Zhou Jianping, chief designer of China's manned space program: What does China's "Tiangong" space station look like?

By the end of 2022, my country's "Tiangong" space station will be fully completed, taking a firm step forward in my country's space exploration. As my country's first space station, what does "Tiangong" look like? What will happen next? Please listen to Zhou Jianping, academician of the Chinese Academy of Engineering and chief designer of China's manned space project, give us a detailed explanation on the CCTV Financial Channel's "China Economic Lecture Hall" program.

On New Year's Day 2023, General Secretary Xi Jinping announced to the world in his New Year's message that China had completed the construction of the space station.

In 1992, China's manned space project was officially launched, and we began to build our own "space home." At the beginning of the design, we aimed at the technical level of the world's third-generation space station, and continued to make breakthroughs and innovations. Over the past 30 years, we independently completed the construction of the manned space project, the space laboratory project and the "Tiangong" space station, and built a complete A national-level space laboratory that operates independently.

In the current space, there are only two space stations, the International Space Station and China's "Tiangong" space station . It can be said that China’s manned space technology has successfully ranked among the top in the world.

So, what is the basic situation of the completed Chinese space station?

When the Chinese Space Station is launched into orbit, the total initial mass of the three modules is about 67.5 tons, which is 1/6 of the International Space Station. The space of the entire sealed cabin is more than 300 cubic meters, and the astronauts’ activity space is 122 cubic meters. This activity space is 1/3 of the International Space Station. In terms of scientific research, our space station has installed 25 experimental cabinets, which is 4/5 of the International Space Station, and has built a national space laboratory. To cover the main areas of space scientific research, the space laboratory must have sufficiently advanced equipment. At present, our "Tianhe" core module actually has the functions of the three compartments of the International Space Station's "Dawn" core module, "Xingchen" service module, and "Unity" node module. From this perspective, the construction of China's space station has been able to basically meet the needs of scientists' scientific research tasks.

The Chinese Space Station flies in low-Earth orbit nearly 400 kilometers above the earth. The manned space shuttle system will send astronauts into space, live and work for a short period of time, and then return to the ground safely. We use the Long March 2F launch vehicle and the Shenzhou series manned spacecraft to transport astronauts.

When the manned spacecraft project started, it faced a major path selection problem. When the expert committee conducted its debate in 1992, there were different path options. The United States developed the space shuttle at that time, the Soviet Union developed the "Buran" space shuttle, and Europe and Japan were also demonstrating the development of space shuttles. So how did China's manned space project start? A team of scientists, experts, and engineers conducted a lot of demonstrations, and finally we chose the path of manned spacecraft.

This is a very important choice. The basic consideration at the time was that although the space shuttle had many advantages as a reusable spacecraft, it also faced some problems. For example, the structure of the space shuttle cannot achieve life-saving, that is, when a flight failure occurs, the safety of astronauts cannot be guaranteed. Moreover, it was very difficult to build a reusable spacecraft based on the technical level at the time. Later practice proved that our choice to start with a manned spacecraft and return with a return capsule can effectively ensure the safety of astronauts.

The Long March 2F launch vehicle and Shenzhou manned spacecraft are a manned transportation system to and from space. So, can they be used to transport goods? Yes, but it won't carry much. In fact, the Shenzhou spacecraft is a mixed bag of people and cargo and can transport about 300 kilograms of cargo upstream. However, the transportation capacity of 300 kilograms is definitely far from meeting the needs. A more economical transportation method is to build a cargo system that can transport large amounts of materials to the space station. This system is the Long March 7 launch vehicle and Tianzhou series cargo spacecraft.

The Tianzhou cargo spacecraft is very unique. Its maximum launch weight can reach 14 tons. It has three configurations: one is a fully sealed cargo spacecraft, which is the current cargo ship docked on the space station assembly. The other two are semi-sealed cargo spacecraft and fully open cargo spacecraft, which will be used to transport large-scale scientific experiment facilities and maintenance equipment in the future.

Another feature of the Tianzhou cargo spacecraft is that the proportion of the uplink cargo it transports to the launch weight of the entire ship reaches 0.51, which means that 51% is the weight of the transported cargo. This is the highest among the different types of cargo spacecraft that have been developed in the world. We are constantly improving efficiency and reducing costs. As you will see, Tianzhou-6 will ensure that our astronauts live and work in orbit for 9 months instead of the previous 6 months.

On May 10, 2022, the Tianzhou-4 cargo spacecraft was successfully launched.

If the space station is compared to a space port, then the transport spacecraft that travel between the ground and the space station, such as the Shenzhou series of manned spacecraft and the Tianzhou series of cargo spacecraft, are members of the "space transportation team". They can transport large amounts of materials and Batches of astronaut crews were transported to the space station in an orderly and safe manner.

After the spacecraft completes round-trip transportation, it needs to complete a rendezvous and docking to connect with the destination. Space rendezvous and docking technology is one of the three key technologies for manned space activities. It is known as the "kiss of space" and is extremely difficult. Since 2011, my country's space rendezvous and docking technology has been developed from scratch, from testing to actual combat, and has successfully implemented more than 20 accurate and reliable dockings so far. More importantly, we completed a two-hour rapid rendezvous and docking with a cargo spacecraft, which is a world record.

"A "space studio" integrating work and life"

Let’s talk about the astronauts’ “space studio.”

There are six astronaut cabins in our space station, three in the core module, and three in the "Wentian" experimental module. The activity space of each cabin is about 2 meters × 2 meters. The space for astronauts' activities is about 122 cubic meters. If we talk about it on the ground, the usable area is more than 60 square meters, which is equivalent to three rooms and two living rooms, plus a storage room. The core module and experimental module of the space station each have two bathrooms, and the manned spacecraft also has a bathroom. It's different in the sky than on the earth. Due to microgravity, you can move in all directions in space, so the space is relatively spacious.

What kind of environment is it in the space station? The temperature is 19℃ to 26℃ and can be adjusted. To reach this temperature, we explored for quite some time. In the early stages of the development of the Shenzhou spacecraft, we set a temperature of 17°C to 25°C, which was based on foreign standards. However, during use, it was discovered that the ambient temperature was on the low side. After a period of flight, we finally found an ambient temperature that is more suitable for Chinese space flight.

The humidity in the space station is 35% to 55%, which is very comfortable. The gas composition is the same mixture of oxygen and nitrogen as at sea level. Why use oxygen-nitrogen mixed gas? This is for security reasons. Because if it is a pure oxygen environment, fire accidents are likely to occur, so we chose a mixture of oxygen and nitrogen. Ensuring such environmental conditions in space is the largest part of our efforts, more than food, clothing, etc. combined.

In space, a person consumes approximately 10 kilograms of various materials every day, including food, water, and purification materials and packaging. Three people weigh 30 kilograms a day, nearly 1 ton a month, and more than 10 tons a year. This will bring high costs and the price will be high. How can we ensure long-term economic operation? We need to find ways to recycle materials.

Astronauts staying on the space station for a long time rely on regenerative life support technology. This technology is like a protective umbrella, establishing an Earth-like circulation system for astronauts on the space station, and realizing the recycling, utilization and regeneration of water, oxygen and other substances through physical and chemical methods. The regenerative life support system of my country's space station includes six subsystems: electrolytic oxygen production subsystem, carbon dioxide removal subsystem, trace harmful gas removal subsystem, urine treatment subsystem, water treatment subsystem and carbon dioxide reduction system. Through the condensation and drying component, the astronauts' sweat and exhaled water vapor are collected and purified into recycled water for drinking. At the same time, urine can also be collected and processed to become drinkable pure water. The circulating water can be electrolyzed to produce oxygen, and its by-product hydrogen can also react with the carbon dioxide collected in the cabin to obtain oxygen again. If astronauts work in orbit for one year, if they do not use regenerative life support technology, they will need more than 10 tons of materials. With the use of regenerative life support technology, only more than 3 tons of materials will be needed to meet the astronauts' daily needs. Reduced dependence on ground supplies.

In the early days, we faced many difficulties. For example, it is very difficult to process urine because urine contains very complex components. Our developers have made a lot of efforts in this area. After the core module was launched into orbit, we basically achieved the regeneration of urine. use.

The treatment of carbon dioxide is even more complicated. At first, we used the physical adsorption method, which adsorbed the carbon dioxide and then analyzed it and discharged it into the vacuum. Later, scientific researchers developed key equipment. Electrolysis of oxygen can produce hydrogen, which can then react catalytically with carbon dioxide to generate oxygen and methane. In this way, using carbon dioxide not only solves the problem of purification, but also solves the problem of recycling and reuse.

In this way, our space station achieves efficient resource recovery and reuse, and environmental protection issues are well solved.

Although space is a microgravity environment, there is still a very thin atmosphere. The resistance generated by the atmosphere will cause the orbit of the space station to attenuate. For example, in years of intense solar activity, atmospheric drag will reduce the orbital altitude of the space station by more than 100 meters per day. The completed three-module configuration of the space station weighs 67.5 tons. If the visiting Tianzhou cargo spacecraft and Shenzhou manned spacecraft are included, the weight will exceed 100 tons. So, how to make such a behemoth operate stably in low-Earth orbit overcoming atmospheric resistance?

Power is a very important element in modern society, especially for spacecraft. The Chinese space station has a great feature: we have both a chemical propulsion engine system and an electric propulsion system, which is the first of its kind in the world. What is chemical propulsion? Chemical propulsion relies on combustion to produce high-temperature and high-pressure gas in the thrust chamber, which is then ejected from the nozzle to obtain huge thrust. Chemical propulsion requires the consumption of propellant. Electric propulsion is the acceleration of inert gas under the conditions of ionization and electric field, obtaining an extremely high ejection speed, and is ejected from the nozzle. Its biggest feature is that its specific impulse is very high. The electric propulsion we are using now has a specific impulse that is five or six times higher than the chemical propulsion in orbit. This is also a feature of the Chinese space station.

Generally speaking, electric propulsion was mainly used in the past to maintain the orbit of high-orbit satellites or in deep space exploration. China is the first company in the world to use electric propulsion technology to maintain the orbit of a space station on such a large assembly. It also went through a very complicated development process. Because when we decided on this matter, the technical level and capabilities of electric propulsion were very limited. At that time, it could only reach the level of 80 mN. Can a space station weighing more than 100 tons use electric propulsion technology? We initially adopted the parallel method, but even 320 mN was not large enough. The key is that we pay enough attention to the electric propulsion technology, which ultimately promotes the rapid improvement and development of domestic electric propulsion technology. As of today, my country's electric propulsion technology has reached a thrust level of several Newtons. It should be said that the Chinese space station has played a very significant role in driving and promoting it.

Power supply is a very important energy source. Whether it is to maintain the operation of the space station or to ensure the lives of astronauts, communications, scientific experiments, etc., electricity is indispensable. Therefore, from the beginning of the design of the Chinese space station, it has always insisted on providing abundant energy, and must ensure high reliability, high safety, and long life. The energy of our space station mainly relies on two pairs of large solar wings on the two experimental modules. A pair of solar wings is 55 meters long, covers an area of ​​more than 270 square meters, and can generate 15 kilowatts of electricity. The two pairs of solar wings on the two experimental modules plus the solar wings of the core module have a total power generation capacity of 38 kilowatts. Moreover, we have made great progress in solar cell technology and energy storage battery technology.

The solar wings of our space station use flexible solar wings. It has an advantage - it can be stored piece by piece in the solar wing box, and then deployed out using a truss structure. Now, after the construction of the space station is completed, the position of the solar wing sail panel of the core module can be freed up, which will be more conducive to other operational activities of the space station in the future. You can see in the near future that our astronauts and robotic arms will work together to remove the solar wing sails from the pair of core modules and then move them to the tails of the two experimental modules. This will be a very complex extravehicular activity, requiring astronauts to leave the vehicle multiple times to complete it. It will also become an important landmark event in the improvement of China's space station capabilities.

After the Chinese space station completes its on-orbit construction, it will enter an application and development stage lasting more than 10 years. In the application phase, astronauts will conduct large-scale scientific experiments in and outside the cabin. At present, scientific experiment projects from 17 countries have been approved and will soon be stationed on the Chinese Space Station. What scientific experiments can be carried out on the space station in the future? What scientific discoveries are worth looking forward to?

One is microgravity. There are not as high levels of microgravity on the ground, whereas there is a constant microgravity in low-Earth orbit. During astronauts’ space lectures, we can see many phenomena that cannot be seen on the ground.

The second type of resource is a high vacuum and high clean environment. Vacuum is a challenge to human survival, but at the same time high vacuum is also a resource. The protection of the Earth's atmosphere prevents terrestrial organisms from the impact of cosmic rays, but it also prevents us from observing the universe. Therefore, space in a vacuum environment is a very favorable scenario for studying the origin and evolution of the universe and studying space astronomy.

Another type of resource is radiation. For example, solar energy is the main source of energy for most spacecraft after entering space.

The scientific research of our space station is organized around these resources. There are 25 space application system experimental cabinets distributed on the China Space Station, as well as multiple extravehicular load mounting points, and there will be expanded experimental platforms in the future. We have completed the entire cultivation process of rice from seed to seed in space. The rice seeds we brought aboard germinated, grew, bloomed and formed seeds in the space station, and the seeds were cultivated and grown in the space station again. In this process, we studied the development of rice under microgravity, including which rice genes are more sensitive to gravity.

Science is a career of exploration, and there are many exciting scientific discoveries waiting for us. The survey space telescope of the China Space Station is a scientific facility worth looking forward to. The China Survey Space Telescope is scheduled to be launched around 2024. What are the characteristics of a survey space telescope? Its aperture is 2 meters and its resolution is equivalent to that of the Hubble Telescope, but its field of view is about 350 times that of the Hubble Telescope, so it can "survey the sky" and can observe a sky area of ​​about 17,500 square degrees. The Hubble Telescope cannot survey the sky. It has only seen a few hundred square degrees so far. However, it has brought us a large number of scientific discoveries. The China Sky Survey Space Telescope has very rich spectral methods. I believe it will continue to bring us exciting scientific discoveries.

At present, we have built a Chinese space station with a three-cabin configuration. The three-cabin configuration includes the "Tianhe" core cabin, the "Wentian" experimental cabin and the "Mengtian" experimental cabin, which we also call the basic configuration. In fact, when designing, we considered the issue of expansion. In the future, the space station can add new cabin sections and expand to a four-cabin cross configuration, or a six-cabin stem configuration, and can be developed to a scale of 180 tons in weight. Of course, this expansion is not that simple. It requires docking nodes, energy expansion, information expansion, environmental control, attitude control, orbit control, etc., involving the entire system.

In addition, China's manned lunar landing plan has been officially implemented. We will use the opportunity of manned lunar exploration to develop a new generation of launch vehicles and manned lunar landing spacecraft, and simultaneously develop new spacecraft. The new spacecraft can accommodate up to 7 people. member.

The design life of the Chinese space station is 10 years. In the future, we will continue to extend its service life through maintenance, upgrades and other means. I believe it can be extended to 15, 20, 25 or even 30 years. Through our long-term efforts in the future, we will surely be able to promote China's space science into the world's first-class ranks.