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The UGM-133A Trident II, or Trident D5 is a submarine-launched ballistic missile, built by Lockheed Martin Space Systems in Sunnyvale, California, and deployed with the US and Royal Navies. It was first deployed in March 1990,〔 and is still in service. The Trident II Strategic Weapons System is an improved Submarine Launched Ballistic Missile with greater accuracy, payload, and range than the Trident C-4, strengthening U.S. strategic deterrence. The Trident II is considered to be a durable sea-based system capable of engaging many targets. It enhances the U.S. position in strategic arms negotiation with performance and payload flexibility that can accommodate active treaty initiatives (See New START). The TRIDENT II's increased payload allows nuclear deterrence to be accomplished with fewer submarines.〔(【引用サイトリンク】url=http://www.dod.mil/pubs/foi/logistics_material_readiness/acq_bud_fin/SARs/2012-sars/13-F-0884_SARs_as_of_Dec_2012/Navy/Trident_II_Missile_December_2012_SAR.pdf )〕 Trident II missiles are carried by 14 US and 4 British s, with 24 missiles on each ''Ohio'' class and 16 missiles on each ''Vanguard'' class. was the first submarine to be armed with Trident IIs, and there have been 157 successful test flights of the D5 missile since design completion in 1989, the most recent being from the in November 2015.〔http://www.sandiegouniontribune.com/news/2015/nov/07/mystery-light-sky-military-navy-drill/〕 The D5 is the sixth in a series of missile generations deployed since the sea-based deterrent program began 60 years ago. It is estimated that 540 missiles will be built by 2013. The Trident D5LE (life-extension) version will remain in service until 2042.〔 〕 ==History== The Trident II was designated to be the latest longer-range missile, performing greater than its predecessor (Trident C-4). In 1972, the US Navy projected an initial operating capability (IOC) date for the Trident II in 1984. The US Navy continued to advance the IOC date to 1982. On 18 October 1973, a Trident program review was administered. On 14 March 1974, the US Deputy Secretary of Defense disseminated two requirements for the Trident program. The first was an accuracy improvement for the Trident C-4. The second requirement asked for an alternative to the C-4, or a new Trident II missile with a larger first stage motor than the C-4. Studies were conducted to determine whether the more-expensive Trident II could be constructed similar to the US Air Force's MX ICBM. This was done primarily to decrease budget costs. It was established that the Trident II would be 83 inches in diameter and 44 ft in length in order to maintain performance with the existing MX ICBM. Modifications to the guidance system, electronics hardening, and external protective coatings were incorporated into the design. While this satisfied the US Naval study requirements, it did not accommodate the US Air Force payload requirements. Propulsion stages were proposed to be used between the first stage and second stage motors, effectively making the Trident II a longer three-stage missile than the C-4. Studies were delayed in 1978 when Congress only approved $5 million of the suggested $15 million for the Naval/Air Force program studies. By December 1978, the US Navy and Air Force studies agreed that the savings made by a similar missile structure would not be effective. It was determined that the US Navy and Air Force maintain and be responsible for their own unique weapon systems. The US Navy continued with their own weapon design of the Trident II. In March 1980, US Secretary of Defense Harold Brown proposed an increased level of funding for the submarine-launched ballistic missile modernization. Emphasis was strained for the need of increased accuracy. The House Armed Services Committee (HASC) recommended no funding, while the Senate Armed Services Committee (SASC) recommended full funding of $97 million. The SASC asked for a plan which incorporates "the fullest possible competition... (and) should consider competing among contractors for each major component, including the integrated missile." $65 million was awarded for the submarine-launched ballistic missile modernization. On 2 October 1981, President Reagan called for the modernization of the strategic forces.〔(【引用サイトリンク】title=Remarks and a Question-and-Answer Session With Reporters on the Announcement of the United States Strategic Weapons Program )〕 The Defense Department directed the Navy to fund all development of the Trident II D5 missile with a December 1989 IOC. All research and development effort would be directed toward "a new development, advanced technology, high accuracy Trident II D5 system." In December 1982, Deputy SECDEF Frank Carlucci advised Secretary of the Navy Caspar Weinberger to include funding for a new RV/warhead combination for Trident II. The reentry vehicle was to be designated as the Mk 5, which was to have an increased yield than the Mk 4. The development contract for Trident II was issued in October 1983. On 28 December 1983, the Deputy SECDEF authorized the Navy to proceed with Full Scale Engineering Development of the Trident II D5. The first Trident II launch occurred in January 1987, and the first submarine launch was attempted by ''Tennessee'',〔 the first D-5 ship of the ''Ohio'' class, on 21 March 1989 off the coast Cape Canaveral, Florida. The launch attempt failed four seconds into the flight because the plume of water following the missile rose to greater height than expected, resulting in water being in the nozzle when the motor ignited. Once the problem was understood, relatively simple changes were quickly made, but the problem delayed the IOC of Trident II until March 1990.〔 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「UGM-133 Trident II」の詳細全文を読む スポンサード リンク
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