Ronald died Sept. 19, 2021, in Brookline, Mass., at the age of 93. 

Born in New York, Ronald spent his youth in Hell’s Kitchen, learning statistics from horse racing and fishing for nickels through subway grates. He graduated from Stuyvesant High School at age 15 before studying engineering at New York University night school and working days for mathematician Richard Courant. In 1952 he earned the first Ph.D. granted by Princeton’s Department of Aeronautical Engineering. 

After serving as a professor at Brown, Ronald joined MIT’s mechanical engineering department in 1962, and served as the Ford Professor of Engineering until retirement in 1996. He played a principal role in many scientific and technical achievements in the post-World War II era, including early spacecraft design, ballistic missile reentry physics, the composition of comet tails, alternative energy sources, and toxic-waste remediation. 

Ronald’s books Hypersonic Inviscid Flow (with Wally Hayes), Synthetic Fuels (with Edwin Hicks) and Physicochemical Hydrodynamics remain reference works on these topics. He was elected to the National Academy of Science, the National Academy of Engineering, and the American Academy of Arts and Sciences, and received a Guggenheim Fellowship. 

He is survived by his son, Sid; daughter Laurie; and three grandchildren.

Graduate memorials are prepared by the APGA.