It is interesting how NASA chose their astronauts for landing on the moon. They chose men between the age of twenty and thirty­five. There were about fifty of them. Many were experienced (有经验的，熟练的) air pilots. Others were scientists with two or three degrees. NASA telephoned each man they were going to choose and told him the dangers he might get in. They then asked him if he was willing to be trained as an astronaut."How could any man refuse such an exciting job？"

　　The health and physical conditions of pilots were, of course, very necessary. Only those in very good health and physical condition were chosen.

　　While being trained to be astronauts, they went through many courses. They studied the star and the moon, and they also studied geology, the science of rocks. They were all trained to fly in helicopters. These helicopters landed directly down to give them some experience of the way the spaceship would really land on the moon. They were also taught the unknown facts about the conditions in space. They visited the scientists and engineers who designed the spaceships and rockets. They visited the factories where the spaceships and rockets were built. They learnt how every part of a spaceship and its instruments work. They also learnt every detail of the ground­control system.

In a word, to be chosen as an astronaut, one must be in good health, well­informed in science and good at piloting.