Becoming an Astronaut: Selection Process
Astronaut selection is extraordinarily competitive. NASA's 2021 selection received over 12,000 applications for just 10 positions—acceptance rates lower than most Ivy League universities. International space agencies have similar competition levels, with ESA's 2022 selection receiving over 22,500 applications for 4-6 positions.
Basic requirements for NASA astronaut candidates include:
- U.S. citizenship (for NASA; other agencies have different nationality requirements)
- Master's degree in STEM field (engineering, biological/physical science, computer science, mathematics)
- Minimum 2 years related professional experience OR 1,000 hours pilot-in-command time in jet aircraft
- Ability to pass NASA long-duration flight astronaut physical examination
However, meeting minimum requirements doesn't guarantee selection. Most selected candidates have exceptional qualifications: advanced degrees (often PhDs or MD/PhDs), years of relevant experience, military test pilot backgrounds, or unique expertise in robotics, medicine, or engineering. Speaking multiple languages, particularly Russian, is highly valued for ISS operations.
The selection process spans 18 months and includes medical examinations, psychological evaluations, interviews, team exercises, and assessments of technical knowledge and decision-making under pressure. Evaluators seek candidates who combine technical excellence with strong teamwork, communication, and adaptability.
Training: Preparation for the Extreme
After selection, astronaut candidates undergo approximately two years of basic training before becoming eligible for flight assignments. This training is intense, comprehensive, and continues throughout an astronaut's career.
Academic and Technical Training
Astronauts study spacecraft systems, orbital mechanics, astronomy, Earth science, and space medicine. They learn to operate and repair ISS systems, conduct scientific experiments, use robotic arms, and perform complex procedures in emergency situations. Much of this involves detailed study of thousands of procedures and technical manuals.
Neutral Buoyancy Laboratory
The Neutral Buoyancy Laboratory in Houston contains a massive pool (62m x 31m x 12m deep) with full-scale mockups of ISS modules. Astronauts practice spacewalks (EVAs) in weighted spacesuits that simulate weightlessness. A single 6-hour spacewalk may require 50+ hours of underwater training.
During these sessions, astronauts practice intricate tasks while wearing bulky pressurized gloves, learning to work efficiently while managing limited oxygen supplies, temperature regulation, and communication with ground control. Divers stand by for safety while instructors monitor every movement.
Survival Training
Since spacecraft can land anywhere on Earth in emergencies, astronauts train for survival in extreme environments: water survival (in case of ocean landing), winter survival in remote forests, and desert survival. They learn shelter building, water procurement, emergency medical care, and radio communication.
NEEMO (NASA Extreme Environment Mission Operations) sends crews to live in the Aquarius underwater habitat for up to 3 weeks, simulating the isolation, close quarters, and communication delays of space missions while conducting scientific research.
T-38 Jet Training
NASA astronauts maintain proficiency flying T-38 supersonic jets. This serves multiple purposes: practicing decision-making in dynamic, high-stakes environments; staying sharp on technical procedures; building team coordination; and experiencing physiological effects similar to spaceflight (rapid pressure changes, high-G forces).
Russian Training
All ISS crew members train in Russia at Star City near Moscow, learning Soyuz spacecraft operations and Russian ISS systems. They must become fluent in Russian technical terminology to communicate with cosmonauts and Russian mission control. Similarly, Russian cosmonauts train at NASA facilities and learn English.
Launch Day: Journey to Orbit
Launch preparations begin weeks in advance with medical checks, final training sessions, and crew quarantine to prevent introducing illness to the ISS. The night before launch, astronauts review procedures, pack personal items within strict weight limits (typically just 1-2 kg), and try to sleep despite excitement and adrenaline.
Launch morning starts early—usually 4-5 hours before liftoff. After breakfast with support crew, astronauts don their launch suits, which provide pressure protection and cooling. A traditional flag-waving ceremony sends them to the launchpad, where they board their spacecraft.
Strapped into seats, astronauts perform final checks during the countdown. At ignition, they experience violent shaking and noise as engines fire. Within seconds, they're accelerating at 3-4 times Earth's gravity. Eight to nine minutes later, the spacecraft reaches orbit—engines cut off, and suddenly they're weightless.
Many astronauts report the stark beauty of first seeing Earth from space as an overwhelming, emotional experience. The planet appears as a fragile blue sphere against the blackness of space, covered in swirling white clouds, without visible political boundaries—an image that permanently changes their perspective.
Daily Life Aboard the ISS
The International Space Station orbits at 28,000 km/h (17,500 mph), completing one orbit every 90 minutes. This means astronauts see 16 sunrises and sunsets every 24 hours. To maintain normal circadian rhythms, the station follows UTC (Coordinated Universal Time) with scheduled wake-up at 6:00 and sleep at 21:30.
Work Schedule
Astronauts work Monday through Friday on a carefully planned schedule. A typical day includes:
- 6:00 - Wake up, personal hygiene, breakfast
- 7:30 - Daily planning conference with mission control
- 8:00-13:00 - Morning work period (experiments, maintenance, exercise)
- 13:00-14:00 - Lunch break
- 14:00-18:00 - Afternoon work period
- 18:00-19:30 - Dinner, personal time
- 19:30-21:30 - Evening activities, prepare for sleep
- 21:30 - Sleep period (in sleeping bags attached to walls)
Saturdays include cleaning, equipment maintenance, and time for personal projects. Sundays are typically off-duty, allowing crew to relax, communicate with family, take photos of Earth, read, or watch movies.
Exercise: Fighting Weightlessness
Without gravity, muscles and bones deteriorate rapidly. Astronauts must exercise 2-2.5 hours daily using:
- ARED (Advanced Resistive Exercise Device): Vacuum cylinders simulate weights up to 270 kg for strength training
- Treadmill: Harness system provides downward force while running
- Exercise bike: Cardiovascular conditioning without impact stress
This rigorous routine significantly reduces (but doesn't eliminate) muscle atrophy and bone density loss. Even with exercise, astronauts can lose 1-2% of bone mass per month in space.
Eating and Drinking
Food aboard the ISS includes thermostabilized pouches (like military MREs), freeze-dried meals rehydrated with hot or cold water, irradiated foods, and some fresh fruits/vegetables delivered by resupply ships. Menus rotate on 8-day cycles with international variety—Russian, American, European, and Japanese cuisine.
Eating in weightlessness requires care—food floats away if not secured. Liquids form floating spheres that must be caught with straws. Salt and pepper are liquid to prevent granules from floating into eyes or equipment. Tortillas are preferred over bread because they produce no crumbs.
The ISS recycles nearly all water from humidity, urine, and even crew exhalation—about 93% recovery rate. As the saying goes, "Today's coffee is tomorrow's coffee." This recycling is essential for long-duration missions and future deep space exploration.
Personal Hygiene
Without running water and gravity, hygiene requires creativity. Astronauts use no-rinse soap and shampoo with wet towels for "showers." Toothbrushing is standard, but toothpaste must be swallowed since there's no sink to rinse. The toilet uses airflow to direct waste, which is then compressed and stored or burned up during reentry.
Scientific Work and Spacewalks
The ISS is primarily a research laboratory. Crew members conduct hundreds of experiments studying:
- Human physiology in microgravity (bone loss, muscle atrophy, vision changes, immune system effects)
- Materials science (protein crystal growth, metallurgy, combustion physics)
- Biology (plant growth, cell behavior, microorganism adaptation)
- Earth observation (climate, weather, agriculture, disaster monitoring)
- Technology demonstrations (3D printing, robotic systems, life support)
Spacewalks (EVAs) are among the most challenging and dangerous activities. Lasting 6-8 hours, they require months of preparation. Astronauts work in bulky suits at 0.3 atmospheres pressure (vs 1.0 inside the station), with limited dexterity and constant awareness that a suit puncture or tether failure could be fatal.
Common EVA tasks include installing new equipment, replacing failing components, and conducting experiments. The work is physically exhausting—astronauts can burn 1,000+ calories during a single spacewalk.
Psychological Challenges
Living in a space the size of a six-bedroom house with 3-7 other people for six months tests psychological resilience. Challenges include isolation from family and friends, confinement, lack of privacy, repetitive routines, and the inability to go outside or escape the environment.
Crews maintain psychological health through:
- Regular video calls with family (though 15-minute delays sometimes occur)
- Care packages and fresh food on resupply ships
- Viewing Earth through the Cupola window (described as therapeutic)
- Team bonding activities and celebrations of birthdays, holidays
- Access to books, movies, music, and email
- Psychological support from ground-based specialists
Crew compatibility is crucial. Astronauts train together extensively before missions, building trust and learning to communicate effectively under stress. International cooperation—particularly U.S.-Russian partnership—demonstrates how shared goals transcend political differences.
Return to Earth
Coming home is almost as stressful as launch. After undocking from the ISS, the spacecraft performs a deorbit burn, slowing enough to reenter the atmosphere. Astronauts experience peak deceleration of 4-5 G's during the fiery descent— plasma glowing outside windows as friction heats the heat shield to 1,600°C.
Parachutes deploy for final descent, with touchdown on land (Soyuz in Kazakhstan) or ocean (Crew Dragon in Atlantic). Recovery teams quickly reach the crew, but astronauts often cannot stand after months in weightlessness. Readaptation to gravity takes weeks—simple actions like walking, lifting objects, or even holding up their heads require relearning.
Most astronauts recover fully within 2-3 months, though vision changes can be permanent for some. Despite challenges, nearly all astronauts describe spaceflight as the most rewarding experience of their lives and many fly multiple missions.
The Future: Mars and Beyond
Current astronaut training prepares for Moon and Mars missions. These will present new challenges: multi-year durations, communication delays up to 22 minutes, no quick abort options, enhanced radiation exposure, and complete self-sufficiency from Earth.
Future astronauts may specialize more—some focusing on piloting, others on geology, biology, engineering, or medicine. Psychological screening will intensify for missions where crew cannot return home for years. Physical conditioning will emphasize maintaining health through long transits in confined spacecraft.
Despite daunting challenges, thousands will continue applying to become astronauts, driven by the fundamental human desire to explore, discover, and push the boundaries of what's possible. The most difficult journeys often prove the most rewarding.