Intrepid explorers Sunita Williams and Butch Wilmore need readjustment to their new ‘earthly’ environment; space travel is inherently dangerous to human body
Sunita Williams and Butch Wilmore. File pic
Two American astronauts, Sunita Williams (of Indian origin) and Butch Wilmore, landed on Earth to much relief and celebrations on Wednesday morning. One could actually hear the world exhale as the astronauts returned, pictorials showing the space capsule deploying its parachute before a splashdown in the ocean off the coast of Florida. There was joy as the spirited twosome were helped out of the capsule.
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The duo, who visited the International Space Station (ISS) on what was supposed to be a one-week stay in the first week of June 2024 on a test mission, found their stay inordinately delayed as the spaceship that took these two astronauts developed a technical snag. As a concerned world looked on, that stay stretched for a nervy nine months.
G-force
Space travel is inherently dangerous to the human body, and the micro-gravity environment affects astronauts’ physiology. When a rocket carrying astronomers lifts off, it reaches a speed of 28,000 kilometres per hour. At that speed, astronauts experience intense G-forces, severe cockpit vibrations, and loud rocket engine noise. This leads to physiological changes in the astronauts, like increased heart rate, possible loss of hearing and body fluid redistribution, which can cause dizziness and swelling. However, the time from liftoff to the designated orbit takes about 10 minutes. Once the spaceship reaches its orbit, astronauts regain their normal senses. It can take a few hours to a day for the spaceship to dock with the ISS. In their spaceship, astronauts start sensing the effect of near-zero gravity.
Mass loss
The human body is a highly complex system of bones and muscles with a highly evolved brain. The brain continuously monitors all the body’s activities and signals its parts to take corrective action if necessary or to adjust to the local environment. The body realises there is no gravity to pull it down and allows astronauts to float effortlessly. Initially, the brain does not view this as a significant issue. However, as the astronomers’ stay in this near zero-gravity environment prolongs, the brain recognises that the function of muscles needed on the surface of the Earth is no longer necessary. As a result, muscles begin to lose mass. The same occurs with bones. To prevent significant muscle loss, astronomers exercise for more than two hours daily in a gym designed for the Station. We had periodic reports about these astronauts working out in space, to arrest muscle and bone mass loss as much as possible.
However, muscle and bone mass loss are inevitable with a prolonged stay in this environment.
Back home
After landing on Earth, astronauts experience “gravity sickness”. This is because their bodies need to readjust to the planet’s gravity. The process of readjustment leads to dizziness, nausea, difficulty with balance and coordination, and potential muscle and bone soreness. Depending upon their stay in space, astronomers can take from a few days to weeks to acclimatise their bodies to the gravity of the Earth. The effects of bone and muscle loss are seen immediately. Earlier, Sunita Williams had spoken about the difficulties she is expected to face when back. She had said that due to the muscle loss in her body, she would find it difficult to do something as simple as lifting a pencil.
We saw as both these intrepid astronauts landed, they needed to be assisted to get out. Now they will need time and rehabilitation to rebuild muscle tissues.
Limb movement
The other physiological aspect is the coordination of limbs, hands and legs. Our inner ear has sensors that detect the posture of our body. This sensor and brain constantly monitor our body and take necessary action under adverse conditions if one is about to fall. Then, the needed action is taken to maintain the balance. Due to the lack of gravity in space, the use of this sensor for checking body balance was not needed. However, after returning to Earth, it takes considerable time for the sensor to readjust to the gravity here, resulting in dizziness, nausea and difficulty with balance and coordination.
Vision worries
On Earth, body fluids are constantly pulled down. But in space, extra fluid can reach the eyes, causing swelling and structural changes. This can lead to vision problems in astronauts. Facial swelling, tight hamstrings and calves have been noticed. These problems remain upon returning to Earth.
Lastly, but importantly, it has been suggested that astronauts experience a temporary decline in cognitive efficiency, such as thinking, learning and judgement, after returning to Earth.
We have seen astronauts performing cutting-edge science experiments in space, but even after returning to Earth, they would provide valuable information about physiological changes in space.
The columnist is the director of the Nehru Planetarium, Mumbai
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