Mercury-Atlas 9 was the fourth and final manned orbital flight of the Mercury program. The flight objectives were to:
(1) evaluate the effects on the astronaut of approximately one day in orbital flight;
(2) verify that man can function for an extended period in space as a primary operating system of the spacecraft; and,
(3) evaluate in a manned one-day mission the combined performance of the astronaut and a Mercury spacecraft specifically modified for the mission…
Mercury-Redstone 4 was the fourth mission in the Mercury-Redstone series and the second U.S. manned suborbital spaceflight. The mission was essentially a repeat of Alan Shepard’s Freedom 7 flight. So why was it necessary to launch another sub-orbital mission? Why not proceed with an orbital flight to match the Soviet Vostok 1? Among other things the U.S. needed more space experience to corroborate the “Man-in-Space” concept. Also the Redstone was the only booster NASA had that was approved for manned launches. The Atlas booster was available but not ready. Atlas was capable of putting a Mercury Capsule into orbit, but it had been launched three times with unmanned capsules, and it had exploded on 2 of the 3 attempts.
Over 52 years ago, in the early hours of May 5th, 1961 the US prepared to launch its first man into space. Three weeks earlier, the Soviet Union had sent Yuri Gagarin on an orbital mission. This was a suborbital mission planed to last only 15 minutes. For the moment that did not matter, the entire nation held its breath while Alan Shepard became America’s first man in space.
“The designers made the Little Joe booster assembly to approximate the same performance that the Army’s Redstone booster would have with the capsule payload. But in addition to being flexible enough to perform a variety of missions, Little Joe could be made for about one-fifth the basic cost of the Redstone, would have much lower operating costs, and could be developed and delivered with much less time and effort. And, unlike the larger launch vehicles, Little Joe could be shot from the existing facilities at Wallops Island.”