In a recent paper (Ref. 1) Dr. Hilton proposed the use of manoeuvres for creating zones of “no boom” which could be employed to protect cities situated along the flight path of a supersonic aircraft. The basic idea was to make use of the fact that curved flight causes a local focus of shock waves and that, in regions closer to the centre of curvature than this focus, shocks do not form.

In investigating this intriguing suggestion, the author found it advantageous to abandon the Huygens-type construction used by Hilton and employ in its place a technique which permits plotting the shock front directly. In applying this approach to manoeuvres of the type proposed for shock avoidance, regions of single, double and even triple shocks were found, but no shockless region. The method used and the results obtained are outlined briefly in the following sections.