sábado, 5 de abril de 2008

Sound-intercepted submarine is nothing but a fish in the fishbowl”

Sound-intercepted submarine is nothing but a fish in the fishbowl”

December last year, it was known that “SON WON IL,” the first state-of-the-art 214 class (1,800ton) submarine which was delivered to ROKN from a German submarine manufacturer, had some operational problems due to its noise. Since, she submarine is tracked by the noise by enemy, high noise is a critical weak point. Reported on 15, March on our paper.


Submarine, be silent or die.

'Be silent, that is a only way to survive.

This is a paragraph representing a war between submarine and noise, in the book «Submarine, that I wanted to talk » recently published by Ret. Adm. Ahn Byung Ku. He had served as the first captain of JANGBOGO, ROKN’s the first German made 209 class submarine, and then commander of a submarine squadron.
If a submarine is detected by enemy due to its noise, it becomes a fish in the fishbowl. Therefore, they do whatever they can do. The submarine makes 4 kinds of noise. Propellent noise from screw, machine noise from equipment in the ship, hydrodynamic sound from cutting water and sound from crew’s moving.

Up-to-date technology to kill the noise

Recent submarine increased the number of screw blade 5 to 7 and changed the shape of it to special bent type to push the water smoothly. In order to eliminate the internal noise, the shock mounts are used. The shock mount, X or H shape of special rubber, is installed between steel stuffs. In early 1990, during acceptance of the first 209 class submarine, JANGBOGO, there was a disturbance because some of these shock mounts were found broken at the final stage. Crew wears so-called « Submarine shoes » which has soft outsoles. Sometime they communicate with manual arts.

Submarine’s history is the history of war with noise.

The submarine was a ship that originally navigated under water only when necessary. However, after world war II, it was changed to a ship that came out to surface when necessary. « Snorkel system » was developed which inhales air under water and drive the generator then recharge the diesel batteries. After submarine disappears under water, human eyes and radar become useless. Radar wave can not work under water, so only noise becomes a clue for tracking the submarine.
A mean for detecting a submarine is so-called SONAR (Sound Navigation And Ranging). However, it is not easy to find a submarine with the sound wave. The sound refracts to low temperature water and in the area where cold and warm current meet, a lump of water is to be seen as a submarine. In the water, sound of waves, marine currents, merchant vessel and fishing boats are mixed. There is a metaphor that to find a submarine in this area is something like listening a musical masterpiece from cassette tape recorder in the noisy discotheque.

Submarine’s noise is the same as the finger print of people.

Submarine’s noise has a special characteristic like human finger prints. Russian submarine has a little higher noise than that of USA. Chinese’s submarine is rather noisy. Japanese submarine is the most silent one in the world. Nuclear submarine makes, due to characteristics of its propellant engine, higher noise than conventional diesel engine type.
The initial type of Los Angeles class SSN of USA is no better than the conventional submarine with the noise 120dB. China’s major Attacking nuclear submarine (SSN), « HAN », a can class with noise 140dB. When condition is good, LA class submarine can catch the noise of « HAN » class at the distance 500km.
Old model of Russian SSBN « Yankee » class was 135 ~ 140dB, but its improved version « Delta III » was reduced to 125 ~ 130dB. The world biggest SSBN « Typhoon » class, a heroine of the movie « Red October », was known as 125dB.
Korean main submarine force, 209 class (total 9 in service), is rather silent with the noise of 100~120dB level. This means that only when 209 class approaches within 2~3km, its noise can be detected. The noise level of the latest SSN of USA « Sea Wolf » and « Virginia » are similar to that of 209 class.

The 214 class which ROKN is introducing as the next generation main submarine force is the improved version of 209 class. However, the noise level of the first submarine « SONWONIL » of 214 class, delivered to ROKN in last December, exceeded the basis level defined by HDW. The basis of noise of « SONWONIL » had to be lower than 100~110dB of 209 class, but in certain situation, it exceeded 40dB, reporter said. That the noise level becomes 40dB higher means it can be detected by enemy at 8 times further distance.

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