Essex-class aircraft carrier
The Essex class is a retired class of aircraft carriers of the United States Navy. The 20th century's most numerous class of capital ship, the class consisted of 24 vessels which came in "short-hull" and "long-hull" versions. Thirty-two ships were ordered, but as World War II wound down, six were canceled before construction and two were canceled after construction had begun. Fourteen saw combat during World War II. None were lost to enemy action although a few sustained crippling damage due to aerial attacks. Essex-class carriers were the backbone of the U.S. Navy from mid-1943 and, with the three carriers added just after the war, continued to be the heart of U.S. naval strength until supercarriers joined the fleet starting in the 1950s. Several of the carriers were rebuilt to handle heavier and faster aircraft of the early jet age and saw service in the Vietnam War, with decommissioned as a training carrier in 1991. Of the 24 ships in the class, four,,, and have been preserved as museum ships.
Overview
The preceding s and the designers' list of trade-offs and limitations forced by arms control treaty obligations shaped the development of the Essex class – a design sparked by the Japanese and Italian repudiation of the limitations proposed in the 1936 revision of the Washington Naval Treaty of 1922. Effectively, this rejection allowed all five signatories to resume the interrupted naval arms race of the 1890s–1910s in early 1937.At the time of the repudiations, both Italy and Japan had colonial ambitions, intent on or already conducting military conquests. With the demise of the treaty limitations and the growing tensions in Europe, naval planners were free to apply both the lessons they had learned operating carriers for fifteen years and those from operating the Yorktown-class carriers to the newer design.
Designed to carry a larger air group, and unencumbered by the latest in a succession of pre-war naval treaty limits, was over sixty feet longer, nearly ten feet wider, and more than a third heavier than Yorktown-class carriers. A longer, wider flight deck and a deck-edge elevator facilitated more efficient aviation operations, enhancing the ship's offensive and defensive air power.
Machinery arrangement and armor protection were greatly improved from previous designs. These features, plus the provision of more anti-aircraft guns, gave the ships much enhanced survivability. In fact, during the war, none of the Essex-class carriers were lost and two, and, came home under their own power and were successfully repaired even after receiving extremely heavy damage.
Debates raged regarding armoring the hangar deck. British designers' comments tended to disparage the use of hangar deck armor, but some historians, such as D.K. Brown in Nelson to Vanguard, see the American arrangement to have been superior. In the late 1930s, locating the strength deck at hangar deck level in the proposed Essex-class ships reduced the weight located high in the ship, resulting in smaller supporting structures and more aircraft capacity for the desired displacement. The which followed armored both the hangar and flight deck.
The larger size of the first supercarriers necessitated a deeper hull and shifted the center of gravity and center of stability lower, enabling moving the strength deck to the flight deck, thus freeing US naval design architects to move the armor higher and remain within compliance of US Navy stability specifications without imperiling seaworthiness. One of the design studies prepared for the Essex project, "Design 9G", included an armored flight deck but reduced aircraft capacity, and displaced 27,200 tons, or about 1,200 tons more than "Design 9F", which formed the basis of the actual Essex design; 9G became the ancestor of the 45,000-ton Midway class.
Development
After the abrogation of disarmament treaties by Japan in 1936, the U.S. took a realistic look at its naval strength. With the Naval Expansion Act of Congress passed on 17 May 1938, an increase of 40,000 tons in aircraft carriers was authorized. This permitted the building of, which was the third -class carrier, and, which was the lead ship of a new class.CV-9 was to be the prototype of the 27,000-ton aircraft carrier, considerably larger than, yet smaller than . The Navy ordered the first three of the new design, CV-9, CV-10 and CV-11, from Newport News Shipbuilding & Drydock on 3 July 1940. These were to become known as Essex-class carriers. Under the terms of the Two-Ocean Navy Act, eight more of these carriers were programmed. Eight were ordered on 9 September, CV-12 through −15 from Newport News, and CV-16 through −19 from Bethlehem Steel's Fore River Shipyard; the last two, and, were authorized 23 December 1941, with the primary intention of keeping existing slipways busy, and were ordered eight days after Pearl Harbor from the Brooklyn Navy Yard and Newport News respectively.
After the US declaration of war, Congress appropriated funds for nineteen more Essex-class carriers. Ten were ordered in August 1942 and three more in June 1943. Only two of these were completed in time to see active World War II service. Six ships ordered in 1944 were canceled before construction was begun.
The Essex-class carriers combined the policy of naming aircraft carriers after historic battles begun with the Lexington class with the policy of naming them for historic navy ships generally followed for the Yorktown class. The first eight hulls were originally assigned names from historic Navy ships. was originally laid down as Cabot, but was renamed during construction after the previous was lost in the Battle of the Coral Sea in May 1942., originally to be named Bon Homme Richard, was renamed after the previous was lost at the Battle of Midway on 7 June 1942. Lexington and Yorktown share the unique distinction of being named after both historic ships and historic battles.
Likewise, 's name was changed from Oriskany after the original was sunk in September 1942 in the South Pacific near Guadalcanal, and 's name was changed from Kearsarge after the original was lost in October 1942 in the Battle of Santa Cruz Islands. The erstwhile Valley Forge was renamed after was sunk in the Battle of Leyte Gulf in October 1944. The names of and were swapped while they were under construction: the John Hancock life insurance company had offered to conduct a bond drive to raise money for Hancock if that name was used for the carrier under construction in the company's home state of Massachusetts. USS Shangri-La was named after a facetious remark by President Franklin Delano Roosevelt suggesting that the Doolittle Raiders flew from the fictional Himalayan kingdom setting of the novel Lost Horizon.
At the conclusion of the war, the six ships ordered but never laid down were cancelled. Of the nine still unfinished, six were completed, two were scrapped, and was taken in hand for modification to an improved design, completing in 1950. In summary, during World War II and until its conclusion, the US Navy ordered 32 aircraft carriers of the Essex class, including the Ticonderoga subgroup, of which 26 were laid down and 24 actually commissioned.
Design
In drawing up the preliminary design for Essex, particular attention was directed at the size of both the flight and hangar decks. Aircraft design had come a long way from the comparatively light planes used in carriers during the 1930s. Flight decks now required more takeoff space for the heavier aircraft being developed. Moreover, US carrier doctrine was premised on the "deck-load strike", launching as rapidly as possible as many aircraft as could be spotted on the flight deck beforehand. Most of the first-line carriers of the pre-war years were equipped with flush deck catapults, but, owing to the speed and size of these ships, very little catapulting was done except for experimental purposes.With the advent of war, airplane weights began to go up as armor and armament got heavier; aircrew complements also increased. By the war's end in 1945, catapult launches would become more common under these circumstances, with some carrier commanding officers reporting up to 40% of launches by catapult.
The hangar area design came in for many design conferences between the naval bureaus. Not only were the supporting structures to the flight deck required to carry the increased weight of landing and parked aircraft, but they were to have sufficient strength to support the storing of spare fuselages and parts under the flight deck and still provide adequate working space for the men using the area below.
One innovation in Essex was a portside deck-edge elevator in addition to two inboard elevators. The deck-edge elevator was adopted in the design after it proved successful on. Experiments had also been made with hauling aircraft by crane up a ramp between the hangar and flight decks, but this method proved too slow. The Navy's Bureau of Ships and the chief engineer of A.B.C. Elevator Co. designed the engine for the side elevator. It was a standard elevator, in platform surface, which traveled vertically on the port side of the ship. There would be no large hole in the flight deck when the elevator was in the "down" position, a critical factor if the elevator ever became inoperable during combat operations. Its new position made it easier to continue normal operations on deck, irrespective of the position of the elevator. The elevator also increased the effective deck space when it was in the "up" position by providing additional parking room outside the normal contours of the flight deck, and increased the effective area on the hangar deck by the absence of elevator pits. In addition, its machinery was less complex than the two inboard elevators, requiring about 20% fewer man-hours of maintenance. The elevator could be folded up by 90 degrees to permit passage through the narrow locks of the Panama Canal.
Ongoing improvements to the class were made, particularly with regard to the ventilation system, lighting systems, and the trash burner design and implementation.
These carriers had better armor protection than their predecessors, better facilities for handling ammunition, safer and greater fueling capacity, and more effective damage control equipment. Yet, these ships were also designed to limit weight and the complexity of construction, for instance incorporating extensive use of flat and straight metal pieces, and of Special Treatment Steel, a nickel-chrome steel alloy that provided the same protective qualities as Class B armor plate, but which was fully structural rather than deadweight.
The original design for the class assumed a complement of 215 officers and 2,171 enlisted men. However, by the end of World War II, most crews were 50% larger than that.
The tactical employment of U.S. carriers changed as the war progressed. In early operations, through 1942, the doctrine was to operate singly or in pairs, joining for the offense and separating when on the defense—the theory being that a separation of carriers under attack not only provided a protective screen for each, but also dispersed the targets and divided the enemy's attack. Combat experience in those early operations did not bear out the theory, and new proposals for tactical deployment were the subject of much discussion.
As the new Essex- and -class carriers became available, tactics changed. Experience taught the wisdom of combined strength. Under attack, the combined anti-aircraft fire of a task group's carriers and their screen provided a more effective umbrella of protection against marauding enemy aircraft than was possible when the carriers separated.
When two or more of these task groups supported each other, they constituted a fast carrier task force. Lessons learned from operating the carriers as a single group of six, as two groups of three, and three groups of two, provided the basis for many tactics that later characterized carrier task force operations, with the evolution of the fast carrier task force and its successful employment in future operations.