PAUL E. RUBBERT (1937-2020)

BY EARLL M. MURMAN

PAUL EDWARD RUBBERT, a pioneer of computational fluid dynamics (CFD) for flight vehicles, died on Dec. 23, 2020, at age 83.

Paul was born on Feb. 18, 1937, to Adolf and Esther Rubbert in Minneapolis, Minnesota, where he grew up with his brother Peter. After graduating from high school, Paul attended the University of Minnesota, graduating with B.S. (1958) and M.S. (1960) degrees in aeronautical engineering. Paul’s interest in airplanes started at an early age with flying model airplanes and looking at the airplane wallpaper in his bedroom. While attending college, Paul met his first wife, Mary Parpart, and they married on Sept. 8, 1958. They had three sons: Mark, David, and Stephen. Upon graduation, Paul and Mary moved to Seattle, Washington, where he started employment with the Boeing Company in 1960 as a research engineer.

Two years after joining Boeing, Paul was sent to the Massachusetts Institute of Technology (MIT) to pursue advanced studies. His doctoral thesis, “Analysis of Transonic Flow by Means of Parametric Differentiation,” completed in 1965 under the supervision of Prof. Mårten T. Landahl, gave him a deep understanding of the mathematics of the aerodynamics that dominate the cruise regime of jet transports. While at MIT, Paul was a Hertz Fellow. Paul and his family returned to Seattle, where he became a lead engineer in aerodynamics at Boeing.

Paul saw the enormous potential of what would become the CFD field to change the design process for flight vehicles. Starting in 1965, when CFD algorithms were limited to linear equations, Paul led the development of three-dimensional panel methods for subsonic potential flow around realistic, complex configurations. The A230 code developed with Gary Saaris became a game changer for Boeing’s aerodynamic analyses and impacted the international development of panel methods. Its application to the complex fan-in-wing configuration received the SAE International Arch Colwell Merit Award in 1969. Further developments led to the PANAIR A502 code in 1975, which became the workhorse subsonic panel method at the Boeing Company.

By the early 1970s transonic potential method algorithms had emerged, and Paul seized the opportunity to make another major impact on Boeing’s aerodynamic analysis capabilities. After a stint as a lead engineer for Boeing’s Advanced Transonic Transport Program, Paul was tapped by Boeing in 1972 to be its manager of aerodynamics and CFD research. He proceeded to assemble and lead a talented team of researchers to develop analysis methods for sub-trans-supersonic inviscid and viscous aerodynamics. A key member of that team, NAE member Forrester Johnson (NAE 2000), said the following:

“In the late 1960s Paul was a very successful and respected supervisor of an aerodynamics analysis group at Boeing Commercial Airplanes. I believe his success and respect from upper management stemmed from his deep theoretical understanding of aerodynamics. I am sure we have MIT to thank for much of that. At the time, computers were just starting to be powerful enough to do limited scientific computations. Paul recognized the long-run potential for computers to be used as tools for solving complex aerodynamic equations, thereby augmenting wind tunnel analyses, and even performing configuration optimization numerically. As with any disruptive technology achieving this potential would be expensive and time consuming. Because of his reputation with upper management Paul was given the resources and time to form a CFD group and pursue his vision. He was very good at evaluating new hires for this group and was a great advocate for their careers as well as a sympathetic listener to their personal issues. He would often tell his team members ‘if you are obsessing over a technical problem and your kid wants you to come and help pound nails, you go pound nails.’ Paul was willing to consider and test radical new ideas along with mainstream approaches. I am not sure how to say this but any time you are developing radical new ideas there will be occasional setbacks and problems. Inevitably they will be accompanied by calls for suspension or cancellation. Paul always resisted them and took the heat himself. In the end he produced a remarkable set of new and powerful aerodynamic analyses and design tools for Boeing’s aerodynamic engineers. These tools are still in use today.”

From his position of leadership for aerodynamic research within Boeing, Paul developed a broad understanding of the opportunities and barriers for progress within and external to the Boeing Company. He became obsessed with and committed to removing those barriers, and he devoted time to interacting with government and academic organizations. In his own words from his NAE Statement of Technical Interests:

“My two areas of interest are: - the conduct and management of research for effectiveness - the continued development and exploitation of computational fluid dynamics. In the first area, I am intensely interest(ed) in improving the conduct of research across all scales, not by adding money but by improving effectiveness. On the broad scale this comprises the national ‘research engine’ involving academia, government and industry. It spans the entire R&D food chain comprising basic research at one end to application and exploitation by industry at the other end. More narrowly it includes the management of a single research group or project. And everything in between. I also maintain an intense interest in observing and leading the evolution and application of CFD within the aerospace industry, which is the area in which I have invested my career.”

Paul’s technical expertise and leadership commitment led to many invitations to serve his profession, including the following: NRC Committee to Assess Current and Future Capabilities and Future Directions in Computational Fluid Dynamics; NRC Panel on Aerodynamics; NRC Panel on Engineering, Mathematics and Computer Science; associate editor of AIAA Journal; general chairman of the 10th American Institute of Aeronautics and Astronautics (AIAA) Computational Fluid Dynamics Conference; member of the NASA Aerodynamics Advisory Committee; member of the NASA Numerical Aerodynamic Simulator (NAS) Project Steering Group; and member of the Visiting Committee of the MIT Department of Aeronautics and Astronautics.

Paul’s accomplishments and contributions were recognized through many awards and honors, including the following: Boeing Technical Fellow; fellow of the AIAA (1980), American Physical Society (1985), American Society of Mechanical Engineers (1986), and Royal Aeronautical Society; the AIAA Wright Brothers Lecture in Aeronautics Award (1994) for “CFD and the Changing World of Airplane Design”; and the University of Minnesota’s Outstanding Achievement Award (1995).

When Paul decided to retire in 1997 his professional colleagues honored him with a two-day symposium titled “Computational Aerodynamics – Past, Present and Future,” which was hosted by the Boeing Company in Seattle. More than 40 speakers from across the U.S. and Europe spoke on topics ranging from panel and boundary layer methods to CFD methodology of the future. The podium and a banquet at the Seattle Museum of Flight provided ample opportunity for colleagues to praise Paul for his technical and leadership contributions. The entire event was recorded on video tapes, which are archived in the MIT Library.

Paul decided to spend his retirement years in Idaho, pursuing the other passions of his life: hunting, fishing, and target shooting. He moved to a remote custom-built Lindal cedar log house on 20 acres in Riggins, Idaho, above the Big and Small Salmon Rivers. At his winter home in Lewiston, Idaho, he spent time building and flying model airplanes. In 2015 Paul was diagnosed with Stage 4 lung cancer and was advised he had only months to live. But Paul was not one to quit. Foregoing treatment, he continued to live in Riggins until early 2020, when he moved in with his son David in Everson, Washington. After his final days at the Whatcom Hospice House, Paul passed away on Dec. 23, 2020. He was survived by his brother, both wives, his three sons, nine grandchildren, one great-granddaughter, and his beloved dog Gabby.