Author: Guo Chaokai
At 23:10 on December 3, the 3000N engine of the Chang'e-5 ascender worked for about 6 minutes and successfully sent the ascender carrying the sample to the scheduled orbit around the moon.
This is the first time that China has realized the takeoff of an extraterrestrial body.
Since the successful setting of the moon at 23:11 on December 1, Chang'e 5 has quickly completed a series of tasks such as “digging”, “packing”, “raising the flag” and “taking off” within about 48 hours. Return to earth.
Source: Photo courtesy of China National Space Administration.
Photograph by Zhang Gaoxiang
"Digging"
As the final battle of the three-step "circle, fall, and return" of the Chinese lunar exploration project, the Chang'e-5 mission will collect about 2 kilograms of lunar samples from the moon and return to the earth.
After smoothly landing in the area north of the Rumke Mountains, Chang'e-5 immediately started automatic lunar surface sampling.
Automatic sampling is one of the core key links of the Chang'e-5 mission.
The detector has to withstand the test of lunar surface high temperature exceeding 100 degrees Celsius, overcome the constraints of measurement and control, illumination, power supply, etc., and realize multi-point and diversified automatic sampling.
The picture shows the automatic sampling of the Chang'e-5 probe on the lunar surface.
Photo courtesy of China National Space Administration issued by China News Service
Researchers have meticulously designed two "digging" modes for Chang'e-5: drilling and surface extraction.
Peng Jing, deputy chief designer of the Chang'e-5 probe system of the Fifth Academy of China Aerospace Science and Technology Corporation, said: “Drilling is through the core mechanism of a hollow drill rod to drill to a depth of two meters below the lunar surface to obtain the layering of deep samples. Information. Table fetching is to use a fixed shovel-digging sampler at the end of a robotic arm to collect surface and subsurface lunar soils to achieve multi-point and multiple sampling." These two methods are mutually backup, which not only improves the success rate of sampling Reliability, and at the same time, a richer variety of samples can be obtained, providing more reliable original data for subsequent scientist research.
"The initial consideration for drilling is 0.5 kg, and the table is 1.5 kg." Pei Zhaoyu, deputy director of the China National Space Administration's Lunar Exploration and Space Engineering Center and spokesman for the Chang'e 5 mission, once revealed.
At 4:53 on December 2, after more than 3 hours of continuous operation, the Chang'e-5 drilling subsystem successfully completed the drilling and sampling task.
On the other side, table sampling and sampling were also carried out in an orderly manner.
The robotic arm used for table picking is quite eye-catching. The arm is 3.7 meters long and consists of dozens of joints.
Due to the better conditions in the landing area, Chang'e-5's sampling work went more smoothly than expected. It only took 19 hours to complete the automatic lunar surface sampling task ahead of schedule.
"Bale"
Compared with the extremely high vacuum environment on the lunar surface, the earth’s surface is surrounded by the atmosphere. There are not only gas components, but also various solid particles floating in the atmosphere. If the lunar sample comes into contact with these substances in the atmosphere, it will cause pollution and lead to the moon. The research value of samples is greatly reduced.
Chang'e-5 has a combined model.
Photo courtesy of Beijing Flight Control Center
How to "pack" the lunar samples 380,000 kilometers away under unmanned conditions and ensure that the samples are not contaminated during the return to Earth?
The Lunar Sample Sealing and Packaging Subsystem developed by the 510 Institute of the Fifth Academy of China Aerospace Science and Technology Corporation gave the "answer". The system can automatically accept and encapsulate lunar samples and has a sealing function device, which can "pack" the collected lunar samples. Return to earth.
It is especially important to do a good job in packaging and "packaging".
In the packaging process, the designer of the 529 Factory of the Fifth Academy of China Aerospace Science and Technology Corporation innovated a "double-tube single-bag" drilling and core plan.
After drilling the lunar sample into the coring tube, the coring soft bag drawstring is lifted up, and the sample is automatically put into the soft bag.
Due to its soft texture, the soft bag can be wound and packaged easily, and then placed in the primary packaging device.
Luan Enjie, an academician of the Chinese Academy of Engineering and former director of the China National Space Administration, vividly likened the process of drilling and packaging to "installing sausages."
During the sampling and packaging process, scientific and technical personnel simulated the geographic model of the sampling area according to the data returned by the detector in the ground laboratory and simulated sampling throughout the entire process, providing an important basis for sampling decision-making and operation of each link.
After about 19 hours of lunar surface work, the Chang'e-5 probe successfully completed automatic sampling of the lunar surface at 22:00 on December 2, and the samples were packaged and stored in the storage device carried by the ascender in a predetermined form.
"Flag Raising"
Apart from the intensive “digging” and “packing” work, the Chang'e-5 probe has not forgotten to perform a sacred “flag raising ceremony” on the moon.
Before taking off, Chang'e 5 carried the combination to realize the deployment of the national flag on the moon. This is the first time that China has realized the "independent display" of the national flag on the moon.
Five-star red flag moon display simulation map
Unlike the five-star red flag on Chang'e-3, Chang'e-4, and Yutu lunar rover that use spraying methods, the "fabric version" of the five-star red flag on Chang'e-5 is a real flag.
This is another successful display of the five-star red flag on the surface of the moon, and it has also allowed the Chinese probe to put the "Chinese logo" on the moon again.
The universe has strong electromagnetic radiation, the lunar surface environment is harsh, and the temperature difference can reach plus or minus 150 degrees Celsius, which determines that the ordinary five-star red flag cannot be used on the moon.
In order to allow the five-star red flag to be successfully deployed on the moon, the China Aerospace Science and Industry Corporation research and development team spent more than a year to select materials, and finally selected 20 or 30 fiber materials as candidates.
Through physical tests such as thermal compatibility, high and low temperature resistance, anti-static, anti-lunar dust, etc., the development team finally decided to adopt a new type of composite material, which can not only meet the strength requirements, but also meet the dyeing performance requirements, so as to ensure that the five-star red flag can resist the moon surface In harsh environments, it does not fade, cross-color, or deform.
The China Aerospace Science and Industry National Flag Display System design team carried out technical seminars.
Source: China Aerospace Science and Industry Corporation
The plane motion envelope of the Chang'e-5 five-star red flag is nearly 2000mm×900mm, but the weight of the entire system is only 1 kg.
"Although this is only a thin five-star red flag, it has a very high technological content." Ma Wei, the commander of the five-star red flag display system project, said with emotion.
"take off"
When Chang'e "Five Girls" finishes her lunar surface work, she will embark on a journey of "back to her natal family".
As the saying goes, everything is difficult at the beginning, and it is not easy to return to Earth. Whether the first step can be "good" is crucial. This involves another first in the history of China's aerospace-the moon's take-off and rise.
The moment the Chang'e-5 riser is ignited. Photo courtesy of China National Space Administration. Photography: Zhang Gaoxiang
After the lunar sample sampling and packaging is successfully completed, the ascender will be ready to take off on the lunar surface, which is a difficult subject.
As we all know, a carrier rocket has a complete launch tower system for take-off from the earth, the ignition and take-off position is also accurately calculated, and the flight path is calculated over and over again.
But take off on the moon is different. It does not have a take-off location for Ma Pingchuan, and there is no mature and complete launch tower. The lander is equivalent to the launch tower of the ascender, holding Chang'e "Five Girls" home.
In addition, the ascender has to overcome the problems of the earth-moon environment difference and the limited space of engine plume diversion.
When taking off on the lunar surface, it is still impossible for ground personnel to complete measurement, adjustment and confirmation before ground launch, like a carrier rocket, and must rely on the spacecraft to "self-reliance" to achieve autonomous positioning and attitude determination during takeoff.
In order to ensure that the ascender can take off and ascend smoothly, the Chang'e R&D team of the Fifth Academy of China Aerospace Science and Technology Corporation conducted a large number of tests and verifications and established a set of interlocking system guarantee missions to help Chang'e 5 successfully take a step home convoy.
At 23:10 on December 3, the "returning with full load" of the Chang'e-5 ascender took off from the moon, achieving China's first extraterrestrial celestial takeoff.
Later, after completing the rendezvous and docking, sample transfer, and waiting around the moon, Chang'e 5 will officially set off to return to Earth.