Over the years, NASA has shifted is requirements for aspiring astronauts. In the past, it sought applicants with military backgrounds and thousands of hours manning a military air craft; today, the national space agency uses a broader spectrum when selecting its next trainee, according to a USA Today report.

That shift began in 1978, according to USA Today. Current astronauts resemble people like Jeanette Epps, an aerospace engineer major who worked at Ford Motor Company and the CIA before joining NASA. Space travelers of the past kept to their individual assignments during the period of shuttle missions, today's astronauts are expected to be competent in all areas. Well-rounded candidates are key, USA Today reported.

"I think our crazy, varied backgrounds contribute to our ability to adapt and learn anything quickly, and then assimilate that knowledge into our skill set," Epps told USA Today.

"If a student comes to me and says, 'I want to be an astronaut,' I tell them, 'Great: Excel in your coursework, go get a piloting license and learn to play the guitar,'" said John Armstrong, a professor of physics at Weber State University.

Not only are candidates versatile, they "excel at everything they do", according to Valerie Neal, curator at the Smithsonian National Air and Space Museum. "They tend to undertake whatever they do with the full force of their abilities to reach a level of excellence," Neal added.

In addition to a distinguished background, potential astronauts must impress on the interview, wrote USA Today. "It comes down to how much of a positive impression you make on the interview panel," said Tom Jones, a former NASA astronaut.

Even then, interviewees must pass a physical with specific requirements for height, weight, and blood pressure - requirements largely out of their control

No matter how strong an applicant is, however, the competition is fierce. This year, NASA received over 6,000 applications; only eight became astronauts, according to USA Today.

NASA has kept some its basic requirements, All astronauts must carry a degree in math, engineering, or science. Most, of course, have multiple degrees and doctorates.