At 23:10 on December 3, Beijing time, the Chang'e-5 ascender took off from the lunar surface and successfully entered the scheduled orbit around the moon with lunar samples. This is the first time that China has realized the takeoff of extraterrestrial celestial bodies.
Five-star red flag moon display simulation map
Before taking off, Chang'e 5 carried the combination to realize the deployment of the five-star red flag on the lunar surface. This is China's first "independent display" of the five-star red flag on the lunar surface. The weight of the five-star red flag shining on the moon is only 1 kilogram, and it can still "maintain its true colors" under a temperature difference of plus or minus 150 degrees Celsius.
The first "Fabric Edition" five-star red flag
The five-star red flag can be displayed independently on the moon, mainly relying on the assistance of the lunar flag display system. The system is composed of three parts: the lunar flag, the compression release device, and the deployment mechanism, and is about half a meter long. The system lifts off with the probe in the folded state, and after landing on the moon, it is unlocked and opened according to the instructions.
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 also allowed the Chinese probe to put the "Chinese logo" on the moon again.
The development team of China Aerospace Science and Industry Flag Display System discussed the manufacturing process. Source: China Aerospace Science and Industry Corporation
In order to develop this distinctive five-star red flag display system with a new level of difficulty in development, China Aerospace Science and Industry Corporation Aerospace Sanjiang Nine Department has experienced many challenges. Ensuring reliability is the first task of the five-star red flag display system. The entire system involves unlocking, stent deployment, and stent fixation steps. If the stent cannot be successfully deployed on the moon, all previous efforts will be abandoned. "Every action must be made to work properly, and this series of actions must be completed within 1 second." said Li Yunfeng, the project leader of the five-star red flag display system.
Pyrotechnics is the most basic part of the entire five-star red flag display system. If it cannot be detonated and unlocked, there will be no follow-up actions. Cheng Chang, the head of the five-star red flag display system technology, said that the pyrotechnics used in the system are among the smallest in the country with the same purpose and function. The development team put the pyrotechnic device in a liquid nitrogen tank of about -200 degrees Celsius and conducted dozens of tests in a high temperature environment to simulate whether it can be used normally under the extreme temperature difference environment on the moon and ensure that the five-star red flag can be smoothly on the moon. Slowly rise.
Material selection time exceeds 1 year
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 the early stage of the five-star red flag display system, the scientific research team designed a variety of display formats, including the memory alloy display program of the five-star red flag by scrolling, the servo flag raising program, and the mechanism display program, as well as a variety of programs that are deployed in the form of folding fans. Despite the different forms, the researchers found after high and low temperature tests that only the five-star red flag unfolded in the form of a scroll is relatively flat and does not appear to be wrinkled.
The China Aerospace Science and Industry National Flag Display System design team carried out technical seminars. Source: China Aerospace Science and Industry Corporation
How to ensure that the five-star red flag has sufficient strength and remains flat when it is deployed, the development team has done a lot of theoretical research and simulation tests around this issue. Cheng Chang said that the scientific research team spent more than a year in selecting materials, and finally selected 20 or 30 fiber materials. After physical tests such as thermal compatibility, high and low temperature resistance, anti-static, and anti-moon dust, they finally decided to adopt A new type of composite material 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 withstand the harsh environment of the moon surface, and does not fade, color, and deform.
"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.
Weighs only 1 kg
The plane motion envelope of Chang'e-5 five-star red flag is nearly 2000mm×900mm, and the weight of the entire system is only 1 kg. Ma Wei said that the selection of this flag size is the result of comprehensive consideration by the development team. The purpose is to highlight the field of view effect as much as possible, so that the photos taken by the camera can see the moon surface, deep space, and the lander; If the five-star red flag is too large or too small, the photos will not show rich elements.
Since the weight of the five-star red flag display system is only 1 kilogram, the development team has made a lot of efforts to reduce the weight of the entire system. Not only must the materials be lighter, but also the equipment must be "slim down." At the beginning of the project, the development team has demonstrated the use of quadrupole, tertiary and second-level poles. However, considering the complexity and weight and other reasons, they finally chose to use the second-level pole to present it.
"The reason why the rod system structure is adopted is that it is considered a relatively mature technology in the aerospace system, including the deployment of solar panels for spacecraft such as satellites and spacecraft. The rod system structure is used, and the purpose is to ensure reliability. ." Li Yunfeng said.
In order to control the weight of the entire five-star red flag display system, the development team also optimized the structure, and made the bracket arm as thin and small as possible on the basis of selecting high-temperature and severe cold-resistant materials. The support structure used in the system can withstand the harsh environment of alternating cold and heat, space irradiation, and extremely low vacuum in a space environment.