The final countdown to the future of spaceflight is here. On December 14, NASA begins its search for new astronauts, who will lead a generation of deep-space explorers and potentially put the first human footprints on Mars.

Officially, NASA requires only three qualifications for astronauts: be a U.S. citizen or dual U.S. citizen; have an undergraduate degree in engineering, science or math and three years of professional experience; and pass a set of vision, blood pressure and height requirements.

Journey to the launch pad

Sounds easy, right? But getting getting selected is tougher than making your way into any top college: In the last NASA astronaut selection in 2013, eight people were selected from 6,100 applicants.

Astronaut José Hernández (NASA)

NASA astronauts come from many backgrounds. Mexican-American José Hernández grew up in California, the son of migrant farmworkers. Hernández says his parents and teachers inspired him, setting high expectations for him in school:

“I think the teachers took me to the next level, saying, ‘Hey, it’s not enough to graduate high school and get your college education. You can reach for the stars as well.'”

After becoming an engineer and applying 11 times to become an astronaut, he finally made it. In May 2004, he was asked to begin training.

For recent trips to the International Space Station, NASA astronauts have joined international partners in Texas, Russia, Japan, Canada and Germany for mission-specific training modules.

Italian astronaut Samantha Cristoforetti simulates a spacewalk in a NASA training pool in Houston. (NASA/ESA)

The astronaut application process may be the easiest part of a journey to space: Candidates typically spend five years preparing for their specific missions. After learning flight systems, simulating weightlessness, and completing language training and endless hours of preparation, Hernandez blasted off on August 28, 2009, aboard the space shuttle. Four hundred kilometers above Earth, he worked on construction of the International Space Station and also launched NASA’s first bilingual Twitter account in space.

The International Space Station, which has been occupied by astronauts from 15 countries since 2002, has built a foundation for tomorrow’s space explorers. Using the science conducted in orbit, humans will be able to launch missions to deep space and, eventually, Mars.

Think you have the right stuff? With a plan, Hernandez says, anything is possible. International astronauts selected from the space agencies of Canada, Japan, Russia, Brazil and Europe currently join NASA astronauts for missions to space.

“I think it’s in our nature to be explorers. And the next natural step is to start journeying beyond.”