30 September 2009 – 11 October 2009 (ISS) Jared Isaacman (American): 15–18 September 2021 (Free Flier) Yusaku Maezawa (Japanese): 8 – 24 December 2021 (ISS) Training The first NASA astronauts were selected for training in 1959. Early in the space program, military jet test piloting and engineering training were often cited as prerequisites for selection as an astronaut at NASA, although neither John Glenn nor Scott Carpenter (of the Mercury Seven) had any university degree, in engineering or any other discipline at the time of their selection. Selection was initially limited to military pilots. The earliest astronauts for both the US and the USSR tended to be jet fighter pilots, and were often test pilots. Once selected, NASA astronauts go through twenty months of training in a variety of areas, including training for extravehicular activity in a facility such as NASA's Neutral Buoyancy Laboratory. Astronauts-in-training (astronaut candidates) may also experience short periods of weightlessness (microgravity) in an aircraft called the "Vomit Comet," the nickname given to a pair of modified KC-135s (retired in 2000 and 2004, respectively, and replaced in 2005 with a C-9) which perform parabolic flights. Astronauts are also required to accumulate a number of flight hours in high-performance jet aircraft. This is mostly done in T-38 jet aircraft out of Ellington Field, due to its proximity to the Johnson Space Center. Ellington Field is also where the Shuttle Training Aircraft is maintained and developed, although most flights of the aircraft are conducted from Edwards Air Force Base. Astronauts in training must learn how to control and fly the Space Shuttle and, it is vital that they are familiar with the International Space Station so they know what they must do when they get there. NASA candidacy requirements The candidate must be a citizen of the United States. The candidate must complete a master's degree in a STEM field, including engineering, biological science, physical science, computer science or mathematics. The candidate must have at least two years of related professional experience obtained after degree completion or at least 1,000 hours pilot-in-command time on jet aircraft. The candidate must be able to pass the NASA long-duration flight astronaut physical. The candidate must also have skills in leadership, teamwork and communications. The master's degree requirement can also be met by: Two years of work toward a doctoral program in a related science, technology, engineering or math field. A completed Doctor