Gato-class submarine

TheGatoclassofsubmarineswere built for theUnited States Navyand launched in 1941–1943. Named after thelead shipof the class,USSGato, they were the first mass-production U.S. submarine class ofWorld War II.
TheGatos, along with the closely relatedBalaoandTenchclassesthat followed, accounted for most of the Navy's World War II submarines;they destroyed much of the Japanesemerchant marineand a large portion of theImperial Japanese Navy. In some references, theGatos are combined with their successors, especially theBalaoclass.
Gato's name comes from a species of smallcatshark. Like most other U.S. Navy submarines of the period, ships of theGatoclass were given the names of aquatic creatures.
TheGato-class ships were considered to befleet submarines, designed to operate as adjuncts to the main battle fleet, based onstandard-type battleshipssinceWorld War I. They were to scout out ahead of the fleet and report on the enemy fleet's composition, speed, and course, then they were to attack and whittle down the enemy in preparation for the main fleet action, a titanic gun battle betweenbattleshipsandcruisers. This was an operational concept born from experience in World War I. To operate effectively in this role, a submarine had to have high surface speed, long range and endurance, and heavy armament.Limitations in submarine design and construction in the 1920s and 1930s made this combination of qualities very difficult to achieve.The U.S. Navy experimented constantly with this concept in the post-World War I years, producing a series of submarines with less than stellar qualities and reliability, theAA-1class(also known as the T class) and theV-boats, of whichV-1throughV-3were an unsuccessful attempt to produce a fleet submarine.
By 1931, the experimental phase of fleet submarine development was over and the Navy began to make solid progress towards what would eventually be theGatoclass. By 1940, a much better developed industrial base and experience gained from thePorpoise-,Salmon-, andSargo-classships resulted in theTamborandGarclasses. Finally, the U.S. Navy had hit the right combination of factors and now had the long-desired fleet submarine.
Timing, however, conspired against the actual use of these ships in their assigned role. Theattack on Pearl Harboron 7 December 1941 destroyed the Pacific Fleet battle line and along with it the concept of the battleship-led gun battle, as well as 20 years of submarine strategic concept development. It left the fleet submarine without a mission. Fortunately, the same capabilities that would have enabled these submarines to operate with the fleet made them superbly qualified for their new mission of commerce raiding against theJapanese Empire.
Timing, however, also conspired to make theGatos a mass-produced class of submarines. Six units were planned in FY41.In the immediate aftermath of theTwo-Ocean Navy Act48additional units were ordered. By the end of 1941, 33Gatokeels had been laid.
TheGato-class design, with a top range of 11,000 nautical miles (20,000 km), was a near-duplicate of the precedingTambor- andGar-class ships. The only significant differences were an increase in diving depth from 250 feet (76 m) to 300 feet (91 m), and an extra five feet in length to allow the addition of a watertight bulkhead dividing the one large engine room in two, with twodiesel generatorsin each room. TheGatos, along with nearly all of the U.S. Navy fleet-type submarines of World War II, were of partialdouble-hulledconstruction. The inner pressure-resisting hull was wrapped by an outer, hydrodynamic hull. The voids between the two hulls provided space for fuel and ballast tanks. The outer hull merged with the pressure hull at both ends in the area of thetorpedoroom bulkheads, hence the "partial" double hull. Operational experience with earlier ships led the naval architects and engineers at the Navy'sBureau of Construction and Repairto believe that they had been unduly conservative in their estimates of hull strength. Without changing the construction or thickness of the pressure hull steel, they decided that theGato-class ships would be fully capable of routinely operating at 300 feet, a 50-foot (15 m) increase in test depth over the preceding classes.
TheGatos were slow divers when compared to some German and British designs, but that was mostly because theGatos were significantly larger ships. Sufficient fuel bunkerage to provide the range necessary for 75-day patrols fromHawaiitoJapanand back could be obtained only with a larger ship, which would take longer to submerge than a smaller one. Acknowledging this limitation, the bureau designers incorporated a negative (sometimes called a "down express") tank into the design, which was flooded to provide a large amount of negative buoyancy at the start of the dive. Based on later wartime experience, the tank was normally kept full or nearly full at the surface, then emptied to a certain mark after the ship was submerged to restore neutral buoyancy. At the start of the war, these ships could go from fully surfaced to periscope depth in about 45–50 seconds. The superstructure that sat atop the pressure hull provided the main walking deck when the ship was surfaced and was free-flooding and full of water when the ship was submerged. When the dive began, the ship would "hang" for a few extra seconds while this superstructure filled with water. In an attempt to speed this process, additional limber, or free-flooding, holes were drilled and cut into the superstructure to allow it to flood faster. By midwar, these measures combined with improved crew training got dive times down to 30–35 seconds, very fast for such a large ship and acceptable to the ship's crew.
The large size of these ships did negatively affect both surfaced and underwater maneuverability when compared to smaller submarines. No practical fix for this was available due to the limitations of the installed hydraulic systems used to move the rudder. Although a point of concern, the turning radius was still acceptable. After the war, a few fleet ships were fitted with an additional rudder topside at the very stern.
The class of ships had numerous crew comforts including showers, air conditioning, refrigerated storage for food, generousfreshwater distilling units, clothes washers, and bunks for nearly every crew member; these were luxuries virtually unheard of in other navies. The bureau designers felt that if a crew of 60–80 men were to be expected to conduct 75-day patrols in the warm waters of the Pacific, these types of features were vital to the health and efficiency of the crew. They could be added without impact to the ship's war fighting abilities due to the extra room of the big fleet ship. The air conditioning in particular had a very practical application, too, besides comfort. Should a submarine submerge for any length of time, the heat generated by the recently shut-down engines, electronic gear, and 70 warm bodies will quickly raise internal temperatures above 100 °F (38 °C). High humidity generated by tropical waters will quickly condense and begin dripping into equipment, eventually causing electrical shorts and fires. Air conditioning, acting mostly as a dehumidifier, virtually eliminates this problem and greatly increases mechanical and electrical reliability. It proved to be a key factor in the success of these ships during World War II.
Like the previous Tambor/Gar classes, the Gato class could substitute mines in place of torpedoes. For the Mk 10 and Mk 12 type mines used in World War II, each torpedo could be replaced by as many as two mines, giving the submarine a true maximum capacity of 48 mines. However, doctrine was to retain at least four torpedoes on mine laying missions, which further limits the capacity to 40 mines, and this is often stated as the maximum in various publications. In practice during the war, submarines went out with at least 8 torpedoes, and the largest minefields laid were 32 mines. Post-war, the Mk 49 mine replaced the Mk 12, while the larger Mk 27 mine (in actuality an acoustic-homing torpedo) was also carried which only allowed one mine replacing one torpedo.
Twelve submarines of this class built by Electric Boat (SS-253 to SS-264) received what would be the final installations of theHooven-Owens-Rentschler(H.O.R.)double-actingdiesel engine. The Navy had been tinkering with this engine off and on since 1937 because its unique design promised nearly twice the horsepower in a package the same size as other diesel engine types. Unfortunately, the Hooven-Owens-Rentschler company ran into severe design and manufacturing problems, and these engines proved to be operational and maintenance nightmares.Frequent breakdowns and utter unreliability had destroyed these engines' reputation with the Navy and they were all removed at the first opportunity and replaced byGeneral MotorsCleveland Model16-278A V-type diesels. The otherGato-class ships received either theFairbanks-Morse38D 8-1/8nine-cylinderopposed-piston engineor theGeneral MotorsCleveland Model16-248 V-type as original installations. These engines were hardy, rugged, and well liked by the crews and served the ships quite well.Both the Fairbanks-Morse and General Motors engines weretwo-stroke cycletypes.
Two manufacturers supplied electric motors for theGatoclass.Elliott Companymotors were fitted primarily to boats with Fairbanks-Morse engines.General Electricmotors were fitted primarily to boats with General Motors engines, but some Fairbanks-Morse boats received General Electric motors.
At the beginning of the war,Gato-class ships, as well as theGarandTamborclasses, had fully shroudedfairwatersvisually similar to modern nuclear submarines. Experience during the war led to the progressive reduction of this structure to reduce visibility and radar profile at the expense of underwater performance and foul-weather operating comfort. Most of the subs in postwar movies show the final result of these modifications. A side benefit of these modifications was the creation of convenient locations for antiaircraft guns.
Seventy-seven of these ships were commissioned from November 1941 (Drum) through April 1944 (Croaker). Twenty of the 52 U.S. submarines lost in World War II were of this class, plusHalibut, a damaged ship that returned to the U.S., but was considered aconstructive total lossand not repaired.
Occasionally, some confusion arises as to the number ofGato-class submarines built, with some sources listing the total as 73, due to the transitional nature of the first four ships (SS-361 through SS-364) constructed under the second contract by theManitowoc Shipbuilding CompanyofManitowoc, Wisconsin. These were originally intended to beBalao-class subs and were assigned hull numbers that fall in the middle of the range of numbers for theBalaoclass (SS-285 to SS-416, SS-425, and SS-426).Manitowoc was a designated follow-on yard to Electric Boat; they used construction blueprints and plans supplied by Electric Boat and used many of the same suppliers. The government-owned shipyards (Portsmouth Naval ShipyardandMare Island Naval Shipyard) began to make the transition to the newBalaodesign in the summer of 1942. Electric Boat, due to the huge backlog ofGato-class construction, was not ready to make the transition to the new design until January 1943. Manitowoc had already completed their allotted production run ofGatos and could not switch over to theBalaodesign until Electric Boat supplied them with the plans. Faced with a work stoppage while they waited for Electric Boat to catch up, managers at Manitowoc got permission to complete four additional boats (SS-361 through SS-364) to Electric Boat'sGato-class plans. Manitowoc's firstBalao-class ship wasHardhead.
TheGatoboats were authorized in appropriations for Fiscal Year 1941, as part of PresidentFranklin Roosevelt's proclamation of "limited emergency" in September 1939.The first boatlaid downwas actuallyUSSDrumatPortsmouth Naval Shipyardon 11 September 1940. She wascommissionedon 1 November 1941, and was the onlyGato-class ship in commission when the war started.Gatoherself was laid down on 5 October 1940 by the Electric Boat Company atGroton, Connecticut, and commissioned 31 December 1941.Due to their large construction capacity, more than half (41) of the class was built at Electric Boat facilities; three new slipways were added to the north yard and four slipways were added to the south yard to accommodate their production. In addition, the government purchased an old foundry downstream from the main yard, constructed 10 slipways, and turned the yard over to Electric Boat. Called theVictory Yard, it became an integral part of Electric Boat operations.A total of 77Gatos were built at four different locations (Electric Boat, Manitowoc, Portsmouth, and Mare Island).
All of theGatos (with one exception,Dorado) would eventually fight in thePacific Theater of Operations. However, in the summer of 1942, six newGatos were assigned to Submarine Squadron 50 and sent toRosneath, Scotland, to patrol theBay of Biscayand to assist in theOperation Torchlandings in North Africa. All in all, they conducted 27 war patrols, but could not claim any verified sinkings. Considered a waste of valuable resources, in mid-1943, all six ships were recalled and transferred to the Pacific.
Once they began to arrive in theater in large numbers in mid-to-late 1942, theGatos were in the thick of the fight against the Japanese. Many of these ships racked up impressive war records:Flasher,Rasher, andBarbwere second, third, and fourth based on tonnage sunk by U.S. submarines.Silversides,Flasher, andWahoowere third, fourth, and seventh place on the list for the number of ships sunk.Gato-class ships sank four Japanese submarines:I-29,I-168,I-351, andI-42; while only losing one in exchange,CorvinatoI-176.
Their principal weapon was the steam-poweredMark 14 torpedoin the early war years, with the electricMark 18 torpedosupplementing the Mark 14 in late 1943. Due to a stunted research-and-development phase in the Depression-era 1930s, and in great part due to the arrogance and stubbornness of its designer, theNaval Torpedo StationNewport under theBureau of Ordnance, the "wonder weapon" Mark 14 proved to be full of bugs and very unreliable. They tended to run too deep, explode prematurely, run erratically, or fail to detonate. Bowing to pressure from the submariners in the Pacific, the bureau eventually acknowledged the problems in the Mark 14 and largely corrected them by late 1943. The Mark 18 electric torpedo was a hastily copied version of capturedGerman G7e torpedoesand was rushed into service in the fall of 1943. Unfortunately, it also was full of faults, the most dangerous being a tendency to run in a circular pattern and come back at the sub that fired it. Once perfected, both types of torpedoes proved to be reliable and effective weapons, allowing theGatos and other submarines to sink an enormous amount of Japanese shipping by the end of the war.
TheGatos were subjected to numerous exterior configuration changes during their careers, with most of these changes centered on the conning tower fairwater. The large, bulky original configuration proved to be too easy to spot when the boat was surfaced; it needed to be smaller. Secondly, the desire to incorporate new masts for surface- and air-search radars drove changes to the fairwater and periscope shears. Third, additional gun armament was needed, and cutting down the fairwater provided excellent mounting locations for machine guns and antiaircraft cannon.The modifications (or mods) to theGato-class conning tower fairwaters were fairly uniform in nature and they can be grouped together based on what was done when:
Variations on the above mods included the 1A (shortened navigation bridge), 2A (plating removed from periscope shears), and the 3A and 4A (which moved the SJ radar mast aft of the periscopes).The conning tower fairwater ofFlasheris preserved in Groton, Connecticut, in the mod 4A configuration, with two single 40 mm Bofors mounts.
Deck gunsvaried during the war. Many targets in thePacific Warweresampansor otherwise not worth a torpedo, so the deck gun was an important weapon. Most ships began the war with a3-inch (76 mm) /50 caliber Mk. 17 gun(although some ships received older Mk. 6 mounts due to shortages). The 3-inch (76 mm) gun was the model originally specified for theGatoclass, but war experience led to the removal of4-inch (100 mm)/50 caliber Mk. 9 gunsfrom oldS-class submarinesto equip front-line ships. Beginning in late 1943, almost all were refitted with a5-inch (130 mm)/25 caliber Mk. 17 gun, and some ships had two of these weapons. Additional antiaircraft guns included single 40 mm Bofors and twin 20 mm Oerlikon mounts, usually one of each.
At the end of World War II, the U.S. Navy found itself in an awkward position. The 56 remainingGato-class submarines, designed to fight an enemy that no longer existed, were largely obsolete, despite the fact they were only two to four years old. Such was the pace of technological development during the war that a submarine with only a 300-foot test depth was going to be of little use, despite being modern in most other aspects. Enough of theBalaoandTenchships, with their greater diving depth, remained that theGatos were superfluous for front-line missions. TheGreater Underwater Propulsion Power Program(GUPPY) modernization program of the late 1940s largely passed these ships by. OnlyBarbandDacereceived GUPPY conversions; these were austere GUPPY IB modernizations under projectSCB 47Aprior to their transfer to theItalian Navy.However, the U.S. Navy found itself new missions to perform, and for some of these theGatos were well suited.The last twoGato-class ships active in the U.S. Navy wereRockandBashaw, which were both decommissioned on 13 September 1969 and sold for scrap.
The advent of thekamikazedemonstrated the need for a long-range radar umbrella around the fleet. Surface shipsrefitted with powerful radar suiteswere put into service, but they proved vulnerable in this role, as they could be attacked as well, leaving the fleet blind. A submarine, though, could dive and escape aerial attack. TwoGato-class ships (GrouperandFinback) received rudimentary conversions to radar pickets before the end of World War II, but were not used in this role. After further experimenting with the concept on fourBalaoandTench-class boats under Projects Migraine I and II, and realizing that a deep diving depth was not overly important in this role, sixGatos were taken in hand (Pompon,Rasher,Raton,Ray,Redfin, andRock) for conversion underProject Migraine III(aka SCB 12A). They were lengthened by 24 feet (7.3 m) to provide additional space for an air control center and had powerful air-search and height-finding radars installed, with the after torpedo room converted into an electronics space with torpedoes and tubes removed. They also received a streamlined "sail" in place of the traditional conning tower fairwater. Redesignated as SSRs, these ships were only moderately successful in this role, as the radars themselves proved troublesome and somewhat unreliable. The radars were removed and the ships temporarily reverted to general-purpose submarines after 1959.
The threat of theSoviet Navybuilding hundreds ofType XXI-derived submarines (eventually the 215-strongWhiskey classand dozens of others) in the Atlantic led the U.S. Navy to adapt submarines to specifically hunt other submarines, a radically new role for the 1950s. Concluding that this role did not require a fast or deep-diving submarine (this line of thought would quickly change with the advent of nuclear power), sevenGatos were converted toSSKs(hunter-killer submarines) between 1951 and 1953, joining three purpose-builtK-1-class SSKsentering service at that time. TheGatoclass was chosen because large numbers were available in thereserve fleetshould rapid mobilization become necessary, and the deeper-diving classes were more suitable for GUPPY rather than SSK conversions. A streamlined GUPPY-style sail was installed, a large sonar array was wrapped around the bow (losing twotorpedo tubesin the process), the ships were extensively silenced including the removal of the two forward diesel engines, and they received asnorkel.Grouperwas converted under project SCB 58 as the test ship for the concept, having her sonar array at the forward end of the sail instead of the better position at the bow. The other ships in the program includedAngler,Bashaw,Bluegill,Bream,Cavalla, andCroaker.
Eventually more advanced sonars were installed on the new nuclear subs:Tullibee, commissioned in 1960, introduced the bow-mounted sonar sphere.Tullibeewas an attempt to develop a slow but ultra-quiet nuclear-powered SSK equivalent; no others were built due to her unexpectedly high cost relative to the more capableThresher, and the SSK mission was folded into the regular attack submarine role.The slow and less capable diesel SSKs were decommissioned or reassigned to other roles in 1959, and all exceptCroakerandCavalla(eventually preserved as memorials) were scrapped in 1968 and 1969.
TheRegulusnuclearcruise missileprogram of the 1950s provided the U.S. Navy with its first strategic missile capability.Tunnywas converted under SCB 28 in 1953 to house and fire this large surface-launched missile and was designated SSG (guided-missile submarine). She could carry two of the missiles in a cylindrical hangar on the aft deck. She madestrategic deterrent patrolswith Regulus until 1964, when the program was discontinued in favor ofPolaris.
With the retirement of the Regulus missile system in 1965,Tunnywas converted into a troop transport in 1966. She was redesignated as an APSS (transport submarine), replacingPerchin this role. Her Regulus hangar became a lockout chamber forUDT,SEAL, andMarine Force Reconteams in theVietnam War. On 1 January 1969,Tunny's designation was changed to LPSS (amphibious transport submarine); however, she was replaced byGraybackand decommissioned in June of that year.
Guavinawas converted under SCB 39 to a SSO in 1950 to carry fuel oil, gasoline, and cargo to amphibious beachheads. She received additional "saddle" tanks wrapped around her outer hull to carry these fuels and a streamlined sail. After a few tests, the concept was dropped in 1951 as impractical, andGuavinaserved in the test role for a few years under the designation AGSS. In 1957, she converted back to the oiler/tanker role and carried the designation AOSS. This time, she experimented with refueling seaplanes at sea, which was potentially important, as refueling the nuclear-capableMartin P6M Seamasterat sea could improve the Navy's strategic strike capabilities. However, this mission, too, was dropped andGuavinawas decommissioned.
The development of advanced sonar systems took on a great deal of importance in the 1950s, and several fleet ships were outfitted with various strange-looking sonar transducer arrays and performed extensive tests. TwoGatos,Flying FishandGrouper(previously the prototype hunter-killer ship) were assigned to these duties and proved to be key players in the development of new sonar capabilities.Grouperhad all her forwardtorpedo tubesremoved and the space was used as berthing for technicians and as a sonar lab.Flying Fishwas decommissioned in 1954, butGroupercontinued in the test role until 1968.
Interested in maintaining a ready pool of trainedreservists, the Navy assigned numerous fleet ships to various coastal and inland ports (even inGreat Lakesports such asChicago,Cleveland, andDetroit) where they served as a training platform during the reservists' weekend drills. Twenty-eightGato-class ships served in this capacity, some as late as 1971. In this role, the ships were rendered incapable of diving and had their propellers removed. They were used strictly as pierside trainers. These were in commission, but classed as "in commission in reserve", thus some were decommissioned and recommissioned on the same day to reflect the change in status.
The large numbers of relatively modern, but surplus U.S. fleet submarines proved to be popular in sales, loans, or leases to allied foreign navies. While most of these ships were of the more capableBalaoandTenchclasses, someGatos went overseas, as well. Italy received two (BarbandDace), which received the only GUPPY conversions given toGato-class ships (Guppy IB).Japan received one (Mingo), Brazil two (MuskallungeandPaddle), Greece two (LaponandJack), and Turkey two (GuitarroandHammerhead). The ships transferred to Japan and Brazil did not receive any modernizations (streamlining and snorkels) prior to transfer, but the four ships sent to Greece and Turkey did receive snorkels and partial streamlining to the fairwater.
SixGato-class submarines are open to public viewing. They primarily depend on revenue generated by visitors to keep them operational and up to U.S. Navy standards; each ship gets a yearly inspection and a "report card". Some ships, such asCodandSilversides, have been used in film production.
The following is a complete list ofGato-class museum ships: