The Supersonic Wind Tunnel was manufactured and designed to provide facilities for experiments and demonstrations in supersonic and subsonic flow and is suitable for use with two dimensional models. The cross-sectional area of the tunnel was arranged with the primary object of illustrating two-dimensional phenomena in supersonic flow. The tunnel operates on the vacuum principle using a roots type positive displacement vacuum pump. Air is drawn into the tunnel from the atmosphere by way of smoothing screens and a contraction cone where it is accelerated with an accompanying fall in pressure. Further acceleration takes place in the working section. For supersonic working the air passes through a throat at which the velocity is sonic, after which the cross-section increases, allowing further expansion and the development of supersonic velocity. During operation the pressure in the working section is substantially below atmospheric.