Astronauts command spacecraft and high-altitude vehicles that venture into space. Astronauts come from a variety of fields, train for a year or two on the chance of being chosen as a member of a shuttle crew, and then return to their original jobs. They rise early and work late into the night, training for potential space missions during which as many hours as possible will be utilized for intensive experimentation. This stamina comes in handy. Most astronauts only sleep for five hours at a time on their missions. Astronauts-in-training participate in scenarios that simulate weightlessness, heavy gravity (excessive G-forces) and navigate nature's call in an unbroachable interstellar suit. Intensive psychological screening, required of all applicants, is supposed to weed out those with claustrophobia, but one or two are discovered annually in the program and dismissed. Other unusual skills astronauts learn include eating and drinking through straws, washing their entire bodies with a hand cloth, and sleeping in a noisy environment, buckled to a bed so they don't float around the craft uncontrollably. Nearly every basic task taken for granted on earth offers unusual difficulties in space and must be relearned. This retraining of basic skills is a difficult coming-down for those scientists--many of whom are Ph.D.s--who are used to navigating more intellectual and more ostensibly difficult tasks. Roughly ten candidates per year are asked to leave because they cannot master these basic maneuvers.
The ability to focus is the most important feature of the successful astronaut, but the ability to make choices under pressured and limited-option situations is also important. In only rare circumstances does an Apollo 13-type crisis situation come to pass; more often, the most difficult decision an astronaut faces is how to juggle a variety of experiments in limited time. Members of shuttle launches (the only space missions of the 1990s) overschedule their time in the event that their mission is delayed; since this is often the case, every potential free moment is scheduled.
The ability to work as part of a team is enormously important, and much of the training associated with becoming an astronaut focuses on developing this team mentality and working together in a cramped environment. The rigorous training fosters a strong sense of camaraderie. While only a few make the final cut to be members of a space-bound crew (the constituency is based on the needs of the mission), over one hundred people train at any given time at the Johnson Space Center, in Houston, Texas. They live, train, eat and exercise together, many of them working in concert on research projects that have components that can only be completed in space. The environment is said to be supportive and mutually encouraging, partly because each astronaut has no idea who will be picked to be a crew member on the next mission, and who they might be paired with.
Nearly every child dreams, at one time or another, of becoming an astronaut, but few carry this dream through to adulthood, and for a good reason: It's damn tough to become an astronaut. Requirements include an excellent academic record (undergraduate and graduate) in any of a number of scientific fields, including aerospace engineering, medicine, biology, chemistry, physics, astronomy, optics, and computer science. Candidates are usually very accomplished in another field before they apply to become astronauts. They must be in excellent shape physically and mentally, between 5'4'' and 6'4'' tall, and be willing to spend a full year training for a space mission. They must also be willing to brave the odds, because in any given year, the greatest number of NASA astronauts that has been assigned to a flight was sixteen. Their year of rigorous training offers no guarantee of being assigned as a crew member on a mission. Most importantly, applicants must pass the NASA standards for astronauts, which includes jet-pilot qualifications and flight experience, a rigorous security check and an in-depth personality profile. The average shuttle launch costs one billion--that's right, BILLION--dollars. Since NASA is footing the bill, they tend to be quite selective about who they offer seats to. Of the eleven to twelve thousand people each year who apply to become astronauts, only between one and two hundred make it through the difficult screening.
Most return to research, teaching, flying, or the military, whatever their occupations were prior to becoming an astronaut; a few, like Senator John Glenn, enter politics. The major difference between becoming an astronaut and going into other professions is that the former is an end in and of itself. One does not progress or advance from being an astronaut; one returns to normal life. Astronauts occasionally become celebrities due to their unusual status, and a few parlay their fame into media-supported careers.