mmix
July 8th, 2010, 11:09 PM
http://media.daum.net/politics/view.html?cateid=1068&newsid=20100708234008289&p=hani
[한겨레] "함수·함미 분리전 다른 원인으로 스크루 훼손 가능성"
지난 5월31일부터 6월7일까지 한국에 천안함 사고 조사단을 파견했던 러시아 정부는, 북한 소행의 결정적 증거로 한국 정부가 제시한 '1번 어뢰'를 천안함 침몰의 '범인'으로 볼 수 없다는 결론을 내린 것으로 확인됐다. 러시아 정부가 '북한의 버블제트 어뢰공격으로 천안함이 침몰했다'고 발표한 한국·미국 정부 등과 다른 견해를 내놔, 천안함 침몰 진실을 둘러싼 논란이 증폭될 전망이다.
러시아 사정에 밝은 복수의 외교소식통은 8일 "러시아 정부는 보고서에서 '1번 어뢰'의 페인트와 부식 정도 등에 비춰볼 때 어뢰가 물속에 있던 기간에 문제를 제기했다"며 "이에 따라 '1번 어뢰'의 출처에 대해서도 의문을 표시했다"고 전했다. 민·군 합동조사단(합조단)은 6월29일 언론단체를 대상으로 한 설명회에서 "어뢰 추진체의 부식상태는 재질과 부위별로 최고 6배가량 부식 두께 차이가 심해 부식 기간이 얼마나 되는지 판단이 어렵다"며 "다만, 금속재질 전문가가 눈으로 식별한 결과 어뢰와 선체의 부식 정도가 1~2개월 경과해 비슷한 것으로 판단했다"고 밝힌 바 있다.
특히 러시아 조사단은 천안함의 스크루가 휘는 등 손상된 사실에 주목하고 있으며, 천안함이 함수와 함미로 분리되기 이전에 다른 원인으로 스크루가 먼저 훼손됐을 가능성을 제기한 것으로 전해졌다. 여러 전직 해군 장교도 < 한겨레 > 와의 통화에서 "경험에 비춰볼 때 스크루가 돌고 있는 상황에서 뻘에 닿으면 천안함과 비슷하게 휘어지는 현상을 보인다"고 지적했다.
이밖에도, 러시아 조사단은 합조단이 제시한 천안함 폭발 시점보다 더 이른 시각에 천안함이 조난 신호를 보낸 사실을 파악한 것으로 알려졌다. 러시아의 조사결과가 사실로 드러날 경우, 최초 사고 시각을 둘러싼 논란이 재연될 가능성도 배제할 수 없다.
드미트리 메드메데프 러시아 대통령은 지난주 이런 자체조사 결과를 후진타오 중국 국가주석에게 전화로 알려줬으며, 러시아 정부는 미국 정부에도 같은 내용의 보고서를 전달한 것으로 전해졌다. 러시아의 조사결과는 천안함 사건과 관련해 '북한 규탄'이라는 문구 삽입 여부 등을 두고 한달 넘게 합의점을 찾지 못하고 있는 유엔 안전보장이사회(안보리) 논의에도 영향을 끼칠 것으로 보인다. 러시아는 외교적 파장 등을 고려해 조사결과를 공식 발표하지는 않을 것으로 전해졌다.
한편, 러시아 정부가 자체조사 결과를 한국 정부에는 알리지 않은 사실에 대해 한국 정부가 상당히 당혹해하고 있다고 외교소식통들은 전했다.
이용인 이승준 기자 yyi@hani.co.kr
Additional:
http://nvo.ng.ru/armament/2010-06-25/8_chonan.html
Torpedo attack?
Sinking of Cheonan. Questions remain.
Sergei Chekulaev
Part 1
The destruction on March, 26, 2010 South-Korean corvette Cheonan has excited all world. ROK asks Security Council of the United Nations to consider the problem on “armed attack of North Korea” on military ship. Under the order of the President of Russia, from May, 31 till June, 7 in South Korea the Russian military experts worked. In the comment the Ministry of Foreign Affairs of Russia from June, 9 is spoken, that experts on a place have familiarized with materials of investigation of destruction Cheonan and after processing the received data they will report on the estimations and conclusions to the Russian government.
While experts prepare for the conclusions, we shall leave for a while political debate and we shall try to understand technical questions of destruction of the ship.
Circumstances
ROKS corvette Cheonan (the name is translated approximately as Heaven’s Peace) has been constructed in 1989 and since then carried out functions of a patrol ship of coastal action. The universal set of arms "for all occasions" included anti-ship missile Harpoon, 76 and 40 mm cannon, 324 mm ASW torpedoes Mk 46 and depth bombs. For supervision and managements of the weapon were available radar and sonar. The length of the ship made 88 meters, keel depth - 2,9 meters, displacement of 1200 tons. Crew 104 persons.
It is interesting, that Cheonan in June, 1999 already participated in the true sea battle, on the other site of sea border. And even has received small damages. In that engagement one of boats of North Korea has been sunk, and some have been seriously damaged. Was lost about 30 North Korean seamen.
Accident of corvette Cheonan has taken place at 21:22 on Seoul time. Navigation passed completely easy as suddenly strong explosion has broken off the ship half-and-half. The ship moved to this moment in a condensed twilight on northwest, bending around island Baeknyeong. The distance up to island was 2 km, up to sea border with NK remained about 15 km, water depth 47 meters. The stern part has sunk almost at once, and current has removed forward part at 6 kilometers from a place of explosion where it also has sunk. As a result of accident 46 seamen were lost.
In April both half of ship have been lifted on surface and are placed on naval base nearby Seoul. Began investigation. Significant event in Cheonan’s case has taken place on May, 10 at next sweeping - fragments of a unknown torpedo have been lifted.
The international commission
The ROK has created the Joint Civilian-Military Investigation Group from 50 Korean and 24 foreign (from the USA, the Great Britain, Australia and Sweden) experts who investigated materials accessible to them.
On the basis of the researches, the commission has come to conclusions, that the reason of destruction of corvette Cheonan was underwater explosion of 200-300 kg charge. Proceeding from character of destruction of the ship hull, coordinates of a point of explosion have been determined as 6-9 meters from the kiel downwards (so - on depth 9-12 м) and 3 meters to the left of the center of turbine section. That is classical non-contact explosion, it is characteristic for the modern sea weapon.
Having investigated the torpedo wreck submitted by the ROK side, experts have found depositions of aluminum oxides ("naval" explosives formed at explosion), to identical same depositions on corvette’s fragments. The design of the torpedo tail corresponded to drawing of North Korean torpedoes available in South Korea, and on one of details of a torpedo marks “№1” has been found out by made by “North Korean font”.
On assurances of the South-Korean side, at time of accident in frontier zone near island, situation controlled by radar-tracking and infra-red supervision, therefore any surface ships, boats or planes could not come for torpedo attack near to Cheonan. And the commission has drawn a unequivocal conclusion, that corvette has been sunk by North Korean torpedo which has been launch from North Korean submarine. Because “there is no other plausible explanation”.
Whether so it? And as far as conclusions of the commission actually are plausible?
Non-contact explosion
It is known, that explosion of a charge on some distance from the bottom of the ship usually is more effective, than contact explosion at board. The case of the ship is influenced all over again with a shock wave, and then the moving stream of the water which have received energy from a gas bubble. Therefore on torpedoes, and then on mines and underwater rockets began to install influence-actuated fuze which first samples have appeared in 1930th years. The action range of modern influence fuze reaches 8 meters. For Cheonan's beam in 10 meters, explosion in 3 meters from a diametrical plane (i.e. through 2 meters from an input of a torpedo in "shadow" of the ship) will quite be coordinated to algorithm of work of influence fuze. Installation of depth of the torpedo 6 meters lower keel depth of the ship is possible for antiship (ASuW) torpedoes with influence fuze.
Homing systems
Torpedo can hit a ship both at an aiming shot, and with help of homing system (HS). The aiming shot demands or exact definition of a target's distance and parameters of her movement, or a shot from close distance, from a "pistol range". So there was the last sinking a surface ship by a torpedo. On May, 2, 1982, during the British-Argentinean war, nuclear submarine Conqueror has fire from a distance less than 1300 meters 3 old torpedoes Mk VIII on ARA General Belgrano. Two torpedoes hit the cruiser and, despite of the considerable sizes (displacement of 13000 tons), the ship has quickly sunk. Was lost more than 300 Argentina seamen.
Homing systems for the first time have been applied in WWII. It were so-called “passive HS” based on definition on a source of noise which the moving ship is her screws and mechanisms. HS of active type with a sonar lidar a target or her wake have later appeared. The place of explosion under Cheonan's turbine section explains occurrence of the version of a torpedo with passive HS as one of the main sources of noise on corvette was the gas turbine. All is interesting, that during time of the same British-Argentinean war, the German export torpedo SST-4 started from ARS San Luis, has precisely struck … an acoustic decoy - a radiator of noise which was towed by British frigate. Cheonan such protection had no.
Part 2
Torpedoes of North Korea
Shown on press conference in Seoul fragments of "torpedo-killer" contain a part of the electromotor, a shaft, a tail part so-called "flameless" type (with specific "clipped" lower rudder) and five-bladed screws of opposite rotation.
Under the statement of representatives of the South-Korean Ministry of Defence, North Korea is armed, makes and suggests on export of a torpedo of calibre 53 cm. Constantly called name «type CHT-02D» belongs to the export torpedo which description to valorous South-Korean special services managed to be got somehow.
The following characteristics of a torpedo are resulted: calibre - 53,4 cm; length - 7,35 m; weight - 1700 kg; a charge - 250 kg; range - 10-15 km. It is informed about an opportunity of homing of a torpedo as by a passive method, and ship wake. It is usually considered, that ASuW torpedoes with passive system of homing have speed up to 35 knots. ROK have declared, that they have a practice (exercise) sample of one of North Korean torpedoes which has been found at coast of South Korea 7 years ago. Probably, it is the origin of the exact drawing of a North Korean torpedo.
In connection with the deep privacy surrounding military programs of North Korea, there are only sketchy data on its torpedo weapon. The first, together with torpedo boats G-5, from the USSR in NK had been put non-homing air-steam torpedoes 53-38. With them North Korean torpedo boats on July, 2, 1950 attacked cruisers of interventionists - USS Juneau and HMS Jamaica. And though boats could not approach to distance of a confident shot and also torpedoes have not struck the enemy, this episode until recently was the most heroic page of North Korean Navy. Commander of group Kim Gun Ok and commander of one of boats Van Gyn was rank of Heroes of the Korean People's Democratic Republic. Who knows, whether new heroes will appear now.
Later, for arming of ships, boats and submarines, NK had receive torpedoes from the USSR and China. Among purchases of torpedos of calibre of 53 cm were Soviet air-steam torpedoes 53-51, 53-56V (non-homing, influence fuze) and 53VA (passive HS). Also electric torpedoes SAET-60 (ASuW, passive HS) and SET-53 (ASW, three-dimensional passive HS) were delivered. There are data on possible purchases of newer export samples SET-65E (ASW, active - passive HS) and 53-65KE (oxygen, ASuW, wake HS). In NK Navy could act Chinese torpedoes Yu-1, Yu-3 and Yu-4, representing copies and the modernized variants of the listed Soviet torpedoes.
In due course, North Korea, on the basis of available foreign samples, began to carry out own researches and development on torpedoes and has their batch production. Drawings of these North Korean torpedos, obviously, have been shown at press conference in Seoul. If to compare the submitted fragments directly they do not correspond to any Soviet torpedo though separate elements and remind our old samples.
Submarines
The international board has considered possible to connect with sinking of Cheonan two North Korean submarines - a 300-ton boat such as Sango and 130-ton such as Yeoneo, one of which could approach to corvette on a distance of shot and to fire a torpedo. These submarines have consist on arms NK Navy and can carry 53-cm heavy torpedo. Sinking of Cheonan has broken 14-years silence Lee Kwang Soo, the waterman of North Korean submarine in 1996. He is only of members of crew, was taken prisoner and now lives in South Korea. On his data if on Sango torpedoes are carry inside torpedo tubes, on smaller Yeoneo they can be placed outside of sub's boards as on German midget submarines of times of WWII. And its can be started practically silently, as against fire from torpedo tubes by air.
There is an opinion, that from small submarines it is impossible to apply "heavy" torpedoes. Certainly our submariners who use sub with displacement in thousands of tons are difficult to present opportunities a small torpedo sub and intuitively it seems that light torpedoes will better. However, battle experience of the WWII has shown, that absolutely small, even tiny, boats can apply heavy torpedoes with success. So, Italian CB (displacement of 50 tons) have been armed two 450 mm torpedoes, charge 200 kg. Japanese sub "type A" (50 tons) at an attack to Pearl Harbour carried 2 torpedoes of 450 mm, charge 350 kg. Despite of ridiculous displacement of German submarines (Biber - 4 tons, Molch - 9 tons, Seehund - 15 tons), all of them carried 2 torpedoes of 533 mm charge 300 kg. All of them sank enemy ships.
Part 3
Questions
Perhaps, in destruction of the ship a mine is guilty? It was one of the first and most logical versions for first moment. The set of various mines has been laid in this area within war 1950-1953. Mine-laying by both sides the next years were quite possible, including secret mining. The variant of a bottom mine disappears because explosion has taken place in 35 meters up the bottom. An anchor mine in given area cannot keep constant depth because of strong tide (up to 6 knots, constantly changing a direction). Theoretically there is an opportunity that has worked more complex device: an floating-up mine either a jet-mine or even a mine-torpedo. In the latter case, the torpedo could be in mine container at sea bottom and to start therefrom after detection of corvette's noise. ASW mines are widely known: American Mk 60 Captor and Russian PMR and PMK. In case of Cheonan emerging mines KRM and RM, created in the USSR in 1957-1965, and also their Chinese analogues are most interesting. They could be put on depths from 40 meters, carried charge 200-300 kg and blew up at emersion on depth about 10 m. Against such version the difficult hydrology of area, and torpedo container or anchor of emerging mine should remain at the bottom.
Why fragments of torpedo look such old? At the first sight the impression is created, that they lain at sea bottom not one year and even have acquired with sea organisms. However, experts explain, that "shells" are the aluminium oxides of postponed on screws of torpedo formed at explosion. And the plentiful rust can be caused by electrochemical corrosion within 50 days, which fragments were in sea water. To the accelerated corrosion promoted full "peeling" of sheetings and high-temperature "burn" at explosion, and also presence of different metals in torpedo design. By the way, eyewitnesses mark, that process of corrosion is observed and on air and now fragments of the torpedo look even more rusty, than one month ago.
Why Cheonan has not found out underwater threat? The answer to this question is not present. “Under the theory”, the ship equipped with sonar should find out a submarine, especially, a torpedo and evades from them. However it was revealed nothing also explosion became completely unexpected. Perhaps, established on corvette old sonar has given failure. Perhaps, the hydrology, that day not in that side turning sound beams is guilty, or noise of tidal current and surf was too great. It is possible also, that sub silently laid on bottom, the torpedo not fire but left the sub "self-swimming" and went to the target on quiet speed.
Whether it was possible to find out and trace underwater objects other means? In materials of JIG there are data of seismic service of South Korea which four stations have fixed explosion. However, there are no records of hydroacoustic stations. The area has not been equipped with stationary systems of hydroacoustic supervision or they did not work? It causes natural questions to the South Korean side. Despite of technical difficulties connected to small depths, currents and the oozy bottom important boundary area it should be supervised in “underwater hemisphere”.
Whether small depths and bad hydrology to become an obstacle to torpedo attack could? Comparison of Cheonan’s destruction with a similar case sinking on December, 9, 1972 Indian frigate Khukri (1535 tons) is interesting. This remarkable episode of the Indian-Pakistan war has taken place in shallow area of Arabian sea, with depths less than 65 meters. Pakistan sub Hangor (1000 tons) attacked two Indian frigates from distance about 5000 meters consistently 3 torpedoes E15, one of which has hit Khukri. E15 - export French sample with passive HS. Characteristics of the torpedo (weight - 1650 kg, charge - 300 kg, speed 25 knots at range 12 km) obviously is not better, than at its North Korean analogue. And taking into account that HS of torpedo Е15 was a little bit improved system of German torpedo of the WWII, comparison and at all becomes not for the benefit of "French". Let's note, that passive systems of homing, as against active, with success work and on shallow water. So, the author observed delivery tests of export torpedoes 53VA on shallow range at lake Issyk Kul. The torpedo with the help passive HS always found its target - sound device, simulating enemy ship, and passed from it on distance sufficient for operation of influence fuze.
Let's sum up our consideration of some technical questions connected to sinking of Cheonan. It is possible to note, that obvious affectations and contradictions in the version of JIG are not visible. Or they are not found out yet? Can the Russian experts will give new food for thought? Wherefore they went to South Korea?
[한겨레] "함수·함미 분리전 다른 원인으로 스크루 훼손 가능성"
지난 5월31일부터 6월7일까지 한국에 천안함 사고 조사단을 파견했던 러시아 정부는, 북한 소행의 결정적 증거로 한국 정부가 제시한 '1번 어뢰'를 천안함 침몰의 '범인'으로 볼 수 없다는 결론을 내린 것으로 확인됐다. 러시아 정부가 '북한의 버블제트 어뢰공격으로 천안함이 침몰했다'고 발표한 한국·미국 정부 등과 다른 견해를 내놔, 천안함 침몰 진실을 둘러싼 논란이 증폭될 전망이다.
러시아 사정에 밝은 복수의 외교소식통은 8일 "러시아 정부는 보고서에서 '1번 어뢰'의 페인트와 부식 정도 등에 비춰볼 때 어뢰가 물속에 있던 기간에 문제를 제기했다"며 "이에 따라 '1번 어뢰'의 출처에 대해서도 의문을 표시했다"고 전했다. 민·군 합동조사단(합조단)은 6월29일 언론단체를 대상으로 한 설명회에서 "어뢰 추진체의 부식상태는 재질과 부위별로 최고 6배가량 부식 두께 차이가 심해 부식 기간이 얼마나 되는지 판단이 어렵다"며 "다만, 금속재질 전문가가 눈으로 식별한 결과 어뢰와 선체의 부식 정도가 1~2개월 경과해 비슷한 것으로 판단했다"고 밝힌 바 있다.
특히 러시아 조사단은 천안함의 스크루가 휘는 등 손상된 사실에 주목하고 있으며, 천안함이 함수와 함미로 분리되기 이전에 다른 원인으로 스크루가 먼저 훼손됐을 가능성을 제기한 것으로 전해졌다. 여러 전직 해군 장교도 < 한겨레 > 와의 통화에서 "경험에 비춰볼 때 스크루가 돌고 있는 상황에서 뻘에 닿으면 천안함과 비슷하게 휘어지는 현상을 보인다"고 지적했다.
이밖에도, 러시아 조사단은 합조단이 제시한 천안함 폭발 시점보다 더 이른 시각에 천안함이 조난 신호를 보낸 사실을 파악한 것으로 알려졌다. 러시아의 조사결과가 사실로 드러날 경우, 최초 사고 시각을 둘러싼 논란이 재연될 가능성도 배제할 수 없다.
드미트리 메드메데프 러시아 대통령은 지난주 이런 자체조사 결과를 후진타오 중국 국가주석에게 전화로 알려줬으며, 러시아 정부는 미국 정부에도 같은 내용의 보고서를 전달한 것으로 전해졌다. 러시아의 조사결과는 천안함 사건과 관련해 '북한 규탄'이라는 문구 삽입 여부 등을 두고 한달 넘게 합의점을 찾지 못하고 있는 유엔 안전보장이사회(안보리) 논의에도 영향을 끼칠 것으로 보인다. 러시아는 외교적 파장 등을 고려해 조사결과를 공식 발표하지는 않을 것으로 전해졌다.
한편, 러시아 정부가 자체조사 결과를 한국 정부에는 알리지 않은 사실에 대해 한국 정부가 상당히 당혹해하고 있다고 외교소식통들은 전했다.
이용인 이승준 기자 yyi@hani.co.kr
Additional:
http://nvo.ng.ru/armament/2010-06-25/8_chonan.html
Torpedo attack?
Sinking of Cheonan. Questions remain.
Sergei Chekulaev
Part 1
The destruction on March, 26, 2010 South-Korean corvette Cheonan has excited all world. ROK asks Security Council of the United Nations to consider the problem on “armed attack of North Korea” on military ship. Under the order of the President of Russia, from May, 31 till June, 7 in South Korea the Russian military experts worked. In the comment the Ministry of Foreign Affairs of Russia from June, 9 is spoken, that experts on a place have familiarized with materials of investigation of destruction Cheonan and after processing the received data they will report on the estimations and conclusions to the Russian government.
While experts prepare for the conclusions, we shall leave for a while political debate and we shall try to understand technical questions of destruction of the ship.
Circumstances
ROKS corvette Cheonan (the name is translated approximately as Heaven’s Peace) has been constructed in 1989 and since then carried out functions of a patrol ship of coastal action. The universal set of arms "for all occasions" included anti-ship missile Harpoon, 76 and 40 mm cannon, 324 mm ASW torpedoes Mk 46 and depth bombs. For supervision and managements of the weapon were available radar and sonar. The length of the ship made 88 meters, keel depth - 2,9 meters, displacement of 1200 tons. Crew 104 persons.
It is interesting, that Cheonan in June, 1999 already participated in the true sea battle, on the other site of sea border. And even has received small damages. In that engagement one of boats of North Korea has been sunk, and some have been seriously damaged. Was lost about 30 North Korean seamen.
Accident of corvette Cheonan has taken place at 21:22 on Seoul time. Navigation passed completely easy as suddenly strong explosion has broken off the ship half-and-half. The ship moved to this moment in a condensed twilight on northwest, bending around island Baeknyeong. The distance up to island was 2 km, up to sea border with NK remained about 15 km, water depth 47 meters. The stern part has sunk almost at once, and current has removed forward part at 6 kilometers from a place of explosion where it also has sunk. As a result of accident 46 seamen were lost.
In April both half of ship have been lifted on surface and are placed on naval base nearby Seoul. Began investigation. Significant event in Cheonan’s case has taken place on May, 10 at next sweeping - fragments of a unknown torpedo have been lifted.
The international commission
The ROK has created the Joint Civilian-Military Investigation Group from 50 Korean and 24 foreign (from the USA, the Great Britain, Australia and Sweden) experts who investigated materials accessible to them.
On the basis of the researches, the commission has come to conclusions, that the reason of destruction of corvette Cheonan was underwater explosion of 200-300 kg charge. Proceeding from character of destruction of the ship hull, coordinates of a point of explosion have been determined as 6-9 meters from the kiel downwards (so - on depth 9-12 м) and 3 meters to the left of the center of turbine section. That is classical non-contact explosion, it is characteristic for the modern sea weapon.
Having investigated the torpedo wreck submitted by the ROK side, experts have found depositions of aluminum oxides ("naval" explosives formed at explosion), to identical same depositions on corvette’s fragments. The design of the torpedo tail corresponded to drawing of North Korean torpedoes available in South Korea, and on one of details of a torpedo marks “№1” has been found out by made by “North Korean font”.
On assurances of the South-Korean side, at time of accident in frontier zone near island, situation controlled by radar-tracking and infra-red supervision, therefore any surface ships, boats or planes could not come for torpedo attack near to Cheonan. And the commission has drawn a unequivocal conclusion, that corvette has been sunk by North Korean torpedo which has been launch from North Korean submarine. Because “there is no other plausible explanation”.
Whether so it? And as far as conclusions of the commission actually are plausible?
Non-contact explosion
It is known, that explosion of a charge on some distance from the bottom of the ship usually is more effective, than contact explosion at board. The case of the ship is influenced all over again with a shock wave, and then the moving stream of the water which have received energy from a gas bubble. Therefore on torpedoes, and then on mines and underwater rockets began to install influence-actuated fuze which first samples have appeared in 1930th years. The action range of modern influence fuze reaches 8 meters. For Cheonan's beam in 10 meters, explosion in 3 meters from a diametrical plane (i.e. through 2 meters from an input of a torpedo in "shadow" of the ship) will quite be coordinated to algorithm of work of influence fuze. Installation of depth of the torpedo 6 meters lower keel depth of the ship is possible for antiship (ASuW) torpedoes with influence fuze.
Homing systems
Torpedo can hit a ship both at an aiming shot, and with help of homing system (HS). The aiming shot demands or exact definition of a target's distance and parameters of her movement, or a shot from close distance, from a "pistol range". So there was the last sinking a surface ship by a torpedo. On May, 2, 1982, during the British-Argentinean war, nuclear submarine Conqueror has fire from a distance less than 1300 meters 3 old torpedoes Mk VIII on ARA General Belgrano. Two torpedoes hit the cruiser and, despite of the considerable sizes (displacement of 13000 tons), the ship has quickly sunk. Was lost more than 300 Argentina seamen.
Homing systems for the first time have been applied in WWII. It were so-called “passive HS” based on definition on a source of noise which the moving ship is her screws and mechanisms. HS of active type with a sonar lidar a target or her wake have later appeared. The place of explosion under Cheonan's turbine section explains occurrence of the version of a torpedo with passive HS as one of the main sources of noise on corvette was the gas turbine. All is interesting, that during time of the same British-Argentinean war, the German export torpedo SST-4 started from ARS San Luis, has precisely struck … an acoustic decoy - a radiator of noise which was towed by British frigate. Cheonan such protection had no.
Part 2
Torpedoes of North Korea
Shown on press conference in Seoul fragments of "torpedo-killer" contain a part of the electromotor, a shaft, a tail part so-called "flameless" type (with specific "clipped" lower rudder) and five-bladed screws of opposite rotation.
Under the statement of representatives of the South-Korean Ministry of Defence, North Korea is armed, makes and suggests on export of a torpedo of calibre 53 cm. Constantly called name «type CHT-02D» belongs to the export torpedo which description to valorous South-Korean special services managed to be got somehow.
The following characteristics of a torpedo are resulted: calibre - 53,4 cm; length - 7,35 m; weight - 1700 kg; a charge - 250 kg; range - 10-15 km. It is informed about an opportunity of homing of a torpedo as by a passive method, and ship wake. It is usually considered, that ASuW torpedoes with passive system of homing have speed up to 35 knots. ROK have declared, that they have a practice (exercise) sample of one of North Korean torpedoes which has been found at coast of South Korea 7 years ago. Probably, it is the origin of the exact drawing of a North Korean torpedo.
In connection with the deep privacy surrounding military programs of North Korea, there are only sketchy data on its torpedo weapon. The first, together with torpedo boats G-5, from the USSR in NK had been put non-homing air-steam torpedoes 53-38. With them North Korean torpedo boats on July, 2, 1950 attacked cruisers of interventionists - USS Juneau and HMS Jamaica. And though boats could not approach to distance of a confident shot and also torpedoes have not struck the enemy, this episode until recently was the most heroic page of North Korean Navy. Commander of group Kim Gun Ok and commander of one of boats Van Gyn was rank of Heroes of the Korean People's Democratic Republic. Who knows, whether new heroes will appear now.
Later, for arming of ships, boats and submarines, NK had receive torpedoes from the USSR and China. Among purchases of torpedos of calibre of 53 cm were Soviet air-steam torpedoes 53-51, 53-56V (non-homing, influence fuze) and 53VA (passive HS). Also electric torpedoes SAET-60 (ASuW, passive HS) and SET-53 (ASW, three-dimensional passive HS) were delivered. There are data on possible purchases of newer export samples SET-65E (ASW, active - passive HS) and 53-65KE (oxygen, ASuW, wake HS). In NK Navy could act Chinese torpedoes Yu-1, Yu-3 and Yu-4, representing copies and the modernized variants of the listed Soviet torpedoes.
In due course, North Korea, on the basis of available foreign samples, began to carry out own researches and development on torpedoes and has their batch production. Drawings of these North Korean torpedos, obviously, have been shown at press conference in Seoul. If to compare the submitted fragments directly they do not correspond to any Soviet torpedo though separate elements and remind our old samples.
Submarines
The international board has considered possible to connect with sinking of Cheonan two North Korean submarines - a 300-ton boat such as Sango and 130-ton such as Yeoneo, one of which could approach to corvette on a distance of shot and to fire a torpedo. These submarines have consist on arms NK Navy and can carry 53-cm heavy torpedo. Sinking of Cheonan has broken 14-years silence Lee Kwang Soo, the waterman of North Korean submarine in 1996. He is only of members of crew, was taken prisoner and now lives in South Korea. On his data if on Sango torpedoes are carry inside torpedo tubes, on smaller Yeoneo they can be placed outside of sub's boards as on German midget submarines of times of WWII. And its can be started practically silently, as against fire from torpedo tubes by air.
There is an opinion, that from small submarines it is impossible to apply "heavy" torpedoes. Certainly our submariners who use sub with displacement in thousands of tons are difficult to present opportunities a small torpedo sub and intuitively it seems that light torpedoes will better. However, battle experience of the WWII has shown, that absolutely small, even tiny, boats can apply heavy torpedoes with success. So, Italian CB (displacement of 50 tons) have been armed two 450 mm torpedoes, charge 200 kg. Japanese sub "type A" (50 tons) at an attack to Pearl Harbour carried 2 torpedoes of 450 mm, charge 350 kg. Despite of ridiculous displacement of German submarines (Biber - 4 tons, Molch - 9 tons, Seehund - 15 tons), all of them carried 2 torpedoes of 533 mm charge 300 kg. All of them sank enemy ships.
Part 3
Questions
Perhaps, in destruction of the ship a mine is guilty? It was one of the first and most logical versions for first moment. The set of various mines has been laid in this area within war 1950-1953. Mine-laying by both sides the next years were quite possible, including secret mining. The variant of a bottom mine disappears because explosion has taken place in 35 meters up the bottom. An anchor mine in given area cannot keep constant depth because of strong tide (up to 6 knots, constantly changing a direction). Theoretically there is an opportunity that has worked more complex device: an floating-up mine either a jet-mine or even a mine-torpedo. In the latter case, the torpedo could be in mine container at sea bottom and to start therefrom after detection of corvette's noise. ASW mines are widely known: American Mk 60 Captor and Russian PMR and PMK. In case of Cheonan emerging mines KRM and RM, created in the USSR in 1957-1965, and also their Chinese analogues are most interesting. They could be put on depths from 40 meters, carried charge 200-300 kg and blew up at emersion on depth about 10 m. Against such version the difficult hydrology of area, and torpedo container or anchor of emerging mine should remain at the bottom.
Why fragments of torpedo look such old? At the first sight the impression is created, that they lain at sea bottom not one year and even have acquired with sea organisms. However, experts explain, that "shells" are the aluminium oxides of postponed on screws of torpedo formed at explosion. And the plentiful rust can be caused by electrochemical corrosion within 50 days, which fragments were in sea water. To the accelerated corrosion promoted full "peeling" of sheetings and high-temperature "burn" at explosion, and also presence of different metals in torpedo design. By the way, eyewitnesses mark, that process of corrosion is observed and on air and now fragments of the torpedo look even more rusty, than one month ago.
Why Cheonan has not found out underwater threat? The answer to this question is not present. “Under the theory”, the ship equipped with sonar should find out a submarine, especially, a torpedo and evades from them. However it was revealed nothing also explosion became completely unexpected. Perhaps, established on corvette old sonar has given failure. Perhaps, the hydrology, that day not in that side turning sound beams is guilty, or noise of tidal current and surf was too great. It is possible also, that sub silently laid on bottom, the torpedo not fire but left the sub "self-swimming" and went to the target on quiet speed.
Whether it was possible to find out and trace underwater objects other means? In materials of JIG there are data of seismic service of South Korea which four stations have fixed explosion. However, there are no records of hydroacoustic stations. The area has not been equipped with stationary systems of hydroacoustic supervision or they did not work? It causes natural questions to the South Korean side. Despite of technical difficulties connected to small depths, currents and the oozy bottom important boundary area it should be supervised in “underwater hemisphere”.
Whether small depths and bad hydrology to become an obstacle to torpedo attack could? Comparison of Cheonan’s destruction with a similar case sinking on December, 9, 1972 Indian frigate Khukri (1535 tons) is interesting. This remarkable episode of the Indian-Pakistan war has taken place in shallow area of Arabian sea, with depths less than 65 meters. Pakistan sub Hangor (1000 tons) attacked two Indian frigates from distance about 5000 meters consistently 3 torpedoes E15, one of which has hit Khukri. E15 - export French sample with passive HS. Characteristics of the torpedo (weight - 1650 kg, charge - 300 kg, speed 25 knots at range 12 km) obviously is not better, than at its North Korean analogue. And taking into account that HS of torpedo Е15 was a little bit improved system of German torpedo of the WWII, comparison and at all becomes not for the benefit of "French". Let's note, that passive systems of homing, as against active, with success work and on shallow water. So, the author observed delivery tests of export torpedoes 53VA on shallow range at lake Issyk Kul. The torpedo with the help passive HS always found its target - sound device, simulating enemy ship, and passed from it on distance sufficient for operation of influence fuze.
Let's sum up our consideration of some technical questions connected to sinking of Cheonan. It is possible to note, that obvious affectations and contradictions in the version of JIG are not visible. Or they are not found out yet? Can the Russian experts will give new food for thought? Wherefore they went to South Korea?