The potential astronauts were chosen from 18,300 applications -- twice as many as the previous record -- whose only requirements were a bachelor's degree in a STEM field, three or more years in a related field (or a thousand hours of flight time in a jet aircraft) and the ability to pass NASA's physical. The candidates will spend two years training, simulating spacewalks in deep pools, learning to fly NASA test craft and taking a host of scientific and expeditionary courses before they will be considered for official missions. These may include trips to the ISS, the moon or to other planets in an Orion capsule atop NASA's Space Launch System -- all wearing the next generation of space suits and protective gear.

As NASA's FAQ notes, this will be the 22nd class of astronauts since the first batch was recruited in 1959 for the Mercury project that put the first American and second human, Alan Shepard, into space. Other milestone classes include the eighth in 1978 that included the first female, African American and Asian American astronauts, and the 21st class in 2013, which was the first to achieve a 50/50 gender ratio. Future groups might get a headstart if more programs like Lockheed Martin's Generation Beyond start preparing tomorrow's astronauts in middle school.