Everything that is known of Thresher’s last six minutes from the surface comes from four people who were within fifteen feet of a loudspeaker on the bridge of Skylark, and from a log kept in pencil by a radioman who had never kept an underwater telephone log before. Skylark had no means of recording the telephone; no submarine rescue ship did in 1963. The court of inquiry questioned the four separately in its first week, three of them on Saturday 13 April and the captain on Monday 15 April, and tried to fix from their memories and the log what the words had been and when they had come. This piece sets the four accounts side by side.

The room

The pilot house was about fifteen feet wide and ten deep, with a curved front. The underwater telephone, which the Navy called the UQC and the sailors called Gertrude, stood on the chart desk, a receiver and a transmitter in one unit with a hand microphone and a loudspeaker. The clock was on the bulkhead above and to the left of the desk, and was reset every morning by the quartermaster against a time signal. The sea was calm, with a slight swell and a wind of seven knots, though the ship rolled, and the radioman described holding on to the bulkhead.

Lieutenant Commander Stanley Hecker had the ship. Lieutenant (junior grade) James Watson, the navigator, an ex-quartermaster with twenty years’ service who had been commissioned three years before and had served in submarines through the Second World War, was at the plotting table immediately below the telephone. Boatswain’s Mate Third Class Roy Mowen, four years in the ship, had taken the watch at 7:45 and was the telephone operator. A radioman third class, whose name is blacked out in the released record, had come up from the radio room at eight and was keeping the log, five or six feet from the speaker, writing the “from” and “to” columns the way he was used to writing them in radio logs, which was the reverse of the way the previous watch had kept them. There were also an officer of the deck, a junior officer, a chief hospital corpsman, a helmsman, a quartermaster and a messenger.

Hecker had not been given Thresher’s trial agenda, which was unclassified. “I did not then, and still have no idea of the capability of the ship relative to depth, speed or compatibility of the sonar equipment with my sonar,” he told the court. He had asked Harvey before the dive for a telephone check every fifteen minutes.

The log before nine

At 7:45 Thresher reported that she held Skylark bearing 147 degrees at 3,400 yards. At 7:47, “Starting deep dive.” At 7:49 she said it was all right for Skylark to manoeuvre so long as she stayed in her present position, and at 7:50 asked for a Gertrude check every fifteen minutes. At 7:52 she was at 400 feet checking for leaks. At 7:54 she said that any future reference to her depth would be given in terms of her test depth, which was classified. At 8:00 her course was 180; at 8:01 Skylark’s was 270, at two and a half knots, just enough for steerage. At 8:09, “Am proceeding one-half set distance”, an entry that confused the court until Watson read it exactly as written. At 8:35, “Proceeding to test depth minus three hundred feet”, and at 8:53, “Proceeding to test depth.” At 9:02 there was an exchange about a course of 090 which Watson read one way and Mowen the other; the court’s reconstruction later put Thresher’s own turn to the east at about 9:10. At 9:12 Thresher asked for a Gertrude check, Skylark answered “Kilo”, go ahead, and Thresher came back with a Kilo about ten seconds later.

The message

The log’s next entry, under 9:12, reads: “Have positive up angle, attempting to blow up.” The radioman told the court that he had been logging something else at the time, “heard it plainly but I didn’t catch what it said, and I logged in what I thought I heard,” and that from the number of words it might have been received about half a minute before it was logged, “which would be 0913 thirty seconds.”

Mowen, at the speaker, gave it as “experiencing minor difficulties; have positive up angle; attempting to blow; will keep you informed,” and the president of the court, Vice Admiral Austin, read it back to him phrase by phrase, “because this is a very significant message and we want to get the best evidence possible as to exactly what the ship said.” Mowen confirmed each phrase. “He didn’t sound panicky at all,” he said. “It was spoken in a normal voice to my knowledge.”

Watson, below the speaker, heard “Have positive up angle. Attempting to blow up,” estimated it at about a minute after 9:12, and thought from the voice that it was the captain speaking, because it “was unhurried and had no note of hysteria.” Hecker, seven feet away, heard “Experiencing minor problem”, a pause, “Have positive angle”, without the “up”, a pause, and “Attempting to blow”. He was sure of “minor”. “The voice was very relaxed and to me appeared not overly concerned, as if it were a normal experience.”

The court’s finding of fact settled on “to the effect, ‘Experiencing minor difficulties. Have positive up angle. Am attempting to blow. Will keep you informed,’” at about 9:13. Hecker’s reading of it at the time was that the submarine had become slightly heavy near her test depth and was putting air into her tanks “to hold himself on the positive side of the test depth.” His one worry, he said, was for his own ship: “that he would come up underneath me.”

The air

All four heard the sound of air after the voice, and no two heard it for the same time. Mowen, who had heard submarines blow before, put it at four or five seconds: “It was just like if you took a shot of high pressure air and put it in an air flask. When you get that first shot, that is what it sounded like.” Watson said “not over three to four seconds that we could hear.” Hecker, asked to be careful, said “about twenty seconds or longer,” then “twenty to thirty seconds. It was a fairly long blow.” The radioman did not think he heard it at all. Part of the difference is that whenever Skylark transmitted, her receiver was blanked, and for a short time after. The Navy’s shore arrays, by the court’s eighteenth finding, recorded two disturbances that could have been ballast being blown, one from 9:09 and a half to about 9:11 and twenty seconds, before the message, and one from 9:13 and a half to 9:14, after it.

The minutes after

At 9:14 Skylark told Thresher there were no contacts in the area; Hecker had ordered it so that she could surface without fear of collision. At 9:15 Hecker took the microphone from Mowen: “My course is 270. Interrogatory range and bearing from you.” No reply. He asked “Are you in control?” and repeated it, by Watson’s count at least four times and by Mowen’s three or four. Mowen stepped back and lit a cigarette.

There were two more transmissions, and this is where the accounts and the findings part. The radioman said one came in, completely unintelligible, about a minute before the one he logged, and he did not log it. The one he logged, at 9:17, began with the two call signs, clear, and then broke up. Mowen heard the call signs and then “test depth”, “but that’s all. I couldn’t say that was for absolutely positive but that is what it sounded like to me.” Watson and Hecker heard “test depth” clearly, with two or three words lost before it, and both felt, “although we can’t be sure,” that one of them was “exceeding”. Asked how he would put it if he had to make a direct statement, Watson said: “I would say this was it.”

The court’s seventeenth finding reads: “That at about 0916R, SKYLARK heard a garbled transmission which was believed to contain the words ‘… test depth’. An additional garbled transmission was received about 0917R, reported as containing the words ‘… nine hundred North’.” The phrase “nine hundred North” does not appear in the testimony of any of the four, in the pages that have been read for this piece; it is the log entry. Since the record was opened it has been read as a depth, nine hundred feet below test depth, which would place her beyond her calculated collapse depth at the moment she said it.

Then there was the sound. “Both of us, shortly after that, heard a sound that registered with me as being familiar because of the fact that I had heard a lot of ships breaking up during World War II after having been torpedoed at depths,” Watson said. “It sounded as though there was a compartment collapsing or something similar to that nature.” Asked to describe it: “It is a rather muted, dull thud.” He could say only that it came more than a minute after the garbled message. Hecker, who had never heard a ship break up, told the court that Watson had asked him that afternoon whether he thought they had heard breaking-up sounds, and that he had said “possibly it may have been, but I could not say.” Mowen heard nothing he would call an explosion. The arrays put the collapse at 9:18 and six seconds, by the court’s finding, and at 09:18:24 by the analyst who briefed the court, Bruce Rule, in his later writing.

“It is too early”

Hecker thought first of the ordinary explanations, a flooded transducer or a thermal layer, and began an expanding square search at 9:21. At 9:31 Skylark began calling by radio every minute, in case the submarine had surfaced out of telephone range. At 9:40 the operations officer asked whether a message should go out, and the reply, the court found, “was to the effect that, ‘It is too early.’” At 10:40 the grenades began, three at a time, at intervals of ten or fifteen minutes: the signal to surface. At 10:45 Hecker ordered the message written; the radio would not raise New London on the first frequency, and the message was receipted at 12:45.

It said: “UNABLE TO COMMUNICATE WITH THRESHER SINCE 0917R. HAVE BEEN CALLING BY UQC VOICE AND CW QHB CW EVERY MINUTE EXPLOSIVE SIGNALS EVERY 10 MINS WITH NO SUCCESS. LAST TRANSMISSION RECD WAS GARBLED. INDICATED THRESHER WAS APPROACHING TEST DEPTH. MY PRESENT POSITION 41-43N 64-57W CONDUCTING EXPANDING SEARCH.” The operations officer had suggested adding the 9:13 message. Hecker decided not to, and no later report from Skylark added it either. “I guess I had no realization of how fast time was passing,” he told the court. Watson and the log did not leave the ship until 12 April, when they were sent across to the destroyer Blandy, and Rear Admiral Ramage, reading the log, “became knowledgeable for the first time of the last communications from THRESHER.”

On 16 April the court named Hecker a party to the inquiry: he had “failed fully to inform higher authority of all of the information available to you,” and the court said in the same breath that “this apparent failure on your part cannot conceivably have contributed in any way to the loss.” He engaged a Connecticut lawyer, Louis Patrick Gray, and waived his right to be present while the technical witnesses were heard, which the court commended. The designation was later withdrawn. The finding against him was the only one the Navy’s press release of 20 June 1963 attached to a name. When Senator Hickenlooper asked the Secretary of the Navy whether Hecker was “being made a patsy,” Korth said he was not, and added: “It was irritating to me to learn that this fellow had the information and I didn’t know about it.” A year later Ramage told the same committee that Hecker had been given command of a submarine.

What changed, and what is still missing

Within the year every submarine rescue ship had a recorder on its telephone, and every post-overhaul deep dive was made in water no deeper than one and a half times the test depth, with a rescue ship in attendance “and tape records all communications.” The log and the memories of four men are therefore the last such record of their kind.

The shore arrays did record, on paper. Rule, who analysed their traces in 1963 and briefed the court in closed session on 18 April, has written that there were no tape recordings, only the visual displays, that the trace shows no propulsion noise and no Doppler, and that the collapse was complete in about a tenth of a second. The team that forced the record open in 2020 reports that the chart Rule briefed is not among the exhibits released; a different chart from the same array, showing the wrong direction, was substituted, and Rule has said it is not the one he used. The entry for 9:17 is still “nine hundred North”, and nobody alive heard it.

Sources

• Record of Proceedings of a Court of Inquiry into the loss of USS Thresher, Volume 1, released 23 September 2020: the testimony of Lieutenant (junior grade) James Watson and Boatswain’s Mate Roy Mowen and of the radioman (13 April 1963), of Lieutenant Commander Stanley Hecker (15 April), the designation of Hecker as a party (16 April) and his counsel’s appearance (18 April); Findings of Fact 12 to 29 and Opinion 48. documentcloud.org
• Joint Committee on Atomic Energy, Loss of the U.S.S. “Thresher”, hearings of 27 June 1963 (Hickenlooper and Korth on Hecker; Maurer on recorders) and 1 July 1964 (Ramage on the new trial rules and Hecker’s command). purl.stanford.edu
• Bruce Rule, “Misinformation About the Loss of THRESHER and the SOSUS Detection Thereof,” 1 July 2013. iusscaa.org
• Captain Jim Bryant and others, “Was the Thresher Ready for Sea?”, Proceedings, April 2023, on the missing chart. usni.org
• David Sharp, Associated Press, 2 August 2021, for the reading of “900 north” as a depth. militarytimes.com