Theoretical and Experimental Studies of the Focus of Sonic Booms

Abstract

Knowledge of sonic booms produced by airplanes in steady rectilinear flight is now sufficient to allow for good predictions of the phenomena. In order to improve the knowledge of the effects of accelerations and curvatures of the flight path, the French Working Group on sonic booms has undertaken a set of theoretical and experimental studies on that subject. Theoretical studies of the propagation of the shock waves have helped identify the different cases of focus (linear acceleration, turn, pushover) and superfocus (entry to turn). They have also shown that, after measurement of the actual characteristics of the atmosphere, it was possible to guide an airplane in order to produce focusing in a measurement zone of realistic size. During the four experimental exercises of “Operation Jericho” the accuracy of prediction of propagation and guidance of the airplane has shown that focus factors are higher than those predicted.