Local Avoidance of Sonic Boom from an Aircraft

Extract

The sonic boom from an aircraft in level supersonic flight has been studied extensively. What is perhaps not so well known is the effect of a curved flight path in causing a local focus of shock-waves, and accentuated boom, and more particularly the production of a zone of silence, or rather “no boom” in other localities closer to the centre of curvature of the curved flight path than the M=1 radius. A steady shock wave pattern cannot rotate at a subsonic speed. It remains to be determined whether the necessary aircraft flight paths can be tolerated by both passengers and aircraft.

The subject is not new, and was theoretically predicted by Bryan and Lamb in 1921, and verified experimentally by the present author in 1938, for the case of propellers or airscrews. Figure 1 shows the effect of progressively tightening the radius of turn of the aircraft.