About 3,200 civil servants, including 110 astronauts, are employed at Johnson Space Center. The bulk of the workforce consists of over 11,000 contractors. As of October 2014, Stinger Ghaffarian Technologies took over United Space Alliance's primary contract.[32] As of May 2018, the center's 12th director is Mark S Geyer,[33] the first being Robert Gilruth.[cần dẫn nguồn]

NASA's astronaut training is conducted at the Johnson Space Center. Astronaut candidates receive training on spacecraft systems and in basic sciences including mathematics, guidance and navigation, oceanography, orbital dynamics, astronomy, and physics.[30] Candidates are required to complete military water survival prior to beginning their flying instruction. Candidates are also required to become scuba-qualified for extravehicular training and are required to pass a swimming test.[34][35] EVA training is conducted at the Sonny Carter Training Facility. Candidates are also trained to deal with emergencies associated with hyperbaric and hypobaric atmospheric pressures and are given exposure to the microgravity of space flight.[30] Candidates maintain their flying proficiency by flying 15 hours per month in NASA's fleet of T-38 jets based at nearby Ellington Field.[cần dẫn nguồn]