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The joint military-civilian investigation team looking into the sinking of the Cheonan is reportedly moving towards the conclusion that it was highly probable that a torpedo sank the warship. This conclusion is based on traces of the explosive RDX and aluminum alloy fragments found on the ship’s funnel, cross section and seabed. RDX is a white, crystalline, water-insoluble high explosive that ignites 50 times faster than TNT and is much more powerful. It is usually used in torpedoes rather than mines.

The site of the sinking, however, is within a Marine Corps firing range, so the possibility is being raised that there was some confusion in the analysis of the explosives and metal fragments. Moreover, since some have pointed out technical limitations, namely that analysis of the explosive residue alone cannot accurately identify the torpedo’s nation of manufacture, there are remaining pieces of information to clarify before a precise cause is uncovered.

A military official said Sunday that the seas where the Cheonan went down are in the same direction of the Marine Corps firing ground on Baengnyeong Island, and that artillery shells contain aluminum fuses. K-9 self-propelled artillery guns with a range of about 40km and KH-179 155mm howitzers with a range of about 30km are based on Baengnyeong Island. When the Marine Corps conducts training sessions, it aims its guns in the opposite direction of the NLL in order not to give the North Koreans reason for conflict.

As a result, the possibility has been raised in some quarters that aluminum fragments and explosives that fell during Marine Corps artillery training could create confusion in the investigation team’s analysis. In response, a military official said that because the RDX found on the Cheonan is not found in artillery shells, and the aluminum fuse used in shells falls intact in the size of a fist, the aluminum fragments discovered on the Cheonan are different. He added that the Cheonan sank 2km out from Baengnyeong Island, while artillery fired 10-20km out. However, in light of the possibility that some shells may have exploded while in flight, some pointed out that the investigation team needs to conduct more thorough analysis.

Another difficulty in uncovering the cause is the technical limitation that makes it impossible to determine a torpedo’s model or nation of origin from analysis of RDX elements alone. A military official said RDX was first created in Germany and produced full-scale by the U.S., but it is now used universally across the world, and it is limited in determining nation of manufacture. In response to some press reports stating that the RDX analysis revealed that the traces of materials are close to Western torpedoes of U.S. or German rather than Chinese manufacture, a high-ranking government official said Sunday it was groundless and that Defense Ministry plans to release a statement Monday.

A Defense Ministry official said as of now, nothing is clear other than the fact that RDX was detected, and that it has been difficult to conclude whether they will be able to determine the make of the torpedo when they announce the results of the investigation around May 20.

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