How did China accomplish another "space drift"?

　　BEIJING, Dec. 17 (Xinhua)

　　Author Guo Chaokai

　　In the early morning of December 17, the Chang'e-5 returner returned to Earth in the form of a "space flotation" and successfully landed in the predetermined area of ​​Siziwang Banner in Inner Mongolia. China's first lunar sampling and return mission was a complete success.

　　"Water Drift" is an ancient and interesting game in China. The return of Chang'e 5 is the second "Space Drift" played by China. The first one has been implemented on the reentry and return flight tester in the third phase of the lunar exploration. .

The reporter interviewed space experts and revealed how China's second "space water drift" was completed?

　　Previously, China had launched more than 20 returnable satellites, and recovered 11 Shenzhou series spacecraft and a new generation of manned spacecraft. The reentry and return flight tester for the third phase of the lunar exploration phase verifies the relationship between China’s moon and the earth in a nearly 1:1 manner. "Drifting" type space return technology.

　　In fact, compared with the earth's orbit, the biggest difference in the return from the moon to the earth is the speed. Chang'e-5 carries a lunar sample to return to the earth at a high speed close to the second cosmic speed, which is about 30 times the speed of sound.

"Drifting" is to allow the returner to consume enough energy during the flight and rise again in the atmosphere to reduce the speed.

　　This "space drift" in China should be called "semi-ballistic jump return" to be precise, that is, after the returner enters the atmosphere for a certain "depth" for the first time and slides for a certain distance, the attitude of the returner is adjusted to make it rise again. high.

As the returner rises, its speed will further decrease. When it drops below the first cosmic speed, the returner no longer meets the basic conditions of becoming an earth satellite and begins to fall again, and then returns in a process similar to the Shenzhou spacecraft. Returning to Earth, the following process will be familiar.

　　Why did Chang'e-5 return to Earth in the form of "floating and floating"?

According to an expert from the 502 Institute of the Fifth Academy of China Aerospace Science and Technology Corporation, the "float" is to take advantage of the east wind of the atmosphere to use the resistance of the atmosphere and the friction between the atmosphere and the return device to consume the kinetic energy of the return device.

It is reported that from its first entry into the earth’s atmosphere to landing, the Chang'e-5 returner has to fly for six to seven thousand kilometers in a state of "speedy and turbulent" and "big ups and downs."

　　Of course, the high-tech blessed "Space Drift" is still different from the "Drift Drift" played by the pond when I was a child. Once the tiles I played in my childhood were thrown out, they were no longer controllable, but Chang'e 5's The entire process of "space water drift" is controllable, but this control is done by the return device itself.

During a flight of six to seven thousand kilometers, the Chang'e-5 returner can "fly freely" within the allowable deviation range.

So, how does the return device realize the "small difference" in the process without the result being "a thousand miles away"?

This relies on the guided navigation and control (GNC) system equipped with 502 for Chang'e-5.

　　According to the expert of 502, the so-called GNC system, G (Guidance) means guidance. The computer in the returner will conduct guidance processing based on the current position and speed information, combined with the position of the landing point, and automatically plan a path from the current position of the returner to the start position. The best flight path of the parachute point; N (Navigation) means navigation, high-precision navigation equipment can obtain real-time information about its own position, speed, etc. in the vast universe; C (Control) means control, which can be controlled by the engine installed outside the returner Send jet control commands, adjust the posture of the returner, and make the returner fly along the planned trajectory.

G, N, and C work together to make the returner "all roads lead to the drop zone."

　　In order to achieve the goal of "smooth jump and accurate landing", scientific researchers have completed tens of thousands of simulated flight tests and simulated millions of flight routes during the development of the GNC system of the returner.

Experts from 502 said that although the final flight trajectory of the Chang'e-5 returner will not be the same as any of those million, it is certainly "unmatched."

(Finish)