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USS ''Shenandoah'' was the first of four United States Navy rigid airships. It was built in 1922–1923 at Lakehurst Naval Air Station, and first flew in September 1923. It developed the U.S. Navy's experience with rigid airships, and made the first crossing of North America by airship. On the 57th flight,〔Hayward (1978) p. 67〕 ''Shenandoah '' was torn apart in a squall line over Ohio in 1925.〔Hayward (1978) p. 66〕 ==Design and construction== ''Shenandoah'' was originally designated FA-1, for "Fleet Airship Number One" but this was changed to ZR-1. The airship was long〔Hayward (1978) p. 64〕 and weighed 36 tons (32658 kg). It had a range of , and could reach speeds of . ''Shenandoah'' was assembled at Naval Air Station Lakehurst, New Jersey in 1922–1923, in Hangar No. 1, the only hangar large enough to accommodate the ship; its parts were fabricated at the Naval Aircraft Factory in Philadelphia. NAS Lakehurst had served as a base for Navy blimps for some time, but ''Shenandoah'' was the first rigid airship to join the fleet. The design was based on Zeppelin bomber ''L-49'' (LZ-96), built in 1917.〔Hayward (1978) p. 62〕 ''L-49'' was a lightened "height climber", designed for altitude at the expense of other qualities. The design was found insufficient and a number of the features of newer Zeppelins were used, as well as some structural improvements.〔 The structure was built from a new alloy of aluminum and copper known as duralumin. Girders were fabricated at the Naval Aircraft Factory.〔 Whether the changes introduced into the original design of L-49 played a part in ''Shenandoahs later breakup is a matter of debate. An outer cover of high-quality cotton cloth was sewn, laced or taped to the duralumin frame and painted with aluminum dope.〔 The gas cells were made of goldbeater's skins, one of the most gas-impervious materials known at the time.〔 Named for their use in beating and separating gold leaf,〔 goldbeater's skins were made from the outer membrane of the large intestines of cattle.〔 The membranes were washed and scraped to remove fat and dirt, and then placed in a solution of water and glycerine in preparation for application to the rubberized cotton fabric providing the strength of the gas cells.〔 The membranes were wrung out by hand to remove the water-glycerine storage solution and then rubber-cemented to the cotton fabric and finally given a light coat of varnish.〔 The 20 gas cells within the airframe were filled to about 85% of capacity at normal barometric pressure.〔Hayward (1978) p. 63〕 Each gas cell had a spring-loaded relief valve and manual valves operated from the control car.〔 As the first rigid airship to use helium rather than hydrogen, ''Shenandoah'' had a significant edge in safety over previous airships. Helium was relatively scarce at the time, and the ''Shenandoah'' used much of the world's reserves just to fill its volume.〔 — the next rigid airship to enter Navy service, originally built by ''Luftschiffbau Zeppelin'' in Germany as ''LZ 126'' — was at first filled with the helium from ''Shenandoah'' until more could be procured. ''Shenandoah'' was powered by , eight-cylinder Packard gasoline engines. Six engines were originally installed, but in 1924 one engine (aft of the control car) was removed. The first frame of ''Shenandoah'' was erected by 24 June 1922; on 20 August 1923, the completed airship was floated free of the ground. Helium cost $55 per thousand cubic feet at the time, and was considered too expensive to simply vent to the atmosphere to compensate for the weight of fuel consumed by the gasoline engines.〔 Neutral buoyancy was preserved by installing condensers to capture the water vapor in the engine exhaust.〔 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「USS Shenandoah (ZR-1)」の詳細全文を読む スポンサード リンク
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