In Memory of My Teacher, Qian Xuesen
Zhu Yilin, Academician of International Academy of Astronautics
Abstract: The author recalled how Qian Xuesen guided and tutored him to study in the engineering mechanics research class, and to get engaged in the early-stage satellite development, joint research of long-distance astronavigation, regulation of aerospace terminology and aerospace knowledge promotion.
First impression
It was 66 years ago when I first learned about Qian Xuesen as a teenager. I was in a junior middle school in Nanjing. One day, I read a piece of news in Central Daily published by the national government that said Chinese scientist Qian Xuesen participated in the development of V-2 missile. I have remembered his name ever since then.
After graduating from college, I taught Theoretical Mechanics at Beijing Iron and Steel Engineering Institute (University of Science and Technology Beijing). The young teachers including me in the research team all majored in engineering and we were eager to enhance our mathematics and mechanics level. We all looked forward to studying with Qian Xuesen and Qian Weichang, two masters in mechanics in China. We always attended lectures in Beijing University and Tsinghua University as well as academic reports in the mechanic research institute of Chinese Academy of Sciences.
On a sunny afternoon in 1956, I went to attend an academic report about earthquake mechanics made by Prof. Fu Chengyi at the mechanics research institute with some of my colleagues. We arrived early and there was no one in the meeting room on the first floor of the building. I took a seat in the middle of the second row because of my near-sightedness. Then, a man came in and sat in the first row right in front of me. He had a pale lively face and his hair was done neatly. Although the blue Zhongshan uniform was not new, it looked straight and clean. It was rare to see such a man with this neat look and elegant style at that time. He spoke standard mandarin in a clear utterance when he made a speech. I was so impressed by his brief but meaningful speech; that gentleman earned my respect right there. On our way back, my colleague told me that he was Mr. Qian Xuesen, who I had been admiring for so long.
Mr. Qian believed that mechanics is a technological science, as well as a bridge that linked basic science with engineering application. It required rigorous theoretical research and should be combined with engineering practice as well to guide the practice.
In early 1957, proposed by Qian Xuesen and Qian Weichang, an engineering mechanics research class was co-established by Chinese Academy of Sciences and Tsinghua University to train high-end talents in mechanics. The two masters were appointed Director and Deputy Director, respectively of the Mechanics Research Class. Well-known mechanics scientists including Guo Yonghuai, Zheng Zhemin and Du Qinghua were hired as teachers. I was fortunate to be recommended by my university to study in the class.
In a shabby office of the Plantation Research Institute of Chinese Academy of Sciences beside Beijing Zoo (We borrowed the rooms of the plantation institute as classrooms), I had the opportunity to meet Mr. Qian Xuesen. He was hosting a class meeting, discussing the teaching of the mechanics research class.
In the second semester of 1958, Mr.Qian Xuesen taught hydrodynamics in person. Students had very high opinions of his class for his clear concept, rigorous argumentation, relevance to practice and vivid language. Unfortunately, I already completed my study in the mechanics class, and never had the chance to attend his class.
One day, I read an essay "Long-distance Astronavigation" by Mr. Qian on the 4th issue of Mechanics Journal in 1957. The essay showed the extraordinary foresight of Mr. Qian as well as his solid knowledge in mathematics and mechanics. When human beings had been successful in overcoming part of the gravity and launched the first artificial satellite to an orbit around the earth, Mr. Qian was already thinking about flying out of the solar system to visit the Centaurus α star and Sirius that were thousands of billions of kilometers away and already began to calculate the speed and flight time. I was neither interested nor ignorant of anything about astronavigation at that time but I still bought a copy of the journal out of my respect for Mr. Qian. Unexpectedly, it was the beginning of my cooperation with Mr. Qian.
Instructions
In 1958, the man-made satellite project of Chinese Academy of Sciences was listed as the No.1 key mission. A working team led by Qian Xuesen was established to coordinate three design institutes to work for the project. No.1 Design Institute was responsible for the general design of the manmade satellite and carrier rocket, coded as No.1001. Some technological personnel from the relevant institutes of Chinese Academy of Sciences as well as teachers and students from universities like Tsinghua University and Harbin Institute of Technology were assigned to the project to establish a research team.
One afternoon in August of 1958, I was digging a swimming pool on Tsinghua campus. Song Zhongbao, the party branch secretary of our class ran to me and told me to attend an important meeting. We didn't know it was the establishment meeting of the 1001 design institute until we rushed to the lecture theatre of the mechanics institute. From there, I became a member of of the aerospace technology team of China. At that time, we knew nothing about rockets and manmade rockets and had to learn all from the beginning. One day, when we were discussing the orbit of manmade satellite, Mr. Qian came and said, "For the orbit of Russia's first manmade satellite, the altitude difference between apogee and perigee was huge (apogee altitude 215km, perigee altitude 947km) and the satellite moved in an ellipse orbit because the control precision of the launcher was not high enough. So the control of the launcher that carries our first manmade satellite must be precise and accurate to make sure it moves in a circular orbit." We were very surprised by his words because we were only beginners in aerospace science and only had the gut to start the research of rockets and satellite under the central government's call of "eliminating superstition and liberating minds". We were not confident enough to launch the satellite at the 10th anniversary of the founding of new China. However, Mr. Qian had always looked ahead and challenged authority. That was why I respected him so much. Meanwhile,I became more confident about my research.
In early 1963, a group of four (Kong Xiangyan, Zhu Yilin, Li Yili and Chu Guibo) was sent to Beijing by Shanghai Institute of Electromechanical to participate in the manmade satellite project directly under the guidance of Mr. Qian. For more than one year, we collected a wealth of technological materials about aerospace science and mastered the basic knowledge of manmade satellite design. We compiled 1963-1964 China Space Technology Development Plan (Draft). As requested by Mr. Qian, we started an astronavigation theory course in University of Science and Technology of China. Working with Mr. Qian,I learned a lot of professional knowledge about space science and technology as well as the spirit and attitude as a scientist.I always remember two things that Mr. Qian said.
First, scientific research is not only limited to the eight hours at work. One should work hard; otherwise, he cannot succeed.Second, learning from documents and materials from overseas doesn't mean to repeat what they say without thinking. One should learn to analyze and think independently.
Although his remarks sounded simple, it could be summarized as willing to devote and daring to innovate and it is the core spirit of what aerospace scientists have been adhering to.
Collaborative research
When I reported the class materials of the last chapter in Several Problems in the Further Development of Astronavigation in Introduction of Astronavigation to Mr. Qian, we talked about flying out of the solar system to the stars. We mentioned his essay on the 4th issue Mechanics Journal in 1957. He said that he was continuing his research and asked me if I was interested in collaborating with him. Of course, I wouldn't say no. He handed me his manuscript that he already finished. In his manuscript, Mr. Qian wrote many complicated equations and deduction process composed of letters, symbols and numbers but everything was written in a neat and clear way.
I transcribed everything in the manuscript overnight and gave it back to Mr. Qian. Then under the guidance of Mr. Qian, I started the subsequent research on long-distance astronavigation for over a year. After going back to Shanghai, I reported the progress of the research to Mr. Qian from time to time. He replied very quickly and from his letters, I could feel his earnest and rigorous research attitude.
Why do we need to have the rigorous attitude? In the 1960s, rocket model development was the only mission and the nation tackled no other research topics like what we have now in National Natural Science Foundation, National High-tech Development Research Program or National Major Technological Special Projects today. Long-distance astronavigation research was actually a personal behavior. Therefore, it was important to properly deal with the balance of personal research, official work and political activities. Mr. Qian attached great importance to this. In the beginning of 1965,I told him that the research was suspended for some time because of the ‘four elimination’ political campaign. He replied "Fortunately, the research is not of urgent practical use. You can work on it when you have time and put it down for a while when you're busy."
The research on long-distance astronavigation needed many calculations. As the computers had not prevailed yet, I planned to ask for help from the computer research institute or entrust them to do the calculating. However, in his letter back he said, "I'd rather believe yourself than computers. You can do it manually first." With his encouragement, I used the electric calculator, the most advanced tool in my institute at that time and spent tens of hours to complete all the calculations and drew the curve graph by hand.
What inspired me most was his idea on research purpose: "The purpose of scientific research is not to publish essays but to seek for the technological methods to accomplish astronavigation". Once I wrote an essay "A Supplementary Essay for Long-distance Astronavigation" and sent it to Mr. Qian for review. He responded: "I've received and read your essay. Your calculation result of multi-level rocket complies with the estimation so the analysis and calculation should be correct. However, if the purpose of the essay is to propose an equation (not limited to w/c value) and a multi-level rocket calculation that are more common than that in my previous essays, it won't be meaningful even if it can be published. We need to know that the science and technology are surely able to realize the interstellar navigation at present and the technological method was clear too. The problem is that we still need to find out the technological method for astronavigation beyond the solar system. Currently, the mission of the scientists is to propose that technological method for astronavigation before it comes true, like Циолковский.
Since an ill trend was prevailing in China at that time, in which scholars only put stress on publishing essays, Mr. Qian's words were significant in bringing order out of chaos.
In order to advance the research, Mr. Qian said, "What we already know is that the fuel with the highest energy is the fusion of hydrogen, deuterium and tritium so we can get w/c of about 0.05. So if you can get v/c≈0.94, the ｗ／ｃ～0.05 multi-level rocket is more meaningful. How to get υｉ of every level? From the estimation of previous literature, υｉ～100 (70，100，150，200）should be allowed. So we need no more than ten levels. If so, there is a way to realize astronavigation. Our work in the future should focus on how to realize it." (In the letter, V is the ultimate speed of the rocket; w/c is the rate of jet velocity of the rocket engine w and light speed c; υｉis the quality rate of i-level rocket, which is the rate of preliminary quality and the ultimate quality of the rocket.)
In another letter, Mr. Qian pointed out: "I think we can break up the frame of deuterium fusion and see what hydrogen fusion can do. Finding solutions from the current physical theories (including high-energy physics), the maximum ideal jet velocity cannot reach 15% of c. If we consider the real technological problems, I'm afraid ｗ／ｃ＜10％. So the astronavigation that we talk about today must be based on that.
Following his advice, I did the calculation in conditions that w/c was 0.01，0.02，0.03，…，0.09，0.1, respectively and draw a curve graph about the results. I mailed it to Mr. Qian and he wrote back and said, "Your calculation and analysis are correct and meaningful."
I also pointed out that it was not enough to only consider the energy needed in the speed-up stage in astronavigation but also the braking stage. If it was a manned navigation, we should also take the energy needed in both speed-up and braking stages in return into consideration. So, we needed four times of the energy, which was 4n.
He wrote back and said, "The 4n problem that you proposed was correct. I also agree that the two speed-up stages cannot be deducted but can you do something with the two braking stages? The spaceship has a giant energy that is close to light speed. The problem is how to emit the energy in order to brake. I think there are two directions that you can consider:
Make use of a star balloon to usher the spaceship into it through the air layer, just like when satellite breaks through the air layer of the earth, it slows down because of the resistance. The temperature of the natural star's air layer is as high as several thousand Celsius degrees. As the spaceship moves in high speed, the temperature of the air attached to the surface can reach 10 million Celsius degrees. So we must make use of the magnetic field to drive the air away from the spaceship surface to prevent the spaceship from burning.
Can a moving object that has a speed close to light speed generate an electromagnetic field around the spaceship so it can send out electromagnetic wave and emit energy? Please think of these problems when you have time.
After that, the research was suspended due to institute relocation and "Cultural Revolution". After Mr. Qian passed away, I published "A Supplementary Essay to Long-distance Astronavigation" that I co-authored with Mr. Qian on the first issue of Spacecraft Engineering in 2010. In the final words, I wrote, "As the rapid development of computer, solving complex integral with numerical method has become much easier. The analysis and solution via variable replacement in this essay is not the best practical method any more. However, the theoretical analysis and result is still significant in guidance for the next 50 years." In January of 2011, according to a report on website Public Science, Mark Millis, a propulsion physicist in America from NASA published a study, which showed that the energy needed for a one-way flight to a star was 1018J, close to the energy consumed by the whole world in a year. It will take about 200 years before an unmanned spaceship can make a voyage to centaurus α star. Therefore, the guiding significance of "Supplementary Essay to Long-distance Astronavigation" will last to 200 years later.
Regulating aerospace terminology
In November of 1972, about half year after I came back from manual labor in a military farmland, I wrote a letter to Mr. Qian to tell him about the problems of the space technology development and satellite model development as well as my personal situation. On December 28 of the same year, Mr. Qian, who was the Deputy Director of the Science Committee of the Ministry of National Defense, had a talk with me. In our meeting, he gave me some positive help and guidance but didn't mention anything regarding my letter, for example, he asked me to study Marxism and Leninism. Liu Xiyao called during our meeting and his secretary asked me to leave for a while. At last, Mr Qian said that in the past, we considered mechanics as a technological discipline. However, we hadn't done enough job to make it play duo parts in guiding engineering technology and promote theoretical study. Today, we should promote the role and significance of space technology more; so why not start from regulating relevant terminologies?
To follow what he said, I got down to the promotion of space technological terminology regulation. Actually, Mr. Qian had been thinking about a consistent, simple and accurate name for "astronavigation", "space navigation" and "space flight". In an article named "Congratulations to the Revival of Aviation Knowledge" published in the January issue of Aviation Knowledge in 1964, he said the navigation inside the atmosphere is navigation; outside the atmosphere, it should be space navigation. On September 11 of 1967, in Meeting Room 911 (plan discussion meeting of Liberation No.1 returnable satellite), Mr. Qian proposed the word "hang tian" (aerospace) for the first time. He also cited a verse of Mao Zedong "The planet rotates in the universe. We humans on the planet look up to the sky, we can see a thousand milk ways." (I met with Mr. Qian on the meeting. He complimented me for dividing the satellite development stages into shaping, first sample, pilot sample and official sample for the first time in the planning report of Liberation No.1 Satellite development.)
Then he suggested naming the navigation inside the atmosphere "hang kong (aviation)"; between the outer atmosphere and the solar system, it is called "hang tian (aerospace)" and the navigation out of the solar system to the infinite space is called "hang yu (astronavigation)", which is the "long-distance astronavigation" that he mentioned in his essay in 1957.
In my work unit, experts were organized to discuss the terminologies and they co-authored an essay "Hang Tian, a Terminology that Is Scientific, National and Popular", in which the authors explained the theoretical evidence and real advantages of unifying terminologies. The essay was mailed to Mr. Qian as well as to Xinhua News Agency, China Society of Aviation,National Defense Industry Press,Science Press as well as other presses to suggest them replace space navigation, interstellar navigation and space flight with "Hang Tian". In January 1976, Mr. Qian recommended my article "About the Use of Term Hang Tian to Aerospace Magazines" for publication to promote standardized terminology.
Initiated by Mr. Qian, on May 4 of 1982, the 26th session of the 5th Standing Committee of the National People's Congress decided to rename No.7 Mechanic Industrial Ministry to Ministry of Aerospace Industry. The word "hang tian (aerospace)" was finally adopted by the highest legislation organization of the country. This was another creative contribution in regulation scientific terminology promoted by Qian Xuesen after he defined "laser". Since then, the word "hang tian (aerospace)" was widely promoted and applied.
Support the popularization of science
Mr. Qian Xuesen always attached great importance to the popularization of science. He used to suggest college students and master degree students writing science popularization articles about their majors in addition to professional essays.
Not only did Mr. Qian ask young scientists to write articles for science popularization, he also did it in person as a role model. On January 2 of 1959, the Soviet Union launched the first space rocket to the moon in the world. He immediately wrote a scientific popularization report "Space Rocket and Interstellar Flight", in which he explained the function, flight, mission of the space rocket, introduced all the planets in the solar system and how to reach the planets on space rockets. The report was published on People's Daily on January 10, 1959.
An article "Technique of Organizational Management- System Engineering" co-authored by Qian Xuesen, Wang Shouyun and Xu Guozhi was published on Wenhui Newspaper on September 27, 1978. The article was a milestone for the education and application of systems engineering in China. Now, the systems engineering has been used in practically every field. The theories and methods are used to solve all kinds of complicated and comprehensive matters. It also won the first prize of the first New March Outstanding Work of Science Popularization in 1981.
I began to write articles about science popularization mainly because of Mr. Qian. In 1964, the then China Society of Aerospace invited Mr. Qian to write an article introducing astronavigation for Aerospace Knowledge. Mr. Qian assigned the task to us, a group of four. We wrote three articles about current situation and perspective of astronavigation in the name of "Qian Xingwu". Since then, I fell in love with writing science popularization articles about aerospace and my articles have since then appeared quite often in Aerospace Knowledge and other journals and newspapers.
Mr.Qian cared a lot about science popularization. Once, I reported to the leaders from the State Commission of Science and Technology for National Defense Industry about the preliminary failure analysis of Practice No.2 Satellite on behalf of the development team of Practice No. 2. After the report, Mr. Qian asked me if I wrote any articles on science popularization recently. I said, "I wrote Secret of V-2." He smiled and said, "What's the secret about V-2?" What he meant was that the facts about V-2 rocket were already known to the public. Why should I bother to make it so mysterious?
In the spring of 1982, knowing that Mr. Qian praised me for my active participation in aerospace knowledge popularization on an internal work meeting, I felt very excited (I was once criticized and ill-treated because of the science popularization articles). I wrote a long letter to Mr. Qian regarding my scientific research and science popularization writing in the recent years. On March 25, Mr. Qian and I had a long yet soothing talk. He pointed out the significance of popularizing aerospace technology in socialist modernization construction. He asked me to write more about advanced articles that tailored to high-rank officials in order to promote scientific decision-making. I sent him two articles that I liked the most and asked for his advice. On the second day, he wrote back and said, "I've read both articles. I like "Space Technology Back to the World" better. The other one "Astronautic Technology into Families" emphasized too much on fun and life, and diverged from the reality in China.In fact, an ordinary science popularization article is not easy to write.
Soon, knowing that I did a self-criticism on a seminar organized by Chinese Science Popularization Writers Association in Bei Dai He, he wrote me a letter to encourage me. "I met with Tang Shougen from Science Popularization Institute and he said that you had a new understanding of the science popularization and did a self-criticism in a meeting not long ago. I'm so happy for you and respect your rigorousness. I wish you new achievements on the new path!"
On May 9 of 1983, Mr. Qian wrote me a letter: "I found on the magazine Aeronautics & Astronautics that there are some assumptions about the application of aerospace technology on military. In addition, the Air Force of United States recently established an air battle command office and it may be a signal for the future development of wars. However, it may be difficult for the high rank leaders to realize the trend. So could you consider writing some advanced science popularization articles and publishing them on magazines like Futurology? It can be of good benefits."
In February of 1987, I was hired as a member of the aerospace experts committee of State 863 High-tech Research and Development Program by the State Commission of Science and Technology for National Defense Industry. After the founding meeting of the 863, expert committees of all professions at Jing Xi Hotel in Beijing, Mr. Qian, along with other leaders from the State Commission of Science and Technology for National Defense Industry came to our room to see us. Mr. Qian asked me again about my science popularization writing, I said that I wrote fewer than before. He asked me to continue. With his encouragement, I have kept writing until the 21st century. Although I didn't write much on comprehensive science popularization article, the writing has enhanced my ability in collecting and organizing information, as well as in-depth analysis & clear and accurate expression. It has laid a good foundation for my research in the satellite and aerospace development strategy in recent years.
Last but not least, I'm very grateful for Mr. Qian's support and help. In one event, Wang Shouyun, who was once the secretary of Mr. Qian and the Vice General Secretary of the State Commission of Science and Technology for National Defense Industry at that time, told me that Mr. Qian had recommended me to be the member of the expert committee. Of course, he did. Most of the seven members were in high rank (above institute director) or of high reputation and I was the only one who was nobody. Without his recommendation, how could I have the opportunity to play my part in the senior aerospace development strategy research institute and make my part to the manned aerospace development strategy of China?
Looking back to the decades, I was so fortunate to be guided, tutored and helped by Mr. Qian Xuesen. His guidance has benefited all my life and I will remember him forever.
(Published on the 4th issue of Spacecraft Engineering in 2011)