Real Story of Scorpion?

By Captain C. A. K. McDonald, U.S. Navy

After the apparent loss of the Scorpion had become public knowledge, many concerned citizens ventured forth to relate their opinions, concerns, and ideas. Initial inquiries to Oceanographic Systems Atlantic for indications on the low-frequency acquisition and ranging grams from the sound surveillance system (SOSUS) arrays proved fruitless. The system could not locate the Scorpion . We did become aware that the Scorpion had given her position at 0000 on 22 May 1968 some 400 miles south of the Azores and had given her estimated time of arrival at Norfolk as 1700 on 27 May 1968. So there we were, with no SOSUS input and only a rough dead reckoning to go on. Things looked bleak indeed.

After a few days, the scientists started to come in. When they realized that Frosch and Craven were in overall charge of the search, they invariably started to rummage through their tapes for anything significant. They, along with naval officers, came bringing tales and tapes, chiefly the former. Frosch—who had earned his Ph.D. in Acoustics from Columbia/Hudson Laboratories and later had become its director—as well as other senior military and civilian officials, dropped in occasionally to check progress. The most productive encounter was with Gordon Hamilton, the Director of Columbia University's Geophysical Field Station in Bermuda. So it was that Columbia University had a dual role in this search. Hamilton did indeed have a recording of what could have been considered breakup noises from the Scorpion . It came from the Columbia University Hydrophone Station Canary Islands, which functioned to provide hydro-acoustic information for missile impact data in the eastern Atlantic.

On the ninth day, a gentleman appeared at the door, saying he had something that should be of great help. It was not quite ready, he said, and he wanted assurances that his identity would not be disclosed. The price of cooperation was absolute anonymity. I looked at Craven, and he did not hesitate. "Of course," he said. Our visitor reappeared the next morning, and Craven proceeded to make his analysis of the newly acquired data from two additional hydrophone arrays. This analysis proved fruitful, and he made his fateful pronouncement to the few of us in the room.

Craven pursued the investigation with the tenacity of a bulldog. The data were supplied to the high-speed computers and technical analysis laboratories for refinement of the information from the mystery source and the Canary Islands station in order to determine the location with precision. Beyond that, the USS Compass Island (EAC-153), a Navy oceanographic and navigation research ship, commenced a controlled series of explosive drops—called the SUBMISS shots—in the by-then focused area to refine the data, improve hydroacoustic assumptions, and establish offsets from the calculated position. She performed this service between 6 and 22 June 1968. After a few days, latitude and longitude had been determined with a great degree of precision. Further analysis revealed that the loss of the ship was precipitated by an explosive event at 1842 on 22 May. This event preceded by 91 seconds the first of a succession of events that logically would be the successive implosions of internal ship bulkheads as the ship descended past crush depth. In all, 15 distinct signals were received over a three-minute period. The Canary Islands station also reported that a minor signal had been received some 20 minutes earlier.

A few days later, Craven mentioned that a curious development had occurred. It seemed that at the time of the initial explosive event, the Scorpion was proceeding on an easterly course, 180 deg opposite the general course toward Norfolk. I explained to Craven that on my recent Polaris command—the USS Ulysses S. Grant (SSBN-631)—a definite procedure was to be followed in the event that a homing torpedo was to have its propulsion motor started accidentally while it was in the torpedo room or the torpedo tube. The ship was to be brought to periscope depth to check for a safe direction to jettison the torpedo. While doing this, however, it was important that the ship be swung 180 deg from the base course in order to activate the anti-circular run feature. This procedure had been put in place because of the possibility that the torpedo with motor running in a non-aqueous environment might overheat and cause auto-ignition of the explosive.

I also went on to explain that because the ship was returning from a three-month deployment and had completed all assigned tasks, she was proceeding independently and hence had no other ships with which to conduct exercises en route home. Moreover, the ship had sent a message containing her estimated arrival time, with all that that triggers. It meant that high-ranking officers would be on the pier, and most likely dependents also would be present. Under these circumstances, and with the exception of listening occasionally for contacts astern by means of course alterations, the ship would be heading inexorably and continuously toward her home port (Norfolk)—that is, unless a torpedo's propulsion motor accidentally had energized.

In early June, the focus shifted toward readying the oceanographic research ship USNS Mizar (T-AGOR-11) for a search using her underwater camera/light combination together with magnetic anomaly and sonar equipment. With an assist from Wagner Associates in probability assessments, Craven devised the search methodology for the Mizar and then monitored the progress on a daily basis. The Mizar arrived at the likely site on 10 June 1968, and she searched diligently for the Scorpion all summer.

Throughout June and July, a Court of Inquiry took testimony in order to establish the Findings of Fact and Opinions with regard to the Scorpion . The court learned that she had an unarmed training Mark 37 torpedo start up accidentally in a torpedo tube on 5 December 1967. The torpedo was jettisoned safely, but this meant that the postulated accidental torpedo activation on 22 May did indeed have a precedent some five months earlier. Before the court adjourned, it concluded that no "incontrovertible proof of the exact cause or causes of the loss" existed. The court implied that the highest probability would be accorded a series of events that involved a Mark 37 torpedo in a torpedo tube starting a "hot run" because of an inadvertent activation of the battery, the ship starting to turn to attempt shutdown of the propulsion motor by the anti-circular run device, the ship releasing the torpedo prematurely from the tube, the torpedo becoming fully armed, and then seeking the Scorpion as a target.

Between logistic stops in the Azores, the Mizar made four search operations throughout the summer months. On 16 October, she embarked on what was to be her last search operation—the fifth. This was to be a research cruise in order to correct deficiencies in the search and navigation systems and to improve the data on detection ranges. For this reason the scientific team was to have most of the operational control. Craven directed the Mizar to search more in line with his thesis, namely east of the most likely position of the first explosive event. Ultimately, the Mizar discovered the Scorpion on 28 October in about 11,000 feet of water. Under Craven's inspired leadership, this was a prime example of the determination and ingenuity of the naval officers, naval scientists, and members of industry and academia who were involved. Unlike the search for the bomb at Palomares and the 1963 search for the sunken nuclear-powered submarine Thresher (SSN593), no on-scene observers could provide a starting point in this case. The only thing known for certain was that the Scorpion was somewhere in the Atlantic Ocean.

When the Court of Inquiry reconvened in November, Craven was certain of his hypothesis. He had overseen a controlled set of dynamic accident simulations at the Naval Ship Research and Development Center. The last exercise postulated that a Mark 37 torpedo had started up accidentally, and the ship responded per standard doctrine and reversed course. Just prior to completing the course reversal, however, the warhead exploded, and the submarine plunged to the bottom, despite best efforts to reverse the casualty. The time difference between the explosion and the passing of crush depth turned out to be 90 seconds, or one second less than the time gap in the actual observed hydrophone recordings. Despite Dr. Craven's opinion, the court did not change its opinion materially concerning the most likely accident scenario.

The following year, the deep submersible Trieste II surveyed the wreckage from 2 June to 2 August, making a total of nine dives. These investigations confirmed that the Scorpion had broken into three large sections. Nothing indicated an external torpedo explosion. On the bow section, the torpedo room was intact, with no sign of an implosion. Apparently, it had flooded and equalized continuously with sea pressure as the ship sank. No identifiable item in the debris field originated in the torpedo room. Two of the torpedo shutter doors either were open or ajar. Surprisingly, both the forward escape and torpedo loading hatches and the forward escape trunk access hatch were missing and located subsequently in the debris field. Apparent on the after section was that the engine room had imploded into the auxiliary machinery room. Frame 90 had imploded as far forward as frame 67. Curiously, the after escape trunk access hatch was open. Also apparently, the operations compartment had imploded probably at about the same time as the engine room. A few battery cells had spilled out, as had the operating mechanism for the negative tank flood valve. This item had torn from the negative tank structure. With one exception—a small flask in the tunnel—all identifiable items in the debris field came from the operations compartment or the sail. For the sail section, the bridge access trunk was missing, and the lower bridge access hatch was located in the debris field. The Number 2 periscope and fairing, the loop antenna, and the helical whip antenna all were in the raised position. The Trieste II found a body on the ocean floor wearing a life jacket, so during the 91-second gap, the ship may have functioned partially.

The Commander Task Unit 41.2.1 Report of Scorpion Phase II On-site Operations mentioned that the bow section appeared to have fallen almost vertically and impacted with a very slight forward motion, possibly with a slight clockwise rotation as viewed from above. This gave credence to the belief that the early flooding started in the forward section of the submarine.

At the Technical Advisory Group's request, a Scorpion Structural Analysis Group (SAG) was organized to review the record to date, including the photographs of the sunken Scorpion , in an effort to discover the cause of the disaster. The SAG convened on 11 September 1969 and issued a comprehensive report to the TAG on 29 June 1970, detailing, among many other aspects, the situation in the battery well. A review of the photographs indicated that threads on the terminal posts were sheared off and that no cover seal nuts remained, thus indicating an internal battery-cell explosion. The Naval Research Laboratory analyzed a recovered red plastic cover for a main storage battery cell terminal connector and determined that the cover had been torn violently and locally. Some 20 tiny fragments of metal had been imbedded at high velocity in both the inside and outside of the sample, indicating that the imbedding must have taken place before flooding. The fragments were identical in composition to the alumina flash arrestors used on the batteries in the Scorpion . The report also noted that the bulkhead between the torpedo room and the operations compartment appeared to be loaded on the operations compartment side.

Since the torpedo room appeared intact, the damage must have progressed from the operations compartment toward the torpedo room. The report also indicated that the explosion of one torpedo should cause the sympathetic explosion of others; in that case, much damage would have been evident in the bow area. In summation, the SAG considered that a main storage battery explosion was the most plausible explanation of the disaster. The SAG felt that the flooding had started from the battery explosion, damaging the negative tank top and tearing out the negative tank operating mechanism. It qualified these remarks by stating that an internal battery explosion would be nowhere nearly severe enough to cause the indicated damage and that it was inconceivable that all 126 cells would explode simultaneously. The report went on to mention that much of the damage must have occurred when the hull imploded.

The TAG greeted the SAG's report with considerable skepticism. For one thing, how could the negative tank flood valve operating gear rupture have been the cause of the flooding and sinking when the general consensus was that the operations compartment imploded? And how is it in this scenario that the torpedo room did not implode? The SAG also seemed to conclude that some hydrostatic force impulse must have blown two hatches in the torpedo room out of the ship when equal and opposite hydrostatic forces were holding the hatches shut. The explosion of a cell in a main storage battery is extremely rare, and, as the report said, for all 126 cells to explode at the same time is inconceivable. The likelihood of the battery explosion to be severe enough to be detected on all of the hydrophone arrays is very remote. Finally, the question of why the submarine was heading in an easterly direction was not addressed.

Nonetheless, there was the gnawing doubt that an accidental startup of a Mark 37 torpedo really caused its warhead to overheat and explode when the submarine apparently took corrective action to avert it. And there things sat for 25 years.

In 1993 the Navy Department released a declassified version of the Report of the Court of Inquiry . It revealed for the first time that the mystery data source was the Air Force Technical Applications Center Atlantic "O" Systems Stations. The center had two stations that provided data for the Scorpion search. These stations are allied with the SOSUS system, but the primary interest is in broadband noise emanating from loud point sources. In 1998 the Navy Department made an additional release, which included declassified reports of both the TAG and the SAG.

In an article titled "USS Scorpion : Mystery of the Deep," published in the 21 May edition of The Seattle Post-Intelligencer , Ed Offley suggested that the submarine was sunk by Soviet action. He made this suggestion despite a lack of any evidence—physical, intelligence, or other—to support it. At the time the Scorpion sank, she was several hundred miles from the closest Soviet forces. That the Soviets had either the search capability, the fire-control capability, or the weapons capability to attack a submerged submarine from such a distance is doubtful, and the probability that this occurred is considered to be quite low.

In an article published in the July 1998 issue of the U.S. Naval Institute Proceedings , "Why They Called the Scorpion Scrapiron," Mark A. Bradley provided a good description of the immense investigative efforts undertaken with regard to the Scorpion . He concluded that the sinking was caused by the slow pace of SubSafe improvements. Actually, these improvements gave the submarine commanding officer a much larger margin of safety when the ship was operating at or near test depth. At periscope depth, however, the SubSafe improvements provided only a minor improvement. The Trieste II search effort noted that the Number 2 periscope and two other antennas were raised, which indicated that the ship must have been at periscope depth or higher. The crew was completing a deployment, should have been well-trained, and should have been more than capable of dealing with a routine flooding casualty at periscope depth. Insofar as a cause of the sinking is concerned, the argument about SubSafe shortcomings becomes somewhat moot, and the probability is again very low.

In the November 1998 book, Blind Man's Bluff: The Untold Story of American Submarine Espionage , Sherry Sontag and Christopher Drew made the stunning revelation of a disastrous test failure of a Mark 46 battery that was to power the Mark 37 torpedo. According to this book, in mid-May 1968 the Technical Director of the Weapons Quality Engineering Center, Keyport, Washington, had advised the Naval Ordnance Command that a torpedo battery had "exploded in flames during a vibration test because a tiny diaphragm had failed." The alert further recommended the withdrawal of all similar batteries from service "at the earliest opportunity." It went on to state that sufficient heat was generated in the test sample to "risk warhead cook-off and loss of a submarine." The engineers reported that a potassium hydroxide battery had a violent explosion, which caused flames to shoot ten feet in the air. The chemical fire extinguishers could not put out the fire. The engineers felt that this event could cause a Mark 37 warhead to explode, and, sequentially, blow the two hatches out of the torpedo room. It is very possible that one of these torpedo batteries was installed in one of the Mark 37 torpedoes in the Scorpion . While this discovery may have come too late to save the Scorpion , that this information was withheld from the fleet and the Court of Inquiry is unconscionable.

Blind Man's Bluff also offers an explanation that the explosion of the Mark 37 torpedo warhead may have been "low order" or have had a yield less than the designed one. This can happen when an explosive is ignited by some means other than the customary exploder activation. In this case, the explosion may indeed have been great enough to blow two hatches out of the ship but still be too small to cause one or more of the other torpedoes to explode.

This revelation and this explanation had the effect of changing the calculus of the Scorpion disaster. Now it can be imagined that the crew might have been confronted with an extremely severe casualty. No one ever will know for certain how the Scorpion disaster occurred, but the probabilities have shifted significantly toward the torpedo-accident scenario.

The crew of the Scorpion did more—much more—than its fair share in fighting the Cold War. These 99 intrepid sailors, who faced impending doom for 91 terrifying seconds, did not die in vain. Out of this tragic occurrence came a new awareness, new horizons, and new capabilities. The importance of deep-ocean search-and-recovery became accepted more widely throughout the Navy and the intelligence community. And in a splendid example of interservice cooperation, Air Force assets had been instrumental in the successful hunt for the Scorpion . For this mission and others that followed, not only would we go to the ends of the earth to support national security objectives; we would go to the depths of the ocean.

Captain MacDonald was Commanding Officer of the Naval Submarine Training Center Pacific from 1970 to 1973 and Special Assistant for Submarines for the Assistant Secretary of the Navy for Research and Development from 1967 to 1970. He was the Gold Commanding Officer of the Ulysses S. Grant (SSBN-631), commanded the USS Barbero (SSG-317), and is a June 1947 graduate of the U.S. Naval Academy with the Class of 1948. He lives in Clyde Hill, Washington.



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