SCORPION Article Published in the Oct 2017 Issue of THE SUBMARINE REVIEW
By Bruce Rule - Oct 8, 2017
Much of the following article has been posted on this site in bits and pieces but it's nice to see it go out in THE SUBMARINE REVIEW, the widely read official publication of The Submarine League.
Why the SCORPION Propeller and Shaft Separated From the Hull
Bruce Rule analyzed acoustic detections of the loss of the USS THRESHER (SSN 593), testified before that Court of Inquiry, and subsequently was the lead acoustic analyst at the Office of Naval Intelligence for 42 years. In 2008, confirmed the USS SCORPION (SSN 589) was lost because the main battery exploded. (1) In 2009, established - for the first time at any security level - that the GOLF II Class Soviet SSB (K-129) was lost because two R-21/D4 ballistic missile fired sequentially to fuel-exhaustion within in the pressure-hull, killing the crew and causing enormous structural damage. (2)
In 2008, Daniel McMillin (1929-2015), an electrical and mechanical engineer who was part of the AT&T Bell Labs “brain trust” involved in the development and evolution of the Navy's Sound Surveillance System, provided the author with a three-minute tape recording of acoustic signals produced by the loss of the USS SCORPION as detected at a range of 821 nm by a single hydrophone located near the island of LaPalma in the Canary Archipelago.
DISCUSSIONS OF ACOUSTIC DATA
Analysis of that recording confirmed the SCORPION pressure-hull collapsed at a depth of 1530-feet (680 psi) at 18:42:34Z on 22 May 1968 while the more pressure-resistant torpedo tubes survived within the wreckage to collapse at depths of 3370-, 3750-, 3810-, 3950-, 4510-, and 4750-feet. (1)
In 2017, refined analysis of those data identified - for the first time - the temporal asymmetry of the compression and expansion phases of the acoustic signal (bubble-pulse) produced by the collapse of a submarine pressure-hull. The duration of the compression phase of the SCORPION hull-collapse was 0.037s ((37 milliseconds (ms) or 1/27th of a second)) while the duration of the expansion (rebound) phase of the noise-radiating bubble-pulse was about 190 ms.
Temporal asymmetry exists between the compression and expansion phases of the bubble-pulse acoustic signal because the duration of the collapse phase is truncated by the collapse phase pressure wave encountering the compacting mass of the hull and internal structures whereas the expansion phase terminates less abruptly when the falling pressure of that expanding wave and its momentum are overcome by the ambient pressure at the collapse depth.
DISCUSSIONS OF IMAGERY OF THE SCORPION WRECKAGE
Extensive imagery obtained of the SCORPION wreck by the US submersible TRIESTE confirmed the engine room had symmetrically “telescoped” 50-feet forward when the cone-to-cylinder transition junction failed between the auxiliary machine space and the engine room. The propeller shaft - with the propeller still attached - was found to have separated from the after section of the hull. It fell separately to the bottom at a depth of 11,100-feet.
Whether loss of the propeller shaft caused the loss of SCORPION or was the result of collapse of the pressure-hull at great depth has been a subject of continuing debate.
As discussed above, analysis confirmed the duration of the collapse phase was 1/27th of a second (0.037 seconds), a time within which the telescoping after hull sections traveled 50-feet, values that require an average velocity of about 900 mph. The velocity of the intruding water-ram which produced that compressive force was 2000 mph.
It was this enormous axially-aligned forward vector - opposed (primarily) by inertial forces (a body at rest tends to stay at rest) acting on both the shaft and the propeller, and (secondarily) by the resistance of the water acting on the effective blade area of the propeller that tore the shaft - with the propeller still attached - from the thrust block and out of the submarine where it fell separately to the bottom to be imaged near the telescoped after hull sections by TRIESTE.
Imagery also showed the retention flange of the shaft was separated from the body of the shaft. Basically, the after sectIons of the SCORPION accelerated forward (away from) the propeller and its attached shaft at 900 mph leaving the unsupported shaft to sink to the bottom.
This assessment resolves the long-standing issue: was loss of the propeller shaft the cause or the result of the loss of the USS SCORPION? The acoustic data confirms it was the result of collapse of the pressure-hull.
An alternate explanation - that the propeller had lost (“thrown”) a blade and the resulting rotational imbalance separated the shaft causing the loss of SCORPION - is disproven.
(1) “WHY THE USS SCORPION (SSN 589) WAS LOST.” Nimble Books LLC, ISBN 978-1-60888-120-8, 31 Oct 2011
(2) THE SUBMARINE REVIEW, Spring 2012 (Pages 98-105), “Russian SSBNs – A 'Dead Man' Launch Capability?”