On June 25, the Chang'e-6 returner returned safely to Earth with the lunar soil collected on the far side of the moon, and the return process was broadcast live throughout the process, attracting great attention from domestic and foreign media. This time the lunar sample returned, many Chinese said that their hearts were very calm, but the foreign media was not calm, especially Britain and the United States were very sour, and even said that China wanted to colonize the moon, properly promoting the theory of the Chinese threat.
The funniest thing is India, when the Chang'e-6 returner returned to Earth, Indian netizens also came to rub the heat, they released a picture of India's recovery of the return capsule, and the paint on their return capsule has not fallen off, and the surface of Chang'e-6 has been scorched, and now the Indians say they won. Many domestic media who don't know the truth are still echoing there, and some media are still serious about making excuses for Chang'e-6, such as the Chang'e-6 returner encountering a lot of space junk and so on, all kinds of reasons.
In fact, the Indian one is not a return capsule at all, the Indians have never launched a rocket from the ground, and then recovered it, and the picture that broke out on the Internet is the escape tower of a manned rocket.
The purpose of this escape tower is to allow astronauts to escape if something goes wrong during the rocket's liftoff to orbit phase. The recovery height of the escape tower that broke out on the Internet is only 17 kilometers, and it has not even reached the edge of the earth's atmosphere, and the speed of its fall is not very fast, and the friction with the atmosphere will not produce high temperatures. So there are no traces of burning on the surface of this escape tower, and the Indians have made a "finger tower as a cabin" this time.
Speaking of Chang'e-6, many people are curious, the surface of the rocket did not burn when it was lifted off, why did the surface temperature of the returner be so high when it came back to re-enter the atmosphere?
In fact, this is a high school physics problem, and the rocket carrying Chang'e-6 is the Long March 5 Yao-8 type, which wants to push the Chang'e-6 probe into space, and theoretically first has to increase the speed to 7.9 km/s, which is the first cosmic velocity. In fact, it can be put into orbit when it reaches 7.8 km/s, and after entering orbit, the fairing is detached and the probe is exposed. At this time, although the speed is high, it has already entered space, and there is no atmosphere, no matter how fast the speed is, there will be no high temperature on the surface.
After entering orbit, Chang'e-6 still needs to accelerate to 11.2 km/s, only in order to break free from the shackles of the Earth's gravity. The spacecraft flew in a parabolic line, gradually increasing the radius of its orbit until it was equivalent to the Moon, and then entered the Moon's orbit. Because the mass of the moon is very small, Chang'e-6 has to slow down, otherwise it will fly overhead. After sampling the moon, Chang'e-6 accelerated its flight and docked with the lunar orbiter, which returned to Earth with the lunar soil.
In the process of returning, the re-entry capsule constantly reduces its orbital radius to the Earth. At this time, the gravitational pull of the Earth is working, so that the speed of the re-entry capsule will become faster and faster, and when it reaches the edge of the Earth's atmosphere, the speed of the re-entry capsule changes back to 11.2 km/s, that is, the second cosmic velocity. It may be smaller, but it is still much larger than the first cosmic velocity. Worse yet, this time it's a test of scorching atmosphere.
How did the Chang'e-6 returner enter the Earth's atmosphere?
It doesn't come in all at once, but rubs it outside the atmosphere a few times, hits a few water drifts, and every time it comes into contact, the surface temperature of the returner rises once, and the kinetic energy is converted into heat energy. The speed slowly decreases and then re-enters the atmosphere, which experts call "semi-ballistic jump reentry".
Even so, the temperature on the surface of the returner is still very high, close to 3000 degrees Celsius, and there are very few metals that can withstand this high temperature, so the surface of the Chang'e-6 returner has black technology developed by the mainland, mainly a honeycomb-shaped thermal insulation layer.
The principle of thermal insulation is very interesting, it burns itself when the temperature rises when it rubs against the atmosphere, and then the substances in the honeycomb are constantly stripped away in the atmosphere to take away the heat. The principle is similar to that of sweating after running, the sweat of the human body evaporates, and the water vapor leaves the body surface to take away the heat, maintaining a constant temperature of the internal organs and brain.
Therefore, do not look at the blackened outside of the returner, the inside is not damaged at all, the lunar soil and the equipment inside have not been affected in the slightest, this technology is also the key to the future manned landing on the moon.
When the returner re-enters the atmosphere, there is another problem, and that is the black barrier. To put it simply, the outside temperature of the whole returner is high like a fireball, and the outside is surrounded by high-temperature plasma, and the electromagnetic wave signal cannot be transmitted or entered. At this time, the attitude control of the returner becomes a problem, at this time, the returner will automatically switch to autonomous navigation mode, fly according to the predetermined line, slow down again, and the communication can be restored after the temperature is reduced.
When interviewed by the staff of the China Aerospace Science and Technology Corporation, the first thing they said was "like shooting a target!" "I don't know how Americans will feel when they hear this. This self-regulating trajectory of the aircraft in the case of a black obstacle is also the core technology on a hypersonic ballistic missile, isn't it like shooting a target? The United States has not yet solved this problem, and what the mainland aerospace experts say seems to be very ordinary depends on the results of the painstaking research of countless scientific researchers.