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|family = |derivatives = |comparable = |status = Active |sites = Cape Canaveral SLC-17 Vandenberg AFB SLC-2W |launches = 153 Delta 6000: 17 Delta 7000: 130 Delta 7000H: 6 |success = 151 Delta 6000: 17 Delta 7000: 128 Delta 7000H: 6 |fail = 1 (Delta 7000) |partial = 1 (Delta 7000) |other_outcome = |first = Delta 6000: 14 February 1989 Delta 7000: 26 November 1990 Delta 7000H: 8 July 2003 |last = Delta 6000: 24 July 1992 Delta 7000H: 10 September 2011 |only = |payloads = |stagedata = }} Delta II is an American space launch system, originally designed and built by McDonnell Douglas. Delta II is part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and two Delta 7000 variants ("Light" and "Heavy"). == History == In the early 1980s, all United States expendable launch vehicles were planned to be phased out in favor of the Space Shuttle, which would be responsible for all government and commercial launches. Production of Delta, Atlas-Centaur, and Titan 34D had ended. The ''Challenger'' disaster of 1986 and the subsequent halt of Shuttle operations changed this policy, and President Ronald Reagan announced in December of that year that the Space Shuttle would no longer launch commercial payloads, and NASA would seek to purchase launches on expendable vehicles for missions that did not require crew or Shuttle support. McDonnell Douglas, at that time the manufacturer of the Delta family, signed a contract with the U.S. Air Force in 1987 to provide seven Delta IIs. These were intended to launch a series of GPS Block II satellites, which had previously been manifested for the Space Shuttle. The Air Force exercised additional contract options in 1988, expanding this order to 20 vehicles, and NASA purchased its first Delta IIs in 1990 for the launch of three Earth-observing satellites. The first Delta II launch occurred in 1989, with a Delta 6925 boosting the first GPS Block II satellite into a 20,000 km high orbit. The first Delta II 7000-series flew in 1990, replacing the RS-27 engine of the 6000-series with the more powerful RS-27A. Additionally, the steel-cased Castor 4A solid boosters of the 6000 series were replaced with the composite-cased GEM 40. All further Delta II launches except three were of this upgraded configuration, and the 6000-series was retired in 1992. McDonnell Douglas began Delta III development in the mid-90s as increasing satellite mass required more powerful launch vehicles.〔 Delta III, with its liquid hydrogen second stage and more powerful GEM 46 boosters, could bring twice as much mass as Delta II to geostationary transfer orbit (GTO), but a string of two failures and one partial failure, along with the development of the much more powerful Delta IV, lead to the cancellation of Delta III program. The upgraded boosters would still find use on the Delta II, leading to the Delta II Heavy. In total, the Delta II family has launched 153 times. Its only unsuccessful launches have been Koreasat-1 in 1995, a partial failure caused by one booster not separating from the first stage, which resulted in the satellite being placed in a lower than intended orbit,〔(【引用サイトリンク】title=Koreasat 1, 2 (Mugungwha 1, 2) / Europe *Star B )〕 and another failure in 1997 when a Delta II carrying GPS IIR-1 exploded 13 seconds after launch when a damaged SRM casing ruptured and triggered the vehicle's flight termination system.〔(The Deadly Aftermath of a Rocket Explosion Seconds After Launch )〕 No one was injured, and the launch pad itself was not seriously impacted, though several cars were destroyed and a few buildings were damaged. In 2007, Delta II completed its 75th consecutive successful launch,〔(【引用サイトリンク】title=DigitalGlobe Successfully Launches Worldview-1 )〕 surpassing the 74 consecutive successful launches of the Ariane 4. With the launch of SMAP in 2015, the Delta II has enjoyed 98 consecutive successful launches, with two more scheduled.〔(【引用サイトリンク】url=http://spaceflightnow.com/delta/d367/#.U9BSVPldV8E )〕 Should these launches be successful, the Delta II would achieve an unprecedented 100 consecutive launch successes.〔(【引用サイトリンク】url=http://www.spacelaunchreport.com/delta2.html )〕 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「Delta II」の詳細全文を読む スポンサード リンク
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