Up to now, Shenzhou 18 has been in orbit for more than 5 months, and the entire mission is nearing the end. Although everyone has a holiday during the National Day, the three astronauts Ye Guangfu, Li Cong, and Li Guangsu who are on mission in the Chinese space station are still carrying out various work. After all, the cost of space flight is very high, and the opportunity to fly is also rare, and astronauts cherish their time in space very much.
In the past five months, the Shenzhou-18 astronaut crew has completed a lot of work, including carrying out more than 90 space science experiments and technical tests, such as life ecology science experiments and material extravehicular exposure experiments. In addition, the Shenzhou-18 astronauts also carried out two out-of-cabin activities, and installed some space debris protection devices on the Chinese space station outside the capsule, which greatly improved the space station's ability to deal with the threat of space debris and small space particles.
Among so many scientific experiments and experiments, the project that has attracted the most attention may be "space fish farming". There is a sealed space fish tank in the Chinese space station, which contains 4 zebrafish, as well as goldfish algae, that is, there are producers and consumers.
Among them, goldfish algae produces oxygen through photosynthesis for zebrafish to breathe, and the system will automatically feed according to the zebrafish's living conditions, and can also control the temperature and light. During the experiment, zebrafish eggs are also collected, which are eventually returned to the ground with the astronauts on a spacecraft, where scientists carry out the next step of scientific research.
Boat 18 is about to return
Now the Shenzhou-18 mission is almost finished, and it is expected to return to Earth at the end of this month, ending its six-month flight journey. When the spacecraft returns to Earth from the Chinese space station, the whole process of returning home is very complicated, requiring a series of operations, and each step has many well-designed links, which are very high-tech.
The first step is to separate. The manned spacecraft needs to be separated from the space station assembly first, because the manned spacecraft is composed of three sections: the return module, the orbital module, and the service module, and the astronauts are landing in the return module, so after the evacuation from the space station assembly, the spacecraft return module will also be separated from the orbital module and the propulsion module. In the process of completing the separation, the flight altitude of the Shenzhou manned spacecraft will also drop from a circular orbit of nearly 400 kilometers to an elliptical orbit with a perigee of less than 100 kilometers, so as to prepare for re-entry.
The second step is re-entry. The process of re-entry can be said to be very thrilling, thrilling, and the one with the highest risk factor. Because the re-entry speed of the spacecraft re-entry capsule is quite fast, exceeding 7 kilometers per second, the spacecraft re-enters the atmosphere at such a fast speed that the temperature outside the re-entry capsule rises sharply, and the temperature in some areas can exceed 1000 °C. Such a high temperature of scorching is not able to withstand ordinary materials.
In order to make the spacecraft return capsule land safely and the astronauts return home safely, the manned spacecraft return capsule has to be specially designed, for example, the outside of the spacecraft return capsule will be coated with ablative materials and thermal insulation materials, which will take away a lot of heat in the process of falling off.
At the bottom of the capsule there will also be an insulated outsole that can withstand very high temperatures. In the process, the kinetic energy of the spacecraft's return capsule is also converted into heat and dissipated, so its descent rate also gradually decreases, from a speed of more than 7 kilometers per second to a few hundred meters per second.
The third step is parachuting. In the process of descending, although the speed of the return capsule has decreased, it still reaches several hundred meters per second, and it is no longer possible to continue to slow down on its own, so other measures need to be taken to reduce the speed of the return capsule descent, that is, to reduce the speed by parachute.
When there are still almost 10 kilometers above the ground, the parachute of the re-entry capsule opens, and with the help of the parachute, the speed of the re-entry capsule can be reduced to 7-8 meters per second. Although the descent speed has been greatly reduced, if you land at this speed, the impact force of the return capsule is still relatively large, and it is also a danger to the astronauts.
Therefore, when the re-entry capsule is still about 1 meter above the ground, the four thrust reverser engines at the bottom of the re-entry capsule will be activated to complete the final stage of deceleration. The thrust reverser engine provides an upward thrust to the re-entry capsule, which finally lands at a speed of 1-2 meters per second. Moreover, the seats in the return capsule of the manned spacecraft also have a cushioning effect, which can further reduce the impact on the astronauts when the return capsule lands, so as to ensure the safety of the astronauts.
Why astronauts are being carried away
When the spacecraft re-entry capsule landed safely, the mission wasn't really complete yet, because there was still a lot of work to be done. Because the capsule landed in a desert area, it was definitely necessary to transfer the capsule back. Moreover, when the spacecraft return capsule lands safely, the astronauts cannot leave the capsule immediately, and the ground staff need to check the return capsule and the physical condition of the astronauts.
After ensuring the safety of the re-entry capsule and the astronauts, the ground crew will open the hatch of the re-entry capsule and carry the astronauts out, rather than letting them walk on their own. What's going on?
Uninformed netizens may think that this is a big fuss, but the actual situation is not as simple as imagined. Because the environment of outer space is completely different from the ground environment, when being in a state of weightlessness in outer space for a long time, the astronaut's body will undergo a series of changes, and the loss of bone and muscle will be accelerated.
This process is very long, and if the astronaut gets up and walks rashly, he may fall or break a bone. Therefore, for the safety of astronauts, astronauts will not stand and walk immediately after landing.