The Chang'e-5 mission is a great feat. It is an action taken by humans to once again enter the moon to collect lunar soil samples in the past 44 years. It is of great significance to the whole of China and the world; even many successful moon landings The United States, which collected lunar samples, did not hesitate to bow its head and wanted to share the results with China.
At present, the Chang'e-5 probe has completed most of its missions in space, from launching close to the moon and circling the moon, to landing on the moon and collecting samples, and to leaving the moon. Everything came quickly, from the time when Fat Wu sent the Chang'e 5 probe away from the earth at 4 o'clock on November 24, to the ascendant of the Chang'e 5 probe sent the lunar samples away from the surface of the moon at 12 o'clock on December 6 In less than 13 days, it's a bit of a quick fix.
Of course, the task of sampling on the moon is far less simple than what I said. It needs to overcome numerous difficulties, as well as continuous trials and attempts to have a large amount of resources and technical reserves. Similarly, it is necessary to overcome many difficulties to return the samples to the ground smoothly.
Everyone should remember the picture of the astronaut getting out of the capsule when the capsule landed on the ground; the astronaut sitting on the stool, and the capsule behind him was completely dark. This is precisely because the super high temperature caused by the friction between the space capsule and the atmosphere when it returns to Earth burns black. Or meteorites dropped to the surface from space. Usually there are burnt marks on the surface. How much temperature does an object like
need to withstand when it lands on the earth and passes through the atmosphere from space?
"thermal barrier" and "black barrier zone"
meteorites flying at high speed enter the atmosphere and rub against the air violently, causing violent combustion to emit light. When the spacecraft completes its mission and returns to Earth, it faces the same cruel living environment as a meteorite. "Research has shown that when the speed of the spacecraft reaches 3 times the speed of sound, the temperature of its front end can reach 330℃; when the speed of the spacecraft is 6 times the speed of sound, it can reach 1480℃. The spacecraft returns from space and reaches 60～70 degrees above the ground. At kilometer, the speed is still more than 20 times the speed of sound, and the temperature is above 10,000 degrees Celsius. This high temperature is enough to turn the spacecraft into a fire." High speed leads to high temperature, which seems to be an insurmountable obstacle. People call this obstacle "thermal barrier."
When the return module descends to a certain height in this area, it will not receive the radio signals sent by the ground, and the ground will not receive the radio signals sent by the return module. Therefore, this area is also called a radio black barrier. Area".
Can precious lunar samples "hold up" the ultra-high temperature friction with the atmosphere?
In fact, my country has already conducted relevant tests in the early years, and made sufficient preparations for the return of the Chang'e-5 probe. In order to prevent the sample from being burned by the ultra-high temperature in the atmosphere, the Chang'e-5 selected the "bounce type" reentry and return technology when crossing the atmosphere. The following is the return model diagram:
When Chang'e-5 enters the atmosphere for the first time, it will enter the second universe at a speed of 11.2 kilometers per second. If it passes through the atmosphere and reaches the ground directly, the sample will be burned in the atmosphere. But as long as the angle of the return capsule is adjusted before it enters the atmosphere for the first time, the return capsule will pop out of the atmosphere and enter the atmosphere for the second time. In this way, the initial speed of the return capsule when it enters the atmosphere is reduced. The lower the initial speed, the lower the maximum temperature of the return capsule in the atmosphere, thereby protecting the safety of the return capsule and the internal objects.
And on the outer layer of the return cabin, a special ablation material is installed. This material has a large heat of vaporization, a large heat capacity, good thermal insulation, and a strong function of radiating heat to the outside. When the return cabin is in violent friction with the atmosphere, the ablated material on the surface will take away a lot of heat through physical and chemical changes such as decomposition, melting, evaporation, sublimation, erosion, etc., to achieve the effect of controlling the surface temperature of the return cabin.
So our astronauts can return to the earth smoothly, it is inseparable from the ablation of the material. I believe that the body of the astronaut can withstand the environment of the return capsule, and the lunar sample can also withstand it. Moreover, the environment of the lunar sample on the lunar surface is already bad , and there is no atmosphere.The surface of the moon covered by layers has a maximum temperature of 160°C during the day and a minimum temperature of -180°C at night. The experimental data of
ablation material
In addition, the landing site of the lunar sample is the Siziwangqi Aerospace Landing Field in Inner Mongolia. The terrain is flat and open, there are no large rivers and lakes, and the whole year is dry and rainless, and the air is highly visible. The surface is solid, which can ensure the safety of the lunar sample. Home.
Summary
Chinese scientists have made full preparations for this mission, and designed a unique "water-drift" return method for the Chang'e-5 probe, as well as special aerospace insulation materials and a safe landing site to ensure The smooth return of Chang'e-5.
Because most of the entire mission has been successfully completed, believes that the final return mission will also be successfully completed, so we will rest assured to wait for the good news of the Chang'e-5 probe!
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