Today, it has been 50 years since the last time humans left the moon, and humans have never been to the moon again. In 2004, the U.S. government proposed to return to the moon in its new space exploration program, and used it as a springboard to implement the manned landing on Mars, announcing the restart of its return to the moon program. In 2017, NASA officially launched the Artemis program, which aims to return humans to the moon in 2024.

The recently focused “space launch system” (SLS) heavy rocket is a key step in the US plan to return to the moon.

The lunar landing at the south pole has both advantages and disadvantages

Unlike Apollo, Artemis planned to land at the south pole of the moon. Recently, NASA announced 13 pre selected landing areas near the south pole of the moon. There are three main reasons for choosing Antarctica.

First, there are some permanently dark meteorite craters at the south pole of the moon that cannot be illuminated by the sun for many years. After radar echo detection, scientists determined that there might be water ice at the bottom of these craters. If the inference of scientists is confirmed, these water ice can not only support the water demand of human lunar base in the future, but also extract hydrogen and oxygen from electrolyzed water to provide fuel for rocket engines. We should know that it is much cheaper to produce fuel from the moon to fill the spacecraft than to take the fuel from the earth, which can greatly reduce the cost of human exploration of deep space.

Second, the highland on the south pole of the moon that can be irradiated by the sun can be continuously irradiated by the sun, and the continuous illumination time can even reach 10 months every year. There is no lunar night in the low latitudes of the moon that lasts for 14 Earth days.

Third, due to continuous light, the temperature in this area does not change much. Unlike in the low latitude area of the moon, the temperature difference between day and night will exceed 250 degrees Celsius. This can greatly reduce the technical difficulty in developing the technical facilities for manned lunar landing, such as the life support system and space suit design.

Nevertheless, there are many unfavorable factors for landing at the south pole of the moon and establishing a human scientific research and living base there. First of all, there is no flat moon sea, and there are many mountains and valleys, so it is very difficult to land and take off. Therefore, there is a high requirement for landing timing. Once the original landing point is missed, it is very unlikely that another flat alternative landing point can be found for the next landing. Secondly, there is not much flat activity space on the highland, which is not conducive to the movement of the manned lunar rover. In addition, there is no sunlight at the bottom of the permanently dark meteorite pit where water ice is stored. Therefore, the energy supply for the detectors and excavation machinery for detecting water ice must be supplied by the base located in the highland. Therefore, the energy transmission from the base to the pit bottom requires additional infrastructure, which must be built in advance before entering the water ice extraction and fuel production stage.

Once the cold moon night is overcome, the moon sea may be more suitable for establishing a base

In contrast, if the manned lunar landing and the future base construction sites are selected in the lunar sea near the zero degree longitude, such as the north latitude and the middle latitude of the moon, there are advantages in other aspects except that there is no water ice like the south pole, the energy demand of the moon night is high, and the temperature difference between day and night is large. For example, the terrain in the lunar sea is flat, which is very suitable for the takeoff and landing of spacecraft, and also convenient for the long-distance driving of manned lunar rover, expanding the range of personnel activities. In addition, there are a large number of oxides in the lunar soil of the lunar sea. Liquid oxygen fuel can also be extracted by reduction method, but the complexity is higher than that of extracting from water, and it consumes more energy. Moreover, in the near future, once the relevant technologies are mature, helium-3, a nuclear fusion fuel, can be extracted from the lunar soil of the lunar sea.

The biggest difficulty in landing in the mid latitude moon sea is to overcome the cold moon night that lasts for 14 Earth days. However, at present, there are a lot of relevant research work under way to provide a feasible solution to the problem of lunar night. For example, during the high temperature on the moon and the sun, a large amount of thermal energy on the surface of the moon is stored and released slowly during the lunar night; In addition, the silicon in the lunar soil is used to build a large-area and high-sensitivity solar panel on the spot, so that it can also use the reflected light of the earth to the solar light to generate a certain amount of electric energy during the lunar night; Another is to arrange a lunar satellite with a solar reflector on the lunar orbit to reflect the sunlight to the large-area solar array of the base for power generation. Of course, if the small and safe nuclear power station can break through its key technologies as soon as possible, it will be easier to solve the problem of the energy demand of the mid latitude lunar base.

As for the living water of the astronauts, it does not seem to be a big problem. According to the recycling technology developed by the earth orbiting space station, the recycling rate of water can reach about 90%. In addition, a small amount of water is continuously supplied from the earth to the moon, and the domestic water of astronauts can be met.

To sum up, in addition to the lunar south pole landing program that NASA is focusing on, the establishment of a manned lunar landing base in the lunar sea in the north and middle latitudes has also attracted the attention of more and more relevant institutions, and has begun to arrange a number of studies.

With the implementation of various lunar landing plans, the goal of returning to the moon in the near future will certainly become a reality. As an indispensable measure in the great rejuvenation of the Chinese nation, it is also an inevitable choice for the development of China’s manned space program. With the completion of the mission construction of China’s earth orbit space station and its entry into the application stage, China has also begun to demonstrate the manned space mission in the next stage, one of which is the manned moon landing. The Chinese dream of landing on the moon will also become a reality in the near future.

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Technological innovation reduces costs and promotes the “return” of manned lunar landing program

Why didn’t humans ever land on the moon after the Apollo program? In fact, the most important issue is funding. In the era of “space hegemony” between the United States and the Soviet Union, the United States government invested a lot of money in the Apollo program for political reasons. At the peak, 6.5% of the government budget was invested in the Apollo program. However, after that, the political needs were no longer so urgent, the political significance of continuing to land on the moon was greatly reduced, and the US government would no longer spend so much money on space exploration projects.

People can’t help but ask: the technological capability of the 1960s may require a huge amount of money for human beings to land on the moon. Now the technology is many times more advanced than that at that time. Does it still need to spend so much money? Let me talk about the characteristics of the government’s space mission. Because the government’s space missions cost taxpayers’ money, it must always ensure that there is no mistake, especially in manned space missions. Although so many years have passed, this characteristic of the government’s space mission has not changed. Therefore, although the technology has improved, the cost of the task has not been reduced, even higher than before. This is why 50 years have passed, and mankind has never returned to the moon again. Even the Saturn 5 rocket, which was used by Apollo to land on the moon at that time and has the largest thrust so far, no longer exists.

However, this situation has changed in recent years. On the one hand, commercial aerospace is gradually rising. Due to different sources of funding and the promotion of the market, the cost of human entering space has been reduced again and again through technological innovation and the development of recycling and reuse technology. At present, it has been reduced to 1 / 10 of the government’s aerospace cost; On the other hand, Europe, Japan, China and India have all launched lunar exploration programs with moderate funds. In particular, China’s “Chang’e project” has been successfully implemented several times in succession, including three successful landings and one successful return of lunar samples to the earth. These plans have broken the monopoly of the United States and the Soviet Union on lunar exploration in the 1960s and 1970s to varying degrees. The pressure of the “space race” has also forced countries to accelerate the testing and research and development of relevant technologies, indirectly promoting the implementation of the manned lunar landing program.

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