Air velocities in supersonic wind tunnels, which have been limited to a mere seven or so times the speed of sound (and then for intermittent periods of a few seconds each), have been eclipsed by the performance of the newly completed wind tunnel at the California Institute of Technology. The tunnel, according to an announcement issued simultaneously by the Institute and the Army Ordnance Department (for whom it was designed and built), has generated an air speed exceeding ten times that of sound which may, by continuous operation of the tunnel, be maintained for extended periods of time. Suggesting obliquely that there must be a limit somewhere between seven and ten times sound velocity beyond which the prefix “super” ceases to apply, the announcement explains that Caltech's is a “hypersonic” tunnel because of the terrific air speeds attained therein.

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