Cleverly captures two "blocking tigers" Chang'e 5 moon sampling returns with glory

　　Beijing BEIJING, December 17 electric

question: Qiao capture two "stumbling block" Chang-e V glory return

　　Author Guo Chaokai Pang Dan

　　On December 17, the Chang'e 5 that "picked the lunar soil" returned in glory and landed steadily in Siziwang Banner, Inner Mongolia. China's first automatic lunar surface sampling and return mission was a complete success.

　　In order for Chang'e-5 to return to the earth safely and smoothly, speed and temperature are two major problems to be solved. These two "blockers" are the key factors determining success or failure.

The reporter interviewed aerospace experts to reveal how the Chang'e-5 spacecraft seized these two "blockers".

Capture speed "blocking the way": "drifting" in space

　　Compared with the four "sisters" of Chang'e No. 1, No. 2, No. 3, and No. 4, Chang'e's "Five Girls" is undoubtedly a lucky one. Because of the automatic sampling and return mission, he got a precious round-trip ticket for Earth and Moon travel. ".

　　It is not an exaggeration to say that this "round-trip ticket" is precious.

Up to now, only the spacecraft of the United States and the former Soviet Union and the Chinese Lunar Exploration Phase III reentry and return flight tester have carried out the reentry and return test by orbiting the moon.

Data show that there are three types of foreign reentry spacecraft: ballistic reentry spacecraft, ballistic-lift reentry spacecraft and lift reentry spacecraft.

The Chinese lunar exploration project adopted a brand-new reentry method-a semi-ballistic jump reentry return.

　　Why choose this re-entry return program with "Chinese characteristics"?

What's the emphasis and approach?

The return speed of the Chang'e-5 returner from the moon is the second cosmic speed of 11.2 kilometers per second, while most of the spacecraft returning from low earth orbit have the first cosmic speed of 7.9 kilometers per second. Don’t underestimate this. A gap of 3.3 kilometers per second.

Aerospace experts used an analogy, which is like throwing a stone. The same stone is thrown at a different speed from one floor than a dozen floors.

In the same way, the speed of a spacecraft's return from a low-Earth orbit hundreds of kilometers high and the return of the moon from a distance of 380,000 kilometers must be different, and the gap is huge.

　　The first thing to solve is the speed problem.

How can I successfully slow down?

This is a world-class problem.

On the basis of repeated study and research on the experience of the United States and the Soviet Union, and based on the actual situation of China’s spacecraft, the orbital designers of the General Design Department of the Fifth Academy of China Aerospace Science and Technology Corporation decided to use the earth’s atmosphere as a natural barrier for the reentry and return of the spacecraft through air friction. The resulting resistance achieves the purpose of deceleration and proposes a bold plan-a semi-ballistic jump reentry return.

　　"Just like flying water in space, the returner first enters the atmosphere at high speed, then jumps out of the atmosphere with the help of the lift provided by the atmosphere, and then plunges into the atmosphere at the first cosmic speed and returns to the ground. It will be completed within 15 minutes.” said Meng Zhanfeng, the overall chief designer of the Chang'e-5 probe, the overall design department of the Fifth Academy of China Aerospace Science and Technology Corporation.

Volt temperature "blocking the way": heat-proof "Neon Feathers"

　　Another obstacle on the way back to the "home" of the Chang'e-5 returner is temperature.

When it enters the atmosphere at high speed, friction will generate violent high temperature, and the sharp increase in heat will also bring great challenges to the return of the spacecraft.

　　Those who have seen the Shenzhou spacecraft return to the cabin must have been deeply impressed by the jet-black appearance.

The reason why the whole body is black is that when the return capsule returns to the earth from low-Earth orbit, it is burnt by the high temperature generated by the intense friction of the atmosphere.

"The speed of re-entry is doubled, and the heat of re-entry will increase by 8-9 times." said Dong Yanzhi, the chief designer of the Chang'e-5 probe structural subsystem of the General Design Department of the Fifth Academy of China Aerospace Science and Technology Corporation.

Once such a high temperature enters the interior of the return device, the consequences will be disastrous.

　　How to prevent heat and how to fight against ablation has become a difficulty that must be overcome.

For this reason, the heat-proof structure design team of the overall design department ingeniously designed a "intimate heat-proof clothing" for the detector.

First of all, in response to the requirements of the lunar orbit return thermal environment, space environment and weight, the design team proposed specific requirements and indicators for ablation resistance and heat insulation of different parts, and selected 7 heat protection materials from 33 new research materials to complete the protection The layout of thermal materials and the design of local heat-proof structure have realized the leap of heat-proof structure design in China from low-Earth orbit reentry to deep-space orbit reentry.

　　Secondly, the design team proposed a three-dimensional heat transfer ablation analysis method, using overall variable thickness, variable density, sub-regional, off-axis design schemes, breakthrough key technologies in lightweight design, and using one-dimensional ablation analysis and three-dimensional temperature field analysis. The combined numerical analysis method realizes the replacement of the whole device ablation test with a comprehensive local ablation test, laying the foundation for the success of the test task.

　　From heat protection structure design, heat protection material forming process research, welding process research, to engineering prototypes, structural devices, thermal controllers, special test verifiers, correct samples... the heat protection "Neon Feathers" of the Chang'e 5 detector It is carefully "sewn" and becomes a life guarantee for a safe and smooth return to the earth.

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