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A depth charge is an anti-submarine warfare (ASW) weapon intended to destroy or cripple a target submarine by being dropped into the water close to its target and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge typically at a preselected depth. Depth charges can be dropped by ships, patrol aircraft, and helicopters. Depth charges have now largely been replaced by anti-submarine homing torpedoes. A depth charge fitted with a nuclear warhead is known as a "nuclear depth bomb". These were designed to be dropped from a patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located a safe distance away. All nuclear anti-submarine weapons were withdrawn from service by the United States, the United Kingdom, France, Russia, and China in or around 1990. They were replaced by conventional weapons whose accuracy and range had improved greatly as ASW technology improved. ==History== The first attempt to fire charges against submerged targets was with aircraft bombs attached to lanyards which triggered them; a similar idea was a guncotton charge in a lanyarded can; two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B". These were effective at a distance of around .〔 A 1913 Royal Navy Torpedo School report described a device intended for countermining, a "dropping mine". At Admiral John Jellicoe's request, the standard Mark II mine was fitted with a hydrostatic pistol (developed in 1914 by Thomas Firth and Sons of Sheffield) preset for firing, to be launched from a stern platform. Weighing , and effective at , the "cruiser mine" was a potential hazard to the dropping ship.〔 The design work was carried out by Herbert Taylor at the RN Torpedo and Mine School, HMS ''Vernon''. The first effective depth charge, the Type D, became available in January 1916. It was a barrel-like casing containing a high explosive (usually TNT, but amatol was also used when TNT became scarce).〔 There were initially two sizes—Type D, with a charge for fast ships, and Type D * with a charge for ships too slow to leave the danger area before the more powerful charge detonated.〔 A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge.〔 Initial depth settings were .〔 Because production could not keep up with demand, anti-submarine vessels initially carried only two depth charges, to be released from a chute at the stern of the ship.〔 The first success was the sinking of ''U-68'' off Kerry, Ireland, on 22 March 1916, by the Q-ship ''Farnborough.''〔 Germany became aware of the depth charge following unsuccessful attacks on ''U-67'' on 15 April 1916, and ''U-69'' on 20 April 1916.〔 The only other submarines sunk by depth charge during 1916 were ''UC-19'' and ''UB-29''.〔 Numbers of depth charges carried per ship increased to four in June 1917, to six in August, and 30-50 by 1918.〔 The weight of charges and racks caused ship instability unless heavy guns and torpedo tubes were removed to compensate.〔 Improved pistols allowed greater depth settings in 50-foot (15-meter) increments, from .〔 Even slower ships could safely use the Type D at below and at or more,〔 so the relatively ineffective Type D * was withdrawn.〔 Monthly use of depth charges increased from 100 to 300 per month during 1917 to an average of 1745 per month during the last six months of World War I.〔 The Type D could be detonated as deep as by that date. By the war's end, 74,441 depth charges had been issued by the RN, and 16,451 fired, scoring 38 kills in all, and aiding in 140 more.〔 The United States requested full working drawings of the device in March 1917. Having received them, Commander Fullinwider of the U.S. Bureau of Naval Ordnance and U.S. Navy engineer Minkler made some modifications and then patented it in the U.S. It has been argued that this was done to avoid paying the original inventor. The Royal Navy Type D depth charge was designated the "Mark VII" in 1939. Initial sinking speed was with a terminal velocity of at a depth of if rolled off the stern, or upon water contact from a depth charge thrower.〔 Cast iron weights of were attached to the Mark VII at the end of 1940 to increase sinking velocity to .〔 New hydrostatic pistols increased the maximum detonation depth to .〔 The Mark VII's amatol charge was estimated to be capable of splitting a submarine pressure hull at a distance of , and forcing the submarine to surface at twice that.〔 The change of explosive to Torpex (or Minol) at the end of 1942 was estimated to increase those distances to .〔 The British Mark X depth charge weighed and was launched from torpedo tubes of older destroyers to achieve a sinking velocity of .〔 The launching ship needed to clear the area at 11 knots to avoid damage, and the charge was seldom used.〔 Only 32 were actually fired, and they were known to be troublesome. The teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943. The charge was of Torpex with a sinking speed of and depth settings of up to .〔 Later versions increased depth to and sinking speed to with increased weight and improved streamlining.〔 Although the explosions of the standard United States Mark 4 and Mark 7 depth charge used in World War II were nerve-wracking to the target, an U-boat’s undamaged pressure hull would not rupture unless the charge detonated closer than about . Placing the weapon within this range was entirely a matter of chance and quite unlikely as the target maneuvered evasively during the attack. Most U-boats sunk by depth charges were destroyed by damage accumulated from a long barrage rather than by a single charge. Many survived hundreds of depth charges over a period of many hours; ''U-427'' survived 678 depth charges fired against it in April 1945. 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「Depth charge」の詳細全文を読む スポンサード リンク
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