The Unexpected Physical Challenges of Long-Term Space Travel
Introduction
Space travel is one of the most extreme and fascinating forms of human exploration. Astronauts endure harsh, otherworldly conditions that push their bodies to the limit. For US astronauts Butch Wilmore and Suni Williams, what was initially supposed to be a 10-day mission turned into a nine-month stay aboard the International Space Station (ISS). Their prolonged exposure to microgravity and the extreme conditions of space will undoubtedly leave noticeable effects on their physical health. Understanding these changes, from height fluctuations to bone density loss, provides a glimpse into the remarkable resilience of the human body and the challenges of long-term space exploration.
The Impact on Height and Bones
One of the most surprising effects of microgravity is the change in height. Astronauts often notice a slight increase in height, sometimes by up to two inches, due to the expansion of spinal discs in the absence of gravity. However, this change is temporary, and the spine typically returns to its normal state once back on Earth. Scott Kelly, who spent 340 days on the ISS, lost the extra height he gained within just two days of returning. While the increase in height is temporary, the loss of bone density is a more concerning issue. Astronauts lose about 1% to 1.5% of bone density each month in space, particularly in weight-bearing areas like the hips and legs. This loss can weaken bones, making them more susceptible to fractures.
Muscle Atrophy and the Challenges of Movement
Muscle atrophy is another significant challenge astronauts face. Without the regular stress of gravity, muscles weaken over time, especially in the legs and lower body. Women are generally at a higher risk due to lower muscle mass and hormonal differences. To combat this, astronauts must exercise rigorously, spending at least two hours daily on treadmills or stationary bikes. Without this regimen, they might struggle to walk or stand upon returning to Earth. The prolonged lack of gravity affects the vestibular system, responsible for balance, leading to a phenomenon known as "space legs," where astronauts feel wobbly and disoriented after re-entering gravity.
Vision Problems and Organ Changes
Long-term space travel can also affect vision, a condition known as Spaceflight-Associated Neuro-ocular Syndrome (SANS). The altered fluid distribution in microgravity can increase pressure on the optic nerve, leading to changes in eye shape. While these vision problems are usually temporary, they can persist for years in some cases. Another critical change occurs in the heart, which becomes less efficient in pumping blood in microgravity. This can lead to low blood pressure and dizziness upon return to Earth. On the positive side, studies suggest that astronauts generally have better cardiovascular health than the average person.
Radiation Exposure and the Risk of Cancer
Astronauts in space are exposed to higher levels of cosmic radiation, which increases their cancer risk. NASA takes protective measures, such as using dosimeters, to keep this risk within acceptable limits, aiming to ensure that it does not exceed 3% above the general population’s risk. Despite these precautions, radiation remains a significant concern for long-term missions.
The Unpredictable Nature of Recovery
Beyond the well-documented physical changes, there are numerous unpredictable elements that astronauts face upon their return. Simple, everyday activities—like sitting in a hard chair—can become challenging after months of floating. Each astronaut’s body responds differently to the stresses of space, and the recovery process is highly individualized. As astronauts Matthew Dominick and Jeanette Epps noted, while some changes are expected, it’s the "little things" that often catch them off guard. Each day back on Earth brings improvement, and while some issues may linger, the human body shows remarkable adaptability in recovering from the extremes of space.
