by Tharien van Eck, AWC Antwerp and Health Team Co-chair
NASA’s Human Research Program (HRP) has studied human health in space for many years, but few could have predicted that Butch Wilmore and Sunni Williams would be stranded in space for nine months. However, they are not the longest-serving astronauts on the International Space Station (ISS). Scott Kelly, Christina Koch, and several others have spent over 200 days in space, with Frank Rubio holding the record for the longest single spaceflight at 371 days.
Spending extended time in space significantly affects the human body due to microgravity, radiation exposure, and the psychological challenges of isolation. NASA categorizes these challenges under the acronym RIDGE, which stands for Space Radiation, Isolation and Confinement, Distance from Earth, Gravity Fields and Hostile/Closed Environments.
Space Radiation
On Earth, our magnetic field and atmosphere protect us from most space radiation, though we are exposed to low levels daily. Astronauts, however, face three major sources of radiation:
- Particles trapped in Earth’s magnetic field
- Solar energetic particles from the Sun
- Galactic cosmic rays
Effects of space radiation:
- Increased cancer risk: Space radiation damages DNA, heightening cancer risk. Long-duration missions, such as those to Mars, expose astronauts to significantly higher radiation levels.
- Cognitive impacts: Radiation may affect brain function, leading to memory issues and mood changes.
Isolation and Confinement
Living in a confined space with limited social interaction for months can have profound psychological effects.
- Stress and anxiety: Extended isolation may cause depression, irritability and emotional strain.
- Circadian rhythm disruption: The ISS experiences 16 sunrises and sunsets per day, which can disrupt astronauts’ sleep cycles, leading to fatigue and cognitive impairment.
- Fatigue management: Astronauts must be trained to handle fatigue, as missions often involve heavy workloads and unpredictable schedules.
Distance from Earth
Astronauts on deep-space missions must be self-sufficient, as they cannot rely on immediate assistance from NASA. This will become even more critical for Mars expeditions, where communication delays of 20+ minutes one-way will be a challenge.
- Limited supplies: Unlike the ISS, which receives regular resupply missions, Mars astronauts must carry all necessary food, equipment, and medical supplies for the entire mission.
- Medical emergencies: Astronauts undergo medical training, learning procedures such as inserting IV catheters and performing ultrasound scans. In the event of illness, they can conduct laboratory tests to aid them in the diagnosis and treatment of an ailment.
Gravity Fields
Transitioning between gravity environments affects astronauts’ orientation, coordination, balance and motion. Many experience space motion sickness upon arrival in microgravity.
Muscular and skeletal changes:
- Bone density loss: Without weight-bearing activity, astronauts lose 1–2% of bone mass per month, increasing the risk of fractures.
- Muscle atrophy: The absence of gravity leads to muscle weakening, particularly in the legs and back. Daily resistance exercises help counteract this.
Cardiovascular effects:
- Fluid shift: Fluids move toward the upper body, causing facial puffiness and thinner legs.
- Heart shrinkage: The heart works less in microgravity, leading to a slight decrease in size and function.
- Orthostatic intolerance: Astronauts may feel dizzy or faint upon returning to Earth due to weakened circulation.
- Spaceflight-associated neuro-ocular syndrome (SANS): Increased pressure in the head can change the shape of the eyeball, sometimes causing permanent vision changes.
Hostile/Closed Environments
- Weakened Immunity: Astronauts become more vulnerable to infections, and dormant viruses (such as herpes or shingles) can reactivate in space.
- Gene expression changes: Studies, including the NASA Twin Study, suggest that space travel alters gene expression. Most changes revert upon returning to Earth, but some may persist.
Countermeasures to protect astronaut health
Pre-mission preparation:
- Psychological training: Astronauts undergo extensive training (300+ hours in simulators) to handle isolation, stres, and emergencies.
- Medical support: NASA employs doctors, psychologists and other specialists to ensure astronaut well-being before, during, and after missions.
During the mission:
- Exercise regimen: Astronauts work out for 2+ hours daily using resistance machines and treadmills.
- Nutrition and hydration: Strict dietary plans help maintain bone and muscle health.
- Radiation protection: Shields and potential medications help reduce radiation damage.
- Communication and support: Astronauts can email, call and video conference with family and friends. They also receive care packages via resupply missions and have access to mental health professionals.
- Medical emergency protocols: Astronauts are trained to handle medical emergencies with diagnostic tools and remote support from Earth.
As NASA and other space agencies prepare for future deep-space missions, continued research and innovation will be vital to ensuring astronaut health and safety on extended journeys beyond Earth’s orbit.
Sources:
- NASA: Space Station Astronaut Record Holders
- NASA: Radiation and Human Spaceflight
- NASA: The Human Body in Space
- NASA Twins Study
- NASA Astronaut Health Care
Image from Canva.com