into stability: walter r evans & the invention of root locus

To be published in 2025! Watch this space.

This forthcoming book will tell the extraordinary story of Walter R. Evans, whose 1948 invention of Root Locus and the Spirule revolutionized control system design, shaping the methodologies taught in classrooms and employed by engineers worldwide. Root Locus stands as one of the most significant contributions of the post-war aerospace industry, profoundly impacting national security and advancing technology.

Drawing from Walter Evans' original notes, hundreds of letters, and firsthand accounts from his colleagues at North American Aviation’s Aerophysics Laboratory—later known as Autonetics—this biography offers unparalleled insight into the life and legacy of a pioneer whose work changed the course of engineering history.

Yet, this is more than a story of technical genius. It is also a deeply human narrative of resilience, love, and partnership. When a devastating stroke struck Walter at the age of 60, his wife, Arline—whom colleague Bob Cannon affectionately called “Saint Arline”—dedicated herself to his recovery and well-being. Together, they overcame immense challenges, proving that triumph can emerge even from life’s greatest adversities.

into stability

A young Walter Evans captured in a pose familiar to those who knew him: engaged, intense, and enjoyi

ALL OF THE ABOVE AND MORE IN THE FORTHCOMING BOOK "INTO STABILITY"

This book, 'INTO STABILITY', explores the extraordinary life of Walter Evans, an engineer turned artist. After suffering a stroke, Evans discovered his talent for drawing with his left hand, creating over 250 remarkable pieces of art. The book delves into his journey, resilience, and creativity, shedding light on his contributions to engineering and art. Summaries of each chapter follow, with draft excerpts of several chapters populating this website.

Pictured on the left: A young Walter Evans captured in a pose familiar to anyone who knew him: engaged, intense (yet relaxed), and enjoying the challenge of solving a problem worthy of his attention and commensurate to his intellect.

SUMMARY OF CHAPTER CONTENT

CHAPTER BY CHAPTER SUMMARY

FOREWORD An introduction from Professor Robert Cannon, providing context for the book's significance and reflecting on Walter R. Evans' contributions to control theory.

AUTHOR'S PREFACE The author shares personal motivations for writing the book, offering insights into the journey of exploring Walter R. Evans' life and work.

INTRODUCTION Sets the stage by outlining the book's structure and themes: roots, feedback, and stability. It emphasizes the importance of Root Locus in engineering and the human story behind its invention.

PROLOGUE Summarizes the state of servo-mechanism analysis before root locus..

PART I: ROOTS

Chapter 1: St. Louis (1920-1941) Covers Evans' early years, including formative experiences at Soldan High School, life on the family farm, and studies at Washington University, where the seeds of Root Locus were planted.

Chapter 2: Schenectady (1941-1946) Describes Evans' time in Schenectady, his relationship with Arline, friendships with colleagues like Gordon Walter and John Moore, and the impact of personal events, such as a poignant letter from home.

Chapter 3: The G.E. Advanced Course (1941-1945) Details the philosophy and structure of General Electric's advanced engineering course, Evans' progression from student to supervisor, and the impact of World War II on his career.

Chapter 4: The Graphical Analysis Paper (1946-1948) Chronicles the pivotal period when Evans developed and published his groundbreaking Root Locus paper, including correspondence with Paul Profos and feedback from the engineering community.

Chapter 5: North American Aviation in 1948 Recounts Evans' transition to North American Aviation, his role in the Aerophysics Laboratory, and the breakthrough moment when the Root Locus idea came to the forefront.

PART II: FEEDBACK

Chapter 6: Aerophysics Lab (1948-1954) Discusses Evans' work on the Navaho missile, his interactions with top engineering talent, and his pursuit of a master's degree, alongside key Root Locus milestones.

Chapter 7: The Spirule (1948-1954) Explores the creation and manufacturing challenges of the Spirule, a teaching tool for Root Locus, the formation of The Spirule Company, and early sales through college bookstores.

Chapter 8: The Root Locus Paper (1948-1950) Covers the development and escalating impact of the Root Locus paper, including interactions with prominent engineers like John Truxal and George Thaler.

Chapter 9: The Textbook (1949-1954) Highlights the journey from Spirule to textbook publication, the commercial success of the book, and Evans' reflections on the method's growing acceptance.

PART III: STABILITY

Chapter 10: Autonetics (1955-1959) Focuses on Evans' career at Autonetics, key professional relationships, and personal letters revealing his thoughts on engineering and workplace dynamics. Colleagues offer memories of Evans.

Chapter 11: The Spirule Company

EPILOGUE

AFTERWORD

ACKNOWLEDGEMENTS

APPENDICES

BiBLIOGRAPHY