Frank Marble, 1918–2014: Tribute to an aerospace giant

Frank Marble, among the nation’s preeminent aerospace propulsion scientists during the second half of the 20th century, has passed away at the age of 96. His pioneering technical contributions changed the direction of several important fields that are foundational to both aircraft and rocket systems. However, quite possibly, Frank Marble made even greater contributions to aerospace engineering through his gifted teaching and insightful training of legions of graduate students at the California Institute of Technology (Caltech), and through his serving as an example of true courage and loyalty during the McCarthy era and long afterward.

Frank Marble (Right) and his former student Sébastien Candel (Left) in 1985. Image courtesy of Sébastien Candel.

Frank recounted his remarkable life experiences in a series of interviews conducted in 1994–1995 through Caltech’s Oral Histories Archive (1). And although, as a former graduate student and longtime friend of Frank’s, I had heard many of the stories recorded in these memoirs, there were many insights that I gained about the man, his contributions, and his experiences from reading the interview series. The reader is encouraged to access this marvelous resource for more information on this remarkable man.

Frank was born in Cleveland, Ohio in 1918, and from a young age developed a passion for two things that remained with him throughout his life: airplanes and music. Ohio in the 1920s and 1930s was growing to become a rather significant player in the development of America’s burgeoning aviation industry. As a young boy, Frank used to take the streetcar regularly to the Cleveland Hopkins Airport, where he would wander into the hangars, look at the airplanes up close, and talk with the pilots and mechanics. This fascination set him on a lifelong journey of discovery with aircraft. Frank’s love affair with music also began at a young age, when he took up the trombone. He showed a great deal of talent, twice winning the state championship in trombone solo.

Frank’s fascination with airplanes eventually won out over his musical focus, at least professionally. With financial assistance from his aunt and sister, Frank entered the Case School of Applied Science (now Case Western Reserve University) in Cleveland as a freshman, majoring in Mechanical Engineering. There Frank’s eyes were opened to the exciting world of aeronautics, the newly established field underlying the mechanics of flight. As Frank’s technical gifts and interests became evident, he dreamed of pursuing graduate studies at Caltech with the eminent fluid mechanician, Theodore von Karman. However, the outbreak of World War II altered Frank’s plans, at least for a time. He completed a Masters of Science degree at Case, and for most of the war worked at the newly established aero-propulsion laboratory in Cleveland, created by the National Advisory Council on Aeronautics (NACA); this was the predecessor of NASA’s Glenn Research Center at Lewis Field. As “Employee number 67” of the NACA Engine Research Lab, Frank was responsible for tackling a number of technological problems related to aircraft engines used in the war effort. Frank was able to solve engine cooling problems on the B-26 bomber (Martin Marauder) as well as the B-29 bomber (Superfortress). And although the propulsion systems for these bombers were of the air-cooled reciprocating/radial type, Frank’s work at NACA also introduced him to gas turbine engine technologies, which showed promise for future air transportation systems. As Frank recounted, although the time he spent at NACA delayed the start of his doctorate studies, the experience changed the direction of his career and focus from aerodynamics to jet propulsion.

After the war, Frank received a National Research Council predoctoral fellowship to study at Caltech, and he and his young wife, Ora Lee, headed to California in their “house trailer.” What started as a short stay for his doctorate turned into a lifelong association for the Marbles with Caltech and Pasadena, where Frank and Ora Lee raised their children, Steve and Patricia. Frank thoroughly enjoyed and excelled in his classes in advanced mathematics and physics, as well as aeronautics. And although his formal doctorate coadvisors in Caltech’s Guggenheim Aeronautical Laboratory were Theodore Von Karman and the rising young fluid mechanician, Hans Liepmann, Frank’s doctorate thesis topic was one that he had brought with him from his work at the NACA, involving the fundamental fluid physics of rotating blades. This pioneering study (2), among the first to use rigorous mathematical methods to analyze blade aerodynamics in turbomachinery, led to Frank’s being hired by Caltech immediately after his graduation in 1948, first as an Instructor in Aeronautics, and later as an Assistant Professor of Jet Propulsion and Mechanical Engineering.

During the course of his junior faculty tenure, Frank encountered yet another unexpected career diversion: his appointment by Prof. Tsien Hsue-shen as the part-time Chief of Combustion Research at Caltech’s new off-campus facility, called the Jet Propulsion Laboratory. This position was concurrent with Frank’s faculty appointment at Caltech. Like his unexpected diversion into gas turbine engines at the NACA, Frank’s work at the Jet Propulsion Laboratory opened up several new research directions for him based on important aerospace propulsion problems of that era. His work on exploring ramjet engines led to a seminal analytical approach for predicting premixed flame stability in shear layers (3), developed with one of his earliest doctorate students, Tom Adamson. This has come to be known as the “Marble–Adamson problem,” and its use of activation energy asymptotics served as a model used later by scores of researchers exploring both premixed and nonpremixed flame stabilization. Frank’s work at the Jet Propulsion Laboratory and Caltech also involved experiments and analysis of the often catastrophic “screech” phenomenon (4) in ramjets and in afterburners; this led Frank and his collaborators to develop one of the first phenomenological explanations of acoustically coupled combustion instabilities and bluff-body flame-holding mechanisms (5).

After he became a full professor at Caltech in 1957, Frank stepped down from his post at the Jet Propulsion Laboratory. However, he continued throughout his career to work as a consultant for numerous government and industrial organizations, pursuing problems relevant to both air-breathing and rocket propulsion systems. These experiences, in addition to his funded research from the US government, led to the exploration of numerous propulsion problems for which Frank discovered new underlying physical phenomena. Hence, Frank made further seminal contributions in the analysis of dusty gases (6), relevant to particulate flows in solid rocket motor nozzles; acoustic attenuation by liquid droplets (7), relevant to noise problems in air-breathing engines; a coherent flame model (8) for the analysis of turbulent combustion, which became the foundation of contemporary flamelet modeling; flame–vortex interactions (9), relevant to turbulent premixed and nonpremixed combustion instabilities; and shock-induced mixing (10) and combustion phenomena, relevant to supersonic combustion ramjets. It is for this extraordinary range of deep, fundamental technical contributions that Frank was elected to both the National Academy of Engineering (1974) and, more rare for an engineer at the time, the National Academy of Sciences (1989). The Daniel Guggenheim Medal (1999), recognized as one of the highest honors that can be bestowed on an American aeronautical engineer, was another of many prestigious recognitions given to Frank for his extensive research contributions.

In the course of these many decades of seminal research, Frank also focused on an aspect of the academic enterprise too often minimized at top-tier research institutions: teaching. He maintained the ability to deliver a rigorous, well-organized set of lectures throughout his career, teaching courses in fundamental fluid mechanics, combustion, and air-breathing and rocket propulsion. Frank’s regular 8:00 AM lectures were absolutely legendary, and these lectures, in addition to his shared insights in research, are perhaps what most of his graduate students remember best about Frank, myself included. As a token of gratitude to Frank, his many generations of graduate students worked to endow both the Frank and Ora Lee Marble Professorial Chair, as well as the Marble Graduate Fellowship at Caltech in 2012 and 2013, respectively (11).

Finally, as noted in the opening paragraph, there is an aspect of Frank Marble’s legacy that cannot be neglected; this has to do with his devotion and loyalty to his friend and colleague at Caltech, Prof. Tsien Hsue-shen (Qian Xuesen). During the McCarthy era, Tsien, who was a pioneering researcher and scholar in fluid mechanics and propulsion, had been accused of being a Communist. Tsien had his security clearance revoked and was put under virtual “house arrest” by the Immigration and Naturalization Service for five years, during which time his Caltech research activities were severely curtailed. Throughout this ordeal, Frank remained absolutely devoted to Tsien and his family, taking him to his legal proceedings, arranging for housing for the Tsiens when they were evicted, and even providing room for them to live in the Marble home. Eventually, the Tsiens left the United States for China. There, Tsien became the father of the Chinese rocketry program, including development of what has become today’s Long March rocket vehicle. Although the entire story is too lengthy to include here, at many levels Frank’s courage and loyalty to his friend and colleague during this difficult time may have been one of his greatest legacies of all.

Frank Marble left this world on August 11, 2014, barely two months after the passing of his beloved wife of 71 years, Ora Lee. He was predeceased in 1996 by his daughter, Patricia, and is survived by his son Steve and his family. Frank was a brilliant scientist, gifted teacher, and devoted colleague and friend. For those of us who were privileged to know him, his loss is deeply felt. There won’t be another like him.