After a career spanning 5 decades it is sad to hear the passing of Sin-I Cheng. He was a pioneer in rocketry helping us to understand the complexity of fluid dynamics in liquid rocket propulsion. In later years he helped us to understand aerodynamics of fast moving gases like air over an airfoil.
“The theoretical understanding provided by this rigorous work was essential in paving the way for reliable rockets as the United States hurdled into the space race after the Sputnik launch of 1957” -Sau-Hai “Harvey” Lam from the Princeton announcement
Cheng earned his PHD at Priceton and was a member of the faculty there for 41 years.