DONALD PERCY LING 1912-1981

BY BROCKWAY McMILLAN

DONALD P. LING died at his home in Albuquerque, New Mexico, on July 14, 1981. Dr. Ling retired as Vice-President of Bell Labora­tories in 1971. Because of his expertise, his thoughtful judgment, and his selfless willingness to probe into questions brought before him, he was widely known and highly respected in government and military circles and among his engineering colleagues. He had been a member of the National Academy of Engineering since 1967.

Educated in languages, music, and mathematics, Dr. Ling spent much of his professional life either working as an engineer or work­ing with engineers. His practice centered on the large, real-time control system. He combined his knowledge of the diverse technolo­gies at issue with the attitude and instincts of a systems engineer. He left his mark on the structure as well as on the details of most systems with which he dealt-this was possible because of his understanding of the complex interactive effects that govern the performance and plague the design of large systems. His best-known work was with guided missile systems, and many of his important contributions are therefore scattered in classified memorandums and reports that have not been published.

During his career Dr. Ling served on literally dozens of commit­tees and advisory panels to the U.S. Government-ten panels alone of the President's Science Advisory Committee during the first half of the 1960s. During the same period he served on other groups that advised the Department of Defense, National Aeronautics and Space Administration, Central Intelligence Agency, and Arms Control and Disarmament Agency.

Dr. Ling's most extensive involvement was with the Nike series of antiaircraft and antimissile systems. None of these systems was with­ out critics, and the antimissile systems were focuses of controversy. It reflects on the respect in which Dr. Ling was held that he, almost alone among employees working on these projects, frequently served on advisory groups convened to review the projects.

Donald Percy Ling was born January 2, 1912, in Albany, New York, and he attended the public schools of Albany. He entered Amherst College in 1928 and later studied piano at the Eastman School of Music in Rochester, returning to graduate from Amherst in 1933 with a B.A. in mathematics. For the next year he studied classical applied mathematics in Cambridge, England. He taught in private schools in New England for three years and then entered Columbia, where he received M.A. and Ph.D. degrees in mathe­matics, and also taught part of the time.

In 1944 and 1945 he worked on aerial gunnery problems with the Applied Mathematics Panel of the National Defense Research Com­mittee. In 1945 Dr. Ling was hired by Bell Laboratories as a research mathematician and was a member of the (then) Mathemat­ical Research Department headed by H. W Bode. He immediately joined a team that included fellow mathematicians Bode and John W Tukey and other physicists and engineers, who prepared a detailed study of a possible antiaircraft guided missile system for the Army. The study broke new technical ground in analyzing the aero­ dynamic control of supersonic vehicles, and it challenged conven­tional wisdom about sensors and about where the control loops should be closed. It also broke new ground among military "systems analyses" of the period in the scope of issues covered and in its penetration of these issues. From this study came the Nike series of guided missile systems.

Dr. Ling remained a member of the mathematical research organ­ization at Bell Laboratories for the next thirteen years. During much of that time he consulted with Nike projects. He himself did the first design of a warhead for Nike Ajax, a controlled fragmentation device. During the flight tests of Ajax, he spent weeks at a time at the White Sands missile test range with engineers from both Bell Labs and Douglas Aircraft Company, the subcontractor. It was in the camaraderie of this field assignment, where everyone was learning, that Don Ling the mathematician formed bonds of friendship and respect, not only with the engineers of his own company but also with their friendly rivals, whom they called "plumbers," from the aircraft industry. He served as liaison between these two communi­ties for the rest of his career.

The mathematical research organization at Bell Laboratories grew in size and in the early 1950s was split into several units under one director. Dr. Ling headed one of the research units. In his group were Sydney Darlington, J. W Tukey, and R. B. Blackman. The guidance algorithms for Nike Ajax and Nike Hercules were designed there, and the programs were written there for the first digital (and solid-state) bombing and navigation computer (Tradic).

In 1958 Dr. Ling left the research organization to become Direc­tor of Military Analysis, building up a group within a newly formed organization for military systems engineering. Another promotion in 1959 saw him reporting to the Vice-President for Military Sys­tems Engineering, to which post he himself succeeded in 1967.

In 1959 studies began that led ultimately to the setting up of a program, called Nike-X, to demonstrate an antimissile system that used as a primary sensor a phased-array radar, tracking both intruders (targets) and interceptors. Into 1962, under Dr. Ling's direction, these studies were continued and compiled into a formal report. The report, in several volumes, outlined the basic plan and proportions of an antimissile system, detailed the development prob­lems, and described a program to address them. The program thus outlined was formally proposed by the Army to the Department of Defense and was approved for initiation. For the next five years Dr. Ling's organization pursued its analyses and consulted in developing detailed objectives for the design of the demonstration system and the conduct of its test. At the same time Dr. Ling was a principal spokesman for Bell Laboratories and Western Electric, the prime contractors, in reporting progress on Nike-X. He appeared regularly in this role before the Secretary of Defense. He also appeared as a spokesman for the Army and the Department of Defense before the President's Science Advisory Committee and other groups. It speaks well of the objective quality of his reports that this record of advocacy was not a bar to Dr. Ling's participation at other times in reviews and critiques of the program.

Neither the inventor (there was none) nor, in any detailed sense, the designer of Nike-X, Don Ling probably did as much to preserve a sound balance among the many objectives of the demonstration program as any individual. That these objectives were technically defensible and that they remained the governing factors in the conduct of the program are important facts for which Dr. Ling and his organization must be given much credit. In addition, Don Ling's personal efforts as a detached and articulate spokesman did much to keep the technical issues clear and separate from the often heated and diffuse arguments about defense policies.

Dr. Ling left his mark on Bell Laboratories. His Military Analysis group, handpicked from the start, grew to a vigorous and productive unit. Its alumni have found their way into influential posts through­ out the company. He early recognized the need for a companywide computing organization and was instrumental in the early decisions that set it up and staffed it with competent people. As Chairman of his company's influential Committee on Education, he initiated a major expansion in the extent and variety of educational opportuni­ties that the company offered to its employees.

Increasingly troubled by a weakening heart, Dr. Ling retired in October 1971. At retirement he was concurrently the Vice-President for Systems Research at Bell Laboratories and President of Bell Comm, Inc. He moved to Albuquerque in the desert country that he loved. He briefly undertook some consulting work for the Uni­versity of New Mexico but not, as he had hoped, in matters related to education.

Dr. Ling was a private man. Cultured, urbane, elegantly articu­late, and gifted with a perceptive sense of humor, he met everyone with courtesy and respect. He was gracious, almost courtly, in social gatherings. But he reserved a private self that was rarely glimpsed. His one marriage lasted only a few years. Alone in retirement, as his health allowed he explored the desert, expanded his mineral collec­tion, and spent time each day at his piano. Scholar and mathematician, he completed a project begun before retirement: the writing of a serious technical book on modern mathematics for the nonmathe­matical reader. His final draft manuscript was completed in 1980.

I last saw Donald Ling in March 1981. I called him from Socorro, New Mexico, to ask if my wife and I could drop in. With character­istic detachment and tact, he referred obliquely to his failing strength and urged that we visit for a short while. In the event, the short while stretched to three hours. We talked of his book, of his hopes for its publication, of his music-he had strength only for short periods at the piano-of his mineral collection, of his health, of his daughter and infant grandson. At our parting, we all knew it was our last. Ever the gracious host, he saw us to the door, instructed us in finding the highway, and bade us a cordial good-bye, just as he would have done thirty years before.