The lunar surface sampling and return mission of Chang’e 5 is coming to an end. The “Five Girls” is expected to return to their hometown on the earth early on Thursday (17th). The landing site of Siziwang Banner in Inner Mongolia will be waiting. Different from China’s previous manned spacecraft’s return, Chang’e-5’s landing and recovery is much more difficult. The search team not only has to perform missions in the icy, snowy and dark nights, but also the volume of Chang’e-5 is much smaller, but the expected landing range is actually 16 times the Shenzhou spacecraft!
CCTV reported on Tuesday (15th) that the Siziwangqi landing site had held the last comprehensive exercise for the landing and recovery of Chang’e 5 in the dark. It’s the mid-winter season, and the freezing snow brings additional difficulties to search.
During the exercise, the search team received a forecast from the Beijing Flight Control Center for the landing of the Chang’e-5 returner, and used off-road vehicles and helicopters to advance by land and air, from the standby point to the returner’s scheduled landing point. The results of the exercise showed that the air squadron arrived at the scene quickly and the ground squadron’s disposal work was orderly. The recovery team’s night search and disposal capabilities and equipment performance indicators were further tested.
Why does Chang’e 5 wait until now?The rock has been dug a long time ago
Complete this difficult maneuver 21 seconds before Chang’e 5 returns home
The difficulty of the landing and recovery of Chang’e 5 lies not only in the conditions on the earth, but also in the mission design itself.
The Chang’e-5 spacecraft returned with 2 kilograms of Moon Rock, and the size of the returner was only about 7 minutes 1 of the Shenzhou manned spacecraft. However, the area of the scheduled landing area of the Chang’e-5 returner is 16 times that of the Shenzhou spacecraft.
Why is this happening?
This is because the Chang’e-5 returner needs to “drift” in the earth’s atmosphere, making it more difficult to narrow down the expected landing range accurately. Chang’e-5 returned from the moon at a speed much higher than that of a spacecraft in orbit on the earth, reaching 10 to 12 kilometers per second. If Chang’e 5 rushed directly into the earth’s atmosphere, it would burn down.
“Drifting” is to make the Chang’e-5 returner return after the atmosphere bounces. The principle is like a rock hitting the water at a high speed and then bounces, and then the speed will drop significantly when it falls. This further raises the requirements for the accuracy of the angle of Chang’e-5 when it returns, so as to prevent the returner from flying to other areas with too much force when it bounces, and even unable to return out of space.
Historic picture Chang’e 5 moon table displaying national flag
So after Chang’e 5 landed, why didn’t Beidou find her?
Beidou satellite navigation system, like GPS, requires the open air to receive satellite positioning signals. The Chang’e-5 returner has to withstand extremely high temperature and pressure when it re-enters the atmosphere. If the satellite positioning device is installed outside the cabin, it will be burned.
The built-in satellite signal transponder must also be used with an external antenna to use the satellite signal indoors.
As for the mobile phone can also be positioned indoors, it is because the mobile phone combines multiple positioning methods such as network signals to generate the final positioning data. This kind of network coverage is quite difficult in the wilderness of the aerospace landing site.
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Editor in charge: Lian Zhaofeng
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