by Donald Ross, PhD May 2006

Although I didn’t know it at the time, April 29, 1952 was to be a decisive day in my life. On that day, on Eleuthera Island in the Bahamas, scientists from Bell Labs demonstrated their new Lofar low frequency passive detection system to a group of high-ranking Navy officials. A US diesel submarine provided services, snorkeling in rectangular box patterns at increasing distances from the island. Two decisions resulted from this successful trial of the new sonar. On that day the Navy decided to proceed with the development and deployment of what was to become the SOSUS network. The second result took longer to materialize. The target sub had been requested to operate two diesels at the same speeds. Several hours into the day, the sub received an amazing radio message: that the port diesel was running 10 rpm too fast. A tachometer check showed this to be true. Naturally, the skipper reported this incident to his superiors. In time it trickled up the chain of command. Whatever it was, the submarine Navy wanted it too. So, in 1953, a task was added to BTL’s contract to investigate the feasibility of applying Lofar technology to submarine platforms. Knowing that this was coming and expecting flow related noises to be important, Bell recruited me for this project in view of my background in fluid mechanics and flow noise.

Before I joined Bell Labs in October 1953, I had never been on a submarine or had much contact with submariners. For the preceding eight years, I had worked on the design of quiet propellers for torpedoes at the Penn State Ordnance Research Lab. There I had also been deeply involved in the hydrodynamic design of the large Garfield Thomas Water Tunnel, which was designed and built there in the late 1940s. My only connection with submarines had been in 1947, when at a Naval Hydrodynamics Symposium in DC I was chastised for suggesting that shaping submarines more like torpedoes, with center-line propellers, would increase both their propulsion efficiencies and their cavitation-free speeds. It was patiently explained to me by a senior naval officer that submarines would always have two screws for maneuverability as well as for safety.

Indoctrination

The BTL submarine project began the day I arrived at Bell. The project was staffed by three engineers and a technician. One of the engineers, Herman Straub, was a Naval Reserve submariner who had served on subs during the war and had even been a skipper at the end of the conflict. The second engineer, Larry Churchill, was skilled in electronics and, like me, had been hired specifically for this project. I was the scientist of the group. As we were all of equal rank, we decided to run the project as a triumvirate without a formal head. All decisions were made by consensus and, although we had many heated discussions, we never had a fight. When we dealt with the Navy we were told that they were more comfortable with a single chief, so we would pretend that Herman was our Head.

Submarine assistance to the BTL project was assigned by CNO to Submarine Development Group Two in New London. Since Larry and I had never been on a submarine, we decided to do a one-day familiarization ride. It turned out to be on a snowy Monday in January 1954. When we arrived in New London by train that Sunday evening, the snow was so deep we had to trudge up Main Street to our hotel. However, by Monday morning the snow had stopped and we were able to get a taxi to the Sub Base. I don’t remember the name of the sub, but it was to be on a daily op in Long Island Sound, and included a qualification exam for one of the officers. LtCDR Bill Banks, the Skipper of the CAVALLA, was the examining officer. At one point, he removed the fuse from the "Christmas Tree" in the control room. Without its vital information, the poor officer lost control and the sub touched bottom. I learned that hitting bottom in shallow water wasn’t too serious. On that first trip, I also learned that periscopes leaked a lot, which was no problem as long as the leak was less than could be handled by the bilge pump. The ship was conducting training drills, which I thought I could safely ignore. However, I was in the forward torpedo room when the drill called for that compartment to be assumed flooded. All hands moved aft. They then closed the hatch and the pressure started to rise. I started to shout and pound on the hatch, not knowing what to expect. Soon a voice over the loudspeaker reassured me that all would be well.

On the CAVALLA (SSK 244)

Following that first experience in January, we made frequent trips to New London to plan our first field trial with the personnel of the Development Group. At that time, four new SSK conversions were assigned to the Group. One of these, CAVALLA (SSK 244) was tasked to work with us. At the pre-trial meetings we explained that our first goal was to determine just how much of the length of the sub could be used for a receiving array and that this required measuring the noise field of each piece of machinery. To do this, ideally all items would at first be turned off and then each operated one at a time. The CAVALLA’s Skipper, LCDR Bill Banks, said that he thought that he would be able to hover the sub by finding a layer of cold water on which to sit. By the time of our trial he had perfected this technique.

We were assigned to the CAVALLA for two weeks in May 1954. The first week the sub was at the pier in upkeep. The Bell Labs team used this week to mount about three dozen hydrophones throughout the superstructure from bow to stern. A total of about a mile of DSS-3 cable was strung from the hydrophones through a special torpedo loading hatch cover to preamps located in oak boxes arranged in racks in the forward torpedo room. When we went to sea the following week, Bill Banks found a useful layer, balanced the tanks and then hovered for significant periods with the sub in dead quiet mode. We were able to record the noise field of each machinery item. Thanks to the excellent participation of CAVALLA the test was 100% successful. The experience of working together was so good that the sub wanted to schedule another week with us within a few months. But we explained that we would need more time to analyze the data and could not profitably go to sea that soon.

From our first CAVALLA tests we learned that only the region forward of the sail was suitable for a low-frequency hydrophone array, limiting us to a length of about 100 feet. With this length limitation, we would have to choose a sonar band centered at about 500Hz, in order to have sufficient directionality as well as array gain. This apparently ruled out Lofar, which operated at much lower frequencies. (Years later towed arrays solved this problem.) We were about to give up all hope of applying Lofar technology to submarines when we read in an ONR-sponsored Jezebel report about a novel application called demodulation Lofar. In this technique, an octave wide input band is demodulated and the resultant signal fed to a standard Lofar. Since the mid frequencies contain most of the same tonal information in their modulation spectra as do the low frequencies, this system promised delivery of Lofar-like signals while using much shorter arrays than those used by SOSUS stations. We called the new system DEMON Lofar.

It was February 1955 before we were ready to try out our new technology on CAVALLA. This time we again mounted hydrophones and loaded equipment in New London during an upkeep. The boat then transitted to Bermuda, where we joined her. Initial tests with DEMON were encouraging when we found that, contrary to regular Lofar, own ship’s machinery did not produce interfering tones. The display was blank except when there was a target. After several days of solo ops off Bermuda, we had the services of a target submarine which snorkeled for about 10 hours per day about 100 to 120 miles from CAVALLA. Since our array in CAVALLA’s bow only formed one beam, perpendicular to the sub, we operated in slow circles in order to sweep the array beam. After finding a potential target, CAVALLA would steam straight, keeping the target on its beam, while we analyzed the signal using both DEMON and a MOD-3 regular Lofar.

We repeated this procedure for five days, using each night to move to a new operating area closer to New London, until the final day’s ops were carried out in shallow waters south of Nantucket. CAVALLA was able to detect the target sub consistently, probably the first time that a submarine was able to track another at such long ranges. Also, quite unplanned, we detected and classified a carrier task force at about 150nm. One wonders whether these detection records set by CAVALLA in 1955 might still stand.

After the 1955 CAVALLA trial, the decision was made to proceed with the engineering development of the DEMON Lofar system as the classification component of a new generation passive/active sonar system being developed by the Navy’s Underwater Sound Lab. in New London.

On the NAUTILUS (SSN 571)

The tests on CAVALLA had demonstrated the feasibility of adapting Lofar technology to a conventional submarine platform, providing the sub could operate quiet enough. However, by 1956 it began to look as though the Navy might switch to nuclear power for submarines, and it was not at all certain that our system would work on a nuclear. The NAUTILUS had a reputation of being very noisy, much more detectible than a snorkel sub. To investigate its self-noise field, the Bell Labs crew installed about a dozen hydrophones in its superstructure, and in March 1956 Herman Straub and I rode her during a 10-day submerged transit from New London to Key West.

The time on NAUTILUS was a memorable experience. Once again we sailed from New London on a snowy, foggy winter day. It was Monday, March 19th, and we were the first boat out. Just outside the river we received a radio message that the weather was too severe and we should return to port. However, our radar was free of targets, and NAUTILUS skipper CDR Dennis Wilkinson radioed back that the visibility was sufficient to proceed, even though he couldn’t see his own bow. This trip was intended to test a new air purification system and during it we established a new record for time submerged without taking in any fresh air. As I was the only civilian aboard, Herman being a Naval reserve officer, I briefly held the civilian world record for submergence time. By the time we took in air, the CO and CO2 levels had become dangerously high in our part of the boat, which may account for some early minor memory loss that I experienced. During this trip I became fully knowledgeable about all systems, making frequent trips thru the reactor compartment. On one occasion I sat on the top hat for several minutes in order to be able to tell my grandchildren that I had once sat on a nuclear reactor. My radiation badge showed no ill effects.

BTL had been assigned a very small space in the forward torpedo room, only large enough for an Ampex 12-channel tape recorder and one analysis Lofar. Our sleeping spaces were on top of two torpedoes. We recorded all of the hydrophone signals for later analysis. As the tape had to be changed every 75 minutes, we never got to sleep more than that at any one time for about eight days. Along with changing tapes, we kept a detailed machinery log and also investigated the sources of any strange noises.

In our time on NAUTILUS we became thoroughly familiar with all the details of it’s plant, and in the process came up with several ideas on how the sub could be operated in a manner less detectible by both SOSUS and other submarines. We reported these ideas to the ship’s officers at meal times. Therein lies a funny story. NAUTILUS had the largest wardroom of any then-existing sub. On the first day, Herman and I had places at the far end of the mess table, next to the junior supply officer. The next day, we found that our napkin rings had been moved one place further up the table. This trend continued for several days until we were seated to the left and right of the Skipper, having replaced the Exec and the Chief Engineer. Clearly the Captain was very interested in what we had to say. The NAUTILUS became a quieter sub from then on; and some 50 years later, I heard from Admiral Wilkinson that our input had been a factor in the Navy’s decision to proceed with a nuclear sub force. Following the NAUTILUS trip we spent months analyzing our recordings and I then wrote the first comprehensive report on nuclear submarine noise. There were some interesting follow ups. Some months later I was called in by Eldon Bissett of the fledgling acoustics branch of Naval Intelligence to interpret Lofargrams that had been made of sounds from a new Soviet submarine. The Russians had claimed they had a nuclear sub. Not knowing that the Nautilus plans had been given to the Soviets by a spy, our Navy had denied their claim. However, after a day of studying the Lofargrams I concluded that the spectra were indeed from a twin-screw, geared, steam-turbine drive and were therefore consistent with nuclear propulsion. This was indeed the first NOVEMBER.

There was a dispute between the SOSUS group at Bell Labs and the radiated noise measurement people at DTMB. Tones from NAUTILUS had literally burned the paper at SOSUS stations while at distances in excess of a thousand miles, implying radiated noise levels at least 10db greater than those of any diesel. Yet DTMB’s measurements showed the strongest tones from NAUTILUS to be similar in strength to those from diesels. I personally knew the people and believed both groups. I was able to explain the discrepancy by considering the different operating depths of diesel snorkels and nuclears. SOSUS has been designed to detect diesels, for which the effective source depths were about 50 feet, generally well within the surface layer. All of that system’s transmission loss measurements had been made for sources at this depth. However the NAUTILUS operated at depths well below the surface layer, in the deep sound channel, for which distant sound propagation was very much better. The same strength source in the deep channel produced a much stronger received signal than from near the surface. This effect of operating depth on detection ranges became a saving grace for SOSUS when Soviet nuclear submarines became quieter.

On the BANG (SS 385)

It was January 1957 before the BTL crew was ready for another sea trial of the DEMON Lofar classification sonar. This time it was the BANG (SS 385) that served as the test platform. Again, as it was winter, the operation was conducted starting in Bermuda, and again a snorkeling target was employed. I have but little memory of the BANG trials. By this time, the work of the initial project team was pretty much over. Shortly afterwards I was assigned to the SOSUS performance team, and Herman Straub prepared for retirement. Actually, while on pre-retirement leave using up his accumulated vacation and sick days, Herman died in a Swiss hospital from a skiing accident.

Larry Churchill and I had joined Bell Labs in our 30’s, instead of right out of college as was the norm. By 1957 we began to realize that because of our late arrivals there were no real career paths ahead of us. That year, I was appointed to a subcommittee on submarine silencing of the Committee on Undersea Warfare at the National Academy of Sciences. There I met Richard Bolt, one of the founders of Bolt, Beranek and Newman(BBN) in Cambridge, Mass. One day he asked me if I might be interested in interviewing with his firm, which I did. In July, I notified BTL that I planned to join BBN but offered to stay six months to produce a Handbook for the SOSUS project. It was the end of January 1958 when I moved with my family to Boston.

How It Felt to be on Submarines and With Submariners

While with Bell Labs, I had become a civilian submariner, fully accepted as such by the submariners with whom we worked. Because of the nature of our project, I had had to learn every system about as thoroughly as did the crew. I knew how to respond to emergencies anywhere on the sub. After the CAVALLA trials, I was awarded a plaque with bronze dolphins, which I still treasure. I have often been asked how it felt to be submerged for long periods. Wasn’t it claustrophobic? The answer was of course "No!" Actually on numerous occasions when tests were over and the sub had surfaced, I stayed below to record data or to pack up equipment. I liked being on a submarine. The freedom from the telephone was great. One could concentrate on what he was doing without interruptions. I also appreciated the all-male society and the cooperative spirit that prevailed. I couldn’t help but notice the sincere interest that the senior officers expressed in the problems as well as successes of each member of their crew.

When we weren’t busy, we could join the crew to watch a movie, often shown backwards; or we could park in the wardroom where we would consume a bowl of ice cream and socialize. Each sub had its own game, usually played after meals, determined by the Captain. On CAVALLA it was cribbage, while on NAUTILUS it was poker. I was quite proud that by the time NAUTILUS had arrived in Key West my accumulated losses at poker were nil.

When we were using Bermuda as our base, we got to spend some time ashore with the ship’s officers. Often we would find a bar, where liar’s dice would become the standard way of selecting the payee for each round of drinks. Our relations with the officers and crew were invariably good, being based on mutual respect. I was also very appreciative of the way the families supported each other when the men were at sea. After each of the Bermuda trials, the Bell Labs team would entertain the ship’s officers and their wives at a restaurant in New London.

Another question concerned fear of a fatal submarine accident. My answer was that the many times when we were operating out of New London, I would drive there from Whippany in Herman’s Volkswagen Beetle. Like CDR Wilkinson, Herman knew only one speed: "full speed ahead". After driving with Herman, being on a submarine felt relatively safe.