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.
The objectives of the Mercury Project, were as follows:
1. Place a manned spacecraft in orbital flight around the earth.
2. Investigate man’s performance capabilities and his ability to function in the environment of space.
3. Recover the man and the spacecraft safely.
After the objectives were established for the project, a number of guidelines were created to insure that the most expedient and safest approach for attainment of the objectives was followed. The basic guidelines that were established are as follows:
1. Existing technology and off-the-shelf equipment should be used wherever practical.
2. The simplest and most reliable approach to system design would be followed.
3. An existing launch vehicle would be employed to place the spacecraft into orbit. 4. A progressive and logical test program would be conducted.