How Astronauts Train for Spaceflight

A trip to orbit may last only a few minutes, but the preparation behind it takes years.

Before astronauts ever strap into a rocket, they have rehearsed spacewalks underwater, floated in diving airplanes,

learned new languages and practiced surviving in a frozen forest in case their capsule lands off course.

From the way candidates are chosen to the specialized drills that turn them into crew members ready for a mission,

here is what that long preparation involves.

Getting Selected in the First Place

Space agencies choose astronauts rarely, and competition is fierce.

When an agency opens applications, thousands of people may apply for a small handful of places.

Exact requirements vary between agencies and have changed over time, but NASA's recent calls give a good idea of what is expected:

• A degree in a science, technology, engineering or mathematics field, typically at the master's level, or equivalent qualifications such as a medical degree or test pilot school.
• Several years of relevant professional experience, or substantial time flying jet aircraft as pilot in command.
• The ability to pass a demanding spaceflight medical examination.
• Strong teamwork, communication and problem-solving skills, assessed through interviews and group exercises.

Candidates do not need to be elite athletes, but they must be healthy and fit.

Agencies look just as hard at temperament: calm under pressure,

adaptable and easy to live with in a very small space for a very long time.

The selection process itself can take a year or more.

It moves from written applications to interviews, medical tests and group exercises for a shortlist of finalists,

and many successful astronauts applied more than once before being chosen.

Basic Training: Back to School

New recruits are called astronaut candidates, and at NASA their basic training typically lasts about two years.

Much of it happens in classrooms.

Candidates study spacecraft systems, orbital mechanics, space station hardware, Earth science, astronomy and space medicine.

Language is part of the package too.

Because crews on the International Space Station have worked closely with Russian partners and flown on Russian spacecraft,

many astronauts have learned Russian, while cosmonauts have learned English.

Candidates also practice public speaking, since sharing their missions with students and the public is part of the job.

Medical skills matter as well.

Crews may be days away from a hospital, so selected members learn to take blood samples, give injections,

handle basic injuries and use equipment such as ultrasound machines while doctors on the ground guide them.

Rehearsing Spacewalks Underwater

The closest thing to floating in space that you can experience on Earth for hours at a time is being neutrally buoyant in water: not sinking,

not rising. NASA's Neutral Buoyancy Laboratory in Houston is one of the largest indoor pools in the world,

about 12 meters (40 feet) deep and holding roughly 23 million liters (6.2 million gallons) of water.

Full-size mockups of space station modules rest on the bottom.

Astronauts in pressurized spacesuits are lowered into the water, where divers adjust weights and floats until the suits neither sink nor rise.

Then crews rehearse every step of a planned spacewalk, often for six hours at a time, while safety divers watch closely.

Other agencies run similar pools, including facilities near Moscow and in Cologne, Germany.

The simulation is not perfect.

Water creates drag that space does not, and inside the suit an astronaut can still feel gravity pulling them toward the helmet when upside down.

Still, rehearsing each task many times underwater is one of the main reasons real spacewalks go smoothly.

Tasting Weightlessness on Parabolic Flights

For genuine weightlessness without leaving the atmosphere, agencies use specially modified airplanes.

The aircraft climbs steeply, then pushes over into an arc that briefly matches the path of a falling object.

For roughly 20 to 25 seconds, everyone inside floats freely.

The plane then pulls out of its dive and repeats the maneuver again and again during a single flight.

These short bursts let astronauts practice eating, drinking, moving and handling equipment without gravity.

The flights have earned the nickname "vomit comet" for good reason.

Some flights also fly shallower arcs that mimic the partial gravity of the Moon or Mars.

Simulators, Emergencies and Robotics

Much of an astronaut's training time is spent inside simulators,

detailed replicas of spacecraft cockpits and station modules connected to computers that recreate each phase of flight.

Instructors deliberately throw problems at crews: engine failures, computer faults, fires, cabin leaks and aborted launches.

The goal is to make responses so automatic that crews stay calm when something goes wrong for real.

Astronauts also train to operate the station's large robotic arm, which is used to move equipment, support spacewalkers and grab arriving cargo ships.

Practicing on simulators first lets them master the slow, precise movements needed to handle objects weighing many tons.

Centrifuges add another layer, spinning trainees to reproduce the heavy forces felt during launch and reentry.

NASA astronauts have also long flown small, fast T-38 jet trainers, which sharpens quick decision-making in a demanding, high-speed environment.

Surviving the Unexpected Landing

A returning capsule can come down far from its planned landing zone.

For that reason, astronauts who fly on Russian Soyuz spacecraft have trained to survive for days in snowy forests, building shelters and signaling rescuers.

Water survival courses teach crews how to exit a capsule bobbing in waves, climb into a life raft and stay afloat until help arrives.

Some training programs include desert survival as well.

Learning to Work as a Team

Technical skill is not enough when a small crew must live together for months.

Agencies send astronauts on expeditions designed to build leadership, communication and what trainers call expedition behavior: looking after yourself,

your teammates and the mission all at once.

These analog missions take place in places that mimic the isolation and risk of spaceflight.

NASA has sent crews to live for days in Aquarius, an undersea research station off the coast of Florida,

while the European Space Agency has run training expeditions deep inside caves.

Wilderness trips and geology field camps round out the experience, teaching astronauts to make decisions together, far from help.

From Candidate to Crew Member

Finishing basic training makes someone eligible for a flight, but not guaranteed one.

Once assigned to a specific mission, a crew begins a new round of training that can last a year or two.

They learn the experiments they will run, the spacecraft they will fly and the spacewalks they may perform.

For station crews, this often means travel between partner training centers in the United States, Russia, Europe, Japan and Canada.

Crews also meet the scientists behind their experiments,

rehearse with mission controllers and spend the last days before launch in quarantine to avoid carrying an illness into orbit.

The Long Road to Launch

Astronaut training blends classroom study, physical endurance, technical mastery and teamwork into one long apprenticeship.

Every hour spent in a pool, a simulator or a snowy forest is meant to make the real mission feel familiar.

That preparation is why, when you watch astronauts at work in orbit, they so often make an extraordinary job look almost routine.