China News Service, Beijing, December 2nd, title: Four ingenious designs to protect the "Five Girls of Chang'e" into the "Guanghan Palace"
Author Guo Chaokai
At 23:11 on December 1, Beijing time, the Chang'e-5 probe successfully landed in the pre-selected landing area near the front of the moon at 51.8 degrees west longitude and 43.1 degrees north latitude, and returned a landing image.
After active deceleration, rapid adjustment, approach, hovering obstacle avoidance, slow descent, and free fall, the steady fall of the "Five Girls of Chang'e" seems light and relaxed, but it contains a lot of wisdom and accumulation of scientific researchers.
The reporter interviewed experts from the China Academy of Space Technology affiliated to China Aerospace Science and Technology Corporation to reveal the four ingenious designs of the Chang'e 5 moon landing.
Design 1: "Accurate site selection and stable settlement"
The setting moon of the Chang'e 5 mission is the same as the braking of the recent moon. There is one chance and only one success.
Since it involves the lunar takeoff of the ascender after sampling, the process of the Chang'e-5 landing on the moon is also to select the "launch site" for the subsequent lunar takeoff of the ascender.
Compared with Chang'e-3 and Chang'e-4, Chang'e-5 has unprecedented high requirements for the location accuracy and flatness of the landing site. This requires no too high bumps, no too deep pits, and gradients in the landing area. To meet the task requirements.
In order to achieve "correct site selection and accurate settlement", Chang'e 5 adopted the "coarse and fine relay obstacle avoidance" method used on Chang'e 3 and 4 of the China Academy of Space Technology 502.
The landing and ascent assembly will hover once when it reaches 100 meters from the lunar surface. By taking pictures of the selected area, the landing point can be accurately identified and selected.
After that, the landing ascending assembly flies diagonally downwards, paying attention to avoiding obstacles while descending, flies directly above the selected landing site and then descends vertically, shuts off the main engine in advance when it is closer to the lunar surface, and then uses the landing legs. Buffer to achieve a soft landing.
Design 2: Landing buffer "show your talents"
The key to the falling moon lies in the word stability.
When the Chang'e 5 landing ascending assembly hits the lunar surface, it will cause a large impact load. It is necessary to design a corresponding landing buffer system to absorb the impact load of landing to ensure that the probe does not tip over or sink. This is the falling moon. One of the technical difficulties.
The landing buffer mechanism, in layman's terms, is the "leg" of Chang'e-5.
Compared with the landing buffer design scheme of Chang'e-3, due to the increased difficulty of the mission, the landing buffer capacity requirements of the Chang'e-5 mission have been increased by 30%, but the agency weight index has been reduced by 5%.
The "legs" of Chang'e 5 inherited the good genes of Chang'e 3 and Chang'e 4. It has a completely independent intellectual property rights of "biased close, self-tightening" scheme, which guarantees simple folding and reliable deployment, and solves the landing buffer. Various issues such as landing stability ensure that Chang'e-5 can complete its "close embrace" with the moon in a stable and reliable manner.
Design 3: "Please close your eyes at dark"
During the landing process, when the Chang'e-5 landing ascending assembly is close to the lunar surface, the main engine will arouse moondust, which will easily trigger the moondust to pollute the star sensor, which will affect the subsequent lunar takeoff of the ascender.
In order not to let the moon dust "fascinate the beautiful eyes of the ascender", the researchers specially designed a cover.
Cover the lens of the star sensor at a certain height from the moon surface. After the moon is set, the moondust will dissipate, and the star sensor will be notified to open the cover. Between the opening and closing, the lander and ascender are combined. Has successfully landed on the moon.
This process is affectionately called "close your eyes when it's dark" by researchers.
Design four: directional antenna "a thread"
The falling moon affects the hearts of Chinese people.
What test is Chang'e 5 going through at a distance of 380,000 kilometers?
All information needs to be transmitted through a small "pot" of the landing and ascent assembly to transmit telemetry data.
This "small pot" is a directional antenna-a transmission conversion device that transmits data from the detector to the ground.
To send data from the moon back to the earth, the communication distance is tens of thousands of times farther than ground mobile phone communication, which requires a special ground directional antenna to send data.
The directional antenna designed by the researchers includes a reflective surface antenna radiator and a biaxial drive mechanism.
In order to reduce the weight of the whole device, this reflector antenna has an extremely lightweight design, which is more than 40% lighter than similar antennas, which is both light and reliable.
Experts from the China Academy of Space Technology said that the dual-axis drive mechanism is like a human shoulder joint and elbow joint. It drives the reflective antenna radiator to rotate flexibly, ensuring that the "small pot" is always aligned with the ground and transmits the moon landing on Chang'e 5 to the earth. Telemetry data.
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