Sonic Boom for Lilliputians

Absurdly tiny models -0.25 to 1 inch in size-were tested in the Ames and Langley supersonic wind tunnels. With such miniaturization, the tunnel walls were up to 150 body lengths away from the models. The Lilliputian models generated shock waves all right, but they were so weak that new pressure sensors had to be conceived. Further, tunnel conditions had to be held more nearly uniform because slight changes in humidity or compressor speed would create transient flow conditions that confused the shock wave data. By taking great care, Whitham’s theory of sonic booms was verified in the idealized environment of the wind tunnel.