In 2021, China Aerospace has given surprises one after another: in April, the core module of "Tianhe" entered the predetermined orbit, marking the beginning of the era of The Chinese space station; in June, the first manned mission of the space station stage, Shenzhou 12 was successfully launched, and three astronauts successfully returned to the ground three months later; in October, the Shenzhou 13 spacecraft was successfully launched, and the Chinese space station welcomed the first female astronaut.
Last week, Zhai Zhigang, Wang Yaping, and Ye Guangfu also brought wonderful space science lessons to teenagers on "Tianhe", so that more people can understand what astronauts do in the sky and feel the vigorous development of China's aerospace industry.
The march into space relied on breakthroughs in space technology and the development of physics. We are fortunate to see this series of grand events, which are inseparable from the efforts and efforts of china's top contemporary scientists and engineers over the years.
In the second season of Tencent's public welfare column "Master Lecture Hall for Children" customized by Tencent and the China Soong Ching Ling Foundation for teenagers, Qi Faxuan, the first chief designer of the Shenzhou spacecraft, Ouyang Ziyuan, chief scientist of China's lunar exploration project, and Wang Yifang, director of the Institute of High Energy Physics of the Chinese Academy of Sciences, appeared in turn to tell the teenagers about the work done by scientists behind their backs.
It is they, as well as a large number of people who are silently dedicated together, carrying the manufacture of various "national heavy weapons", whether it is the Chinese space station that is ready to go, the lunar research station that is still in the concept, or the upcoming Jiangmen neutrino experimental station... Let us take firm steps in the exploration of the universe.
From Shenzhou manned to the Chinese space station
Qi Fa Xuan @ master lecture hall for children
In the 1960s, Qi Faxuan, who was still working on rocket launch missiles, did not expect that he would one day study how to carry people. In 1992, China launched the 921 Project, officially launched the three-step manned space industry, successively presided over three generations of Dongfanghong satellite design, and was appointed as the chief designer of the Shenzhou spacecraft in the same year.
We all know the story behind, in 2003, the father of Shenzhou signed Yang Liwei to the sky and personally took him back.
Qi Faxuan introduced the unique features of Chinese spacecraft design in the "Master Lecture Hall"
China's manned spacecraft tests were thirty years later than those of the former Soviet Union and the United States, but this has the advantage of being able to make full use of the experience and knowledge of previous generations and avoid starting from scratch. The most technological innovation significance of Shenzhou is the unique orbit retention scheme: in the past, the spacecraft of other countries became useless space garbage after the separation of the orbital module and the return module, and the orbital module of the Shenzhou spacecraft could stay in orbit for half a year and continue a series of observations.
Project 921 plans to build China's own space station on the basis of launching manned spacecraft and breaking through the out-of-bay technology and rendezvous and docking technology. The space station refers to a manned spacecraft that operates for a long time in low Earth orbit and can accommodate multiple astronauts to stay for a long time to carry out experiments.
We spent 30 years of trial and error to get close to this goal, and on April 29, 2021, the era of the Chinese space station began as a new generation of carrier rockets, the Long March 5B, sent the core module of the Tianhe into a predetermined orbit. Launched in the same year, Shenzhou XII and Shenzhou XIII will verify the key technologies of the space station. In 2022, two experimental modules will be launched, "Qingtian" and "Dream", and the core module will form a T-shaped structure. Named "Tiangong", this space station will orbit the earth 16 times a day from 300 kilometers above our heads, and you can see it skimming under the right weather conditions.
In 2022, the Chinese space station will complete the construction on orbit
Not only is it a tool for "sitting on the ground and walking day by day, surveying the sky and watching from afar", the Tiangong space station is an excellent experimental field. The 110 cubic meter sealed chamber is planned with 16 special scientific experiment cabinets and 7 general experimental cabinets, and 3 extravehicular exposure experimental devices can carry out various research such as space physiology, life science, fluid physics, materials science, astronomy and Earth observation.
The space station has many experimental conditions that are not available on the ground. For example, an important physical feature in space is weightlessness, and what effect does weightlessness have on organisms at the cellular and tissue level?
It's a question Tricia Larousse from the Norwegian University of Science and Technology's School of Medicine and Health Sciences, whose project "Tumors in Space" is expected to hit the Chinese space station around 2025. The researchers are going to send three-dimensional stem cell organs from the same person's health and cancer tissues into space to see how the cells' DNA is affected by weightlessness and cosmic radiation, and even if there is an opportunity to find new therapies. Unlike previous studies in space that used only simple two-dimensional cells, the organ model used in this experiment is closer to the natural form and has the characteristics of the organ being imitated.
Space exploration is a cause that belongs to all mankind
In July this year, the journal Nature revealed that the China Manned Space Engineering Office (CMSA) has preliminarily approved more than 1,000 experiments, some of which are recommended by the United Nations Office for Outer Space Affairs (UNOOSA), and the Chinese space station that will be put into operation is open to all countries in the world, as Academician Qi Faxuan said in an interview, "Conditions should be created to serve humanity in the whole world."
From Chang'e lunar exploration to lunar research stations
The exploration of the moon is related to the future of mankind
I still remember that more than a decade ago, China had just entered the initiation stage of the lunar exploration project, and we can often see the elderly Ouyang Ziyuan, who was nearly ancient at that time, rushing to various venues to explain to the audience who questioned this why he spent a lot of money to shovel back a handful of soil on the moon. In fact, this money is not much compared to many ground works, but its use seems too far away.
"Circling, falling, and returning", Chinese astronauts have divided the lunar exploration mission into three cautious steps. In 2007, Chang'e-1 achieved the goal of "orbiting" in the first phase; in 2013, Chang'e-3 successfully landed in the area east of the lunar rainbow bay, achieved the goal of "falling" in the second phase, broke through and mastered the soft landing technology of extraterrestrial bodies, on this basis, chang'e-4 completed the feat of the first human probe landing on the far side of the moon in 2018; in 2020, Chang'e 5 landed near the Lymuk Mountain in the northern part of the lunar storm ocean, collected 1731 grams of lunar soil samples and returned to the ground, thus achieving the goal of the third phase of "return".
Less than two kilograms of extraterrestrial soil, the historical significance is extraordinary, this is the first time in 44 years that humans have returned to the moon to bring back new lunar samples, and it is also the first alien object sampling mission completed by China.
More than forty years ago, Ouyang Ziyuan, a scientist studying geochemistry, and his peers received half of the lunar soil that U.S. President Carter's security advisers at the time gave to Chinese leaders. With this 0.5 grams of research material, they published a total of 14 papers, and it was at that time that Ouyang Ziyuan came up with the idea that we would also go to the moon. From 1958 to 1993, he spent 35 years preparing for lunar exploration, followed by another 10 years to demonstrate feasibility and necessity.
Moon Rock carries many secrets that we want to know
From a purely scientific point of view, exploring the Moon is essential to understanding Earth's early history. One theory is that 4.6 billion years ago, Earth was born out of the dust of the solar system, collided with a planet named Theia in the first billion years, and the debris from the impact eventually became the moon through continuous fusion. Since then, the earth has undergone earth-shaking changes, with oceans, unique atmospheres, countless creatures, and to this day, the original face is unrecognizable, and we hope that the cold moon still retains ancient historical materials that can be traced.
The moon has the enviable reserves of nuclear fuel
From a practical point of view, the Moon, as the closest object to Earth, is our outpost to deep space. It is necessary to explore the available resources and develop and utilize the above channels. The Moon has a large number of ideal nuclear fusion fuels helium-3 that Earth does not have, and the composition of lunar rocks is basically close to that of Earth, containing oxide-based minerals such as silicon, aluminum, iron and magnesium. If you want to make better use of the moon, it is obviously unrealistic to rely on spaceships to travel back and forth, and the most effective thing is to establish a lunar research station.
The next stop, the Lunar Research Station
At the end of April this year, the 2021 China Space Conference and the June 16 Global Space Exploration Conference revealed the next step of the Chinese lunar exploration team, preparing to build a station in the lunar antarctic region, starting with unmanned autonomous operation, and then joining people to participate in the vision. In the near future, the Chang'e-7 mission will carry out a detailed survey of the lunar antarctic resources, and conduct comprehensive exploration of the topography, material composition and space environment there.
From the Daya Bay neutrino experiment to the Jiangmen neutrino experiment
Wang Yifang @ Master Lecture Hall for Children
In the 1980s, Wang Yifang studied high-energy particles in Europe with Nobel laureate Ding Zhaozhong. He always remembered that his mentor said that to do experiments, you must do the best experiments, and all aspects must be ahead of the international level. This concept allowed him to strive for perfection and advancement in the experimental design that followed.
He later returned to China and entered the Institute of High Energy Physics, and soon after devoted himself to the construction of the Daya Bay Neutrino Experiment.
What are neutrinos? It is our most common stranger visitor in the world. Trillions of these particles pass through your body every second. But don't say you can't perceive it, and scientists have been helpless about it for a long time — it barely works with other matter, and can only be captured with the help of sophisticated experimental equipment.
Its discovery is a ghost story in the field of physics. About a hundred years ago, it was discovered that when the nucleus decays in radioactive β, the electron energy emitted is always different, and no one can explain how this phenomenon of shaking the conservation of energy occurs.
In 1930, physicist Pauli claimed to have found a desperate remedy, assuming that the electrons released from decay also emitted another electrically neutral, weakly interacting particle with very little mass. He called it neutron, but because it was the same name as the neutron we now know, another physicist, Fermi, changed his name, that is, neutrino, which means small neutral thing.
Neutrinos, known as a ghost particle
Embarrassingly, all the experimental means at that time could not find it. It wasn't until the 1950s that things took a turn for the better, when some of the world's large nuclear power plants appeared that could serve as abundant neutrino sources, and some detectors seized the clues.
What is the point of finding a particle that doesn't seem to have anything to do with the world? For high-energy physics researchers like Wang Yifang, it contains new physics, "Neutrinos are a scientific rich mine, a golden key to open the mysteries of the universe." We want to understand the origin of the universe, we want to understand many of the problems in supernova explosions, we want to know why matter is much more than antimatter... It may all start with neutrinos.
The Daya Bay Neutrino Experiment made an important discovery about neutrinos in December 2011, found its third oscillation pattern, and together with four other neutrino oscillation experiments, won the 2016 International Breakthrough Prize in Fundamental Physics. Neutrino oscillation refers to the fact that neutrinos change from one type to another as they propagate (there are known to be three types of neutrinos).
Physics experiments are very demanding on designers
There are still many questions to be solved about neutrinos, such as how do the three known types of neutrinos compare their masses? To find out, larger detectors are needed to capture more neutrino signals.
The Daya Bay Experimental Station will be retired at the end of 2020, and the next one to be given high hopes is the Jiangmen Neutrino Experimental Station. Scheduled to be operational in 2022, it will be one of the most powerful neutrino experiments in the world.
In order to build the Jiangmen experiment, which is 1,000 times larger than the Daya Bay experiment, Wang Yifang and the construction team dug into the ground 700 meters deep and placed a 13-story plexiglass ball shell, which was covered by 43,000 light detection photocells and injected with 20,000 metric tons of special formula liquid. When neutrinos emitted by nuclear power plants or underground elemental nuclei decay arrive at the detector, some of them will interact with the liquid and emit scintillation light, which can be captured by photomultiplier tubes and recorded as electrical signals.
Neutrino detection requires extremely sensitive photomultiplier tubes
The team and cooperative units of the Institute of High Energy Physics have developed the photomultiplier tubes needed for the experiment, designed themselves, and found their own places to produce. Why do people who are engaged in high-energy particles still have to engage in photocells? One is to save a lot of money, of course; the other is because the best photomultiplier tube detection efficiency is only 15%, and their own design has increased to 30%. This means that the same effort can be doubled in return.
In different times and different fields, some people go to heaven and some people enter the earth, all in order to answer the doubts that may change the fate of mankind and lead us to the future that can be expected. Three master classes for children, through the basic introduction of subject knowledge, and a very inspiring story, conveyed the most sincere love of scientists for science, and high hopes for the future who will inherit their scientific careers. May you catch this courage to embrace the unknown and explore the world.
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[7] Ray Jayawahana et al., Neutrino Hunter, Shanghai Science and Technology Education Press, 2015
[8]https://mp.weixin.qq.com/s/qt-jtVhlSqNpNlj0BYNP-g
[9]https://www.scientificamerican.com/article/powerful-new-observatory-will-taste-neutrinos-flavors