Astronauts, Types of

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Astronauts, Types of

Astronauts are persons trained to fly or operate systems aboard a spacecraft. "Astronaut" is the term typically applied to those who fly on U.S. spacecraft, whereas "cosmonaut" refers to crewmembers who have flown on Russian space vehicles. The National Aeronautics and Space Administration (NASA) selected the first American astronauts in 1959 to pilot the single-seat Mercury spacecraft. These "Original 7" were all chosen from the ranks of military test pilots.

Qualifications for these first astronauts were extremely high. Not only were the Mercury and Gemini astronauts professional test pilots, but they also had to meet strict standards for eyesight, health, and physical size (because of the tight confines of the spacecraft cockpits). In advance of the Apollo Moon landings, six scientists were selected for astronaut training in 1965, but only one made it to the lunar surface (compared with eleven former test pilots) before the Apollo program ended in 1972.

NASA drew up new qualifications for astronauts in 1978, with the advent of the space shuttle. The shuttle cabin could handle crews of up to seven astronauts, and its varied missions required a broader mix of skills from an array of technical backgrounds. Scientists, engineers, and physicians were now eligible for selection, and prior flying experience was no longer mandatory. Current shuttle astronaut candidates apply for one of two career positions: pilot astronaut or mission specialist astronaut.

Pilot astronauts have primary responsibility for guiding the space shuttle safely to and from orbit. Pilot astronaut candidates must have professional test piloting experience; most gain that skill in the military. Shuttle pilots monitor the controls during liftoff, maneuver the spacecraft in orbit, guide the shuttle to dockings with the space station , and fly the shuttle back to a precision runway landing. Pilot astronauts fly first as a copilot and, with experience, advance to command of a shuttle mission.

Mission specialist astronauts train to operate the space shuttle's experiment payloads and conduct a variety of activities in orbit. They have primary responsibility for science tasks and assist the pilots with spacecraft operations. Mission specialists maneuver the shuttle's robot arm to release or retrieve satellites. They also conduct space walks for satellite repairs or space station construction. Experienced mission specialists serve as "payload commanders," responsible for controlling a major scientific payload or suite of experiments.

A typical shuttle crew is composed of two pilots and anywhere from three to five mission specialists, depending on the mission's complexity. The crew trains intensively as a team for a year or more to prepare for a mission. The crew may include a "payload specialist," a scientist or engineer from outside the astronaut corps, selected to operate a specific experiment aboard one or two shuttle flights.

Space station crews consist of a commander and two or more flight engineers, with the role of the latter being similar to that of mission specialists. Station crewmembers are drawn from the astronaut corps of the United States, Russia, and the other countries that are international partners. Another category of astronaut—one involved in commercial activities—may soon go to work aboard the International Space Station.

see also Career Astronauts (volume 1); Careers in Spaceflight (volume 3); Cosmonauts (volume 3); Mission Specialists (volume 3); Payload Specialists (volume 3).

Thomas D. Jones