All content in this article is based on official and reliable sources, and the specific information is detailed at the end of the article.
Preface
Chang'e-6 returns to Earth! Achieve the world's first sample return from the far side of the Moon!
After successfully completing the task, it returned with honors, and in the midst of congratulations, the focus of netizens gradually deviated.
It is obvious that the surface of the returner is "black and scorched", and netizens bluntly said that it looks fragrant.
Why is it that when I return, it is always dark, but when I lift off, there are no burn marks?
What happened to our Chang'e-6 in the sky?
A charred exterior, a solid heart
At 2 p.m. on June 25, Chang'e-6 landed safely in a predetermined area in Inner Mongolia!
After 53 days, I finally returned to the embrace of the motherland!
Because Chang'e-6 collected samples on the far side of the moon, it circled the vast expanse of space before returning to its homeland.
Reference source: People's Daily client 2024-6-25The Chang'e-6 mission was a complete success to achieve the world's first sample return on the far side of the moon
I believe that many people are waiting in front of the TV to watch this historic moment.
However, many people still found a "bright spot", how did the surface of the returner look like it was burned?
It can be seen from the appearance that it is not easy for Chang'e-6 to return, but how did that black cause it?
Could it be that the mainland's aerospace fire prevention and heat insulation technology is not mature enough? The answer is obvious, definitely not.
Then we have to start with the process of Chang'e-6's return, and the "zoom" was caused on the way back.
You must know that the speed of Chang'e-6 in the sky is very fast, so it is almost impossible to land upright.
Therefore, the return method of Chang'e-6 adopts a jump re-entry and return, which is also jokingly called "drifting" return by netizens.
The whole process is divided into five stages, taxiing section, initial re-entry section, free flight section, secondary re-entry stage, and landing stage.
When Chang'e-6 was 5,000 kilometers from Earth, the orbiter and returner began to separate.
After the returner separated, the first step of single-cabin taxiing began, which meant that it officially said goodbye to space.
When the returner glides to an altitude of 120 kilometers, the returner first enters the atmosphere at a small angle of -6 degrees, and the speed is close to the second cosmic speed, up to 10.9 kilometers per second!
What is this concept? The high-speed returner rubs against the air, and the high temperature generated can reach more than 2,000 degrees.
So what is the result of high-temperature roasting, when it burns, it is the surface that we see burned.
The high temperature of 2,000 degrees Celsius is enough to turn objects into ashes in an instant, but you don't have to worry about the inside at all, because there are no injuries inside.
It's not that there are no heat-resistant materials, but it is the most powerful proof that heat-resistant materials resist high temperatures.
The returner decelerates for the first time after being dragged by the atmosphere, and the speed decreases rapidly, but the first reentry time does not exceed 300 seconds, so the speed is not low enough.
After jumping into the atmosphere, reaching a position of about 60 kilometers, the Chang'e-6 returner jumped out of the atmosphere by the lift of the atmosphere, and the returner reached the third stage of free flight.
And free flight is not a random play regardless of it, but is controlled by a attitude control engine.
After a period of free flight, the returner lasts about 500 seconds and begins to gradually lose altitude due to the gravitational pull of the Earth.
In the second re-entry phase, the returner re-enters the atmosphere again for about 400 seconds, which is already below the first cosmic velocity.
In the atmosphere, the speed will continue to decrease, and the fifth step will be reached.
At an altitude of about 11 kilometers, the two-stage parachute opens step by step, and finally relies on the parachute to control the speed and achieve a smooth landing.
That's also friction with the atmosphere, why didn't Chang'e-6 see a little spark when it lifted off?
Escort Chang'e-6
According to the China Aerospace Rocket Institute, the heat-proof structure of the Chang'e-6 returner is made of lightweight honeycomb reinforced heat-proof materials, which have the advantages of low density, light weight, excellent ablation and heat protection effect, good consistency and high reliability.
It also said that the temperature difference in the lunar orbit is ±150°C, there is cosmic radiation in the environment, and the atmospheric friction is up to 3,000°C during flight.
The heat-resistant materials used in the Chang'e-6 returner have been optimized on the basis of the materials used in the Chang'e-5 returner.
After several rounds of screening, researchers have developed continuous fiber-reinforced SPQ materials, polyimide wave-transmitting antennas, thermal control coatings, etc., to escort Chang'e-6.
Reference source: China Aerospace Rocket Institute2024-06-25 The aerospace materials of the Rocket Institute escort the Chang'e-6 returner in an all-round way
When the returner landed, it was scorched black, which caused a lot of heated discussions, and the question of why it was as smooth as new when it was lifted off once again became the focus of public attention.
If it is said that the returner burns violently because of the friction with the atmosphere, then doesn't it also have to go through the friction with the atmosphere when it takes off?
Why is there such a big difference between the two?
When I think carefully about the launch of Chang'e-6, it was also so much attention, and there was no sign of scorching black.
It turned out that when it lifted off, the Chang'e-6 probe was not directly exposed to the outside.
At the very top, there is a powerful fairing rushing to the front, like a solid shield against the high temperature that friction may bring.
Although the rocket is accelerating, the atmosphere is still relatively dense and cannot reach high speeds.
Therefore, the speed is not reached, the friction is not so intense, and the temperature does not rise above 1,000 degrees.
Besides, the detector is not directly exposed, so not to mention that it burns and turns black.
It wasn't until the rocket successfully sent Chang'e-6 out of the atmosphere that the fairing also completed its mission and separated from it.
Chang'e-6 finally arrived at the designated location to carry out the first lunar sampling of all mankind.
In the end, Chang'e-6 lived up to expectations and successfully sampled, which not only took the first step in sampling the back of the moon, but also proved China's strength.
The countries that looked down on China in the past have been impressed by us, and the moon back sample has become a common expectation of scientists around the world.
China is also willing to share samples of the moon's back and work together for the progress of mankind.
epilogue
Chang'e-6 has achieved the first lunar sampling, which is a big step for China and a big step for the world.
The hard work of countless scientific researchers behind the scenes enabled Chang'e-6 to successfully complete this mission and let the world see China's strength.
We want to refuel China's aerospace, although it started late and there are many difficulties, but now China has been at the forefront of the world.
From frontal sampling to behind-the-back sampling on the moon, China is willing to share its achievements with the world and is committed to making positive contributions to the progress of all mankind.