I am proud to hear "it feels good", see the national flag flying and welcome the space hero home. what do you think?

The return capsule of Shenzhou 13 manned spacecraft landed successfully in Dongfeng landing field. Three astronauts successfully returned to the ground. After landing, Zhai Zhigang, Wang Yaping and Ye Guang Fu reported that they felt good! The latest news is that the manned mission of Shenzhou XIII was a complete success. The Engineering Mission Command of the Manned Space Station decided that the Shenzhou XII spacecraft will return to Earth on September 17.

Three astronauts on business in space are going home. What barriers do astronauts have to go through when they leave the China Space Station and embark on the road back to Earth? What was the reason for landing at Dongfeng landing site for the first time? Interview with Yang Yuguang, vice chairman of IAF's Space Transportation Committee and researcher of the Second Academy of China Aerospace Science and Industry Group.

Three astronauts on business in space are going home. The risk of astronauts returning to earth is high. The three astronauts who boarded Shenzhou XII for the first time set off from space and returned to their homes on earth. What is the general process? Returning to earth is a high-risk process. The spacecraft orbits the earth at a speed of 7.8 kilometers per second. The characteristic of space orbit motion is that if the spacecraft originally runs in a circular orbit, it will enter an elliptical orbit as long as it slows down slightly, and the closest point of this elliptical orbit to the earth is perigee. When the speed drops to a certain extent, the near-site can be lowered into the atmosphere, and then the atmospheric resistance can be used to slow down.

The intersection of the spacecraft and the earth's center line and the ground is called the sub-star point. The spacecraft operation and the earth's rotation make the sub-star point move on the earth's surface, forming the sub-star point trajectory. When the trajectory runs near the southern tip of Africa, the ground will send a braking command to the spacecraft, and after slowing down, it will enter the elliptical orbit after the perigee is lowered. When passing over Karachi, the spacecraft touched the atmosphere and started pneumatic heating, and then entered China through Xinjiang. When the flying altitude reaches about 10 km, the spacecraft opens its parachute, further reduces its speed, and throws away the heat-proof outsole below. About one meter from the ground, several small solid rocket engines in the spacecraft further slowed down, allowing the astronauts to land at a comfortable speed.

The successful landing and return process of the spacecraft return capsule at the Dongfeng landing site is complicated, and no mistakes can be made in any link. First of all, the intense friction between the spacecraft and the atmosphere will generate huge heat, so the spacecraft has an aerodynamic shape with a heat-resistant outsole under it, which can withstand thousands of degrees of high temperature and prevent heat from being transmitted to the interior of the spacecraft. This is the key problem that affects the safety of the spacecraft during its return. Second, parachutes must work normally, which is why shenzhou spaceship designed two sets of umbrellas, the main umbrella and the backup umbrella. Parachutes have had problems in the history of human spaceflight. In the 1960s, the Soviet Union "Soyuz-1" had a parachute winding problem, but it did not open. The return capsule rose immediately after hitting the ground at an extremely fast speed, and the lesson was painful.

In addition, there are a series of operations, such as seat lifting and buffering, maintaining cabin pressure and so on. Ensure that astronauts land safely. I think there are two main differences. First, Shenzhou 12 docked with the core module of the space station for three months. Shenzhou spaceship didn't fly for so long before. In these three months, the space radiation environment has had an impact on the spacecraft equipment. Before the spacecraft is separated from the core module, we will conduct a comprehensive test on these equipment to ensure that there are no problems before leaving.

Three astronauts successfully returned to the ground. This is the first time that shenzhou spaceship has landed at the Dongfeng landing site. In the past, shenzhou spaceship landed at the Siziwangqi landing site. Why did you change places this time? In the past, shenzhou spaceship returned from a fixed altitude, but in the space station stage, shenzhou spaceship's orbit time became longer, and the orbit was influenced by the orbit planning of the space station, so the altitude changed greatly, so it was not necessary to return from a fixed altitude.

The change of altitude means that the range of the spacecraft returning to the landing site may change greatly, mainly in the east-west direction. Dongfeng landing site is located in Gobi area, which is wide in the whole east-west direction, and most of it belongs to no man's land or relatively safe area, so landing is more controllable and convenient. Beidou navigation terminal accurately locates the position of the spacecraft, and the measurement and control station monitors the flight of the spacecraft in the whole process, and the optical equipment and radar track and predict the trajectory.

The astronauts "feel good" and are proud to see the national flag flying. The spacecraft returned in a semi-ballistic way, which was controlled as a whole and had a landing point in theory. However, the spacecraft will be disturbed during reentry, and the atmospheric density and high-altitude wind field will have an impact on the trajectory of the spacecraft. When the parachute of the spacecraft is opened, the influence of the wind will be greater. But this does not mean that the landing of the spacecraft is uncontrollable. Return landing is a systematic project, which needs cooperation in many aspects. The landing site system and the ground measurement and control system need a lot of work. Many monitoring stations at home and abroad monitor the flight of spacecraft, and optical equipment and radar track and predict the trajectory.

After landing, the navigation terminal is still valid, and the search and rescue personnel can know the longitude and latitude coordinates of the spacecraft. On the premise of accurate forecast, the ground search and rescue team can reach the landing site quickly after the spacecraft lands. There are also wireless beacons and flashlights on the spacecraft to help search and rescue personnel find the spacecraft. Then after the evacuation of Shenzhou XII, our Tianzhou cargo ship did something. Our Tianzhou-2 was originally docked at the backward docking interface of this space station. It had to be separated and then flew to the front docking interface of the space station, and then docked with the front docking interface of the space station.

After the conclusion and docking, I will use the mechanical arm to assist it to carry out such a transposition experiment, just like our future experimental cabin will transfer it to the lateral docking interface, which is an experiment to verify the key technologies. So after that, in fact, we are going to launch our Tianzhou-3 cargo spacecraft, in which all the passengers of Shenzhou-13 ate and drank for six months. In other words, our Tianzhou-3 cargo spacecraft is about to launch and dock with our space station.

Our Shenzhou XIII spacecraft. Shenzhou 13 spacecraft will stay in orbit for six months, just like our normal crew rotation in the future, and each wave of crew will stay for the same time. That is to say, if the Shenzhou XIII mission can be implemented smoothly and normally, it means that we have completely mastered the key technologies of 1.000% needed for astronauts to stay in orbit for a long time. Therefore, the Shenzhou XIII mission will be our last manned mission in the key technology verification stage of the space station, which should be said to be very important.