined:
    Jan 28, 2011
    Messages:
    1,871
    Likes Received:
    1,429
  11. warrior monk

    warrior monk Regular Member

    Joined:
    Nov 24, 2014
    Messages:
    590
    Likes Received:
    731
    Location:
    Odisha
    Normally the SL level difference at cruise speed , tactical speed and operation in ultra quiet mode varies between 15 db but seeing that Shang class is a double hulled and twin LEU reactor with multiple turbines and reduction gears operating a mechanical drive will have SL level relative to 1 Pa at 1 m at 120 db similar to that of Victor III class [671RTM Shchuka (Pike)] with which Shang class is normally compared to , so a 110 db acoustic signature is optimistic at best .
    An SSN cannot hope to be not moving especially is hostile waters .
     
  12. warrior monk

    warrior monk Regular Member

    Joined:
    Nov 24, 2014
    Messages:
    590
    Likes Received:
    731
    Location:
    Odisha
    1 ) Canned motor reactor coolant pumps will definitely help to reduce the SL level only if you are successful in miniaturizing to be fitted into the hull .

    2) Adopting a "digital instrumentation and control (I&C) system will improve the functioning and reliability of the reactor but might not reduce the SL level as the mechanical drive is unchanged which includes the reduction gears but if China moves to an electric based system the propulsion and auxiliary steam turbines are replaced so that the main turbine generators convert all the available reactor power into electrical power, which is then sent to a common electrical bus for allocation which can be used for better power orientation , this reduction in mechanical drive to electrical drive to a common bus can reduce SL level.

    3} Ducted fan to shroud the propeller will reduce SL level by reducing cavitation which can be picked up by sonobuoys or any passive detector arrays but it will increase drag so somewhat inefficient .
     

Share This Page