The feat of conquering the moon: the four major challenges and technological breakthroughs facing my country's manned lunar landing

my country has announced its goal of achieving its first manned lunar landing by 2030. The initial plan for manned lunar landing is to use two launch vehicles to send the lunar lander and manned spacecraft to the Earth-Moon transfer orbit, the spacecraft and lander will rendezvous and dock in the lunar orbit, and the astronauts will enter the lunar lander from the spacecraft. Afterwards, the lunar lander will descend and land in a predetermined area on the moon, and the astronauts will go to the moon to conduct scientific investigations and collect samples. After completing the established tasks, the astronauts will take the lander to rise to the lunar orbit to rendezvous and dock with the spacecraft, and return to Earth on the spacecraft with the samples. So, my country will face a series of important difficulties and challenges in achieving its first manned lunar landing by 2030. Let's explore these challenges one by one and see what challenges and technical difficulties the researchers need to overcome in order to achieve this great goal?

First of all, one of the keys to achieving manned lunar landing is to have a powerful heavy-lift launch vehicle. In order to send manned spacecraft and lunar landers into low-Earth orbit, a huge carrying capacity is required, about 140 tons of low-Earth orbit carrying capacity. If a single launch and moon-circling assembly plan is adopted, it is necessary to develop a new super-heavy launch vehicle with a take-off weight of about 4,000 tons and a body diameter of about 10 meters. This carrying capacity is equivalent to the Saturn V rocket of the US Apollo program, which can increase the low-Earth orbit carrying capacity to 140 tons and the Earth-Moon transfer orbit carrying capacity to 50 tons. However, such a plan is extremely difficult to develop and the research and development cycle is also long.

In order to achieve the goal of the first manned lunar landing before 2030, we chose a two-launch, circumlunar assembly plan with a relatively low difficulty in developing a carrier rocket. This is the purpose of our development of the Long March 10 carrier rocket. The Long March 10 rocket is about 88.5 meters long, with a maximum takeoff thrust of 2,678 tons. Its low-Earth orbit carrying capacity is about 70 tons, which is comparable to the US Space Launch System (SLS rocket). In the Earth-Moon transfer orbit, the Long March 10 rocket has a carrying capacity of 27 tons. It is expected that the Long March 10 rocket will complete its first flight around 2027. The Long March 10 rocket adopts a modular assembly solution and inherits the five-meter diameter rocket body structure and 120-ton thrust liquid oxygen-kerosene engine of the Long March 5. The first stage of the rocket uses three 5-meter diameter modules in parallel, each module is equipped with 7 120-ton thrust liquid oxygen-kerosene engines. This design solves a series of problems in the development of heavy rockets.

Another challenge is to develop a new generation of manned spacecraft. The biggest difficulty and challenge of the new generation of manned spacecraft is that the speed when returning to the earth from the moon and rushing into the atmosphere is greater than that of the Shenzhou spacecraft working in low-Earth orbit, close to the second cosmic speed, about 11 kilometers per second. This means more intense friction, and the heat resistance of the spacecraft must be improved. The new manned spacecraft has a 3-4 times increase in heat resistance compared to the Shenzhou spacecraft. In addition, based on the technology of the Shenzhou spacecraft, the new generation of manned spacecraft has applied a large number of advanced technologies in spacecraft structure, propulsion, recovery, energy, thermal control, electronics, etc. The spacecraft is reusable, and the crew has been increased to 4-7 people. Its test ship has been successfully launched in 2020.

The third challenge is the lunar lander. The lunar lander needs to complete the landing and return mission on the lunar surface, but this is a high-risk mission that must overcome challenges such as the complex terrain and craters on the lunar surface. Especially when returning, the lander needs to take off again, which requires highly reliable technical support. According to the preliminary plan of the model exhibited by the lunar lander, the lander consists of two parts: one is the "lunar module" and the other is the "propulsion module". The propulsion module is not only the power module for the combination to brake and control the orbit when approaching the moon, but also undertakes the power deceleration task during the descent process of the moon landing. The lunar module will not be separated until it is close to the lunar surface. The purpose of this design is to save fuel for the lunar module. It is worth mentioning that the lunar module not only serves as a part of the lander during landing, but also serves as an ascender for the astronauts to leave the lunar surface. Such a design makes the lunar lander more flexible, which is crucial to the successful implementation of the manned lunar mission.

The fourth challenge is the overall design and flight test. In the next seven years, my country will achieve the grand goal of manned lunar landing in three stages. In the first stage, we will focus on completing the research and construction tasks of key subsystems. This includes the research and development of a new generation of manned carrier rockets, a new generation of manned spacecraft, a lunar lander, and flight products such as lunar suits and manned lunar rovers. At the same time, we will build the assembly and launch facilities of the Long March 10 rocket at the Wenchang Space Launch Site, and complete the construction of related ground equipment and facilities such as the measurement, control, communication and landing site. After entering the second stage, we will use the new generation of manned carrier rockets, a new generation of manned spacecraft and a lunar lander to conduct unmanned flight verification. Through actual flight verification, we will test the reliability of key subsystems and verify the feasibility of the overall plan. This stage is an important flight test stage to make full preparations for the subsequent manned lunar landing. Once the second stage mission is successfully completed, we will usher in the third stage, which is to implement a real manned lunar landing flight. Before 2030, our goal is to let Chinese astronauts land on the moon and realize the century-old dream in the history of Chinese spaceflight.

In general, my country's manned lunar landing program is a grand and challenging goal. Through the joint efforts of scientific researchers and institutions, and by fully solving the above difficulties and challenges, my country will surely achieve manned lunar landing and move towards a broader path of space exploration!

Author: Zhou Binghong, Researcher, National Space Science Center, Chinese Academy of Sciences

Produced by: Science Popularization China