About the Book
In 1950, a young engineer named Walter R. Evans introduced a revolutionary graphical method for analyzing feedback control systems. His paper, "Control System Synthesis by Root Locus Method," transformed the practice of control engineering and became one of the most influential contributions in the history of the field.
In Into Stability, Walter's son, Gregory Walter Evans-himself an engineer-tells the untold story behind that breakthrough. Drawing on family archives, correspondence, and rare photos from aerospace history, Evans reconstructs the inventive process that led from wartime analog computers to the elegant logic of Root Locus. He reveals how his father's inventive spirit was shaped by mentors at Washington University in St. Louis, by the entrepenurial environment at North American Aviation, and by a lifetime devoted to clarity, precision, and education.
The book follows Walter Evans through the founding of The Spirule Company, the enterprise that brought his invention into classrooms and laboratories worldwide, and explores how the Root Locus method continues to guide modern control design-from aircraft and missiles to robotics and medical systems.
Part biography, part history of technology, and part personal memoir, Into Stability captures the human side of engineering creativity-the curiosity, discipline, and humility that define real innovation. More than a chronicle of one man's achievement, it is a portrait of a generation of engineers who shaped the modern world through insight and perseverance.
About the Author :
Gregory W. Evans is an engineer, author, and historian. A graduate of the California Institute of Technology (B.S., 1969) and Stanford University (M.S., 1975), Evans built a career at the intersection of technology and defense electronic systems.His latest work, Into Stability: Walter R. Evans and the Story of Root Locus, celebrates the life and legacy of his father, Walter R. Evans-the engineer whose Root Locus method revolutionized control-system design and became a cornerstone of modern engineering education. Drawing from decades of correspondence, laboratory reports, and aerospace archives, Evans reconstructs the mid-century world of Autonetics, Caltech, and the early missile and guidance systems that shaped the space age.Beyond chronicling a pivotal technical innovation, Evans's writing highlights the personal qualities that drive creative problem-solving-curiosity, persistence, and humility-and explores how these values link generations of engineers. His research spans not only control theory but also family history, with earlier works focused on nineteenth-century emigration, faith, and resilience among ancestors in Wales, England, and the American Midwest.In Into Stability, Evans traces the invention and evolution of one of engineering's most enduring analytical tools. Using thousands of pages of letters, technical papers, and family archives, he reconstructs not only his father's professional life but also the postwar world of American aerospace innovation at North American Aviation and beyond.Beyond engineering history, Evans has authored five and edited twi works of genealogical nonfiction that combine meticulous documentation with an engaging narrative style to bring both technical and personal histories to life.A lifelong photographer, Evans lives in California. When not writing or editing, he enjoys exploring landscapes with a camera. Through his books, he celebrates the spirit of invention that connects past and present generations of engineers. Robert H. Cannon Jr. (1923-2017) was a Stanford aeronautics & astronautics professor and control-systems pioneer. MIT PhD; led Stanford Guidance & Control, chaired Caltech Engineering (1974-79), and earlier worked at North American Aviation with Walter R. Evans on stability and automatic control.
Review :
John Doyle, Professor of Control and Dynamical Systems at Caltech"This is a wonderful book about a giant of classical control who inspired me as an undergrad at MIT. Reading this book reminds me of what I missed in knowing the methods but not the man."Don Evans, Former United States Secretary of Commerce "Fueled by a passion for lifelong learning, teaching, and love of country, Uncle Walter was one of America's most impactful engineers." David A. Peters, McDonnell Douglas Prof of Eng'ing, WashU in St. Louis"This is the fascinating story of Walt Evans, the man who invented the Root Locus design tool -- and changed the world. We would not have made it to the moon without this methodology, which is still in common use today. This book is a must-read for anyone with interest in the history of technology and in the human stories behind it."Richard Murray, Professor of Control and Dynamical Systems at Caltech"Greg Evans tells the fascinating story of his father, Walter Evans, whose development of the root locus method transformed control engineering. foundational ideas to the clever "spirule" tool, this book captures the blend of insight and ingenuity that shaped the field."Qimin Yang, Professor of Engineering at Harvey Mudd College"This book provides an intimate memory of Evans' life and his invention, his deep connections to people in academia and industry, and the critical impact of his work in the post war aerospace industry. I"Shalom Ruben, Teaching Professor of Mech. Eng'ring at Univ. of Colorado"The son of Walter Evans weaves a compelling history of a 1948 transformation in control engineering that remains a cornerstone of engineering education and practice today. This is a story of how family, teachers, and colleagues created an environment that nurtured the critical thinking needed to bring such an out-of-the-box idea to the world.
