Take a look inside the Gato: the US Navy’s first massproduced submarine
An archaic design principle yielded what soon became one of the US Navy’s best and most successful submarine types
The Gato Class (and its slightly improved Balao derivative built from 1942 onwards) marked the high point of the US Navy’s desire for a ‘Fleet Submarine’. Conceptually, this placed these large oceangoing vessels as scouting elements for a main surface battle fleet, designed to range ahead and locate the opposing fleet, launching torpedo attacks to whittle its strength before the main fleet, centred on battleships, engaged the enemy. Such strategic thinking dated back to World War I, when the battleship still reigned supreme, but the loss of four battleships and another four damaged by the Japanese attack on Pearl Harbor on 7 December 1941 forced an urgent reappraisal of the US Navy’s Pacific doctrine.
Thanks to its intended use being to accompany a main battle fleet at sea, the Gato was a large ocean-going submarine, heavily armed and designed with considerable attention paid to habitability for a large crew on extended patrols expected to last over two months. Refrigeration units, individual bunks, laundry facilities and air conditioning helped to maintain crew health and efficiency in predominantly warm tropical waters – far more than the facilities provided by all other nation’s navies.
USS Drum was the premier Gato boat commissioned on 1 November 1941. It was the first of 77 to be commissioned by April 1944, carrying the brunt of the US Navy’s submarine war in the Pacific, while a small number were also used within the Atlantic, most notably as reconnaissance off the North African coast in advance of Operation Torch in 1942.
“THE GATO WAS A LARGE OCEAN-GOING SUBMARINE, HEAVILY ARMED AND DESIGNED WITH CONSIDERABLE ATTENTION TO HABITABILITY FOR A LARGE CREW”
ARMAMENT
Gato’s primary weapon was the 21-inch torpedo. The six bow tubes and four stern tubes provided great offensive power, the boat also carrying 14 reloads. Unfortunately, the US Navy suffered severe torpedo malfunctions because of inept research and testing, akin to that suffered by the Kriegsmarine, and not fully resolved until the end of 1943. The Gato boats could also carry 40 moored mines for deployment by torpedo tube. Above decks, two positions were available for a main cannon, up-gunned from 3-inch to 5-inch as the war progressed, and frequently used in action against small Japanese sailing vessels. Likewise, antiaircraft positions changed along with frequently developing conning tower configurations as greater calibre weapons became available, and the Japanese aerial threat grew through increasing surfaced actions as the Japanese merchant fleet was decimated, becoming reliant on small transport vessels.
ENGINES
Gato submarines were driven by a dieselelectric drive, ie. diesel combustion engines. They were not connected to the shafts, but instead charged generators, providing energy for either loading batteries or powering the electric motors coupled to the propellor shafts at all times through reduction gears. Pioneered by the Swedish Navy during the early 20th century, this eliminated the former ‘parallel’ diesel or electric drive system in which electric motors for submerged use and diesel for surfaced were coupled to the same shaft; the motor used as a generator while surfaced, diesel disconnected while submerged. Although with some disadvantages, such as a decrease in diesel fuel efficiency by conversion to electrical output, the advantages included reduction in external noise by isolating diesels from the shafts, ship speed independent of diesel speed allowing optimised engine use, and flexibility in diesel engine positioning.
DESIGN
Gato was comprised of an entirely welded partial double-hull construction, the inner pressure hull covered by a hydrodynamic outer casing with which it merged at either tapered end. Between the two lay six ballast tanks and four fuel bunkers. Internally the boat was subdivided into eight watertight compartments, the pressure hull thickness of 14.3mm was later increased to 22.2mm using a newly developed high-tensile steel alloy, resulting in the related Balao Class, capable of an increased test depth of 140 metres (400 feet). The Gato possessed a large, frequently modified conning tower configuration that contributed to a slow diving time – unacceptable if in action, such as with the fastmoving Atlantic convoy battles, but adequate for the Pacific.
INTERIOR
The pressure hull interior placed great emphasis on crew habitability, including the use of air conditioning, which was luxurious in comparison to other navies. However, bearing in mind that the Pacific was the likely theatre of war for the US Navy, as well as maintaining crew comfort within an interior that could reach sweltering heat levels in tropical sea, air conditioning also reduced humidity that could coalesce into condensation and cause dangerous electrical shorts. Refrigerated food storage and a Kleinschmidt freshwater distillation plant supplied provisions for long-distance patrols, and an excellent Torpedo Data Computer provided accurate firing solutions, though often rendered futile by malfunctioning torpedoes until defects were rectified.
“AMERICAN SUBMARINES GENERALLY OPERATED INDEPENDENTLY IN RADIO SILENCE WHILE AT SEA RATHER THAN USING THE KRIEGSMARINE’S ‘WOLF PACK’ APPROACH”
SERVICE HISTORY
The Gato Class – an improved Balao – was a continuation of tried and tested
Fleet Submarine designs that allowed the US Navy to take the fight to the Japanese mainland. American submarines generally operated independently in radio silence while at sea rather than using the Kriegsmarine’s ‘Wolf
Pack’ approach. The lessons of radar direction finder technology and codebreaking that destroyed German U-boat hopes were not lost on American naval commanders, and the nature of the Pacific war differed to the Atlantic. Japan did not employ convoying on anywhere near a European scale and, despite unrestricted submarine warfare being employed against Japan from the opening of hostilities, targets were fewer, frequently smaller and far more geographically spread than within the Atlantic. Nonetheless, the second most successful American submarine of the war was Gato-class USS Flasher, which sank 21 Japanese ships totalling 100,231 tonnes. The top ten scoring submarines were all either Gato or the improved Balao Class boats.
By the war’s end the Gato Class was largely obsolete and superfluous. Two vessels received modernisation before being transferred to the Italian Navy, serving right up until 1973. The final two US Navy Gato boats were finally decommissioned in September 1969.