Mach 1: Assaulting the Barrier

In 1947, no airplane had ever gone faster than the speed of sound.

The Douglas D-558-2 Skyrocket (shown here at Edwards Air Force Base circa May 1949) pushed past Mach 2 on November 20, 1953, beating an advanced X-1 to the record. (US Navy via National Air and Space Museum. Photo SI A-5168-C.)
Air & Space Magazine

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As an airplane increases speed, the wave fronts ahead of it get closer and closer together. When the airplane reaches Mach 1, the wavefronts overtake one another and pile up in a concentrated front, a “shock wave.” A shock wave marks an instantaneous change in air pressure, temperature, and density.

Past Mach 1, the combined motions of the airplane and the pressure waves still radiating outward form a conical front, which moves continuously with the airplane and which engineers call a “Mach cone.”

This article first appeared in the December 1990/January 1991 issue of Air & Space.



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