The Seven in front of an Air Force craft. Glenn is third from left. (NASA)

The Seven in their Mercury spacesuits (NASA)

In 1958, the newly formed National Aeronautics and Space Administration (NASA) needs astronauts. President Eisenhower and the U.S. Congress have made it NASA's job to put the first human into space and restore America's standing in the world. President Eisenhower tells NASA to choose only military test pilots. Astronaut candidates must be no taller than 5 feet 11 inches, between the ages of 25 and 40, and have at least 1,500 hours of flying time.

NASA considers 508 servicemen. During tests, these pilots are shaken, blasted with noise, made to sit with their feet in ice water, and forced to blow up balloons until they are exhausted.

Finally, on April 9, 1959, NASA chooses seven astronauts — who instantly become famous as the Seven. John Glenn, Jr. is one of them. At 37, he is the oldest and holds the highest military rank — Lieutenant Colonel in the Marines. Born July 18, 1921, in Cambridge, Ohio, Glenn flew combat missions in both World War II and the Korean War. The red headed, freckle-faced man and his wife Annie have a teenaged son and daughter.

The astronaut candidates are asked to recommend one of their classmates to take their place if they themselves aren't selected to go to space. If you had to do the same, what criteria would you use to make your choice?