American astronaut Scott Kelly spent 340 days on the International Space Station, setting the record for the longest single space mission by an American astronaut. Astronaut Peggy Whitson has spent 665 days in space, the longest cumulative time spent in space by any American astronaut.
Scott Kelly and his twin brother Mark Kelly were studied by NASA to study the effects of the space environment on the human body. Scott Kelly spent 340 days on the Iss between March 2015 and March 2016, while Mark Kelly was living on Earth. A comparative study of the two men's physical conditions showed that After about a year in space, Scott Kelly lost weight, his carotid arteries dilated, his DNA methylation levels changed, and his gut flora changed. Some indicators returned to their previous levels within six months of Scott Kelly's return to Earth, but others remained unrecovered and some gene expression was disrupted.
According to NASA, tracking changes in the human body in the space environment and conducting relevant research will help optimize the design and function of space suits, develop astronaut health standards and fitness programs, and conduct physical and psychological adaptation training in preparation for longer human deep-space missions.
According to NASA research, the space environment affects astronauts in five main aspects, including space radiation, physical and psychological effects of being isolated from the outside world, the inconvenience of being far from Earth, the health effects of microgravity and the effects of prolonged confinement on the human body.
Astronauts in space are exposed to much more radiation than on Earth. The longer they stay in space, the more radiation they receive, and the risks they face include radiation-induced diseases and changes in the central nervous system. Researchers are simulating the cosmic radiation environment on the ground to study its effects on human health, and tackling the effects of space radiation by measuring radiation more accurately and developing more advanced radiation shielding materials.
During space missions, astronauts are isolated from the outside world and stay in a closed environment for a long time, which may cause sleep problems, fatigue, depression and changes in the immune system. NASA is trying to improve the effects of a closed environment by adjusting the brightness of the space capsule and using virtual reality equipment to simulate a relaxing environment. Astronauts are being encouraged to de-stress by keeping diaries and growing vegetables in space.
The slightly heavy or weightless environment of space can also affect the human body. According to NASA, the mineral density of weight-bearing bones decreases by an average of 1 to 1.5 percent per month while astronauts are in space. They lose muscle mass faster; Body fluids flow up to the head in microgravity, which can put pressure on the eyes and cause vision problems. Researchers are tackling these effects with a range of measures, from wearing negative pressure devices to control the flow of fluid to developing a drug called potassium citrate to combat kidney stone risk.
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