NASA Astronaut Corps their home agency but trained with and serve alongside their NASA counterparts. International astronauts, Payload Specialists, and Spaceflight Participants are not considered members of the NASA Astronaut Corps. The term "Astronaut Candidate" (informally "ASCAN") refers to individuals who have been selected by NASA as candidates for the NASA Astronaut Corps and are currently undergoing a candidacy training program at the Johnson Space Center. The most recent class of Astronaut Candidates was selected in 2017 after receiving more than 18,300 applications. Upon completion of a two-year training program, they will be promoted to the rank of Astronaut. Selection as an Astronaut
Astronaut training the ISS. The Tsukuba Space Center also includes medical facilities for assessing suitability of candidates, an isolation chamber for simulating some of the mental and emotional stressors of long duration spaceflight, and a hypobaric chamber for training in hull breach or Life Support System failure scenarios resulting in a reduction or loss of air pressure. Although official detail of the selection process for the Shenzhou program is not available, what is known is that candidates are chosen by the Chinese National Space Administration from the Chinese air force and must be between 25 and 30 years of age, with a