USS Greenfish (SS-351) after GUPPY III modernization. Visible on deck are the three distinctive shark-fin domes of the PUFFS sonar.
USS Piper (SS-409) with BQR-4A bow sonar
The Second World War had ended, and on the following March 6, 1946, Winston Churchill, the retired British prime minister, delivered a speech at Westminster College in Fulton, Missouri. In it he said, “An iron curtain has descended across the continent.” In so doing he not only described the state of hostility between America and Britain on the one hand and the Soviet Union on the other, he defined in one statement the future, four-decades-long power contest that was to embrace the military establishment of the United States.
During the war the mission of the American Pacific Submarine Force had been clear: sink Japanese ships. Having accomplished that formidable task, American submarines fell into a morass of uncertainty after the war ended. The later hulls were “mothballed” to spend their retirement years up the Sacramento River. Others were used as targets and met their fate in ignominious plunges to the bottom. Some friendly nations were rewarded with submarines, most of which were overhauled and brought up to near-perfect condition. In those years the submarine force struggled to find a new identity.
In the years immediately following the close of the Second World War, the submarine force continued to think in terms of attacking enemy surface ships. Friedman’s description of the era might be paraphrased as, “Submarine planners first denied that any change had to be made in submarine force doctrine. Then it entertained the possibility of change, but had no idea as what the future of submarines might be. Finally, it recognized its obligation to redefine the submarine’s mission in terms of Cold War realities.”
At the same time, American engineers were dissecting advanced German technology incorporated in the German Type XXI submarine. High-capacity batteries, hull design for great underwater speed, and the snorkel were only some of the Type XXI characteristics. The Germans had not conquered the difficulties of building a watertight telescoping snorkel, but this seemed to be the boat’s only shortfall. It was apparent to American engineers that the fleet-type submarine had to be modernized while a successor submarine was designed and built along the lines of the Type XXI. Any open conflict with Russia would be preceded by Soviet submarine incursions into American waters and in all probability in advanced submarines of the Type XXI quality.
The immediate postwar period was also marked by the formation of the Bureau of Ships, or BuShips. The Bureau of Construction and Repair had been staffed by naval architects, while the Bureau of Engineering had housed most of the Navy’s engineers. There had been a natural competition between these two aspects of submarine design since they tended to approach submarine innovation from the opposite direction. Architects centered their work on the theoretical factors of hull volume and weight to give the best possible submerged vehicle. Engineers were more practical. They added up all the equipment that would be needed to meet the demands of a reconstructed Cold War mission, then designed a platform to carry the underwater load. Engineers looked on the problem from the view of its many component parts. They saw the problem from the inside out and naval architects worked from the outside in.
While competition stimulated some vigorous work, such duplication could no longer be accepted in view of budgetary constraints. BuShips was confronted simultaneously with several design projects. The advent of the nuclear age was evident as civilian contractors visualized nuclear power plants as a means of cheap energy. The concept of nuclear propulsion for ships was a concept that could not be ignored by BuShips. If the Navy were to seriously engage in a long-range nuclear ship building program it would draw funds from the Type XXI postwar fast attack project. The many fleet-type boats resting in America’s rivers could be modernized to incorporate the innovations of the Type XXI design. BuShips then pushed ahead with three concepts: the nuclear ship; the Type XXI boat, to be called the Tang-class submarine; and the stopgap conversion of fleet-type hulls into Cold War–capability submarines.
It was clear to many in BuShips that if America was to build a nuclear reactor that could be a source of propulsion for Navy ships, the natural platform for such a reactor would be the submarine. A reactor that could provide heat for propulsion would not need oxygen as a constituent of fuel. It was obvious to Captain Hyman G. Rickover that the real future of American submarines lay in the development of a reactor that would be the foundation of a new class of true submersibles. Gaining the support of Congress to allocate significant funds for so radical an idea would take painstaking patience and determination. Rickover was single-minded as he assumed the lead in this effort. He was a naturally competitive naval officer and was willing to do whatever it would take to win. Captain Cutter described a fleet exercise in which fuel oil conservation was one of the competitive factors:
Take Rickover, Admiral Rickover. He was on the New Mexico as a lieutenant. Well, Rickover was doing his job. I mean it was dishonest. For the fuel situation he bribed the oiler who came alongside, gave him a bottle of booze or something so he would give the New Mexico 100 extra gallons and take them away from the next ship or something. Turned off all the lights and turned down the ventilators so people would be miserable, but it would save oil—anything to win that efficiency pennant for engineering. I don’t think Rickover did it for his career so much as the fact that he was a competitor, a great man. I have always admired that fellow. I don’t think we would be where we are today if it weren’t for him, in the nuclear power business.
For the United States Navy to embark on an experiment of such extravagant technical dimensions and at such huge cost required it to have a steadfast faith in the outcome. It would take a person of Rickover’s drive to stay at the helm through the manifold problems and to never let obstacles get in the way of the final goal—a submarine nuclear power plant for a breakthrough type of submarine.
But the transformation of the nuclear power concept into reality would take many years, and the Navy had to fill these years with a counter to the Soviet submarine threat. Thus, as work began on the nuclear power plant and the Tang-class boats were moving from the drawing board to shipyard construction, it was necessary to fill the gap with what the Navy had in its pocket: the fleet boats quietly resting in mothballs in the fresh water rivers of the United States. BuShips started with de-mothballing a series of Tench-class fleet-type boats. The superstructures were modified and streamlined by sloping the vertical plates to minimize deck width. The prow was rounded and an aluminum sail covered the conning tower and periscope shears. All guns and other deck equipment were removed or made flush with the deck. For example, the cleats were pivoted to fold into the deck. The battery was doubled in size from 126 cells to 252 cells, and a telescoping snorkel was inserted into the aft area of the sail. Twenty-seven tons of air conditioning and the elimination of the battery exhaust system helped in habitability. These features and others made up the GUPPY, acronym for Greater Underwater Propulsive Power.
During the 1950s, GUPPY submarines were stationed in Groton, Norfolk, Charleston, Key West, San Diego and Pearl Harbor. Each station had a designated submarine operating area. Some lucky boats had operating areas close enough to allow daily operations. The resulting overnight liberty was good for morale and these boats had brows bouncing as their crew members ran to 0800 quarters after overnight liberty. The ritual morning quarters lined the enlisted men on one side of the after deck and the officers on the other. A few short words from the captain and executive officer ended in, “Set the maneuvering watch, make preparations for getting underway.”
Norfolk submarines were not so fortunate since the distance through Hampton Roads to the operating area meant weekly operations: out on Monday mornings and in on Friday afternoons. On these Fridays competitive captains drove their boats on an all-ahead-full bell, the quicker to get home and the better to beat out rivals for coveted pierside berthing. Those in maneuvering added turns of their own as each boat raced from sea up the channel entrances to their respective tenders and piers. When close to the berth assignment, the captain entered the next phase of self-made competition. The number of maneuvering bells (changes in twin screw manipulation) was the subject of crew pride stemming from admiration of the captain. The “three-bell landing” was the best. It was forbidden to change from an ahead bell directly to a back bell. Such a command placed a hardship on the maneuvering watch while straining the main motors. This mistake marked the conning officer as an amateur and invited ridicule from other officers. Certainly, the captain was bound to order an “all-stop” bell before going to “all-back-full.” The boat would shudder as the propellers dug into the sea at full power. If the landing was perfect, the boat would come to rest alongside the pier with the final order, “All-stop. Secure main engines. Get over all lines.”
Pride in one’s submarine was built on such competence. Each crew member of each boat knew that his submarine was the best and that his responsibility was do his job to keep it that way. GUPPIES spent much time at sea diving, surfacing, snorkeling and conducting each exercise as expertly as possible.
The relationship of pride in one’s submarine and one’s job directly affected the proficiency of the fire control party. The GUPPY was the Navy’s workhorse during the decades following the Second World War, when the fire control problem shifted from periscope information to sonar-only information. The difficulty of submarine vs. submarine tactics demanded mathematically based analysis and innovative methods. Dedicated minds worked to improve the quality of undersea tactics.
The GUPPY assumed several roles in the 1950s and ’60s. It played the hostile submarine when providing services to ASW surface units, it performed sonar picket duties when operating as a part of a hunter-killer group, and it trained its crew in practice periscope and sonar attacks. It departed its home base to render services to Navy and Allied units in the Western Pacific, Mediterranean Sea, North Sea and other locations. Finally, of greatest importance, it conducted special operations, which involved surveillance of Soviet forces and installations. About every other year, the GUPPY had an overhaul at one of the Navy’s shipyards in addition to upkeep periods alongside its tender. This period was usually about six months in length and was intended to make major repairs and alterations in response to the ever-changing demands of the Cold War.
There were a series of improvements starting in the latter part of the 1940s and continuing into the 1970s. The GUPPYs continued as the workhorse of the submarine fleet even as nuclear powered submarines were entering service. The first of the series was the Odax (SS-484), a GUPPY I. Thereafter, modified fleet-type boats were put in commission as fleet snorkels, and GUPPY IIs. Special conversions included special BQR-4 bow-mounted sonars. These were to be used as listening posts at the ocean’s choke points.
The most prevalent modification was the GUPPY IIb with a step sail, chin-mounted BQR-2 passive sonar array, and deck-mounted transducer. In the mid–1950s fiberglass full sails called northern sails replaced the aluminum step sails. The GUPPY III offered improved bridge visibility, at the expense of increased underwater drag.
Sonar improvements concentrated on detection of modern Soviet submarines that were anticipated to represent improvements in the best German designs. Detection of hostile submarines would rely upon sonar as its primary source of target information. The periscope would become a secondary tool of torpedo fire control as the submarine’s primary mission was redefined as a member of an ASW group that included surface, air and undersea components.
The GUPPY JT sonar was a passive listening device not significantly different from its first installation in 1942. It was retained for a number of years as an additional passive sonar to the postwar BQR-2. The sonar head or hydrophone was approximately 5 feet in horizontal length and was located forward of the conning tower. It had a shaft that could be trained to locate the bearing of a sound source such as a ship’s propeller or submarine internal noises. American submarines would continue to use JT sonar with improved bearing deviation indicators which could detect surface ships at ranges approximating 4000 yards.
The Germans had used a passive array sonar called “Gruppenhorchgeraete,” which was a horseshoe-shaped array equivalent to a straight-line array.5 The GHG was installed on the converted American submarine Cochino (SS-345) in 1949. It formed the basis for further American sonar improvements during the 1950s, including a bearing deviation indicator with a radar-style plan position indicator. This improved sonar was mounted on the USS Clamagore (SS-343) in 1948. Further improvements in the array-type sonar resulted in the BQR-2. This version of the original German GHG had 48 vertical staves, each 3 feet long, in a 6-foot circular width housed in a 5-foot-high dome. The array operated at 150 Hz to 15 kHz. A later, improved model, the BQR-2b, had an improved display that included a bearing time recorder (BTR). A paper rolled down past the BTR stylus that moved horizontally, reflecting a full commutator scan. The BTR provided a record of the target’s motion as well as its bearing. This innovation was to have enormous benefit as a source of bearing change rate necessary for plot analysis.
In the early 1950s the Naval Underwater Sound Laboratory at New London worked on further improvements to the BQR-2b. By the end of the 1950s the renamed Naval Undersea Systems Center produced the BQR-5 and 6. These advanced passive sonar systems incorporated both detection and automatic target tracking.
The wardrooms of the GUPPY II type boats were modified in the 1950s to provide a makeshift attack center. Geographical plot and Ekelund ranging techniques were performed on the wardroom table while the opaque panel separating the wardroom from the passageway was replaced with a transparent plexiglass relative-bearing compass rose display. A quartermaster in the passageway kept a relative-bearing plot on the display and fire control communication linked sonar, the attack center and the conning tower. This system, as crude as it may sound by today’s standards, worked well, and each person in the fire control party performed specialized functions in relative comfort.
The wardroom navigational plot consisted of a dead reckoning tracer or DRT mounted into the eating table. It had a glass top through which could be seen a light point driven from the master gyro compass and pit log. A sheet of graph paper overlaying the glass top represented a geographical plot with automatic own ship inputs represented by the moving point of light. Above the dead reckoning tracer was a small repeater for target bearing and course information from the TDC.
The GUPPY II fire control organization was divided between the conning tower, wardroom and sonar space. With the TDC in the conning tower and the various bearings-only plots in the wardroom, communication and coordination were critical to smoothly functioning fire control. The system included a direct sound-powered telephone link between the plot coordinator in the wardroom and the assistant approach officer in the conning tower who monitored the set-up in the TDC and advised the approach officer of the best solution for target course, speed and range. The plot coordinator had another link with the sonar supervisor so that the wardroom acting as attack center became the crucial analysis station in submarine-versus-submarine sonar-bearings-only approaches. The role of the TDC became one of receptor of information coming from plot.
The GUPPY III conversion included a modification to accommodate the ever-more-complex demands of expanded fire control equipment and organization. One of the four engines was removed to make room for the pumping equipment that was formerly located in the pump room below the control room. The vacated space below the control room became the attack center where various plots were managed in the bearings-only fire control analysis. Because the periscope wells occupied the center of the pump room, the location was far from ideal as a dedicated fire control space. The dimensions of the Mark 101 fire control console made it impractical to place it in the pump room. Additionally, the captain, acting as approach officer, was committed to the conning tower. As a result, the ultimate GUPPY III conversion lengthened the conning tower to accommodate the Mark 101 fire control console as well as its associated sonar display. The final version of the modification included an outsized fiberglass sail that reduced underwater speed.
Most GUPPY IIs used the wardroom as an attack center with the eating table converted to accommodate a DRT from the master gyro (Submarine Research Center).
Any sound can be analyzed into components by centering on different frequencies. A truly random signal carries all frequencies at about the same level of amplitude, but screw and equipment noise displayed a distinctive spectrum or signature on sonar screens. For example, a snorkeling submarine produced a strong signal at a discrete frequency from emitted noise of combined engine vibration and screw cavitation. If the pattern of a noise source was traced by stylus on a uniformly moving roll of graph paper, the sonar operator could examine the narrow spikes and determine the nature of the noise source. The pattern was referred to as a signature because it was consistently distinctive. Even a submerged submarine running on the battery would emit a signature noise, although much less apparent. This noise would be represented by a mix of flow noise over the submarine’s hull, noises from inboard piping, screw cavitation and pumps.
GUPPY III conversions initially used the pump room as an attack center by removing an engine and placing the pump equipment in the vacated space. Some conversions removed both engines in the after engine room and placed the fire control plots in the vacated space (Submarine Research Center).
Low-frequency components of sound can travel great distances through the sea without serious distortion. The sea produces a variety of ambient noises and the sonarman had to know these sounds in order to eliminate them as potential contacts. Shrimp make a clacking noise like fans at a football game and whales sing songs of long-distance romance. In addition, one’s own submarine makes abundant noise that had to be filtered out in the receptors and minds of the sonarmen. Bow plane noise was the most egregious and its placement in future submarine design would become a subject of concern. Sonar operators prided themselves on being able to identify the noise pattern of a specific submarine, even through all the background interference. Soon, the Navy’s sonar schools were training sonarmen to recognize the noise patterns of the various Soviet submarines.
Sonar could provide a reasonably accurate estimate of target speed. The sonar operator counted the rhythmic beat of a target ship’s screw, which indicated the speed of the propeller, the probable size of ship being driven by it, and the most probable speed of the ship through the water. Operators became proficient at this analysis and comparison sound tables were at hand to match target sound with known profiles.
The time-bearing plot furnished valuable information for other plots requiring accurate estimates of bearing change rates. The plot was a board upon which bearings were marked against their corresponding times. When sonar reported an initial bearing drift, bearings along the abscissa were noted at specific bearing intervals. The times of sonar-reported bearings (normally at four-minute intervals) were noted along the ordinate of the plot board. A mark was placed where the two intersected. As multiple contact reports from sonar were plotted, they emanated from the lower portion of the plot, starting with the time of the first reported sonar bearing. Since sonar bearings were not without error, it was necessary to reduce the bearing errors to as close to zero as possible. This was accomplished graphically to obtain the best indication of target bearing change rate. Straight-line fairings indicated a constant bearing change rate from which other plots could estimate target range, knowing target speed. The time-bearing plot could also signal possible changes in target speed or course or both when the array of time-bearings bent downward or upward.
One of three true bearing indications told the approach officer the relative movement caused by own ship’s course and speed and those of the target:
The time-bearing plot can illustrate target motion changes (speed and/or course) and can assist in estimating range (Submarine Research Center).
1. If true target bearing was drawing toward the bow, own submarine was losing true bearing and the target would pass ahead.
2. If true target bearing was drawing toward the stern, own submarine was gaining true bearing and the target would pass astern.
3. If true target bearing was remaining constant, the lead angle was correct and the submarine was closing the target.
Within the limits determined by target speed and course, the submarine could control the rate of true bearing change by changing own speed and lead angle; however, the submarine had only a limited amount of control over the change in true bearing, since its own speed depended on battery state, need for silent running and sea temperature/salinity condition. The optimum tactic by a submarine, particularly early in the approach, was to maintain a steady bearing or nearly steady bearing, to ensure closing the target to an effective weapon range.