CCTV News: The process of astronauts returning to the earth is simply to separate, cross the atmosphere, and land. It sounds very simple, but in fact, each step has many carefully designed links, and the technological content is very high.
The first step for astronauts to go home is to separate. During this process, the manned spacecraft must be separated from the space station assembly, and the return capsule must also be separated from the orbital compartment and propulsion compartment. After the separation is completed, the Shenzhou spacecraft will change orbit from a circular orbit at a height of 400 kilometers to an elliptical orbit at a height of less than 100 kilometers perigee, thus preparing for reentering the atmosphere.
Reentering the atmosphere is the most risky step on the astronauts' journey home. During the reentering process, the return capsule will rub against the atmosphere, creating a high temperature of thousands of degrees, which ordinary materials cannot withstand at all. At this time, heat-proof clothing is needed.
CCTV reporter Li Ning: What we see now is the heat-proof bottom of the Shenzhou spacecraft return capsule. This honeycomb-shaped heat-proof material can be seen very clearly on it. This is its heat-proof clothing. We need to burn this heat-proof material to take away heat, so as to ensure the safety of astronauts.
Peng Huakang, overall deputy chief designer of manned spacecraft system of the Fifth Academy of Aerospace Science and Technology Group: The carbonization and peeling of high-temperature materials will take away a lot of heat, and the kinetic energy of the return capsule will gradually decrease, and its kinetic energy will gradually be converted into heat dissipation. Then its speed will gradually decrease from the first cosmic speed, that is, the speed of several kilometers per second at 7:00 to several hundred meters per second.
After experiencing the test of the atmosphere, astronauts can see the ground. At this time, in order to make the return capsule land smoothly, the parachute will be opened when ten kilometers away from the ground, further reducing the speed of the return capsule. At the same time, the engine will also be prepared for landing buffering.
Peng Huakang, overall deputy director of the manned spacecraft system of the Fifth Academy of Aerospace Science and Technology Group: When the return capsule lands about one meter above the ground, the landing reverse push engine work, which generates an upward impulse, further reducing the speed of the return capsule to 1 to 2 meters per second. Then there are buffered seats in our cabin, and there are also some buffered materials in the seats, which can further ensure that the impact of the return capsule landing is smaller and ensure the safety of astronauts.
Return capsule Parachute: The safety protection umbrella for astronauts to return home
After the Shenzhou 14 return capsule passes the test of the atmosphere, it will usher in the next difficulty - slowing down. Due to the effect of gravity, the return capsule is descent very fast. To reduce it to a landing speed that an astronaut can withstand, another magical artifact - a parachute. The parachute in the return capsule is divided into three umbrellas: guide umbrella, slowing umbrella and main umbrella. First, the return capsule automatically opens the umbrella hatch cover at a height of about 10 kilometers from the ground, pulls out the guide umbrella, guides the umbrella and then pulls out the speed of the deceleration umbrella. At this time, the return capsule speed is about 180 meters per second. After working for 19 seconds, the speed reduction parachute is separated from the return capsule and the main parachute is pulled out at the same time. At this time, the descent speed of the return capsule is gradually reduced from 80 meters per second to 40 meters per second, and then reduced to 7-8 meters per second. During the entire process, in order to avoid excessive overload, the speed reduction parachute and the main parachute cannot be opened all at once.
Rong Wei, deputy chief designer of the manned spacecraft system of the Fifth Academy of Aerospace Science and Technology Group: If we directly open the main umbrella of 1,200 square meters, it will have a very powerful driving force on the return capsule, which is equivalent to reaching about 100 G. In this way, astronauts will definitely not be able to stand it inside. Therefore, in order to slow down the return capsule and enable astronauts to achieve more comfortable overload conditions, just like we are driving, we must slow down slowly and gradually slow down, which is equivalent to reducing its speed a little first and then reducing it.
In order to prevent the main umbrella from malfunctioning, the return capsule is also equipped with an umbrella. When the return capsule descends from a height of 6 kilometers to 5 kilometers, if it takes less than the predetermined time, the system will determine that the main umbrella system is working abnormally, thereby automatically starting the backup umbrella to ensure the safety of the astronauts.
Rong Wei, deputy chief designer of the manned spacecraft system of the Fifth Academy of Aerospace Science and Technology Group: Since the beginning of the development of the umbrella, it has been deployed with aircraft and has been tested and verified by more than 100 times. In order to ensure the safety of astronauts, there will generally not be much improvement, but some of our new technologies may be used in some new models of missions. Another thing is to ensure its reliability, we have adopted some new methods and means to further improve the reliability of the products and ensure the safety of astronauts' lives.
