Selection of the Mercury astronauts began in January 1959. Due to the rigors of space travel, only military test pilots from the U.S. Air Force, Navy, and Marine Corps were considered for America's first manned space program.
110 men from a total of 508 service records screened met the basic requirements.
Candidates had to be younger than 40, no taller than 5' 11", and weigh no more than 180 pounds (due to the small size of the Mercury space capsule). They were also required to hold a bachelor's degree in engineering, have graduated test pilot school, and have 1,500 hours of flying time.
Thirty-two men who made it through a tough interview process in Washington, D.C, were sent to Lovelace Clinic in Albuquerque, New Mexico, where psychological and physical tests were conducted.
next slide will load in 15 secondsSkip AdSkip AdHere, doctors performed over 30 different lab tests.
Test pilots were poked, probed, and measured for things like blood volume, water volume and total-body radiation count.
After one week of medical evaluations, the pilots were shipped off to Wright Air Development Center for Phase 4 of the selection program.
Each candidate had to prove his physical endurance through an elaborate series of vibration, heat, and pressure tests.
A candidate prepares to be whipped around in a human centrifuge, used to expose astronauts to g-forces they would experience during launch and re-entry.
next slide will load in 15 secondsSkip AdSkip AdFeet are submerged in ice water to see how it affects pulse and blood pressure.
Candidates must perform this movement for five minutes.
Then walk on an treadmill as the incline increases one degree every minute.
Candidates were evaluated on their responses to questions like "Who am I?" and "Whom would you assign to the mission if you could not go yourself?"
Only seven men made it through the exhaustive physical and mental exams.
next slide will load in 15 secondsSkip AdSkip AdNASA introduced the "Mercury Seven" to the public at a press conference in Washington, D.C. On April 9, 1959.
That month, the Original Seven reported to the Manned Spacecraft Center in Texas (later named the Johnson Space Center), for two years of training.
During the training period, astronauts spent hours in the classroom mastering the details of the Mercury craft and learning more about meteorology and engineering.
Contraptions like the Gimbal Rig simulated an uncontrolled spin in space flight. Nitrogen-gas jets twisted three aluminum cages around at speeds up to 30 revolutions per minute. The pilot was strapped into a plastic seat at the center of the cage, leaving only his arms free.
Zero-gravity flights, nicknamed the "vomit comet" because of the nausea it often produces, were used to simulate weightlessness.
next slide will load in 15 secondsSkip AdSkip AdTo prepare for landing off-course, the astronauts were left in the Nevada desert for four days with a mockup of the Mercury spacecraft, a parachute and a survival scenario. They emerged with clothing made out of the parachute material and beards.
Their training efforts ultimately paid off. On May 5, 1961, Alan Shepard became the first American in space, aboard Freedom 7.
Over the next two years, six of the Original Seven (Slayton was the exception) flew Mercury missions. The five-year-program, which also included five unmanned flights, paved the way for future human space travel.
Now remember the first man on the moon.