How Project Mercury Worked

By: Craig Freudenrich, Ph.D.

The Right Stuff

America's Mercury astronauts Top row (L-R): Shepard, Grissom, Cooper Bottom row (L-R): Schirra, Slayton, Glenn, Carpenter
America's Mercury astronautsTop row (L-R): Shepard, Grissom, CooperBottom row (L-R): Schirra, Slayton, Glenn, Carpenter
Photo courtesy NASA

In 1958, the early days of Project Mercury, it was not clear what type of person could be an astronaut. Several types were considered, including stunt men, circus performers, swimmers and race-car drivers. President Eisenhower decided that the astronauts should be military pilots, particularly test pilots. Furthermore, they should be college-educated, family-oriented, of average height and build, in excellent health and dedicated to flying advanced aircraft.

NASA officials began screening the service records of military flyers. They narrowed the field of 508 down to 110 pilots from the Marines, Navy and Air Force (no Army pilots were invited because none had graduated from a test-pilot school). Of these 110 men, 69 reported to Washington, D.C. in February 1959 for the screening tests, which included interviews (technical and psychological), written tests and medical examinations. Of these 69 men, 32 were selected and agreed to undergo further testing in Ohio and New Mexico. These tests included extensive medical and psychological evaluations, as well as stress tests in conditions such as high G-forces, vibration and isolation.


On April 9, 1959, at a press conference in Washington, D.C., NASA introduced the Project Mercury astronauts:

  • Lieutenant Malcolm S. (Scott) Carpenter (U.S. Navy)
  • Captain Leroy G. (Gordon) Cooper (U.S. Air Force)
  • Lieutenant Colonel John H. Glenn (U.S. Marine Corps)
  • Captain Virgil I. (Gus) Grissom (U.S. Air Force)
  • Lieutenant Commander Walter M. Schirra (U.S. Navy)
  • Lieutenant Commander Alan Shepard (U.S. Navy)
  • Captain Donald K. (Deke) Slayton (U.S. Air Force)

Most of the Mercury astronauts were veterans of World War II and/or the Korean War. They had extensive flight experience and were in excellent health.

Mercury astronauts during desert survival training
Mercury astronauts during desert survival training
Photo courtesy NASA

After selection, the crew underwent several years of training in the Mercury-spacecraft systems, as well as flight training, continuous medical evaluations and survival training in many environments (such as desert, jungle and ocean). They worked hard, played hard and endured many hours of separation from their families, each crew member vying to become the first American in outer space.

The astronauts became celebrities as the press and public focused on them. They made public appearances for NASA to promote the fledgling space program, and they used the public attention to increase their influence in the program.

In addition to training and public relations, they consulted on the development of the Mercury spacecraft. Despite objections from the engineers who designed the spacecraft, the astronauts insisted on having a window, manual re-entry thruster controls and an escape hatch with explosive bolts -- they wanted the ability to actively fly the spacecraft and, if necessary, escape from it. They were pilots, and the thought of merely riding in a totally automated spacecraft went against their nature.

After years of preparation, the initial flight assignments were made: Shepard would be the first American in space, followed by Grissom and then Glenn.