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Mercury-Redstone 3, or ''Freedom 7'' was the first United States human spaceflight, on May 5, 1961, piloted by astronaut Alan Shepard. It was the first manned flight of Project Mercury, the objective of which was to put an astronaut into orbit around the Earth and return him safely. Shepard named his capsule ''Freedom 7'', setting a precedent for the remaining six Mercury astronauts naming their spacecraft. The number 7 was included in the spacecraft name to honor NASA's first group of seven astronauts. Shepard's mission was a 15-minute suborbital flight which reached an altitude of and traveled a downrange distance of . It was the third Mercury flight launched with the Mercury-Redstone Launch Vehicle, from Cape Canaveral, Florida, close to the Atlantic Ocean. During the flight, Shepard observed the Earth and tested the capsule's attitude control system, turning the capsule around to face its blunt heat shield forward for atmospheric entry. He also tested the retrorockets which would return later missions from orbit, though the capsule did not have enough energy to remain in orbit. After re-entry, the capsule landed by parachute on the Atlantic ocean off the Bahamas. Shepard and the capsule were picked up by helicopter and brought to an aircraft carrier. The mission was a technical success, though American pride in the accomplishment was dampened by the fact that just 3 weeks before, the Soviet Union had launched the first man in space, Yuri Gagarin, who completed one orbit on Vostok 1. ==Preparation== The ''Freedom 7'' spacecraft, Mercury capsule #7, was delivered to Cape Canaveral on December 9, 1960. It had originally been expected that a mission could be launched soon after the spacecraft was available, but Capsule #7 turned out to require extensive development and testing work before it was deemed safe for flight. However, as it had been earmarked since the summer as the first crewed spacecraft, the decision was taken to delay the mission until this particular capsule was ready, with a tentative launch date of March 6, rather than use an alternative capsule.〔''This New Ocean'', p. 342〕 The booster originally intended for the flight, Redstone #3,〔''This New Ocean'', p. 342〕 had been delivered to the Cape in early December;〔Grimwood, p. 118〕 however, it was then used on the MR-1A test flight on December 19.〔Grimwood, p. 119〕 The replacement, Redstone #7, did not arrive at the Cape until late March; by this time, however, the mission had already been postponed to await the results of another test flight.〔Grimwood, p. 129〕 In late 1960, there had been a growing number of concerns about the standards of the Redstone launch vehicle; the MR-2 test flight, crewed by a chimpanzee, had had technical problems during the launch leading to the spacecraft flying too high, too far and too fast.〔''This New Ocean'', p. 315〕 As a result, the mission was two minutes longer than planned, and the re-entry subjected the passenger to 14.7g rather than the planned figure of approximately 12g. The splashdown point was sixty miles from the nearest recovery ship, and it was over two and a half hours before a helicopter could recover the capsule and its passenger - by which time it had almost sunk.〔''This New Ocean'', p. 316〕 As a result, NASA was unwilling to launch the MR-3 mission without further development work; by late February, there were still seven major alterations they had made to the booster which required testing.〔''This New Ocean'', pp. 323-4〕 An additional testing flight was accordingly added to the schedule, MR-BD (for "Booster Development"; it was originally known as MR-2A). This would launch on March 28, pushing the MR-3 flight back a month to April 25.〔''This New Ocean'', p. 324〕 The MR-BD flight was almost completely successful, ensuring that the crewed MR-3 flight could proceed without further significant delay.〔''This New Ocean'', p. 330〕 The pilot for MR-3 had been chosen several months in advance, in early January, by the head of the program, Robert R. Gilruth. He had selected Alan Shepard as the primary pilot, with John Glenn and Gus Grissom as his backups; the other members of the Mercury Seven continued to train for later missions. The three names were announced to the press on February 22 without any indication as to which of the three was expected to fly the mission.〔''This New Ocean'', p. 342〕 Shepard's name was only announced publicly after the initial launch attempt had been canceled, as Gilruth wished to keep his options open in the event that last-minute personnel changes were required.〔''This New Ocean'', p. 350〕 Glenn served as Shepard's backup on launch day,〔''This New Ocean'', p. 351〕 with Grissom focusing on training for MR-4, the next suborbital mission.〔''This New Ocean'', p. 365〕 The initial launch attempt, on May 2, was canceled due to weather problems two hours and 20 minutes before the launch time, with Shepard waiting in a hangar already suited and prepared. The flight was rescheduled for two days later, when it was delayed one more day due to inclement weather conditions, until 5 May, with an expected launch time of 7:20 a.m. EST.〔''This New Ocean'', pp. 350-351〕 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「Mercury-Redstone 3」の詳細全文を読む スポンサード リンク
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