Japan can sample asteroids, why can't it go to the moon? The core technology can't be conquered in seventeen years.

On June 6th, 2020, 65438+February 6th, 2020, China's Chang 'e V elevator and orbital return assembly completed the first automatic docking of lunar orbit in human history, and completed the encapsulation and transfer of lunar soil. Coincidentally, almost at the same time, Japan's Hayabusa II asteroid probe also threw its asteroid rock samples into the desert area of southern Australia and successfully recovered them.

Although the deeds of Hayabusa II were insignificant under the glory of Chang 'e V, such voices appeared on the Internet afterwards. It is said that it is much more difficult for Hayabusa II to collect asteroid samples than for China to collect lunar soil. Japan's probe flew 5.2 billion kilometers and completed soil collection in microgravity, which is much more difficult than landing on the moon. So the question is, what did this Hayabusa 2 do? Is landing on an asteroid really more difficult than landing on the moon?

What's the point of collecting asteroid samples?

Asteroids refer to some small celestial bodies in the solar system that revolve around the sun, and the diameter is generally not more than 100 km. It looks strange because of its limited size and weak gravity, which is not enough to turn itself into an approximate spherical planet. Most of these asteroids are distributed in the inner solar system, on the asteroid belt between the Earth and Mars.

Exploring these asteroids is of great significance to human beings, because some asteroids are as old as the earth and have no geological activities, so the structure and soil of asteroids have always remained in the initial state. Therefore, bringing asteroid samples back to the earth for research may reveal the secrets of the geological features of the early formation of the earth. Moreover, in the mainstream view of academic circles, liquid water on the earth is actually brought into the earth's atmosphere by asteroids and meteors. If water is found in the process of detecting asteroids, it can also be said that the water of the earth is foreign.

Therefore, the exploration of asteroids is of interest to all countries in the world, and China also plans to carry out asteroid-related exploration after 2020. Then, as the first country in the world to bring asteroid soil back to Earth, what is their space technology level?

The unfortunate Hayabusa

Let's take a look at Japan's efforts to detect asteroids. On May 9, 2003, Japan launched the first asteroid probe Hayabusa. From the beginning, they wanted to bring asteroid samples back to Earth, with the goal of Sichuan asteroid 300 million kilometers away from the Earth. However, this mission can only be described as ill-fated.

On the way to Itokawa asteroid, Hayabusa encountered many problems. Less than four months after launch, the ion thruster failed. Then in 2005, only one of the three thrusters used to adjust the attitude was still working normally. In June+February, 5438, Hayabusa deviated from its orbit because of the fuel leakage of the chemical engine, and as a result, it lost contact with the ground. It was not until seven weeks later that the ground received the weak signal sent back by it, and it was only a short 20 seconds at a time.

Fortunately, the ground crew was really awesome, and only with such a short operation time, they issued instructions step by step to adjust the Hayabusa back to its normal position, ensuring the smooth progress of the next task. On June 3, 20 10, Hayabusa finally returned with samples and burned in the earth's atmosphere, while the sample cabin successfully landed in the preset land area of Australia as planned.

It is a miracle that Hayabusa can complete the task and bring back samples. The Japanese people were greatly encouraged by this news, and Hayabusa was given the title of "immortal bird". Japan also made a film called Hayabusa, which showed this hard-won victory. However, compared with the folk carnival, Japanese academic circles have been poured cold water. Because the falcon brought back too few asteroid samples. According to official data, the rock samples brought back this time are about 1500, which sounds quite bluffing. In fact, the weight of these samples is measured in milligrams.

It is more appropriate to say dust than stone. This is also expected, because the falcon did not land on the asteroid to dig, but raised dust through a slight impact, and then sucked the sample in to complete the collection. At this point, no one wants to let go, so Hayabusa II was put on the agenda.

The stronger Hayabusa II

Based on the last experience and lessons, Hayabusa II has improved and upgraded its shortcomings on the basis of Hayabusa I. Its ion engine thrust is 25% higher than the original. In fact, an extra propeller was added, and the communication part was also changed to a dual antenna configuration, so that it would not be embarrassed by signal interruption. In addition, in order for Hayabusa II to collect samples of ancient rocks deeper in the asteroid, it also carried two cylindrical impactors, which are equivalent to explosives, and blasted the older rock layers by blasting.

In order to better find a flat collection site, the number of marker balls used by Hayabusa II for fixed-point landing has also increased from 3 to 5. However, the way the falcon collects samples is still very touching. Moreover, the duration of the whole sampling process is only about one second, which is more suitable to be described as dragonfly. This time, the target is the Dragon Palace asteroid, which is 340 million kilometers away from the Earth.

As a result, Hayabusa II, launched on 20 14, finally threw the sealed cabin with samples back to Earth on June 6, 2020. On the whole, Hayabusa II is much more successful than the original. However, if you really want to see it, how many rock samples it brings back is the key. At first, scholars themselves were not very confident, and the estimated weight was only 0.1g.

However, as far as the published results are concerned, the rock samples brought back by Hayabusa II already contain hard rocks with the size exceeding 1.3 cm, which shows that the method of blasting collection is still very effective. Because only two of the three sample capsules have been opened, how many have been brought back is unknown. But compared with its predecessors, Hayabusa II did become stronger.

So, is the technical difficulty of Hayabusa II really more difficult than landing on the moon?

Conquest 17 years, Japan still can't go to the moon.

In fact, to answer this question, just say why Japan has not launched a lunar lander so far, and the answer will be solved.

In fact, as early as 199 1, Japan successfully launched the Tian Fei lunar orbiter, becoming the third country in the world with the ability to orbit the moon. Later, before Chang 'e-1, Japan launched another moon-orbiting satellite, the Moon Goddess. But after that, Japan's lunar exploration project was hastily terminated. Like China, Japan will make progress little by little, and finally achieve the goal of sampling lunar soil. According to Japan's "Moon -A Plan", they should be able to launch the lunar lander in 1995, but in 2007, after 17 years of research and development, the lunar lander was still unsuccessful. Finally, the Space Development Committee of the Ministry of Education, Culture, Sports, Science and Technology of Japan agreed to the termination report of the project. It can be seen that Japan has not mastered the technology of soft landing of the moon until now.

The first technical difficulty encountered by Japan in landing on the moon is the power system.

Hayabusa II launched by Japan weighs only 0.6 tons, while Chang 'e V weighs 8.25 tons. Such a disparity in weight allowed the propeller of Chang 'e V to complete the soft landing of the moon and return to the lunar orbit. Hayabusa II's propeller is only enough for it to get close to the microgravity asteroid. If the target is the moon, it will only be smashed to pieces. Of course, some people may say that Hayabusa is small and light, and it was deliberately set up to get close to asteroids. We only need to look at Japanese rockets to know the answer.

The rocket used by Japan to launch Hayabusa II is the M5 carrier rocket developed by Japan, which belongs to the solid fuel rocket for small satellites. The H-series and J-series launch vehicles with stronger carrying capacity can only put a one-ton satellite into Earth orbit. Compared with China's Long March 5 carrier rocket, one is a cannon and the other is a shotgun. So far, Japan has no rocket system to launch a lunar lander.

The second is the technical difficulty of re-entry.

Although Hayabusa II has brought back more rock samples than its predecessors, its weight is still limited. In addition to contact collection, the number of samples is limited, and the way of returning to the atmosphere also limits the size of the sample bin. Hayabusa II's return mode is the most traditional ballistic reentry. To put it bluntly, it is to slow down from earth orbit and enter the atmosphere, just like a football thrown out. In order to resist the high temperature of 3000 degrees caused by air friction, the return capsule has to be loaded with more heat-resistant ablation materials. Moreover, in order to realize deceleration, the process design of throwing away the shell of the return cabin is also designed to reduce the overload pressure of the deceleration umbrella. All these have reduced the weight of the sample bin.

The return mode of Chang 'e V is called "high-speed semi-ballistic jump and then return to trajectory". Generally speaking, it is to use the principle of throwing water to complete a jump in the earth's atmosphere, thus reducing the speed. This return mode is in a leading position in the world, reducing the proportion of heat-proof materials as much as possible and expanding the cabin space of the return cabin. As a result, the moon rock samples brought back by Chang 'e V were more than six times that of the former Soviet Union, reaching 2 kilograms. However, if Japan wants to break through this technology, it still needs a lot of time to sum up experience.

The third is landing docking technology.

China's Chang 'e V used autonomous control when landing, and the whole power descent voyage was hundreds of kilometers. In this process, the ground did not interfere, and it was the landing zone of its own choice. The landing detection method of Hayabusa II is simply outrageous. It actually needs to throw several marker balls with cameras at the asteroid first, and then the ground personnel determine the flat landing site according to the pictures taken. Of course, it is understandable to choose such an embarrassing way. After all, Hayabusa II can't stop on an asteroid, and whether the samples collected are good or not depends on the land position.

It was this marker ball that captured the first microscopic asteroid structure in history. However, this thing will not bloom no matter how it is blown. Besides, it's made in Germany.

On the other hand, the record set by Chang 'e V in China is far ahead of the world. First of all, the automatic rendezvous and docking of deep space orbit detectors and the transfer and encapsulation technology of on-orbit samples are unique to China. In addition, the technical problem of the rise of the moon surface has been overcome by us. The technology of Chang 'e V can be transplanted to the future Mars exploration program. Although Hayabusa II has nothing to do with the soft landing technology of the planet, it is not easy for the Japanese to catch up with China in the future.

To put it bluntly, Japan is too small. If you want to have a global satellite monitoring station, you must rely on the help of NASA, and you will inevitably be controlled by others in the future. China has built a global deep space monitoring and control network, and we can launch whatever we want. Based on this, it is an international joke for Japanese aerospace industry to surpass China.