Welfengarten 1, 30167 Hannover, Germany
In 1929 Flügge-Lotz earned a doctorate in engineering from Technical University of Hanover.
Welfengarten 1, 30167 Hannover, Germany
In 1929 Flügge-Lotz earned a doctorate in engineering from Technical University of Hanover.
educator engineer mathematician scientist
Irmgard Flügge-Lotz was born in Hamelin, Germany on 16 July 1903. Her father, Oskar Lotz, was a journalist and amateur mathematician. Her mother, Dora (Grupe) Lotz, came from a family that had been in the construction business for generations.
When Flügge-Lotz was a teenager, her father was drafted into the German army during World War I. To help support her mother and younger sister, she began tutoring fellow students in mathematics and Latin. She continued this work after her father returned from the war in ill health. After graduating from high school in 1923, Flugge-Lotz studied applied mathematics and engineering at the Technical University of Hanover. In 1929 she earned a doctorate in engineering. Her dissertation explored the mathematical theory of circular cylinders and heat conduction.
Later in life the University of Maryland awarded her an honorary degree, citing “contributions [that] have spanned a lifetime during which she demonstrated, in a field dominated by men, the value and quality of a woman’s intuitive approach in searching for and discovering solutions to complex engineering problems”.
Opportunities for women in engineering were limited in the 1930s, and Flugge-Lotz had difficulty finding a level of employment that was commensurate with her engineering education. When she began working at the Aerodynamische Veruchsanstalt (AVA) research institute in Goettingen, she spent half of her time as a cataloguer. Perceptions of Flugge-Lotz’s abilities changed dramatically after she solved a problem that had stymied Ludwig Prandlt and Albert Betz, two leading aerodynamicists at the AVA (Betz was the director of the institute). A decade earlier, Prandlt had developed a differential equation for his theory about the lift distribution of an airplane wing. However, he had made little progress in solving the equation. Flugge-Lotz tackled the problem and solved the equation for the general case. Continuing to work with the equation, she developed it so that it had widespread practical applications. Her cataloguing days ended, and she was named supervisor of a group of engineers who researched theoretical aerodynamics within the AVA.
In 1931 Flugge-Lotz published a technique she had developed for calculating the lift distribution on aircraft wings. Later dubbed the “Lotz method”, it is still used today. Continuing to delve into wing theory, she added to the knowledge base of the effects of control surfaces, propeller slipstream, and wind-tunnel wall interference.
The course of Flugge-Lotz’s career changed in 1938 when she married Wilhelm Flugge, a civil engineer from Goettingen. The husband and wife team went to work at Berlin’s Deutsche Versuchsansalt fur Luftfahrt (DVL), a German agency similar to NASA (National Aeronautics and Space Administration). Beginning work as a consultant in flight and aerodynamics, Flugge-Lotz conducted groundbreaking research in automatic control theory, especially pertaining to on-off controls. Subsequently, these controls came into widespread use because they were reliable and inexpensive to build.
In 1944 Flugge-Lotz and her husband moved to the small town of Saulgau, where they continued to work for the DVL. After Germany’s defeat in World War II, the town and its surrounding area became part of France. The Flugges joined the staff of the French National Office for Aeronautical Research (ONERA) in Paris. Flugge-Lotz headed a research group in theoretical aerodynamics and continued her work in automatic control theory. In 1948 the couple accepted positions at Stanford University in California.
Flugge was hired as a professor at Stanford. Nepotism regulations prohibited his wife from holding a similar position, so she was hired as a lecturer. Flugge-Lotz developed graduate and undergraduate courses in mathematical hydro- and aerodynamics and automatic control theory. She also designed a weekly seminar in fluid mechanics that was attended not only by Stanford students but also by young engineers from the National Advisory Committee for Aeronautics—NASA’s predecessor. The seminar has continued to serve as an important forum for faculty and students of varying specializations to share their findings.
In addition to teaching, Flugge-Lotz also continued her research while at Stanford. She applied numerical methods and analog computer simulations to boundary layer problems in fluid dynamics and continued studying automatic control theory. Her 1953 book, Discontinuous Automatic Control, presented the theoretical foundation for using discontinuous controls for flight paths of missiles. Specifically, the problem concerns a missile in flight encountering some force (such as a wind gust) that causes it to begin oscillating. An automatic control mechanism could be used to counteract the vibration. Flugge-Lotz was particularly interested in discontinuous controls, which could be activated only when needed. A simple analogy is a furnace thermostat, rather than continuously adjusting the amount of heat generated by a furnace, the thermostat simply turns the furnace on when needed and off when the proper temperature is achieved. The fact that discontinuous automatic controls were simpler and cheaper to make than continuous-control mechanisms made them particularly desirable for one-time use in missiles that would crash after flight.
Flugge-Lotz’s second book, published in 1968, presented techniques for optimizing discontinuous automatic controls for objects such as airplanes, rockets, and satellites. In the preface to Discontinuous and Optimal Control, she noted that optimal control theory literature was difficult for practicing engineers to read because it was so mathematically rigorous. “The purpose of this book,” she wrote, “is to acquaint the reader with the problem of discontinuous control by presenting the essential phenomena in simple examples before guiding him to an understanding of systems of higher order.”
Flugge-Lotz attended the First Congress of the International Federation of Automatic Control in Moscow as the only female delegate from the United States. Upon her return from that congress, Stanford University finally offered her a professorship in 1961. In fact, she was granted that rank in two departments— aeronautics and astronautics, and engineering mechanics. She retired from teaching seven years later. Flugge-Lotz continued her research activities, however, studying heat transfer and the control of satellites. Her retirement years were physically difficult, due to progressive arthritis.
During an era when there were few women engineers, Flugge-Lotz was named the first female professor at Stanford University’s College of Engineering. She conducted pioneering studies of aircraft wing-lift distribution and made significant contributions to the modern aeronautic design.
Flugge-Lotz's technique, which she had developed for calculating the lift distribution on aircraft wings, is still used today - it was later named the “Lotz method”.
The Society of Women Engineers gave Flugge-Lotz its Achievement Award in 1970. The American Institute of Aeronautics and Astronautics (AIAA) chose her to deliver the prestigious annual von Karman Lecture in 1971 and elected her as its first woman fellow.
Flügge-Lotz was a senior member of the Institute of Electrical Electronics Engineers and a member of the Society for Industrial and Applied Mathematics and of Sigma Xi.
Quotes from others about the person
“[Flugge-Lotz's] work in fluid mechanics was directed toward developing numerical methods for the accurate solution of problems in compressible boundary-layer theory. She pioneered the use of finite-difference methods for such purposes and was quick to employ the emerging capability of computers to deal with the large computations inherent in the use of these methods ... She applied these methods to solve a series of important and previously unsolved problems in compressible boundary-layer theory.” - John R. Spreiter and Wilhelm Flugge wrote in Women of Mathematics, describing Flugge-Lotz's twenty-year career at Stanford
Lotz married Wilhelm Flügge on June 4, 1938. The Flügges had no children, but they frequently invited their students to their home for dinner parties with other faculty members and visitors.
