|John Glenn sitting in a rotating chair for a "disorientation" test (1961) (NASA)|
|Glenn at the entrance to an altitude test chamber (1961) (NASA)|
NASA needs to make sure. The country is counting on success. Astronaut training is difficult. In one test, the astronauts are spun around at high speed until the pressure on their bodies is 16 times that of their own weight. Glenn writes to a friend, "It took just about every bit of strength and technique to retain consciousness."
A NASA plane, dubbed the Vomit Comet, flies up and then down like a roller coaster. At the top of each arc, the men are weightless. Instead of getting sick, Glenn does flips and walks on the ceiling. He says, "I have finally found the element in which I belong."