From Young Scholar to World-Class Scientist

1 Young Scholar at Caltech

In 1939, after receiving his doctorate, Qian Xuesen had intended to return to China to participate in the Anti-Japanese War. To serve his own country with his talent would be his earnest wish. However, addressing cutting-edge problem and breaking new scientific ground in a supportive environment would be a good opportunity for him. Theodore von Kármán, his mentor, earnestly invited him to be a member of the aeronautics staff at Caltech. After much consideration, Qian Xuesen decided to stay at Caltech as a research fellow. His research interest gradually extended from aerodynamics and thin shell theory to rocket technology, engineering cybernetics and physical mechanics. A young scientific star, known as a “first-class star”, emerged many years later.

The decision to stay at Caltech

Since the emergence of modern science and education systems, the cultivation of scientific and technological talents has abandoned the traditional “teacher-apprentice” and “mentorship” has become an important part of the modern education system. Undoubtedly, mentor plays a very important role in the growth of young scholars.

Theodore von Kármán was a giant in aeronautical circles, regarded as the scientific genius of the aerospace era in the twentieth century. Qian Xuesen first met Kármán when he sought Kármán to inquire about graduate studies at Caltech. Kármán was undoubtedly a key figure in his journey to the world’s top scientist (Fig. 1).

Fig. 1

Self-portrait of Qian Xuesen in his office at Caltech

From October 1936 to May 1939, Qian Xuesen completed his doctoral thesis under the guidance of von Kármán. During the three years of his doctoral studies, they had maintained important intellectual and personal relationships. In a casual conversation, Qian jokingly described himself as Giulio Douhet, the “Father of the Air Force”, (the originator of the theory of air power), predicting that their research work would make them the “father of missiles.” During his doctoral studies, the most important academic idea that Qian Xuesen learned from von Kármán was that “theory must be used to solve the key problems in practice”, i.e., the integration of theory and practice.

In the fall of 1938, Qian Xuesen’s doctoral dissertation was almost finished, and he began to prepare for PhD defense. Meanwhile, he began to plan for his return to China to join the Anti-Japanese war after graduation. When he told his mentor about his plan, Kármán suggested Qian Xuesen to stay at Caltech for the reason that “doing scientific research in the United States can also strengthen the anti-fascist force.” At that time, Kármán had many scientific research projects commissioned by the U.S. military and needed young talents like Qian Xuesen to help him complete the projects.

The second World War has just began and the war between China and Japan was in full swing. Qian Xuesen followed his mentor’s advice and decided to stay after careful consideration. Thus, Qian Xuesen became a young research fellow in the Department of Aeronautics at Caltech. It should be noted that the student visa Qian Xuesen applied for when he went abroad was valid for 34 months (from July 1935 to April 1938). After receiving a reply letter from Tsinghua University agreeing to his second extension of scholarship in 1938, he applied to the Los Angeles Immigration Bureau for an extension of his visa. His visa was extended from April 4, 1938 to November 13, 1940. Since Qian stayed had a contract of employment at Caltech, his visa was extended for one more year until November 13, 1941. Thereafter, due to the recommendation and guarantee provided by his mentor von Kármán to the U.S. Department of War, Qian’s student visa was extended every year. During this period, Caltech also decided to grant Qian Xuesen a visiting scientist visa valid for 18 months on August 25, 1941, which was later extended several times.

The extension of passport and visa validity ensured Qian Xuesen’s legal residence in the United States, while the visiting scientist treatment served to reduce the review process for participation in classified research projects. Another important external factor that enabled Qian to participate in U.S. defense research projects was the Sino-American alliance during World War II, which provided a rare historical opportunity for Qian. Many Chinese scientists had participated in U.S. defense research projects, which helped improve the defense research level on the part of the United States.

Qian Xuesen’s graduation from Caltech and becoming its staff member was the starting point of his “institutionalized” path of scientific research and a key turning point in his life. Without von Kármán’s acceptance of Qian as a doctoral student and his recommendation to stay at Caltech after graduation, Qian’s life would have been on a different trajectory. Von Kármán and Qian Xuesen were intellectual partners as well as close friends. In 1988, when Science Press asked Qian Xuesen to evaluate the scientific contributions of Von Kármán, the always rational Qian Xuesen showed his rare emotion and politely declined. He said: “Von Kármán was my respected teacher. I had strong personal feelings for him, and I was afraid I could not evaluate him fairly [1].”

“Double-shouldered” in research and teaching

It was Qian Xuesen’s tenacity and his gift in applied mathematics that won Kármán’s recognition. Kármán was indeed an insightful supervisor who had not only used students’ works but also created opportunities in fostering them. In 1940, when Guggenheim Aeronautical Laboratory of the California Institute of Technology’s (GAL-CIT) decided to build a supersonic wind tunnel for ballistic test, Kármán entrusted the task to Qian, which enabled him rich accumulation of practical engineering experience, during the process of independent investigation, calculation and design.

At Caltech, Qian attended the annual conference of the American Institute of Aeronautical Science (IAS), and presented his paper. Attended by hundreds of people every year, this conference was a great event for scientists in the field of aeronautical science to exchange and discuss their ideas. For Qian Xuesen, the eighth annual conference of IAS in 1940 was an unforgettable event. This was his debut at an international academic conference as a young scholar after graduation. He had prepared for long time in the writing of the academic report entitled “The Influence of Curvature on the Flexural Properties of Structures”. This report was entirely his research result out of academic interests. Years later, Qian Xuesen especially emphasized that, “It was an independent research work.”

During World War II, the United States had a strong need to improve the combat performance of its aircraft in order to suppress the German and Japanese air forces, thus creating a strong demand for aviation science research. Against this background, Qian Xuesen joined the American Air Jet Corporation as a consultant (Theodore von Kármán’ as general manager and Frank J. Malina as treasurer) in March 1941 and began to participate in Air Force research projects.

In 1942, the U.S. War Department began to entrust von Kármán with a classified military project. Von Kármán then enrolled Qian Xuesen into the research team. However, since Qian Xuesen was not allowed to participate in military-related classified projects as he was not a U.S. citizen, von Kármán vouched for his personal reputation. He wrote:

Qian had lived in the United States for seven years and was now a researcher and lecturer at Caltech. He was one of the leading experts in the field of supersonic flight research in the United States. He had published a number of academic papers, including those on ballistics, which had made him famous throughout the United States. Hiring Qian would help us complete the research work in the contract, and I had not the slightest doubt as to Qian’s loyalty to the United States.

On December 1, Qian Xuesen received a letter of permission to participate in classified military projects, and was allowed to participate in classified projects of the Navy, Army and Army Air Corps, War Department and Office of the Scientific Research and Development. Since then, Qian Xuesen had been working on projects almost every day for a long time, and had played an important role in promoting the scientific research capability of the United States in aviation. However, even with the von Kármán’s guarantee, Qian Xuesen was still under scrutiny of U.S. government. For example, on December 16, 1944, the U.S. War Department wrote separately to W. R. Sears and Louis J. Dunn to confirm Qian’s loyalty (Figs. 2 and 3).

Fig. 2

Qian Xuesen’s 1944 technical report for the National Advisory Committee for Aeronautics, entitled “The ‘Limiting Line’ in Mixed Subsonic and Supersonic Flow of Compressible Fluids”

Fig. 3

This declassified file, dated November 4, 1980, shows that on December 16, 1944, the U.S. Department of War investigated Qian Xuesen’s loyalty through his colleague Louis J. Dunn (the original version was kept in the U.S. National Archives)

Fig. 4

Qian Xuesen in the classroom at Caltech

Moreover, Qian Xuesen combined teaching and research quite well at Caltech. In addition to completing his annual research and thesis tasks, he also undertook teaching duties (Fig. 4). On the one hand, as an academic assistant to Von Kármán, Qian became a “part-time tutor” and was a teaching assistant for graduate students. On the other hand, in 1942, the U.S. military commissioned Caltech to hold a training program on jet technology, and Qian was one of the instructors. Year later, he recalled, “I was one of the instructors and had contact with the technical staff of the Army, Navy and Army Air Corps, and later many of the officers in the U.S. Army in missiles and rockets were students in this program.” Qian Xuesen learned to move smoothly among the spheres of academia, industry and goverment. In his early thirties and at the very height of his creative powers, Qian Xuesen had every confidence in scientific research especially after he was promoted to an associate professor in 1945 at Caltech.

2 An American “Army Colonel” on Europe Trip

The Second World War highlighted the importance of science and technology in warfare, especially aircraft carriers, missiles, aircraft and radar. In 1944, when the outcome of World War II had been decided, the United States began to set up the Army Air Forces Scientific Advisory Group (SAG) to plan the development of postwar military science in order to maintain absolute military superiority, especially against the increasingly powerful Soviet Union. Qian Xuesen was recommended by his mentor to be a member of SAG and had the opportunity to participate in the code name Operation Lusty, to travel to Europe to inspect the situation of military science research in Germany and other countries. On the eve of his preparations for the mission, Qian Xuesen encountered the so-called “re-entry” problem.

“Re-entry” problem

After the outbreak of World War II, the United States began to invest heavily in military science and technology in order to upgrade its aviation science and technology to counter and surpass Germany and to maintain a strategic advantage over the Soviet Union after the war. To this end, the United States also accepted scientists persecuted by the Nazis on a large scale, a movement historically known as the “intercontinental transfer” of science and technology.

By 1944, when the United States took the initiative of the War and was about to win, it began to think about how to take control of the airpower after the war. In September of that year, after a secret meeting between five-star general Henry Harley Arnold and Von Kármán in an Air Force sedan at New York’s LaGuardia Airport, they decided to establish Army Air Forces Scientific Advisory Group (SAG) to plan the development of cutting-edge military science for the United States in the next twenty to fifty years after the war (Fig. 5).

Fig. 5

U.S. Department of Defense Army Air Forces Scientific Advisory Group (SAG) established on December 1, 1944 (Qian Xuesen was standing in the second from left in the back row)

The Scientific Advisory Group was headed by Theodore von Kármán, and its members were mainly scientists and engineers from universities and research institutions, as well as high government officials. On December 1, 1944, the first plenary meeting of the advisory group was held. In early 1945, when the United States began to take full control of the European battlefield, the military decided to send an advisory group to Germany to inspect their research and development facilities and gather information on the Germans by interviewing aerodynamicists in neighboring neutral countries such as Switzerland and Sweden. After receiving the mission, the advisory group began to prepare for the visit and select the personnel to form the mission group on April 19. On March 25, Qian Xuesen was appointed as a research advisor to the U.S. Defense Research Board.

As Frederic E. Glantzberg, director of the Advising Panel, was compiling the list of visitors, it was discovered that Qian Xuesen had a “re-entry” problem. As the only Chinese scientist in the group, Qian Xuesen still possessed a student 4E visa from 1936 and a passport from China. Getting out of the United States was not a problem but Qian was worried that he might encounter difficulties with the Immigration and Naturalization Service when the European service was over and not be able to get back in. Kármán wanted Qian to come along, so he asked U.S. Department of War to explain the reason to INS to ensure Qian’s exit and reentry so that he could resume his student status upon returning to the United States. On April 23, the INS granted Qian a special waiver so that he could return with the same status he possessed before departure. On April 24, the Air Force promoted Qian to be the assimilated rank of colonel and gave him the title of expert consultant. The Air Force issued two identification cards for Qian Xuesen. One was general identification card to prove that he was a field grade colonel and was mainly used for identification inside the U.S. Army. The back of the document had Qian’s fingerprints. The other was special identification card because the war was not really over and the U.S. Army prepared for the possibility of the SAG members being captured by enemy forces. This special identification card was a non-combatant identification issued by the U.S. Department of War, showing that Qian Xuesen was employed as a consultant. This identification card also had Qian’s fingerprints on the back, but was specifically marked “VALID ONLY IF CAPTURED BY THE ENEMY”. It was specifically stated that if captured by the enemy, he was to be treated as a prisoner of war in accordance with the provisions of Article 81 of the Geneva Convention of July 27, 1929, at the rank of colonel (Figs. 6, 7, 8, 9 and 10).

Fig. 6

Qian Xuesen’s U.S. Department of Defense Army Air Corps Scientific Advisory Corps Member ID

Fig. 7

List of visitors compiled by Air Force Colonel Frederic E. Glantzberg, head of the Advisory Corps Office

Fig. 8

Special permit issued by the U.S. War Department for Qian Xuesen’s visit to Europe (April 24, 1945)

Fig. 9

Qian Xuesen’s “general identification document” and the bottom is Qian Xuesen’s “special identification document”

Fig. 10

Badge used by Qian Xuesen during his stay in the United States

A participant of code name Operation Lusty

Interestingly, the U.S. military also humorously gave the expedition a special code name, Operation Lusty, which was derived from the word Lust, meaning strong desire. Everything was ready, and on April 29 Qian Xuesen, as a participant in Operation Lusty, left for Europe on a C-54 military aircraft from Virginia’s Crushed Rock Island military airport at Gravelly Point. During the expedition, Qian Xuesen was dressed in a U.S. Army uniform, wearing a military cap, looking handsome and dashing.

The team’s destination was mainly Germany, including Britain, France and Switzerland. The expedition was of great significance both to U.S. military science and to Qian Xuesen, especially in that it made a comprehensive study of the state of German military science and technology research on rockets, aerodynamics, engines and so on, and obtained first-hand reliable information. For example, in a dry well near an aerodynamical laboratory in a village outside the city of Braunschweig, the group retrieved thousands of top secret documents weighing 1,500 tons. In response, the U.S. Navy and Army set up a special Military Technical Intelligence Agency to sort through the documents. Since then, the agency has grown into the U.S. Defense Technical Information Center, which is today a worldwide center for the aggregation and analysis of defense science and technology intelligence.

During May and June, Qian Xuesen inspected wind tunnel facilities in Germany and throughout Europe and wrote several reports such as “Arrow Wing”, “Rocket”, “Supersonic Aerodynamics”, “Ramjet Engine”, “Pulsating Air Jet Engine”, and “Installation of Turbojet Engine on Aircraft” and so on. These reports recorded a full and accurate development of aircraft, rockets and bombs in Germany. For example, Qian Xuesen found that the arrow-shaped wing research in Germany was much more in-depth than that in the United States during his inspection.

The group also found a large number of research reports and experimental equipment that the German army tried to destroy during withdrawal. It was found that, as early as 1936, Germany had concentrated on the development of rockets, trying to use them as power propulsion devices for fighter acceleration, torpedo launch and so on. Later, in his report “Rocket”, Qian analyzed the structure and performance of rockets developed by Germany, and pointed out that Germany had conducted research on rockets in three categories: solid propellant rockets, solid–liquid propellant rockets, and liquid propellant rockets.

On May 5, Qian Xuesen interviewed Wernher von Braun in the German village of Kochel and asked him to prepare a report detailing the rocketry research he had engaged in and his predictions for the future. He also interviewed mechanics master Ludwig Prandtl, Kármán’s teacher. Ironically, the war turned the academic community of the Göttingen School into the victor and the defeated. Von Kármán said jokingly later on (Figs. 11, 12 and 13):

I suddenly realized how peculiar this meeting was. One was my most brilliant student, who finally returned to China, and the other was my great mentor, who had worked for Nazi Germany. How incredible were the circumstances that divided three generations of aerodynamicists. They were meant to work together in harmony.

Fig. 11

Qian Xuesen’s Europe inspection

Fig. 12

Three generations of masters of mechanics, from the left: Ludwig Prandtl, Qian Xuesen, and von Kármán

Fig. 13

From the second left: Ludwig Prandtl, von Kármán and Qian Xuesen, taken at the Hohenheim Institute, Germany

However, this historical scene occurred again eleven years later, that was, Qian Xuesen’s special visit to the Soviet Union as mentioned in the Preface. Although it was not in the sense of the victor and the defeated, it turned the relationship of harmonious supervisor and student into opponents.

After finishing his visit to Germany, Qian Xuesen went with the group to England, France, Switzerland and other countries. A group of SAG members prepared to go on to Japan to inspect the aerodynamic facilities there. Qian Xuesen was to be one of them, but for reasons unknown, he did not go to Asia. The Asian group included Fritz Zwicky, Frank L. Walden and William H. Pickering. When they were in China, they suggested Gu Yuxiu to travel to Japan together and asked General Douglas MacArthur’s allied headquarters to select a batch of research equipment to be transported to China. On June 20, Qian Xuesen returned to Washington and prepared for the writing of Toward New Horizons. This series of reports later pointed the way for the development of cutting-edge military science in the United States after the war, and was of great significance in the history of American military and science and technology.

Towards New Horizons

Towards New Horizons was a series of technical reports in thirteen books, expanding on Kármán’s theories in detail. It included topics in aerodynamics, aircraft power plants, aircraft fuels, rocket propellants, guided missiles, pilotless aircraft, explosives, terminal ballistics, radar communication, aviation medicine and psychology. The reports provided a blueprint for the development of a modern air force. Qian Xuesen provided his own insight and ideas for Towards New Horizons. As part of his contribution for the series, Qian Xuesen wrote seven reports and he summarized his findings in Germany and Switzerland, devoting considerable space to describing different wind tunnel facilities, the swept-back wing concept, and propellant fuels. He also elaborated on the theoretical analyses conducted at Caltech or JPL during the war years. The following is a list of the seven reports written by Qian Xuesen.

• 1. Recent Developments of Several Selected Fields of Aeronautics in Germany and Switzerland

• 2. High Speed Aerodynamics

• 3. Experimental and Theoretical Performance of Aeropulse Engines

• 4. Performance of Ramjets and Their Design Problems

• 5. Future Trends in the Design and Development of Solid and Liquid Fuel Rockets

• 6. Possibilities of Atomic Fuels for Aircraft Propulsion Power Plants

• 7. The Launching of a Winged Missile for Supersonic Flight.

The series Towards New Horizons was the result of collective wisdom, and 31 scientists, including Qian Xuesen, participated in the writing. On December 21, General Henry Arnold, chief of the Army Air Corps, signed a citation recognizing each member who had participated in the expedition, and on February 13, 1946, Arnold gave Qian an official commendation for his “excellent and complete” survey of ramjet and rocket performance and “invaluable” contribution to the field of propulsion and nuclear energy (Fig. 14).

Fig. 14

Letter from General Henry Arnold, Commander of the Army Air Corps, U.S. Department of Defense, honoring Qian Xuesen

This European trip was of great significance for Qian Xuesen. He not only gained practical experience in the formation of his own technological and scientific thought, but also confirmed his thought of combining scientific theory with engineering practice. He gained a deeper understanding of the relationship between nation and science so that he was able to “think big and far” in his own words.

3 First Chinese Professor at MIT

The so-called “Von Kármán School Exodus” is a notable incident in the history of Caltech. As the successor of Von Kármán School, Qian Xuesen chose to leave Caltech and joined the department of aeronautics of MIT in the fall semester of 1946. In May 1947, MIT started the staff promotion process and Qian Xuesen was promoted to tenured full professor. It was a year that Qian Xuesen became the first Chinese professor in MIT’s history at the age of thirty-six. Subsequently, Qian Xuesen applied for a permanent residency status in the United States in order to have higher level of treatment. Since then, he had taught at MIT’s Department of Aeronautical Engineering until the summer of 1949.

Joining Department of Aeronautics at MIT

In August 1946, Qian Xuesen officially resigned his position at Caltech and left the Pasadena campus, where he had been studying and working for ten years. In the fall of that year, he joined MIT as an associate professor in the Department of Aeronautics. Qian Xuesen had transitioned from a student to a young scholar, and became a rising star in the field of aeronautical science research. A direct reason for Qian’s departure from Caltech could be his mentor von Kármán, who left Caltech in 1944 for his disagreement over research and teaching philosophies with the university.

Qian Xuesen later recalled, “I quitted my job because of Professor Von Kármán’s disagreement with the Caltech authorities, and as a student of Von Kármán, I also wanted to express my disagreement.” On November 7, Qian Xuesen, Lin Jiaqiao, Qian Weizhang, and Guo Yonghuai sent a joint letter to von Kármán, expressing their desire to leave the university. They wrote in the letter:

We are writing to confirm that you may not return to the university within the next six to eight months. We understand very well the reasons for your choice, and we will also reconsider our positions.

Firstly, we are only “guests” in the United States, and we do not intend to stay here permanently. Secondly, we are just scientists. We like to work in an atmosphere of inspiration and interpersonal enthusiasm, and it is you who create such an atmosphere. Without your presence, we feel tremendously uncomfortable. Thirdly, we love theoretical research work, and we feel that it will be difficult to do so without your guidance.

For these reasons, we are considering other choices and we need your advice on whether we should stay at Caltech or not. We fully respect your opinion. We have preliminary plans, but we will make a final decision based on your advice.

Qian Xuesen considers for a two- or three-year faculty position, or research position similar to the work he participated in during the war, probably at the University of California; Guo Yonghuai considers a research position with preference, possibly at Princeton University; Qian Weizhang considers a faculty position or a research position similar to the U.S. military research program in which Qian Xuesen had participated in; Lin Jiaqiao considers a research or teaching position in applied mathematics at one of the top universities in the east.

We are very sorry that our decisions may upset you. But you are our mentor, and we would not have done anything without your advice.

Qian Xuesen’s original plan was to go to the University of California. But it was MIT, the school where he had studied for his master’s degree that finally offered him an invitation, recommended by Jerome C. Hunsaker, the head of MIT’s department of aeronautics. Hunsaker, who had been the departmental chair when Qian was studying at MIT, was impressed with the student from China. It was not known how Hunsaker convinced Qian to come to MIT, but on June 14, 1946, Hunsaker wrote to the dean of MIT to inform him explicitly that Qian would teach at MIT in the fall semester, and that Caltech might “pressure” him to prevent a brain drain.

At this time, Qian Xuesen was invited by von Kármán and was attending the first meeting of the U.S. National Advisory Committee on Aeronautics at the Pentagon in Washington, D.C., on June 17. After the meeting, Qian flew back to California, going through resigning procedures. He and Guo Yonghuai then drove from the west coast to the eastern part of the U.S. and Qian drove alone to Boston after sending Guo to Cornell University for his posting. In a commemorative essay for Guo Yonghuai’s Collected Works, Qian Xuesen still recalled with fondness:

In the fall of 1946, Guo Yonghuai took a teaching position at School of Aeronautics, Cornell University, chaired by W. R. Sears, and I went to MIT. Both universities were in the eastern part of the United States nearly 3,000 km away from Caltech, so he and I drove to our destinations. It was a rare chance to have such a confidant traveling with me, so when he arrived at Cornell and I had to drive on eastward to MIT alone, I felt a little lonely [2].

On August 31, Qian Xuesen officially joined the MIT Department of Aeronautics as an associate professor but MIT offered him a professor’s annual salary. Perhaps, Hunsaker had promised to give him full professorship when he recommended Qian Xuesen to MIT.

Becoming a full professor at MIT

Within months of his arrival at MIT, the faculty considered promoting Qian Xuesen to full professorship immediately. In MIT’s “President’s Files”, a memo from T. K. Shewood, dean of the School of Engineering, to the president was kept. The memo, dated January 29, 1947, was about Hunsaker’s visit to T. K. Shewood on January 15 to discuss the promotion of Qian Xuesen. The memo recorded:

Hunsaker thought it was appropriate to promote Qian Xuesen to be a full professor because Qian Xuesen had a clear research direction and was doing excellent work. Recently, Qian’s research contributions in the field of supersonic aerodynamics and his proposed research program for supersonic vehicles with Mach 1.0 or higher had led Hunsaker to believe that we had a “first-class star.”

Jerome Hunsaker also asked von Kármán in February 1047 to provide a recommendation for Qian’s promotion to tenured full professor. Kármán wrote:

Dr. Qian is certainly one of the leading men in the field of application of mathematics and mathematical physics to problems in aerodynamic and structural elasticity. He has a very broad knowledge in applied mathematics, as well as in the sub-disciplines of physics and mathematics. He has the ability to combine mathematical skills with natural phenomena and engineering vision. I was very impressed with him when he was a young student working with me, and he used his talent to help me solve and clarify several scientific problems.

I believe that, in his new position, Dr. Qian will lead young scholars and engineering students to build a solid foundation for their future research. In fact, Dr. Qian has inspired many aviation researchers in the field of aerodynamics and elasticity during his three or four years at Caltech.

I believe he has the maturity required for a full professorship. I believe he is a good teacher and that he also has a talent for organization. His intellectual honesty and sincere devotion to both science and the institution which gives him the opportunity for working scientific research represent great assets, which I am sure you will appreciate.

Hunsaker’s efforts and von Kármán’s letter of recommendation helped. On March 7, the MIT Technology Review officially announced the results of the promotion, in which twelve people were promoted to be full professor, and Qian Xuesen was among them. Qian Xuesen was then thirty-six years old.

In his recommendation letter, von Kármán emphasized that “He also has a talent for organization”, which played an extremely important role when Qian returned to China to lead the missile development project. It was this organizational ability that made Qian Xuesen a strategic scientist and was the basis for his research on organizational management, system engineering, and systems science in his later years.

In twelve years, since Qian Xuesen set his foot in U.S. soil, he was transformed from a student to a professor. This was an “upgrading” in his life through his own efforts. In his words, “I had climbed to the top in the American academic world.”

Applying for a U.S. permanent residency status

When Qian Xuesen joined MIT, he was still a member of the U.S. Aeronautics Advisory Board (the predecessor of NASA), which meant that he had to travel to Washington frequently to attend meetings. At MIT, he taught aerodynamics, a course for graduate students. In the first half of 1948, Qian Xuesen offered a course “Rocket Engineering” and co-chaired a seminar on aeronautics with Lin Jiaqiao.

Claude Brenner, a former graduate student at MIT, recalled that Qian Xuesen was already famous, “a great guy” before he came to MIT. But Qian’s classes were not popular, and Claude Brenner even used the word “terrible” to describe them. It was not that Qian’s classes were terrible, but the way they were taught made many students “unable to keep up”, said Claude Brenner.

His course was terrible because he didn’t allow any questions! We had learned that early. We sat in the classroom while he stood and wrote on the blackboard. Five minutes into the lecture, someone interrupted him and said, “Excuse me, sir. I didn’t understand the equation.” He turned around and said, “Have you studied it in advance?” “Yes.” “Well, then you didn’t need my explanation.” He continued his lecture and we sat there, dumbfounded. In the next class, someone asked another question and he turned around and said, “Did you pay attention?” “Yes.” “Then, you didn’t need an answer.” We studied in his classroom for a whole year and never asked another question! We just copied his equations and listened to his lectures. At the end he gave us a test and the question had nothing to do with aviation! To a large extent, it was a math test on hypothetical situations, testing our mathematical understanding of what he taught us, and the concepts of what he taught us. He was a very tough teacher.

In fact, Qian Xuesen’s lecture on compressible fluid aerodynamics was a cutting-edge subject, and the lecture was based on his latest research. Many students in his class were not up to date with their knowledge, and therefore found it quite difficult. But Claude Brenner recalled the Chinese teacher’s class, “It was a very interesting moment.” In Claude Brenner’s view, Qian Xuesen was a very good friend and “a very charming person socially.” Maybe it was because Qian Xuesen would meet with his students for dinner almost once a month to talk with them about life and ideals.

Fig. 15

Qian Xuesen’s U.S. Permanent Residence Permit

The year 1947 was a turning point in Qian Xuesen’s life when, at the age of thirty six, he became the first Chinese professor in the history of the MIT. In addition, after receiving full professorship, Qian Xuesen applied for a permanent residence permit (No. 4656868), or “U.S. Green card”, from the U.S. Department of Justice Immigration Service on April 21 in order to facilitate his participation in classified programs (Fig. 15). This meant that he could stay in the United States permanently without a visa and enjoy all the civil rights of the United States except the right to vote and to be elected, and more importantly, to participate in classified projects. There were six levels of confidentiality for U.S. researchers, namely, the “unclassified, declassified, classified, confident secret, top secret and topmost secret.” According to Zhu Kezhen’s diary, Qian Xuesen was able to read the “confident secret” grade file. There was no doubt that Qian Xuesen’s access to the files at confidential level played an important role in the enhancement of his scientific vision. This was also the reason why the U.S. military immediately revoked Qian’s secret status license after the so-called “Qian Xuesen case.”

A green card holder is not only able to enter and leave the United States without a visa, but his/her spouse is also able to enter the United States legally. Thus, when Qian returned to China in the summer to visit his family and married Jiang Ying, he applied for a visa for Jiang Ying from the U.S. Consulate in Shanghai.

In the history of MIT, Qian Xuesen was a “special” person. In a way, MIT was the “lucky place” where Qian became a world-renowned scientist. MIT continued to keep an eye on Qian Xuesen after his return to China, and when China achieved the “two-bomb combination” in 1966, the MIT Technology Review reported on November 4, 1966, with the headline “Chinese bomb expert MIT grad”, recalling the alumnus who had studied and taught at MIT and claimed, “What he learned at MIT and Caltech undoubtedly helped to make Red China a nuclear power.”

4 Summon from China

The year of 1947 coincided with Qian Xuesen’s big year (one’s year of birth considered in relation to the Twelve Terrestrial Branches), and his promotion to full professorship was an important turning point in his scientific career. From July to September, Qian Xuesen delivered speeches on the topic of engineering and engineering science in Zhejiang University, Jiaotong University and Tsinghua University on the occasion of his return to China, systematically expounding his thoughts on the ideological system of technical science, including scientific connotation, research objects and research methods. It symbolized the formation and perfection of Qian Xuesen’s technical scientific thought. During this period, he plainly realized that “the first-class technical scientists were all spontaneous dialectical materialists”, but it was not until he returned to China that he realized that the methodology of technical scientific thought had already been expounded in the classical works of Mao Zedong’s philosophical thoughts On Practice and On Contradiction. This realization remained ideological basis for him to become a firm Marxist.

An invitation from Alma Mater Jiaotong University

On April 21, 1947, Zhang Sihou wrote to Wu Baofeng, President of Jiaotong University, and Li Zhenwu, Provost of Jiaotong University, informing them that Qian Xuesen would return to China soon, and he proposed:

Qian Xuesen planned to return to China this June and would stay for one or two months. I had asked him whether he could make speeches at Jiaotong University one hour every day for two weeks. Qian was very influential in the American aviation industry. He was one member of the Scientific Advisory Group of the United States to travel to Germany to inspect the situation of military science research. If the alma mater could deliver lectures in the summer and students and researchers specialized in aviation from Beijing, Shanghai and Hangzhou could be invited to gather together, it would be beneficial to promoting the research atmosphere. If Mr. Hesun (Cao Hesun, Director of Department of Aeronautics of Jiaotong University) and Mr. Junliao agreed to this proposal, please send messages to Prof. H. S. Tsien, Department of Aeronautics, MIT. For any assistance, please send message to S. H. Chang, 48 Conant Hall Cambridge 38 Mass.

Zhang Sihou, Cao Hesun and Qian Xuesen were graduates of Jiaotong University. Zhang and Cao was majored in electrical engineering while Qian Xuesen in mechanical engineering. Cao obtained a doctorate from the University of Turin and Zhang was then studying for his doctorate at Harvard University.

On May 27, Wu Baofen sent Zhang Sihou a signed formal invitation which was then sent to Qian Xuesen. When Qian Xuesen received the invitation letter, he made a decision to give a lecture to spread the frontiers of the scientific theories to the domestic scientific, engineering and educational communities at his alma mater during his summer return to China.

On the evening of March 31, 1947, Professor Zhao Yuanren of Harvard University hosted a banquet at his home in Boston for Zhu Kezhen, President of Zhejiang University, who was then visiting the United States. On November 3, 1946, Zhu Kezhen went to Paris as a member of the National Government delegation to attend the founding conference of UNESCO. On February 13, Zhu left New York for Cambridge, where he was greeted at the train station by the couple of Zhao Yuanren. Qian Xuesen was invited to the reception dinner, and during the meeting Qian Xuesen and Zhu Kezhen had a pleasant talk. When Zhu Kezhen learned that Qian Xuesen was the son of his friend Qian Junfu and that Qian would return to China during the summer vacation, he immediately invited him to come to Zhejiang University to deliver a speech. After Zhu learned that Qian Xuesen had returned to Hangzhou on July 14, he invited him to have dinner at school the next day, accompanied by Tan Jiazhen, Zhu Zhengyuan, Fan Xuji, Su Buqing, Li Qiaonian, Wa Renxuan, Wang Jinfu and others from the College of Engineering of Zhejiang University.

At 7:00 a.m., on July 28th, 1947, Qian Xuesen came to Classroom 61 in the College of Engineering, Zhejiang University and delivered a lecture on “Engineering Science and Engineering”, which lasted for two hours. More than 40 teachers and students, including Zhu Kezhen, Zheng Xiaocang, Yue Yijie, Fan Xuji, Pan Yuan and Ding Xubao, attended the lecture. Zhu Kezhen put down the main content of the lecture in his diary:

Firstly, the development of engineering science must depend on basic science. In ancient times, applied science and pure science were unified but tended to diverge in the 19th century. The recent developments of both had made them interconnected with each other. Secondly, pure science could solve some problems without proof of experiments. Some people might say that theory and experiment were two different things and it was not justifiable as sometimes theory was not correct. Thirdly, the impact of the theory on the future development of engineering science, such as jet propeller, fuel problem and so on, was elaborated. Finally, Qian talked about the kind of education required for engineers.

In August, Qian Xuesen went to his alma mater Jiaotong University to deliver a lecture. The Frontline Daily, a Shanghai newspaper, reported in its education column on August 2, 1947, that Qian Xuesen, a renowned professor at MIT, would come to Shanghai in mid-August at the invitation of Jiaotong University to give a lecture on the topic of “The Development of Aeronautical Engineering in the Last Ten Years.” The lecture was hosted by the Department of Aeronautics of Jiaotong University, and students and teachers from other departments crowded in to attend the lecture. Chen Guoxiang, a teacher of the Department of Mechanical Engineering was responsible for recording the content of the lecture, which was later published in Engineering World (Vol. 2, No. 12, December 1947), edited by the Chinese Association of Science and Technology, under the title of “How to study engineering science and what to study”, providing valuable materials for studying Qian Xuesen’s thoughts on science and technology.

In this speech, Qian Xuesen elaborated on the outstanding achievements of aircraft and atomic energy in recent ten years. He said:

In the past, progress in engineering often depended on more experience or experimentation, and less on theoretical analysis. Engineering progress was much slower as the accumulation of experiences was a long-term process. Currently engineering was in rapid development with the support of analyses and theory. In the past, we thought that what engineers needed was to have experiences while theoretical science was useless. This was a misconception. For example, Isaac Newton was a great scientist and people always thought that he did not know about engineering, but he designed a bridge in Oxford, England.

Leonhard Euler was also a scientist, but his cylinder calculation formula solved the most important cylinder problem in civil engineering. The list of examples could go on and on. Science and engineering were connected in the past, but with the rapid development, the knowledge scopes of both had extended. Since an individual’s ability was limited and it was impossible to learn everything, practical engineering and theoretical science were separated. Some people focused on engineering or manufacturing rather than general theories; others paid attention to science or basic principles but ignore practical problems. For example, in fluid mechanics, there were two basic assumptions: one was that water cannot be compressed; the other was that water was not adhesive. With these two assumptions, the properties of the fluid can be studied. However, the engineers did not think it was practical, because water can actually have a little compressibility and adhesion. Therefore, based on the results of experiments, engineers had a practical science of hydraulics, and hydraulics, strictly speaking, was just a collection of empirical formulas and coefficients, many of which were worthless in the view of theorists. The situation of lack of cooperation between engineering and theoretical science did not change until the beginning of the 20th century, when scientific theories were gradually applied to engineering.

Subsequently, Qian Xuesen advocated an independent scientific system between natural science and engineering technology, namely, engineering science. He further pointed out that engineering science had two research directions: “There were two major types of research problems. One was the pure problem of science or engineering and the other was the general research of a certain phenomenon. Examples of the former were the design of rockets, and the latter, the turbulence. If the problem of turbulence could be solved, it was not only meaningful for hydraulics, but also directly helpful to aerodynamics, meteorology and the design of engine combustion chamber.”

As for the research methods of engineering science, Qian Xuesen proposed to “simplify the problem” and that “experimenters should cooperate closely with theorists.” What was included in the knowledge scope of engineering science? He put:

There were two basic research tools: practical experience and basic science. The former was the foundation of manufacturing technology and mathematics, while the latter the foundation of modern physics, chemistry and mathematics. For example, in the past, the theory of molecular nucleus and molecular motion was discovered because of the explanations of the properties of matter, and the success of the atomic bomb was just to further prove the accuracy of this theory. The previous conclusions were the basis of the current research. Mathematics, being a reasonable inference, was also one of the research tools. In addition to several basic mathematics courses learned in engineering schools, there were some more to be learned, namely, Analysis, Partial Differentiation and Integral Equation, and Computing Machine. While Analysis and Partial Differentiation were frequently used in engineering, the modern computing machine could be used to solve complex differential equations and calculate the trajectory and range.

Qian Xuesen urged young engineering students to think of themselves as scientists rather than high-paid technicians. He advised them to take courses not only in engineering but also in mathematics, chemistry and physics. The training of a competent engineering scientist, Qian Xuesen put, was a long process, but as long as one became an experienced master, every problem could be solved easily. He outlined the merits of a university doctoral program: “The free academic atmosphere in an educational institution was certainly conducive to thinking, which was, after all, the only way to gain wisdom.” The recent development of engineering science and the invention of atomic bomb, radar, rocket and plastic body were all due to this group of well-trained scientists.

Finally, Qian Xuesen pointed out the directions of engineering science and foresaw engineering applications in the fields of hydrodynamics, elasticity, plastics, thermodynamics, combustion problems, electronics, materials and nuclear research. Qian stressed that any researcher aspiring in engineering science must also have the spirit of the times, because “the responsibility of engineering science was to solve any problem related to scientific progress.” He ended his speech by inspiring the students and teachers in the audience with the words of Harold Urey, the well-known American atomist, “It is our duty to remove discomfort, dissatisfaction and poverty, and we are to contribute to the comfort, leisure and grace of mankind.”

On August 26, 1961, when Qian Xuesen was visiting his friends in Beijing, he was invited to Tsinghua University to give another lecture on engineering science, which was presided over by Tao Baokai, dean of the School of Engineering of Tsinghua University. The lecture was attended by Mei Yiqi, Ye Qisun and others. On July 17, 1961, Peng Bingpu, a 1950 graduate of Tsinghua University who was present at the speech, wrote to Qian, saying: “I was deeply impressed by your lecture on engineering sciences.” Two days later, on August 28, Qian delivered a second speech on his most recent research in mechanics of rarefied gas at the science museum in Tsinghua University.

Technical scientific thought and Marxist philosophy

In these lectures, Qian Xuesen systematically elaborated the concept of engineering science, (the concept of technical science was used after his return to China in 1955) for the first time, and he finished the first draft soon after his return to the United States. In 1948, Qian published the paper entitled “Engineering and Engineering Sciences” in the Journal of Chinese Institute of Engineers (1948, Vol. 6), which attracted great attention from the American scientific community.

The core of technical science is to combine science and engineering, which is a concept commonly advocated today, but it was still a frontier theory back then. More importantly, the value of technical scientific thought is that it has laid the ideological foundation for Qian Xuesen as a staunch Marxist. Combination of “practice and theory” in the thought of technical science comes down in one continuous line with the viewpoint of practice and contradiction in Marxist philosophy. In 1956, Qian Xuesen was invited to participate in a written discussion organized by the Bulletin of Research in Natural Dialectics, and he wrote an article entitled “Methodological Problems in Technical Science”, in which he wrote:

In the study of technical science, we should combine theory and practice flexibly and not act in a rigid way. I thought this flexible combination of theory and practice was also the true essence of dialectical materialism. Therefore, I thought that the world’s first-class technical scientists were also dialectical materialists, and their research methods were worth summarizing. And we could also apply dialectical materialism to the study of technical science to improve the efficiency of research.

Qian Xuesen’s understanding of Marxist philosophy had a solid practical foundation. Therefore he could not wait to start studying Marxist philosophy after his return to China in 1955, as his secretary Zhang Kewen recalled, “When I was in the Institute of Mechanics, I often saw Mr. Qian Xuesen and Mr. Guo Yonghuai studying and discussing Chairman Mao’s Theory of Contradiction and Theory of Practice in those evenings.” Because of this, Qian Xuesen always adhered to Marxist philosophy as a guideline in guiding his scientific research practice and academic research, and he learned to analyze and deal with problems with dialectical materialism and historical materialism.

As late as the 1980s, Qian Xuesen still firmly pointed out: “Basic research, whether purely basic or basic applied research, was highly exploratory work. Human initiative was very important. Mechanical materialism sometimes will lead us to failure; therefore we should ground our research on the sharp ideological weapon of dialectical materialism.” Qian Xuesen summarized up his academic research experiences in his later years: “I started on the road from engineering technology to technical science, then to social science, and I ultimately knocked on the door of Marxist philosophy.”

5 A Presentation at the American Rocket Society Conference

It is generally accepted that Qian Xuesen’s 1954 publication of Engineering Cybernetics established his worldwide academic status, especially with Theodore von Kármán’s widely circulated comment, “You have now surpassed me in scholarship!” Qian Xuesen’s academic status as a world-class scientist could be traced back to his presentation at American Rocket Society conference in 1949, taking the triple role as a member of the American Rocket Society, Goddard Chair Professor at Caltech and Director of the Guggenheim Jet Propulsion Center. Qian Xuesen’s presentation was not really an academic report, but a working report with a summary and an outlook. It was through this presentation that Qian Xuesen had established himself as “an academic leader” in the field of aeronautical science.

Return to Caltech

In 1948, the Guggenheim Foundation decided to establish jet propulsion centers at both Caltech and Princeton University. The foundation promised to provide $500,000 to each center over the next seven years to cover the salaries of the center’s researchers, graduate student scholarships and other related expenses. The centers’ offices and laboratories, and equipments were provided by the host universities. On the establishment of the two centers, von Kármán commented: “A new era had opened up in both engineering and human thought that would affect the future more profoundly than was now anticipated.”

In fact, before the establishment of the Guggenheim Jet Propulsion Center, Caltech already had two institutions that focused on aeronautical science research: the Jet Propulsion Laboratory (JPL) and the Guggenheim Aeronautics Laboratory (GAL). Although the research fields of these three institutions were all aeronautical sciences, their specific research directions and focus were different. Guggenheim Jet Propulsion Center was responsible for the triple goals of teaching, research and industry. To be specific, firstly, it was to train young engineers and scientists in the field of rocket and jet propulsion technology, to push the aviation frontier to a higher level. Secondly, it was to promote advanced research in the fields of rocket and jet propulsion. Thirdly, it was to promote the commercial and scientific application of rockets and jet propulsion in peacetime. Actually, in the process of teaching, the three institutions shared each other’s faculty and the Guggenheim Jet Propulsion Center had unconditional access to JPL and GAL’s expensive laboratory equipment.

When both Caltech and Princeton University identified candidates for the directorship of the Center, the first choice was Qian Xuesen. The first person to extend an invitation to Qian was Caltech President Lee Alvin DuBridge, who wrote to Qian Xuesen on September 29, 1948, expressing his desire for the appointment, “Both Princeton University and Caltech were planning to build the Guggenheim Jet Propulsion Center, and it immediately occurred to me that you were the right person to lead this laboratory, and I hoped you would accept Caltech’s invitation.”

On October 7, after careful consideration, Qian Xuesen wrote to DuBridge accepting the offer and agreeing to serve as Goddard Professor and Director of the Guggenheim Jet Propulsion Center. Harry F. Guggenheim, chairman of the Guggenheim Foundation, officially announced the establishment of the Guggenheim Jet Propulsion Center at Caltech. At the inauguration ceremony, DuBridge announced to the news media that:

Dr. Xuesen Qian, a 38 year-old Chinese student at Caltech and a member of Caltech’s Academic Council, will lead the Center. Dr. Qian is now a professor in the Department of Aeronautics at MIT.

On December 27, Qian Xuesen wrote to his friend Frank J. Malina, informing him that he had decided to leave MIT to take his post at Caltech. In the letter, he wrote:

The atmosphere here is very rigid and stagnant. It doesn’t fit well with me as a “Caltechite” or “Von Kármánite.” To be honest, I’m not happy here. I don’t think Hunsaker would be upset about me leaving! Anyway, I don’t fit in at all in this old aeronautical engineering department!

In the first half of 1949, Qian Xuesen had already begun preparations for his next semester at Caltech, and during the summer of 1949, Qian Xuesen and Ying Jiang packed their household goods and gave them to a transportation company to be shipped to Pasadena, Los Angeles, while they took their infant son, Qian Yonggang and drove themselves to Pasadena. They also made a special stop at Cornell University to meet with the couple of Guo Yonghuai and Li Pei, and W. R. Sears.

During their stay at Cornell University, they not only exchanged pleasantries, family stories and went sightseeing, but also discussed in depth the problem of singular regimes in transonic aerodynamics. Guo Yonghuai had already conducted in-depth research, and in 1953, when Guo Yonghuai went to Caltech for a visit, Qian Xuesen again discussed further with him. The Poincaré–Lighthill–Kuo Method was completed before Qian’s return to China in 1955, after many years of research and synthesis of Kuo’s method with that of Poincaré and Lighthill [3]. When Qian returned to Caltech, he was no longer the associate professor when left Caltech a few years earlier. Of course, his return was not because of his status as a student of von Kármán, but rather as a rising “first-class star” in the field of aerospace science (Fig. 16).

Fig. 16

The first page of the printed version of The Poincaré–Lighthill–Kuo Method completed by Qian Xuesen (96 pages in total). The paper was later included in the book Advances in Applied Mechanics, published by Academic Press, New York

A Presentation at the American Rocket Society Conference

Shortly after his return to Caltech, Qian Xuesen established his worldwide academic status in the field of aeronautical science by making a presentation at the annual meeting of the American Rocket Society held at the Statler Hilton Hotel in New York City on December 1, 1949, as a member of the Society, Goddard Professor and director of the Guggenheim Jet Propulsion Center at Caltech. The annual meeting of the American Rocket Society was an international academic conference in the field of rocket, aerospace and aerodynamics research in the United States. Qian Xuesen’s presentation at the conference was “Instruction and Research at the Daniel and Florence Guggenheim Jet Propulsion Center”.

Strictly speaking, Qian Xuesen’s presentation was not really an academic report, but a working report with a summary and an outlook. The report was divided into three parts: the introduction of the Jet Propulsion Center, the teaching and research plans of the Jet Propulsion Center, and the recent research projects of the Jet Propulsion Center, which included characteristics of rocket and jet propulsion engineering, material problems, heat exchange, combustion, and performance of rocket and jet propulsion vehicles. The mainstream American news media reported that it was not a conventional academic conference, but was of great significance. In addition, the Guggenheim Foundation held a press conference in New York to announce that Qian Xuesen would attend the conference.

The reason why this conference attracted the attention of the New York Times, the Washington Post, the Los Angeles Times and other mainstream media was because Qian Xuesen proposed in his outlook that “a 9,140 mph spacecraft was technically feasible.” To put in other words, “an intercontinental rocket could cross the entire country in one hour.” Although this was only a conjecture, it attracted a lot of attention from the society because it was very likely to be the dawn of a new era. The Washington Post reported on December 2, 1949:

This is an artist’s concept of a rocket ship which, according to scientists, will fly from New York to Los Angeles in less than an hour. The blueprint was described by Dr. Qian Xuesen at Caltech to the American Society of Mechanical Engineers in New York yesterday. Dr. Qian Xuesen said it would fly almost 10,000 miles in one hour, but land at the speed of only 150 miles.

The concept of rocket spaceship was very imaginative and almost science fiction at that time, but it was the basis for “Qian Xuesen trajectory” proposed in 1952 and now becomes a necessary trajectory for the development of manned spacecraft. In addition, Qian Xuesen stressed that fuel of rocket spaceship was not a hard issue as several raw materials could be mixed with liquid oxygen to make liquid fuel as power. But there was no doubt that a high-speed rocket was a better choice than an aircraft, because the materials of aircraft must be able to withstand long-term wear while the rocket only took a few minutes or even seconds. He concluded: “The designing of rocket ship aimed at several minutes rather than thousands of hours in flying and we were able to use pressure-resistant materials that withstand tremendous stress instead of wear resistant materials.”

The annual conference of the American Rocket Society was followed by the second conference of the Guggenheim Foundation. The conference had two agendas: one was to pass the Guggenheim Jet Propulsion Center Fellow selection process and membership development plans for the coming year, and the other was to focus on current programs and future perspectives at the Centers. Qian Xuesen attended the meeting as the director of the Jet Propulsion Center at Caltech, where he emphasized the importance of the educational work of the Jet Propulsion Center as an important location for the nation’s graduate education and training in rocket and jet propulsion, with the hope of producing outstanding engineers for industry and government departments. He then introduced the curriculum of the Guggenheim Jet Propulsion Center at Caltech, as well as the research work of fifteen researchers. Finally, Qian suggested that since there was no journal dedicated to publishing rocket research results, each Goddard professor could become an editor of the Journal of the American Rocket Society to add up to the publications of rocket research (Fig. 17).

Fig. 17

Qian Xuesen’s central position in the photo indicates his important role

In a sense, it was a conference symbolizing the transition from the old generation to the new generation. In fact, before the official meeting of the second Guggenheim Foundation conference, Qian Xuesen was the representative who thanked von Kármán for his outstanding and groundbreaking contributions to the world of aerodynamics research. At this time, Von Kármán had already returned to Europe to organize a team of scientists for NATO to carry out aeronautical research, and was gradually taking a back seat. It can be said that Qian Xuesen’s work report at this conference means that he had become the academic leader, planning the direction and future of aerodynamics. In this conference, Von Kármán and Qian Xuesen completed the academic “honorary” handover.