NASA
The old fashioned way to becoming an astronaut is to go through NASA. Applicants can come from either military or civilian backgrounds, though this job is only open to U.S. citizens. You will need to have a bachelor’s degree in engineering, biology, physical science, or math and at least three years of job experience or 1,000 hours of pilot-in-command time in a jet aircraft (whichever comes first).
There are currently 52 active astronauts at NASA and another 41 employed at the agency who are no longer eligible for flights. This is down from an all-time-high of 149 in 2000. NASA has scaled down their astronaut corps since the retirement of the space shuttle fleet. Each new class of astronauts gets a funny nickname, such as “The Maggots,” “The Flying Escargot,” “The Penguins,” and, most recently, “The Chumps.”
NASA opens up its astronaut selection ever few years and gets plenty of qualified applicants. The agency will be announcing the results of its latest search, which closed in January 2012, during the summer. They usually have another round of astronaut hires every few years.
Chances of becoming an astronaut this way: 1-3 in 600 (< .17 percent)*
NASA is still your best bet for becoming an astronaut. Each new round, NASA gets 2,000-6,000 applicants, and usually no more than 10 become actual astronauts. This means your odds are not too bad at 1-3 in 600 (< .17 percent).
Image: NASA