21. Having two years of training
It takes about two years for an astronaut candidate to complete training. This includes training in surviving in water, robotics skills, and space physiology and medicine.
22. Having military experience — though it’s not essential
Having military experience on your application is not a necessity, but it doesn’t hurt. John Glenn, the first American to orbit Earth and oldest man to fly into space (he joined the shuttle Discovery mission in 1998 at the age of 77), served with the Marines. When NASA selected its first group of astronauts in 1959, they sought test pilots from the military.
23. Showing curiosity and energy
NASA wants its astronauts to show curiosity and energy. Curiosity is important for NASA. No wonder the agency named its Mars rover “Curiosity.”
24. Distinguishing yourself from the competition
With so many people applying for so few astronaut opportunities, candidates who excel at a particular hobby or avocation — such as an athletic skill or a musical talent — have an advantage when the NASA committee considers their candidacy
25. Being a U.S. citizen
Applicants for the U.S. astronaut program must be American citizens. NASA also accepts candidates with valid U.S. dual citizenship.