Astronaut John Glenn was one of the Mercury Seven, the first Americans trained for spaceflight. Before Glenn became the first American to orbit the Earth in his Friendship 7 mission on February 20, 1962, he went through a lot of training.
In 1962, space travel wasn't what you'd call an "exact" science. NASA was only a few years old and nobody really knew how humans would cope outside the atmosphere. Now, 50 years after his historic orbit, John Glenn recalls what his doctors thought would happen in zero gravity.