Astronauts aboard the International Space Station (ISS) follow a rigorous exercise routine to counteract the lack of gravity, which affects muscles and bones. While missions usually last six months, some astronauts stay up to a year. Researchers are confident in maintaining astronaut health over this duration.
On Earth, even basic movement builds muscle and strengthens bones due to gravitational resistance. However, in orbit, astronauts rely on three exercise machines, including a resistance device installed in 2009. This device simulates free weights using vacuum tubes and flywheel cables.
A two-hour daily workout routine is essential for astronaut fitness. “The best results that we have to show that we’re being very effective is that we don’t really have a fracture problem in astronauts when they return to the ground,” said Bokhari. However, bone loss remains detectable in scans.
Balance and fluid shifts pose major concerns
Space travel disrupts balance, affecting all astronauts, even those on short missions. Emmanuel Urquieta, vice chair of Aerospace Medicine at the University of Central Florida, stated that astronauts must undergo NASA’s 45-day post-mission rehabilitation program to retrain their bodies.
Another issue is “fluid shift,” where bodily fluids move toward the head in microgravity. This can increase calcium levels in urine, raising the risk of kidney stones. Additionally, fluid shifts can lead to increased intracranial pressure, altering the shape of the eyeball and causing spaceflight-associated neuro-ocular syndrome (SANS), resulting in mild-to-moderate vision impairment.
Interestingly, in some cases, SANS has led to improved vision. NASA astronaut Jessica Meir, for instance, experienced a rare benefit. “When I launched, I wore glasses and contacts, but due to globe flattening, I now have 20/15 vision—most expensive corrective surgery possible. Thank you, taxpayers,” she remarked.
Managing radiation risks
Radiation exposure remains a significant concern. While the ISS passes through the Van Allen radiation belt, Earth’s magnetic field offers some protection. However, radiation levels remain higher than on Earth. NASA aims to limit astronauts’ increased lifetime cancer risk to within three percent.
Future deep-space missions to the Moon and Mars will expose astronauts to even greater radiation levels. Astrophysicist Siegfried Eggl explained that while heavy materials like lead or water provide effective shielding, their vast quantity requirements make them impractical.
Space probes could offer some warning for coronal mass ejections—plasma clouds from the Sun—but cosmic radiation remains largely unpredictable.
Possible solutions: Artificial gravity and propulsion advancements
One solution to counteract health issues is artificial gravity, created by rotating spacecraft frames, which could help astronauts remain functional after extended travel. Another approach is using powerful acceleration and deceleration to simulate Earth’s gravity, reducing both the effects of microgravity and radiation exposure. However, this method requires nuclear propulsion technologies that are still under development.
Psychological challenges in space missions
Beyond physical health, maintaining team dynamics in confined environments is crucial. Joseph Keebler, a psychologist at Embry-Riddle Aeronautical University, highlighted the difficulty of long-duration space travel.
“Imagine being stuck in a van with anybody for three years: these vessels aren’t that big, there’s no privacy, there’s no backyard to go to,” he explained. “I really commend astronauts that commit to this. It’s an unfathomable job.”