In order to welcome the Shenzhou XIV spacecraft's triumphant return, the Jiuquan Satellite Launch Center's landing site system carried out the last all-process, all-element search and rescue ensemble practice during this time. Although we have completed many search and recovery missions for the Shenzhou spacecraft's return capsule before, the Shenzhou XIV mission return was even more difficult than the previous ones, and can be called the most difficult one in history.
Because the Shenzhou XIV spacecraft returned at night, coupled with the fact that it is now December, the temperature is very low, and the temperature at the landing site can be as low as more than 10 degrees Celsius below zero. This is the first nighttime low-temperature return mission at the Dongfeng landing site, and the low-temperature environment is also a challenge for search and rescue team members. Because it is a night return, so the night search is also very difficult, for the night search of the existence of difficult problems, scientists based on China's Beidou navigation system to build a sky-ground integration of the search and guidance system, in addition to the deployment of a small micro-optical equipment with micro-light, infrared function, to enhance the search and rescue personnel in the night to discover the ability of the return capsule.
In response to the problem of extremely cold temperatures that may lead to abnormalities in the equipment, the staff also gave the equipment protection against low temperatures, such as adding a low-temperature start-up device to the car, and equipping those communication devices with enough batteries. The on-site medical ambulance was also upgraded, such as installing a fuel fan to regulate the temperature of the compartment, so that the temperature inside the compartment could be maintained at more than 20 degrees Celsius, so that the astronauts would have hot meals on site after returning to Earth. In addition, the staff also prepared the astronauts warm baby, insulation quilt, insulation blanket and other insulation facilities.
From the scene, the astronauts need the help of the staff when they leave the cabin, and they don't stand and walk immediately after leaving the cabin, but sit on chairs to rest. This is because the astronauts after six months of space flight, the body has been adapted to the weightless environment of outer space, and now back to the ground, we have to re-adapt to the environment of the ground gravity, and even need to re-learn how to stand up and walk. In addition, we can also see that the external part of the return capsule is black, or even completely disfigured, how is this? What happened to the spacecraft when it returned to Earth?
I believe we have all seen meteor showers in the night sky, and the process of the spacecraft returning to Earth is in fact similar to meteor showers, except that those meteor showers directly in the atmosphere burned fiercely into ashes, while the spacecraft return capsule will be safe to land on the ground or in the ocean.
Ships and meteors burn violently when they enter the atmosphere because they travel very fast. Spaceships flying in near-Earth orbit can reach speeds of about 7.9 kilometers per second, and if they are returning to Earth from the Moon or Mars, they are even faster, reaching or approaching Earth's escape velocity of 11.2 kilometers per second. When the spacecraft enters the Earth's atmosphere at such a fast speed, it will be subject to air resistance, at which time the aerodynamic heating effect will be very strong, and the temperature outside the spacecraft will rise sharply to thousands of degrees Celsius, or even thousands of degrees. The picture below shows the return capsule of the Shenzhou 13 spacecraft, which is partially black.
If the spacecraft is in near-Earth orbit, the speed is relatively slower, the aerodynamic heating effect is relatively weaker, and the temperature will be relatively low; if the spacecraft returns to Earth from the Moon or Mars, the speed is faster, the aerodynamic heating effect is stronger, and the temperature will be higher. So before Chang'e 5 detector return vehicle in the return to earth will use "playing water" way in the atmosphere "drift" "drift" and then return to earth, so that the speed of the This reduces the speed. The picture below shows the Chang'e 5 probe's return vehicle, which is just as dark.
After the spacecraft enters the atmosphere, the effect is similar to that of a meteor entering the atmosphere, and there is a violent burning phenomenon. This is the reason why some satellites, cargo ships and other spacecraft are controlled re-entry into the atmosphere and burned, while manned spacecraft need to take into account the safety of the astronauts landing, so the manned spacecraft return capsule has been specially treated to withstand the burning of the spacecraft re-entry into the atmosphere at a temperature of thousands of degrees Celsius. Although the temperature outside the spacecraft is very high, the temperature inside is very comfortable. After a period of burning, the spacecraft becomes slower and slower, and gradually the aerodynamic heating effect disappears and the burning phenomenon ends. Finally the return capsule of the ship landed steadily on the ground after a series of decelerations.
That's why the exterior of the capsule looks so dark, because the spacecraft was burned at high temperatures during its return to Earth. Astronaut Wang Yaping recalled in a previous interview how he felt when the spacecraft returned to Earth, like the Monkey King in the alchemist's furnace, the exterior of the porthole burned red, and there was a crackling sound, which was very shocking and thrilling.