Meet you on the back of the moon

At 2:23 on December 8, 2018, China successfully launched the “Chang’e 4” detector with the “Long March 3B” carrier rocket at the Xichang Satellite Launch Center, opening a new journey for lunar exploration.

The back of the moon is not equal to the “dark side of the moon”, it can also receive the sun.

On January 3, 2019, the “Chang’e IV” landed on the back of the moon at the von Carmen crater in the South Pole-Aitken basin.

This is the first time a human detector has landed softly on the back of the moon. In 1959, the Soviet “Moon 3” detector gave people a glimpse of the back of the moon. In 1968, the American “Apollo 8” astronaut saw it for the first time with the naked eye.

As an ordinary person, although you can wear a space suit in the game “Super Mario: Odyssey” released by Nintendo, you can enjoy a good time in the so-called “dark side of the moon”, but what you see is not as good as it is in reality. “. The Aitken Basin is the second largest crater in the solar system and is more than 2,500 kilometers in diameter. Scientists wanted to see it in the 1990s, where the rock may have a history of 4 billion years and contain a considerable amount of helium-3 and liquid ice (a special mixture of ice and water).

In February 2018, India declared that “Moonboat 2” will detect the area. It is also where NASA has long hoped to “fall” and send robots to retrieve rock samples. However, in the end, China’s moon goddess “Chang’e” took the lead.

Moon back
On Earth, the back of the moon is an invisible “blind zone.” Therefore, conspiracy theories about it are extremely popular.

For example, the movie “Transformers 3: When the Moon is Dark” has changed the history of the moon landing of “Apollo 11”. In the film, former US President Kennedy reminded astronauts to pay attention to the whereabouts of aliens before the landing of “Apollo 11”. Sure enough, the astronauts found the spaceship “Ark” and the old car man “The Royal Enemy” on the moon. Suddenly, the live broadcast of the global live broadcast was interrupted for dozens of minutes. Kennedy ordered Armstrong to spare no effort to run to the back of the moon, from where to bring back the core technology of Transformers – just a story to listen to.

The moon itself is completely integrated. The reason why there is a frontal and a backal view from the earth is because the moon not only revolves around the earth, but also rotates around its own axis, and its rotation speed is exactly the same as that required to revolve around the earth. Equal time—this principle is also called “tidal lock”. Large celestial bodies form tidal forces on small celestial bodies, so that small celestial bodies always “show people” on the same side. If one day people stand on Mars, they will also find that Mars’ satellites, Phobos and Fire Guards, also have a “tidal lock” phenomenon.

In other words, the moon’s revolution period and rotation period is 1:1, so in the eyes of people on Earth, the moon always reveals its front. Due to the phenomenon of the moon’s “shaking” caused by the intersection angle of the orbital surface, the front surface of the moon is larger than the back surface, accounting for 59% of the surface area of ​​the moon.

In fact, the back of the moon is not equal to the “dark side of the moon”, it can also accept the sun, just because the back is not facing the earth, can not reflect the sun to the earth.

It is worth noting that the “Chang’e 3” and “Chang’e 4” explore the high latitudes of the moon. For example, the former landed in the Hongwan area with a 44.1° north latitude and a 19.5° west longitude. In the past, the United States and the Soviet Union have launched many detectors on the moon, but most of them are limited to strips within 27° on both sides of the equator, including the astronauts’ range of activities at low latitudes.

Landing at low latitudes is usually considered in several ways: First, the ideal illumination near the equator of the moon (the intersection of the equatorial plane of the moon and the ecliptic plane is only 1.54°), the optical equipment can be clearly explored, and the solar cell can work better. Secondly, if the “Apollo” series of spacecraft is manned, it needs to return to Earth, then it will be lifted from the low latitude of the moon, which is convenient to use the large line speed near the equator to save fuel. Thirdly, the detectors or manned spacecraft that have been transferred from the near-Earth orbit, if they enter the near-moon descent orbit that is basically “coplanar” with the lunar orbit, then land near the lunar equator (the lunar orbit). The angle of intersection with the lunar equatorial plane is less than 7°), which can avoid the tossing to the high latitude.

The coordinates of the von Carmen crater are 45.5° south latitude and 177.6° east longitude. The land is not easy to land and is relatively limited in solar energy supply. Obviously, the “Chang’e IV” is on the rise.

“Yu rabbit, come home!”
“Chang’e 4” is actually a “prepared tire.” Its original destiny was to make a backup detector for the “Chang’e III.” However, in 2013, the “Chang’e III” successfully completed its mission, landing in the Hongwan on the front of the moon, and left a lurking lunar rover “Jade Rabbit”. In this way, “Chang’e IV” has a new mission.

At present, “Chang’e 5” is scheduled to be launched around December 2019.

It includes landers and rover cars. The lander weighs 1.2 tons and the rover weighs 140 kilograms. The lander has a radioisotope thermal motor that can power the scientific instrument on board for a three-month mission. The rover is the protagonist of the back of the moon, and after nearly 450,000 Chinese citizens voted, its name is “Yu Rabbit No. 2” to commemorate its brother or sister – after 972 days of lunar work on the moon “Jade Rabbit.”

Shortly after the separation of the Jade Rabbit II and the lander, the surveillance camera on the lander photographed its “footprint”, which was transmitted back to Earth via the “Bridge Bridge” relay star. Afterwards, in order to meet the challenge of the high temperature of the moon, “Yu Rabbit No. 2” plans to sleep for a while and then wake up.

From the “configuration” of “Yu Rabbit No. 2”, there are solar panels, tools for excavating and analyzing soil samples, equipped with panoramic cameras to capture three-dimensional images of the lunar surface, and also equipped with detection radar, visible light and near-infrared imaging. Spectrometer to detect the topography and mineral composition of the back of the moon.

It also comes with a 3 kg sealed container containing potatoes, Arabidopsis seeds and silkworm eggs to test whether plants and insects can co-exist on the moon. Once the silkworm eggs hatch, the larvae produce carbon dioxide, and the germinated plants release oxygen through photosynthesis, which is expected to build a micro-ecosystem in the container. This experiment was designed by 28 Chinese universities. In 1982, the Soviet “Salute 7” space station planted some Arabidopsis, which bloomed and died in space, with a life span of 40 days.

It is reported that “Jade Rabbit No. 2” will accompany the “Jade Rabbit” and will remain on the surface of the moon forever. However, they will soon be able to wait for “Jade Rabbit No. 3” to “go home.”

“Chang’e project” small three steps
The “Chang’e project”, led by the China National Space Administration and launched in 2003, is divided into “big three steps” and “small three steps.”

The “big three steps” are “exploration”, “boarding” and “resident” – no one is going to explore the moon, manned to the moon, and stays in the moon for a long time. Among them, “exploration” is divided into “small three steps”, that is, “around”, “fall” and “back”.

“Chang’e No. 1” and “Chang’e II” are doing “winding”. Launched in 2007, as a lunar orbiter, they fly around the moon at a height of about 2,000 kilometers from the surface of the moon for global exploration.

“Chang’e 3” and “Chang’e 4” did the “fall”. In 2013, it launched the lunar lander, landed on the surface of the moon, released a lunar rover, and carried out detailed detection in the landing zone.

“Chang’e 5” and “Chang’e 6” will launch the moon automatic sampling returner. After it has landed on the lunar surface to collect samples, the returner will return to Earth. This is “back”. The 1970 Soviet “Lunar-16” detector did this at the earliest. At present, “Chang’e V” is scheduled to be launched around December 2019, and “Chang’e VI” is scheduled to be launched in 2024.

Waiting for this “small three-step” to be completed, “manned to the moon” will be put on the Chinese space program, and will be realized in the 21st century.

As far as the “Chang’e IV” has just landed, it is similar to the structure of the “Chang’e III”. The tasks completed are similar, and the technical difficulties of breakthrough are relatively close.

There is no atmosphere on the surface of the moon, and it is impossible to land by means of pneumatic deceleration. “Chang’e IV” first relies on its own propulsion system to reduce the speed of nearly 1.7km / s, which requires its own propulsion system speed increment must be large enough. At the same time, during the descent process, the quality of the detector is continuously reduced, the gravity is also changed, and its own thrust can be adjusted.

The process of soft landing is a short time, large speed change, irreversible process, can not rely on the ground to implement guidance and control, can only rely on its own GNC system – using sensors based on monthly speed, ranging and terrain identification, Conduct full autonomous guidance, navigation, and control. Moreover, there are few “complete” places on the back of the moon, and there is a certain degree of autonomous obstacle avoidance.

When landing, there must be a “landing buffer system” to absorb the impact load that hits the moon, and it is also necessary to ensure that the lander does not fall over or fall.

The process of patrolling detection is also complicated. Rover vehicles must make forward, retreat, turn, climb, and overcome obstacles under limited energy, and maintain the stability of the movement. Wheel form, suspension form, moon soil passability and mobility performance simulation are all issues to be addressed.

After arriving at the scheduled work location, the lunar rover must also have the ability to identify hazards in the environment, determine its own posture, identify the target location, and plan to reach the target location. This requires path planning techniques based on the fusion of multiple sensor information.

These difficulties, “Chang’e III” and “Chang’e IV” have been overcome. “Chang’e 4” is mainly to optimize the guidance process of the landing process, and the rover will wait for the power to be full and work again.

What is the moon?
Earth people have long remembered “on the moon”. “Qiong Yuyu, the heights are not cold.” Science fiction writer Jules Verne wrote “From Earth to the Moon”, which attracted Lu Xun to translate. In the preface, he repeatedly praised: “The human beings, the creatures with hope for progress, are also part of the light, but they don’t know what to do, they don’t know what to expect, they want to suck, they take the air, they are stunned, and there are no obstacles. “”

Of course, on the moon, on the one hand, it is to satisfy the curiosity of scientific exploration, and on the other hand, there are many realistic factors. The samples brought back by the “Apollo” series of spacecraft confirmed the existence of Helium-3. According to the detection results, the Helium-3 content on the moon is estimated to be more than 1 million tons. Helium-3 is one of the isotope of thorium. The reserves on the earth are extremely rare, only 10-15 tons. Nuclear reactors using helium-3 do not have neutrons because the thermonuclear reaction of pure helium-3 produces only protons that are not radioactive and therefore do not produce radiation.

According to experts’ calculations, if the nuclear fusion reaction is carried out using helium and neon-3 to generate electricity, the total annual power generation in the United States only needs to consume 25 tons of helium-3. Based on current global electricity prices and space transportation costs, the value of 1 ton of helium-3 on the moon is about $4 billion. But with the maturity of space technology, transportation costs will definitely decline. French scientists have announced that they will use Helium-3 for commercial power generation in 2030.

The image of the “Yu Rabbit No. 2” photographed by the lander’s topography camera at point A

India has long been targeting the Helium-3 on the moon. The purpose of “Yue Ship 2” is here. However, for lunar mining, only the United States and Luxembourg have passed legislation that allows commercial entities to take space mining as their own. At present, there are no relevant international treaties.

The Aitken Basin on the Moon’s Antarctic is the rich storage of the J-3. The “scientific goal” of “Chang’e project” includes “assessing the resources and distribution of Helium-3 in the lunar soil”.

In addition to providing energy for the planet, the moon’s biggest role is to be a “transfer station.” For example, the construction of the Observatory, because there is no atmospheric occlusion, no electromagnetic interference, is definitely the best place for astronomical observation. In addition, the depth of the universe can be seen from the back of the moon, and the center of the Milky Way can be seen from the moon’s south pole.

It is also particularly advantageous to build a rocket launch site on the moon. First, the fuel can be taken locally; secondly, the gravity is small and the launch is easy. Therefore, the long-term space exploration program in the United States is to establish a lunar base first, and then explore Mars from the lunar base.

Space race
Compared with the “leading lead” of the US space industry and the solid foundation of the Soviet-Russian, India has always hoped to stabilize the “third place” position, but this wish has not been achieved smoothly.

After the United States and Russia, China is the third country to send its astronauts into space with its own rockets. The first manned action was in 2003, and since then, China has sent 11 astronauts into space. In 2016, two Chinese astronauts stayed in China’s second space laboratory, Tiangong No. 2, for 30 days.

In 2018, China launched 38 rockets into space – the first time it surpassed other countries in number; in October, one launch mission failed, but the protagonist was China’s first private carrier rocket “Suzaku No.1”. As China’s largest new-generation launch vehicle, the “Long March 5” heavy rocket will assume greater responsibility in the future, such as launching the “Dongfanghong 5” satellite.

In September 2014, the Mars orbital probe launched by India successfully entered the orbit of Mars.

It is a pity that the first Mars probe in the Chinese Mars Exploration Program, Firefly One, was launched on a Russian probe in November 2011, but the Forbes provided by the Russian Federal Space Agency. The “soil” detector failed to change course as planned, and as a result, both were trapped in low-earth orbits of 206 to 340 kilometers from the surface. Russia has not succeeded in two rescues. “Firefly One” finally fell into the Pacific Ocean in January 2012.

India broke a record on Mars. In September 2014, the Mars orbital probe launched by India successfully entered the orbit of Mars, making India the first country in the world to successfully enter the first attempt, only after Russia, the United States and Europe. But apart from this, whether it is launching rockets, satellites, or manned, lunar exploration, India’s speed is not too fast.

India’s moon landing plan is also divided into three phases. The first phase is the launch of the unmanned detector “Moon Ship No. 1”, which was reached in 2008. The second stage is the launch of the moon landing robot. The original “Yuezhou 2” will be launched in January 2019, but for some reason, the official said that it is currently impossible to determine the date of launch.

On December 28, 2018, the Indian cabinet meeting approved the “Gangangyang” plan for manned seven days in space. This is India’s first manned space mission, which will launch the “Gangangyang” orbital spacecraft with the GSLV Mark III rocket, carrying three astronauts to a space orbit 400 kilometers from the surface. The mission is planned to cost Rs 100 crore and will be carried out in 2020.

Space exploration is an extremely time-consuming and financially-funded thing that no small country can do. For large countries, space exploration must be a national priority, and it is not affected by political and economic fluctuations to ensure the stable implementation of the plan. The time, place, and difficulty of exploration are like the medals of the country. This honor is recorded in the history of mankind.

The “Chang’e IV” successfully landed on the largest impact basin on the moon so far, narrowing the gap between China and the United States in landing on the moon. The Pink Floyd band has a famous album “The Dark Side of the Moon” (1973), which won the “Billboard 200” 917 week championship. This album focuses on the theme of universal human values, and adds experimentality to psychedelic rock, creating the era of “space rock”. Band member Roger Waters said: “The album has a core idea, that is, human life is only once, so you have to choose and explore, so the lyrics say ‘I will be in the dark side of the moon (actually refers to the back of the moon) ) Meet you.”