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United States Navy Submarines - Part II

June 3, 2020

The Nuclear Age and the Cold War

 

USS Nautilus and SSN SUBMARINES
Traditionally USN submarines have designations based on a combination of their propulsion and/or armament and mission capabilities. For instance, most diesel electric subs were “SS” to denote “(S)ubmarine (S)team,” however there were variations including “SSR” for “(S)ubmarine (S)team (R)adar picket.” And, with the advent of nuclear propulsion a number of new designations were derived, the most common being “SSN” for “(S)ubmarine (S)team (N)uclear,”  SSBN for “(S)ubmarine (S)team (B)allistic missile (N)uclear” and “SSGN” for “(S)ubmarine (S)team (G)uided missile (N)uclear.” SSNs are also referred to as Attack Submarines or “Fast Attacks”, and SSBNs as “missile boats,” or “boomers” because of their massive destructive power. A single SSBN is capable of demolishing an entire continent.
The USS Nautilus SSN-571 was the world's first nuclear-powered submarine. Named for the fictional submarine in Jules Verne's classic Twenty Thousand Leagues Under the Sea, Nautilus broke new ground in submarine design and was capable of previously unheard-of submerged speeds and duration, and shattered numerous long-standing performance records. The Nautilus was launched 21 January 1954 and christened by Mamie Eisenhower, First Lady of the United States and wife of 34th U.S. President Dwight D. Eisenhower, then Commissioned 30 September 1954.
It’s design and construction was planned and supervised by Captain (later Admiral) Hyman G. Rickover USN, renowned as the "Father of the Nuclear Navy” who directed the development of naval nuclear propulsion and managed its operations for three decades as director of the U.S. Naval Reactors office.  Adm. Rickover is remembered as one of history’s most important naval officers, and the Los Angeles-class submarine USS Hyman G. Rickover SSN-709 was named for him and commissioned two years prior to his death, one of the few Navy ships ever named after a living person.
Nautilus put to sea on her maiden voyage on 17 January 1955, transmitting the historic message, "Under way on nuclear power." And, she was a game changer because prior subs had to surface periodically to charge their batteries using diesel engines reliant on combustion air. However, the Nautilus’ nuclear power plant facilita
ted her staying submerged for months with the only operational limitations being food supply constraints, and systems and crew endurance. The submarine was powered by the Submarine Thermal Reactor (STR), a pressurized water reactor produced by the Westinghouse Corporation and later designated the (S2W) that provided zero-emissions and eliminated the requirement for combustion air for the diesels.
Nautilus was decommissioned in 1980, designated a National Historic Landmark in 1982, and has been preserved as the center piece of the Submarine Force Library and Museum in Groton, Connecticut.
Next up was USS Seawolf SSN-575 a one-of-a-kind submarine that was the third ship of the United States Navy to be named for the Seawolf (Wolfish), and the second nuclear submarine. It was the only USN submarine built with a liquid metal cooled (sodium) nuclear reactor dubbed the Submarine Intermediate Reactor (SIR) and later-on the (S2G). Her overall design was a variant of Nautilus, however with a conning tower added, a stepped sail, and the AN/SQS-51 active sonar capability.  
Nautilus became the standard for all subsequent USN submarines of the early 1960s including the Skate class which was the Navy's first full production run of nuclear-powered boats. They served for many years with the last being decommissioned in 1989. And, USS Skate SSN-578 holds the distinction of being the first submarine to surface at the North Pole on 17 March 1959. The Skate class comprised four boats Skate SSN-578, Swordfish SSN-579, Sargo SSN-583, and Seadragon SSN-584.
The next evolution was the Skipjack-class that entered service in 1959 thru 1961 with its lead boat being USS Skipjack SSN-585. Powered by the (S5W) reactor the Skipjacks were the fastest nuclear submarines until the Los Angeles-class submarines which entered service in 1974. And, they utilized the high-speed hull design of USS Albacore AGSS-569, a research submarine and test platform that pioneered the teardrop hull for modern submarines and that was derived through extensive hydrodynamic and wind tunnel testing with an emphasis on submerged speed and maneuverability.  Skipjack was quite different from the preceding Skate class in that the new hull design was maximized for underwater speed by streamlining it similar to a blimp shape and had a single propeller aft of the rudders and stern planes that had been a matter of debate within the submarine force as the traditional two shaft arrangement offered redundancy and improved maneuverability, especially at low speeds. And, although the advanced hull shape reduced her surface maneuverability it was essential for vastly improved submerged performance. Like Albacore, the Skipjacks used HY-80 high-strength steel having improved tensile and compressive strength that remained the standard submarine hull material through future deep diving submarines.
Next, the Permit-class submarine that was originally designated the Thresher class but re-designated when the lead boat USS Thresher SSN-593 was lost at sea with all hands in 1963; it’s sometimes referred to as the Thresher/ Permit class. The class was in service from the early 1960s until 1996 and they were a significant improvement over the Skipjacks having greatly improved sonar, deeper diving depth, and advanced stealth capabilities. Therefore, they became the forerunners of all subsequent US Navy SSN designs such as the Sturgeon and Los Angeles classes. The new class was a radical change in many ways having angled, amidships torpedo tubes and a bow mounted sonar sphere for optimum detection of targets at long range; engineering spaces were also redesigned, with the turbines supported on "rafts" that were suspended from the hull on isolation mounts for acoustic quieting. Too, hull drag was reduced with deck fittings kept to a minimum, the sail was reduced in size, and pressure hulls were produced using an improved design that extended test depth to 1,300 ft.
 Thresher had the smallest sail ever fitted to an SSN to compensate for the inherent increased drag of the longer hull giving it a top speed of 33 knots, same as the Skipjacks. However, the smaller sail offered space for only one periscope and a limited number of electronics masts, with uncomfortable surfaced operation in rough seas, and an increased possibility of "broaching" at periscope depth. Too, it was fitted with a five-bladed symmetric screw like those originally on the Skipjacks which allowed her to reach higher speeds. However, during sea trials, it was found that the propeller produced noise the source of which was blade-rate from the blades of the screw vibrating when encountering the wake coming off the sail and control surfaces that could carry for long distances under water and could be detected by enemy sonar to set up a target firing solution because the frequency of blade-rate was directly related to the speed of the submarine based on the RPM of the screw. Therefore, the solution was either a smaller prop or have a larger slower rotating one that moderately interacted with the disturbed water flow. The latter solution was adopted for all subsequent American SSNs, so consequently, Permit and later submarines of this class had seven-bladed skewback props having the blade tips swept back against the direction of rotation, and the blades tilted rearward along the longitudinal axis giving the propeller an overall cup-shaped appearance. The design preserved thrust efficiency while reducing cavitation, and thus made for a quieter stealthy prop which reduced the problem of blade-rate, however, reduced the submarines' top speed to 29–28 knots.  
Commissioned in April 1960, USS Tullibee SSN-597 was the product of Project Nobska a USN study that emphasized the need for deeper-diving, ultra-quiet submarines using long-range sonar.  At 273 feet long and 2,640 tons displacement Tullibee was the smallest attack submarine ever except for the Navy research submarine NR-1 and had a crew complement of seven officers and sixty enlisted men. It incorporated three design changes; a bow-mounted spherical sonar array that required the second innovation of angled torpedo tubes amidships. And thirdly, Tullibee was propelled by ultra-quiet turbo-electric transmission powered by a S2C reactor. She achieved many submarine firsts including having submerged and surfaced 730 times and traveled approximately 325,000 nautical miles equal to the distance from the earth to the moon and halfway back.
The Sturgeon-637-class of SSNs in service from the 1960s thru 2004 is renowned as the "workhorses" of the Cold War. They were lengthened and improved variants of the Thresher/Permit class having a five-compartment arrangement including the bow compartment, operations compartment, reactor compartment, auxiliary machinery room #2, and the engine room. A lengthier operations compartment accommodated larger torpedo racks for additional Mark 37 torpedo storage; the sub met SUBSAFE standards, with seawater, main ballast, and other systems redesigned for improved reliability. It had a larger sail with a second periscope and additional intelligence-gathering masts. And, the fairwater planes mounted on the sail could rotate 90 degrees for surfacing through the arctic ice pack; because of their larger displacement, speed was reduced 26 knots. The last nine Sturgeons were lengthened 10 feet to provide more space for electronic equipment and habitability and to facilitate dry deck shelters for delivery of SEAL teams. The boats were phased out in the 1990s and early 21st century as the Los Angeles class, followed by the Seawolf and Virginia-class boats, entered service.
USS Narwhal SSN-671 was another unique boat and was the third Navy ship of the to be named for the white arctic whale with a unicorn-like ivory tusk. Launched on 9 September 1967 and commissioned on 12 July 1969, little of her design was based on the Sturgeon-class and so it was a class of one. The power plant, engine room, and forward compartment layouts provided expanded crew living and birthing space and access aft was provided by two separate reactor tunnels with individual water-tight doors and a large engine room. And, although some elements of her propulsion were incorporated in later submarine classes including the Ohio class, no others have incorporated all of Narwhal's innovations that included a natural circulation reactor plant, scoop seawater injection, the ability to cross connect main and auxiliary seawater systems and a directly coupled main engine turbine with two speed  reactor coolant pumps. The result was the quietest submarine ever giving her stealth, equaled only by the Ohio class and finally surpassed by the Seawolf class.
Another one of a kind submarine was USS Glenard P. Lipscomb SSN-685, named for the deceased U.S. California Congressman that was the Navy's second submarine design to utilize a turbo-electric transmission. Projected to test the potential advantages of the propulsion system to provide quieter submarine operations, and with a displacement of 6,400 tons and a length of 365 feet she was heavier and larger than similar vessels having conventional drive trains which resulted in slower speeds, and because of reliability issues too it wasn’t used for the follow-on Los Angeles-class submarines.
The ensuing class led by USS Los Angeles SSN 688 has more active submarines to date than any other class in the world with 66 having been built and approximately 30 still in commission. With the exception of USS Hyman G. Rickover SSN-709, they are named after major American cities, such as Albany, New York; Los Angeles, etc., a change from the tradition of naming Attack submarines after marine animals.
In 1982  the class underwent redesign adding 12 vertical launch tubes to deliver Tomahawk cruise missiles and the final 23 built had a significant upgrade with the 688i improvement program and are quieter, with more advanced electronics, noise-reduction technology, and retractable diving planes located at the bow rather than on the sail. The Navy acknowledges its top speed as exceeding 25 knots and although the actual maximum is classified, published estimates have it at 30 to 33 knots with a test depth of 650 Ft. and maximum diving depth is 1,475 ft.
The 688s intended replacement is the Seawolf class and design work began in 1983 with a proposed fleet of 29 submarines to be built over a ten-year period, but that was reduced to 12 because the end of the Cold War and budget constraints led to the 1995 cancellation of any further additions to the fleet leaving the Seawolf class limited to just three boats. The Seawolf’s cost $3 billion per unit the most expensive USN Attack submarine ever and was intended to combat the threat of advanced Soviet ballistic missile submarines such as the Soviet Typhoon class, and Akula class attack boats. Seawolf-class hulls are constructed from stronger HY-100 steel to withstand water pressure at greater depths; their test depth is 1600 feet. And, with a top speed of 35 knots, they are faster, significantly quieter, carry more weaponry, and have twice as many torpedo tubes allowing them to launch up to 50 UGM-109 Tomahawk cruise missiles against land and sea surface targets. They have shallow water operations capability and employ the more advanced ARCI Modified AN/BSY-2 combat system, which includes a larger spherical sonar array, a wide aperture array (WAA), and a new towed-array sonar. Their propulsion is a single S6W nuclear reactor, delivering 45,000 hp to a low-noise pump-jet. The three boats of the Seawolf class are the USS Seawolf SSN-21, USS Connecticut SSN-22, and the USS Jimmy Carter SSN-24.
The Virginia class Attack boats, also known as the SSN-774 after the lead ship USS Virginia are currently coming into service and are the Navy’s latest undersea warfare platform that incorporates stealth, intelligence gathering and weapons systems technology. Designed for a broad spectrum of open-ocean and littoral missions, including anti-submarine warfare and intelligence gathering operations they are scheduled to replace the 688s, will be acquired through 2043, and will remain in service into the 2070s.
The Navy’s early Attack submarines were key in the defeat of the Soviet Union that led to the fall of the Berlin Wall and the end to the Cold War. They dogged the Soviet missile boats 24/7, often shadowing them at close range, deep depths and high speeds while evading enemy attack boats and surface craft.  As well, they routinely participated in top secret covert intelligence missions by direct order of the president of the United States that the American public will never learn the details of as all submariners are sworn to secrecy. And, the new crop of USN Attack submarines stands ready to accomplish any mission far into the future.

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