Military authorities believe that a strong external shock was the reason for the sinking of the Navy corvette Cheonan, on March 26, with a torpedo, mine or depth charge the most likely to generate enough impact. The most likely suspect is a torpedo.
◆ Torpedo, Mine or Depth Charge?
Torpedoes and mines attack from under the surface of the ocean, while depth charges are thrown into the water from airplanes or ships to hit submarines. Torpedoes travel between 60 km/h to 70 km/h powered by propellers and can hit targets that are between hundreds of meters to tens of kilometers away. Torpedoes also use sonar detectors to zero in on their targets.
In contrast, mines have no propulsion mechanisms and simply await their targets while floating on the surface of the ocean or submerged. They either collide with unsuspecting ships or are drawn to vessels by the sounds of their propellers or their magnetic fields. This causes floating mines to have a much smaller attack radius than torpedoes.
Depth charges are limited in terms of their targets or methods of attack compared to torpedoes or floating mines. They simply explode due to underwater pressure after sinking into the depths.
◆ Why a Torpedo?
If any of the depth charges that were stored at the rear of the Cheonan had exploded, the blast could not have caused the vessel to split in half. And the absence of any suspicious aircraft or vessels near the South Korean Navy corvette at the time of its sinking rules out the possibility of depth charges being used against it.
There are two possibilities regarding a mine. One is an accidental collision and the other is an intended attack. There is no chance that a mine left over from the 1950-53 Korean War had been floating around for 60 years until it hit the Cheonan. And mines laid near Baeknyeong Island around 1975 to prevent a landing by enemy forces have all been deactivated, Defense Minister Kim Tae-young told lawmakers on Friday. It is highly unlikely that a North Korean mine had simply floated south, since that would be completely opposite the direction of the currents in that area, and officials say it would have been far too difficult for North Korea or another enemy to set a floating mine there so that it would eventually make contact with the Cheonan because the corvette sank in an area where it only traveled 15 times before and which is more frequently used by fishing boats.
Even if torpedo fragments are found at the site of the sinking, it would still be very difficult to determine the mode of attack. Two North Korean mini-submarines were unaccounted for during March 24 and 27, but it remains unclear whether this may have any direct link to the Cheonan, government and military officials said.