Mercury-Redstone 3

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 crewed flight of Project Mercury. The project had the ultimate objective of putting an astronaut into orbit around the Earth and returning him safely. Shepard's mission was a 15-minute suborbital flight with the primary objective of demonstrating his ability to withstand the high g-forces of launch and atmospheric re-entry.

Shepard named his space capsule Freedom 7, setting a precedent for the remaining six Mercury astronauts naming their spacecraft and the format of their names, the number 7 later included in all the crewed Mercury spacecraft names not to honor NASA's first group of seven astronauts but it stood for the McDonnell Model #7 space capsule used in the Mercury Program. His spacecraft reached an altitude of 101.2 nautical miles (116.5 statute miles, 187.5 km) and traveled a downrange distance of 263.1 nautical miles (302.8 statute miles, 487.3 km). It was the fourth 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 re-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 North Atlantic Ocean off the Bahamas. Shepard and the capsule were picked up by helicopter and brought to U.S. Navy aircraft carrier USS Lake Champlain.

The mission was a technical success, though American pride in the accomplishment was dampened by the fact that just three weeks before, the Soviet Union had launched the first human in space, Yuri Gagarin, who completed one orbit on Vostok 1. In 2017 the first National Astronaut Day was held on May 5 to pay tribute to this first U.S. flight.

The spacecraft for MR-3, 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. The booster originally intended for the flight, Redstone #3, had been delivered to the Cape in early December; however, it was then used on the MR-1A test flight on December 19. 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.

In late 1960, there had been a growing number of concerns about the safety of the Redstone launch vehicle; the MR-2 test flight, carrying Ham the chimpanzee, had experienced technical problems during the launch, leading to the spacecraft flying too high, too far and too fast. As a result, the mission was two minutes longer than planned, and the re-entry subjected Ham 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. 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. 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. The MR-BD flight was almost completely successful, ensuring that the crewed MR-3 flight could proceed without further significant delay.

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 (Navy) as the primary pilot, with John Glenn (Marine) and Gus Grissom (Air Force) 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. 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. Glenn served as Shepard's backup on launch day, with Grissom focusing on training for MR-4, the next suborbital mission.

Captain Shepard dubbed his capsule "Freedom 7". Per Shepard, "Pilots have always named their planes. It's a tradition. It never occurred to me not to name the capsule." Shepard discussed the name with his wife, Louise, backup pilot John Glenn, and Robert R. Gilruth, and all liked it.