This article is from WeChat official account: Tencent space (ID: qqtaikong) , Author: Joe Hui, from the title figure: Vision China

At 4:30 a.m. on November 24, 2020, my country’s Long March 5 carrier rocket was launched at the Wenchang Space Launch Site in Hainan, carrying my country’s Chang’e-5 lunar probe, and it achieved complete success!

This is my country’s first lunar sample return mission, and it is also the most complicated space mission performed by my country so far.

It is reported that this space mission has 11 major flight phases, 23 major orbit control, 6 major separation control and other complicated links, as well as spacecraft lunar landing, lunar take-off, and “unmanned rendezvous” in lunar orbit. High-risk links such as “docking”. The entire sampling return process lasted as long as 23 days, and the launch and take-off was only the first step in the long march.

1. Why must the Long March 5 rocket be used for this mission?

Long March 5 Rocket(commonly known as “Fat Five”) is my country’s current rocket with the strongest carrying capacity, with a carrying capacity of 25 tons in low earth orbit and 6 tons in ground fire transfer orbit. The carrying capacity of the Earth-Moon transfer track is 8.2 tons.

Long March 5, Yaowu carrier rocket for vertical transport.

Previously, the Long March 3A rocket, the Long March 3C rocket, and the Long March 3B rocket undertook the mission of launching our lunar probe, successively launching Chang’e 1, Chang’e 2, Chang’e 3 and Chang’e 4 The four lunar probes completed the orbiting detection, landing detection and patrol detection of the moon.

However, the Chang’e-5 launch mission is none other than the Long March 5. Why is this?

In principle, the rocket-launched detector with a large carrying capacity depends on two factors: one is to see how heavy the detector is, and the other is to see where the detector is going. Let’s take a look at the situation of Chang’e 5 in detail: The Chang’e 5 probe weighs about 8.2 tons and the destination is the moon 380,000 kilometers away. my country’s current long march 5 rocket with the strongest carrying capacity It just meets the requirements, so it must be launched with the Long March 5 rocket.

On July 23, 2020, the Long March 5 carrier rocket also successfully launched the “Tianwen-1” Mars probe, which is currently on its way to Mars.

2. What is the difference between Chang’e 5 and previous Chinese lunar exploration missions?

The logo of the China Lunar Exploration Project.

The China Lunar Exploration Project is the first lunar exploration project launched in my country. It was officially launched on January 23, 2004. It is divided into three parts: winding, falling, and returning.

1. “Orbiting” means launching lunar satellites. Chang’e-1 and Chang’e-2 have been realized;

The flight track of Chang’e 1 (left), and the flight track of Chang’e 2 (right).

2. “Land” means a soft landing on the surface of the moon. Chang’e-3 has achieved a soft landing on the front of the moon, and “Chang’e-4” has also achieved a soft landing on the back of the moon, and scientific exploration is carried out on the back of the moon. This is the first time in the world. Although Chang’e-4 is the backup star of Chang’e-3, it has achieved many innovations.

The Chang’e-4 lander on the moon.

3. “Back” means to sample from the surface of the moon and return to the earth. This is the mission carried out by Chang’e-5, which plans to bring 2 kg of lunar soil samples back to the earth..

It is worth mentioning that, later, my country expanded the mission of “Lunar Research Station”. The mission was completed by the subsequent “Chang’e-6”, “Chang’e-7” and “Chang’e-8”. It plans to land on the lunar south pole and conduct more complex scientific research.

3. How many lunar samples have been collected by the United States and the former Soviet Union?

We know that so far, only two countries have successfully brought back samples from the moon: the United States and the former Soviet Union.

The moon rock recovered by the Apollo 15 astronauts.

Among them, in the 1960s and 1970s, the United States used six manned moon landings in the Apollo program and retrieved a total of 381 kilograms of lunar soil and lunar rock samples from the moon.

The lunar soil collected by the Apollo 17 astronauts.

The former Soviet Union used three unmanned probes on Lunar 16, Lunar 20 and Lunar 24 to retrieve a total of 330 grams of lunar soil samples in the 1970s.

From the last Soviet Lunar 20 probe in 1976Starting from the next lunar sample return, mankind has not obtained lunar samples for 44 years.

4. What does the Chang’e-5 detector look like?

The Chang’e-5 probe consists of four major parts: orbiter, lander, ascender and returner.

The orbiter refers to the lunar orbiter. After Chang’e 5 enters the lunar orbit, the orbiter first resides in the orbit, waiting for the subsequent return to the earth to be carried by the returner.

The lander is equipped with a reverse thrust rocket to perform a soft landing on the lunar surface, and automatically perform operations such as lunar surface sampling and sample packaging.

The ascender uses a lander as a launch pad to take off power from the lunar surface, carry lunar soil samples into the lunar orbit, and transfer the lunar soil to the returner.

The returner is the part of the structure that will eventually carry the lunar soil sample back to the earth, and it will withstand the high temperature and impact when it enters the earth’s atmosphere at high speed, protecting the sample from being affected.

Chang’e-5 is tested on the ground.

V. What dangers will the Chang’e-5 probe go through?

At the beginning of the article, we mentioned that this space mission has 11 major flight phases, 23 major orbital controls, 6 major separations and other complex links, as well as spacecraft landing on the lunar surface, taking off on the lunar surface, and orbiting the moon. “Unmanned rendezvous and docking” and other high-risk links. Without discussing the technical details, we mainly look at these 5 key points.

1. Rocket launch: Even today in the 21st century, rocket launch still has a relatively large uncertainty. In 2017, my country’s Long March 5 Yao-2 launch vehicle failed and failed to put the payload into orbit. Happily, both the Changwuyaosan launch vehicle launched in 2019 and the Changwuyao four launch vehicle launched in 2020 were perfectly successful.

2. Lunar landing phase of the probe: We know that previously, the Chang’e-3 and Chang’e-4 lunar probes achieved soft landings on the front and back of the moon, respectively, and achieved soft landings on the moon. The key is the power decline phase.

Because there is no air on the moon, if the probe wants to land on the moon softly, it must use a reverse thrust rocket to slowly descend, and carefully choose a relatively flat landing site to prevent “rollover” accidents, which is also a high-risk key link . In 2019, the Israeli lunar lander and the Indian lunar lander crashed on the lunar surface one after another.

Chang’e-5 landing on the lunar surface (art picture).

The situation of Chang’e 5 on the moon (art picture).

3. Lunar take-off phase: When Chang’e-5 has obtained enough samples from the lunar surface, the ascender uses the lander as a launch pad, carries the samples and ignites from the lunar surface, and then The first cosmic speed accelerating to the moon enters the lunar orbit and is ready to dock with the orbiter waiting on the lunar orbit.

Although the gravity of the lunar surface is only one-sixth of that of the ground, it is still very difficult to take off from the moon 380,000 kilometers away, and this is our first attempt, and there is a lot of uncertainty.

Chang’e 5 ascender carrying lunar soil samples ascending (art image).

4. Lunar orbital junction and docking: When the carrier sample’s ascender enters the lunar orbit, it must be docked with the orbiter waiting there to transfer the sample to the orbiter and returner combination Body. We are very proficient in the rendezvous and docking of spacecraft in Earth orbit, but it is the first time for us to rendezvous and dock in lunar orbit, and there are still many technical details to be explored.

The ascender and orbiter of Chang’e 5 are preparing for lunar orbital rendezvous and docking