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Vanguard TV3 was the first attempt of the United States to launch a satellite into orbit around the Earth. It was a small satellite designed to test the launch capabilities of the three-stage Vanguard and study the effects of the environment on a satellite and its systems in Earth orbit. It was also to be used to obtain geodetic measurements through orbit analysis. At its launch attempt on December 6, 1957 at Cape Canaveral, the booster ignited and began to rise; but about two seconds after liftoff, after rising about four feet (1.2 m), the rocket lost thrust and began to fall back to the launch pad. As it settled the fuel tanks ruptured and exploded, destroying the rocket and severely damaging the launch pad. The Vanguard satellite was thrown clear and landed on the ground a short distance away with its transmitters still sending out a beacon signal. The satellite was damaged, however, and could not be reused. It is now on display at the National Air and Space Museum of the Smithsonian Institution.〔 The exact cause of the accident was not determined with certainty due to limited telemetry instrumentation at this early phase,〔 〕 but Martin-Marietta concluded that low fuel tank pressure during the start procedure allowed some of the burning fuel in the combustion chamber to leak into the fuel system through the injector head before full propellant pressure was obtained from the turbopump. GE on the other hand argued that the culprit was a loose fuel connection. The actual truth appeared to be somewhere in-between as the two seconds of telemetry data from TV-3 indicated a sudden pressure surge at ignition which caused the rupture of a fuel line. GE technicians had failed to catch this design flaw during testing and it was ultimately solved by increasing tank pressure and also injecting the LOX into the combustion chamber 3-6 seconds before RP-1 injection. The X-405 engine did not fail again on subsequent launches and static firing tests. == Satellite construction project == The history of the Vanguard TV3 project dates back to the International Geophysical Year (IGY). Initiated in 1952, orbiting a satellite became one of the main goals of the IGY. This was an enthusiastic international undertaking that united scientists globally to conduct planet-wide geophysical studies. The IGY guaranteed free exchange of information acquired through scientific observation which led to many important discoveries in the future.〔Lina Kohonen. “The Space race and Soviet utopian thinking” Sociological Review; Vol. 57, May 2009, page 114〕 As early as July 1955, President Dwight D. Eisenhower announced, through his press secretary, that the United States would launch “small, unmanned, earth-circling satellites as part of the U.S. participation in the I.G.Y.” 〔John P. Hagen, “The Viking and the Vanguard”, in Technology and Culture, Vol. 4, No. 4, (Baltimore: The Johns Hopkins University Press), Autumn 1963, page 437)〕 On September 9, 1955, the United States Department of Defense wrote a letter to the secretary of the Navy authorizing the mission to proceed. The US Navy had been assigned the task of launching Vanguard satellites as part of the program. Project Vanguard had officially begun.〔John P. Hagen, “The Viking and the Vanguard”, in Technology and Culture, Vol. 4, No. 4, (Baltimore: The Johns Hopkins University Press), Autumn 1963, page 439)〕 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 TV3」の詳細全文を読む スポンサード リンク
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