|
The ''Pennsylvania'' class consisted of two super-dreadnought battleships built for the United States Navy just before the First World War. The ships were named and , after the American states of the same names. They constituted the United States' second battleship design to adhere to the "all or nothing" armor scheme, and were the newest American capital ships when the United States entered the First World War. The s represented a marked increase in the United States' dreadnought technology, and the ''Pennsylvania'' class was intended to continue this with slight increases in the ships' capabilities, including two extra guns and improved underwater protection. The class was the second standard type battleship class to join the United States Navy, along with the preceding and the succeeding , and classes. In service, the ''Pennsylvania'' class saw limited use in the First World War, as a shortage of oil fuel in the United Kingdom meant that only the coal-burning ships of Battleship Division Nine were sent. Both were sent across the Atlantic to France after the war for the Paris Peace Conference of 1919, and were then transferred to the Pacific Fleet before being significantly modernized from 1929 to 1931. For the remainder of the inter-war period, the ships were used in exercises and fleet problems. Both ''Pennsylvania'' and ''Arizona'' were present during the Japanese attack on Pearl Harbor. ''Arizona'' was sunk in a massive magazine explosion and was turned into a memorial after the war, while ''Pennsylvania'', in dry dock at the time, received only minor damage. After a refit from October 1942 to February 1943, ''Pennsylvania'' went on to serve as a shore bombardment ship for most of the remainder of the war, an exception being the October 1944 Battle of Surigao Strait, the last battle ever between battleships. ''Pennsylvania'' was severely damaged by a torpedo on 12 August 1945, the day before the cessation of hostilities. With minimal repairs, she was used in Operation ''Crossroads'', part of the Bikini atomic experiments, before being expended as a target ship in 1948. == Background == The preceding ''Nevada''-class battleships represented a leap forward from previous American battleship technology and from most contemporary foreign designs. These ships were the first in the world to employ the "all or nothing" armor scheme that characterized every succeeding American battleship. Devised with the knowledge that engagement ranges between battle fleets was growing greater as main battery sizes increased, the system moved away from previous designs that used heavy, medium, and light armor, in favor of using only heavy armor to protect vital areas on the ship. The new system envisioned that, at long ranges, ships would be attacked with only armor piercing (AP) projectiles, stoppable only by heavy armor. Medium or light armor would only serve to detonate the shells. By removing gun turrets and reducing the overall protected length of the ship, the navy's designers were able to devote the weight savings to the belt, as well as extra deck armor to protect against plunging shells.〔Friedman, ''Design and Development'', 65–66; Friedman, ''U.S. Battleships'', 101–02.〕 In issuing desired specifications for the design that would become the ''Nevada'' class, the navy's General Board asked for triple gun turrets, i.e. three guns mounted per turret. They were very unsatisfied with the awkward placement required on classes preceding the ''Nevada''s, which had five and six two-gun turrets—yet moving back to the four two-gun turrets of the would be a significant loss in firepower. Although a triple turret was first proposed in American professional magazines in 1901 and briefly considered for the ''South Carolina''s, it was not even in the experimental stage—the first turret was authorized in 1911 and would not be ready until months after contracts for the new ships would be signed with the shipbuilders. The decision to go ahead with the turret was a calculated gamble, but proved to be a qualified success: the only issue came with shell interference when the center and outside guns were fired simultaneously, which was easily solved by delaying the firing of the center barrel by a small fraction of a second. The major benefit, though, came from the weight savings from the reduction of an armored barbette and turret. These gains were used in heavier armor, making the "all or nothing" concept a reality.〔Friedman, ''Design and Development'', 134–35; Friedman, ''U.S. Battleships'', 102, 107, 111.〕 The ''Nevada''s were also the first American battleships to use exclusively oil fuel, which had greater thermal efficiency than firing with coal or coal sprayed with oil. The cumulative effect of the change was measured by the navy as a fifty-five percent increase in steam production per pound of fuel (in a design for an oil-fired version of the ). This would give oil-fired vessels additional range, an important consideration for ships based in the Pacific Ocean, but the United States Navy's Bureau of Construction and Repair (C&R) pointed out what it saw as the unfortunate side effects, including a lower center of gravity, higher metacentric height, and the loss of coal bunkers, which were employed as part of the armor protection. However, just a few years later oil tanks below the waterline were considered indispensable parts of the underwater armor scheme employed in American dreadnoughts.〔Friedman, ''Design and Development'', 93–95; Friedman, ''U.S. Battleships'', 102, 104–05.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pennsylvania-class battleship」の詳細全文を読む スポンサード リンク
|