He said that it was very difficult to become an astronaut. I said that I knew.  You had to become an officer in the air force and you had to take a lot of orders and be prepared to kill other human beeings,  and I couldn't take orders. Also I didn't have 20/20 vision which you needed to be a pilot. But I said that  you could still want something that is unlikely to happen.

~ The Curious Incident of the Dog In the Night Time. Mark Haddon