THE SUBMARINE REVIEW, November 2015 Issue.
By Bruce Rule - Feb 27, 2016
￼INTRODUCTORY NOTE: Site members will have read bits and pieces of the following article in my earlier postings but here it is in one document as published in the November 2015 Issue of THE SUBMARINE REVIEW.
APPARENT FAILURE MODE OF THE PRESSURE-HULL OF THE ISRAELI (INS) SUBMARINE DAKAR by Mr. Bruce Rule
Bruce Rule was the lead acoustic analyst at the Office of Naval Intelligence for 42 years. In 2003, he wrote the Navy position-paper on the acoustic, dynamic and temporal characteristics of submarine pressure-hull and bulkhead collapse events. From 2007 to 2015, he analyzed open-source acoustic data to determine why several submarine loss events occurred. (1,2) This effort included - in 2009 - providing the Navy with the first reanalysis of acoustic detections of the loss of the USS SCORPION in 40-years which confirmed that disaster was the results of a bettery explosion.
A June 2013 MIT doctoral thesis in Ocean Engineering (3) describes failure modes for the hydrostatic collapse of test cylinders. One mode involves deformation and failure along the entire length of the cylinder.
A former British T Class diesel submarine recommissioned as the INS DAKAR was lost in the Mediterranean in Jan 1968 while in transit to Israel. A schematic derived from imagery obtained when the wreck was located in 1999 indicates the DAKAR pressure-hull appears to have failed linearly along a significant part of the entire length of the structure: “from the control room to the stern.”(4)
One of the main propulsion electric motors was imaged near the bow. Collectively, these observations indicate the DAKAR pressure-hull collapsed—initially well aft—at great depth creating ￼￼a high-velocitywater-ram that tore the motor loose from its ￼mounting.
￼When SCORPION collapsed at a depth of 1530-feet, an after compartment was telescoped within a forward compartment by a distance of 50-feet in less than 0.112 seconds: the duration of the compression phase of the collapse event, i.e., half the reciprocal of the bubble-pulse frequency of 4.46 Hz. Those values correspond to an average forward velocity of 300 mph for the after compart￼ment.
￼The collapse depth derived from detection of the acoustic bubble-pulse frequency are known for THRESHER, SCORPION and the Soviet NOVEMBER K-8. Respectively, those values in feet—compared to the estimated collapse depth - are: 1950/2400 actual, 1050/1530 actual, and 1250/2020 actual. Actual collapse depth exceeded predicted collapse depth by an average of 44 percent.
￼If the DAKAR pressure-hull survived by a similar margin beyond the predicted collapse depth of 626-feet, collapse would have occurred at about 900 feet (400 psi). This assumption is consistent with the condition of the wreck – especially the location of the propulsion motor—and indicates the pressure-hull of the￼DAKAR was intact until it collapsed.
￼No submarine pressure-hull or internal compartment collapse event bubble-pulse frequency, the duration of the initial collapse- expansion cycle of air within a collapsing structure - has exceeded 0.3 seconds. Half that value, the 0.15 second duration of the collapse phase of the event, is the period within which all structures internal to the pressure-hull would be completely destroyed.
￼Since 0.15 seconds also is the sum of the minimum human retinal and cognitive integration periods, no crew lost to collapse of a submarine pressure-hull or internal compartment at great depth would be aware of the event. That assessment includes the crew of the INS DAKAR.
￼The main section of the DAKAR wreck, the stern section and the sail (fin) are within a debris field with a diameter of about 800- feet at a depth of 9514-feet (4) after falling as separate sections through about 8600-feet of water, an observation consistent with conclusions derived from analysis of acoustic detections of the loss of SCORPION and imagery of that wreck: all sections of hydrostatically destroyed submarines sink nearly vertically. Note: the dynamic forces associated with structural collapse at great depth are sufficient to cancel all pre-existing directions of motion.
￼1. THE SUBMARINE REVIEW, SUMMER 2012, pp, 141, Letter to the
￼2. THE SUBMARINE REVIEW, SPRING 2012, Article, pp. 98-106, “Russian
￼SSBNs - A 'Dead Man' Launch Capability?”
3. MIT DOCTORAL DISSERTATION (OCEAN ENGINEERING), JUNE 2013: “ANALYTIC AND NUMERICAL STUDY OF UNDERWATER IMPLOSIONS” Author of dissertation: Lynn Andrew Gish. B.S., United States Naval Academy (1993) M.M.E, Catholic University of America (1994) S.M., Massachusetts Institute of Technology (2004) Naval Engineer, Massachusetts
Institute of Technology (2004)