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The Vanguard rocket〔( "The Vanguard Satellite Launching Vehicle — An Engineering Summary". B. Klawans. April 1960, 212 pages. ) Martin Company Engineering Report No 11022, PDF of an optical copy.〕 was intended to be the first launch vehicle the United States would use to place a satellite into orbit. Instead, the Sputnik crisis caused by the surprise launch of Sputnik 1 led the U.S., after the failure of Vanguard TV3, to quickly orbit the Explorer 1 satellite using a Juno I rocket, making Vanguard I the second successful U.S. orbital launch. Vanguard rockets were used by Project Vanguard from 1957 to 1959. Of the eleven Vanguard rockets which the project attempted to launch, three successfully placed satellites into orbit. ==Overview== In 1955, the USA announced plans to put a scientific satellite in orbit for the International Geophysical Year (IGY) in 1957–1958. The goal was to track the satellite as it performed experiments. At that time there were three candidates for the launch vehicle: The Air Force's SM-65 Atlas, a derivative of the Army Ballistic Missile Agency's SSM-A-14 Redstone, and a Navy proposal for a three-stage rocket based on the RTV-N-12a Viking sounding rocket.〔 The Army's Redstone-based proposal would likely be first ready for a first satellite launch. Its connection with German-born scientist Wernher von Braun, however, was a public-relations risk.〔Correll, John T. "(How the Air Force Got the ICBM )" ''Air Force'', July 2005.〕 In any case, the Atlas and Redstone ballistic missiles were top-priority military projects, which were not to be slowed by pursuing a secondary space launch mission. Milton Rosen's Vanguard was a project at the Naval Research Laboratory (NRL), which was regarded more as a scientific than a military organization. Rosen and Richard Porter (IGY satellite chief and head of the American Rocket Society) both lobbied for the Vanguard and against using the Altas or von Braun's rockets.〔Drew Pearson, "USA Second Class Power?", Simon & Schuster, 1958〕 They emphasized the non-military goals of the satellite program. Besides the public-relations aspect, a non-military satellite was considered important, because a discussion of whether overflights of foreign countries by satellites were legal or illegal was to be avoided.〔McDougall, Walter A., (1985) ...the Heavens and the Earth〕 In August or September 1955, the DOD Committee on Special Capabilities chose the NRL proposal, named Vanguard, for the IGY project. The Martin company, which had also built the Viking, became prime contractor for the launch vehicle.〔("Satellite Rocket Will Resemble Shell." ) ''Popular Mechanics'', June 1956, p. 70.〕 The Vanguard rocket was designed as a three-stage vehicle. The first stage was a General Electric X-405 liquid-fueled engine (designated XLR50-GE-2 by the Navy), derived from the engine of the RTV-N-12a Viking. The second stage was the Aerojet General AJ10-37 (XLR52-AJ-2) liquid-fueled engine, a variant of the engine in the RTV-N-10 Aerobee. Finally, the third stage was a solid-propellant rocket motor. All three-stage Vanguard flights except the last one used a motor built by the Grand Central Rocket Company. Vanguard had no fins, and the first and second stages were steered by gimbaled engines. The second stage also housed the vehicle's telemetry system, the inertial guidance system and the autopilot. The third stage was spin-stabilized, the spin being imparted by a turntable on the second stage before separation. 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「Vanguard (rocket)」の詳細全文を読む スポンサード リンク
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