The Shenzhou 14 astronauts are back home! Do you know how many difficulties the astronauts have to overcome to get home?

China Science and Technology News Network, December 5 (Jin Xi) At 21:01 Beijing time on December 4, Shenzhou 14 astronauts Chen Dong, Liu Yang, and Cai Xuzhe all returned safely and exited the spacecraft in good health. Every time we see astronauts exiting the spacecraft, they need to be carried by others. Do you know why this is? How many difficulties do astronauts have to overcome to return home from space?

Astronauts are carried when they leave the spacecraft for safety reasons: Astronauts are in a state of weightlessness for a long time in space, and their bodies have adapted to the microgravity environment, which leads to decreased endurance, weak muscles, osteoporosis, etc. In space, blood is evenly distributed throughout the body, but when they return to Earth, gravity can cause short-term mental, physical and psychological discomfort, and blood will quickly flow back to the lower limbs, causing ischemia in the brain and upper body, which can easily lead to fainting and other conditions.

In addition, when riding in the return capsule and quickly passing through the atmosphere, astronauts need to withstand huge rotations and impacts. Their bodies, which have long adapted to the space environment, suddenly have to withstand the test of the earth's gravity. This huge contrast will bring extreme discomfort to the body. Moreover, the vestibular nerves responsible for maintaining balance cannot react quickly at this time, resulting in balance and orientation disorders. Forcing themselves to stand at this time can easily lead to posture disorders, falls, or fractures.

When returning home, astronauts need to wear customized space suits. After the return capsule, orbital capsule and propulsion capsule are separated, they will enter the atmosphere at an altitude of about 100 kilometers. At this time, there will be intense friction between the return capsule and the atmosphere, and the surface temperature can reach up to 2000 degrees Celsius. Looking out of the porthole of the return capsule, you can only see a scorching red.

When the return capsule descended to an altitude of about 80 kilometers, the friction between the return capsule and the atmosphere formed a plasma layer that attracted electromagnetic waves, causing the ground and the return capsule to lose contact, which is what we often call the "black barrier zone." In the black barrier zone, which lasts for about 4-7 minutes, the return capsule enters a true vacuum environment. It is not until the return capsule descends to about 25 kilometers from the ground that it can completely pass through the black barrier zone and re-establish contact with the ground.

In addition to these, the process of returning to Earth from a weightless environment has different degrees of impact and challenges on the various organ systems of astronauts. After returning to Earth, astronauts will have to undergo a six-month recovery training, and then return to normal training after careful observation and evaluation. Therefore, every departure of astronauts is an adventure for the brave.