The means of determining the depth of implosion was not as 

 straightforward as originally planned. Pressure transducers were 

 installed on the hull, but these were inoperative at the time of implo- 

 sion. During launching of the structure, which was off the stern of an 

 offshore work vessel, a small hull penetration became damaged and 

 resulted in a leak of about 25 gallons (95 liters) of seawater per min- 

 ute. The weight of the structure increased until a safety link in the 

 lowering line parted, which occurred at a depth of 2,900 feet (884 

 meters), as recorded by the pressure transducers. From this depth 

 on, the structure free-fell through the water column until implosion 

 occurred. 



Data from acoustic depth-recording instrumentation were continu- 

 ously being recorded on tape during this sequence of events . The 

 noise generated by the implosion of the structure was also recorded. 

 This signal had a rather long duration and showed that implosion could 

 have occurred at a depth between 4,500 feet (1370 meters) and 4,700 

 feet (1430 meters). Seafloor depth was 4,700 feet (1430 meters). 



It was known from data on tape that the time between the start of 

 free-fall and implosion was 160 seconds. By analytically bracketing the 

 free-fall velocity of the structure between 11.2 ft/sec (3.4 m/sec) and 

 12.5 ft/sec (3.8 m/sec), it was calculated that the structure free-fell 

 between 1,790 feet (546 meters) and 2,000 feet (610 meters). Adding 

 these numbers to 2,900 feet (884 meters) gave the total depth range as 

 4,690 feet (1430 meters) to 4,900 feet (1494 meters). Hence, it was 

 apparent that the structure hit the seafloor at a depth of 4,700 feet 

 (1430 meters) before imploding. 



A manned submersible inspection by the Navy's Sea Cliff was 

 conducted in 1978 to determine whether the structure imploded after 

 impacting the seafloor. The tight grouping of fragments confirmed that 

 the structure hit the seafloor first. If the structure had imploded 

 during free-fall descent, the fragments would have been scattered. 

 The inspection also confirmed that the cylinder section imploded rather 



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