Reply to Comment on “Underwater Explosion (UWE) Analysis of the ROKS Cheonan Incident” by K. S. Kim

Abstract

On choosing two net explosive weights (NEW) (250 kg and 136 kg) to primarily focus on: 250and 136-kg net explosive weights—the case of a DPRK torpedo and the case of an ROK LCM—were researched by the MCMJIG (2010) with the conclusion that the UWE source had to be a 250-kg NEW according to the evidence. During the course of our research we have been led to have serious doubts on the authenticity and veracity of this evidence provided by the MCMJIG (including chemical residue and the torpedo submitted as proof). Coupled with the often overlooked or ignored fact that at least two antisubmarine warfare (ASW) warships—the ROKS Cheonan (PCC-772) itself and the ROKS Sokcho (PCC-778); the PCC class series 761–785 were specifically designed for ASW)—were in the area at the time of the UWE incident and both failed to detect either a DPRK sub or a torpedo travelling through the water, this makes it extremely unlikely that a torpedo fired from a DPRK sub is the culprit. Another important fact is that there is ample evidence of the Cheonan having serious navigational problems (i.e., partially running aground) leading up to the incident. Now there is sufficient evidence that there was some sort of underwater explosion (UWE) from seismoacoustic analyses. The only two plausible UWE source possibilities are a mine or a torpedo. Of course it could also theoretically be a hybrid, i.e., a torpedo launched from a mine. However, if it is not a DPRK launched torpedo, then it has to be a mine. A friendlyfire torpedo has also been raised as a possibility, but that involves many more players and would be much more difficult to cover up, especially in a very wired country such as the ROK. Our premise is that the most likely source of this UWE is a ROK littoral ‘‘land control mine’’ (LCM) naval mine. This premise is the basis of our hypothesis, but of course it cannot be definitively concluded due to the lack of access and transparency regarding this incident. Various net explosive weight (NEW) variables were hypothetically tested in this paper, with 250 kg being pointed out for being the NEW asserted by MCMJIG and 136 kg being pointed out for being the NEW for the ROK LCM naval mine. In the case of the 136-kg NEW of the ROK LCM, the variables fall within the allowable parameters and we are asserting this as the most likely UWE source. In the case of the 250-kg NEW DPRK torpedo, the variables fail to fall within the parameter limits. On the question of the pertinent equation to use: there seems to be some confusion regarding the equations. The commentator stated that we had to use Eq. (3) of the SWISDAK (1978) report. However, the third equation is a ‘‘correction equation’’ that may be utilized but is not necessary in every situation where the surface, bottom, or both could potentially influence the bubble. The basic equations of the bubble pulse period and the maximum gas bubble radius (SWISDAK 1978) are as follows: