January 11, 1961: Edwards Air Force Base Shock Wave Demonstration

  • Published
  • Air Force Flight Test Center

Following complaints from Los Angeles-area residents regarding shock waves from high-speed pullouts, a shock wave demonstration was held at Edwards Air Force Base for the benefit of news representatives at the request of the Armed Forces Public Information Office in Los Angeles. Dive tests were conducted by Lt Col Fred J. Ascani and Maj Frank K. “Pete” Everest in F‑86E aircraft. No further complaints about “mysterious explosions” were heard from Los Angeles after the demonstration.

In physics, a shock wave is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a medium but is characterized by an abrupt, nearly discontinuous, change in pressure, temperature, and density of the medium.  For the purpose of comparison, in supersonic flows, additional increased expansion may be achieved through an expansion fan, also known as a Prandtl–Meyer expansion fan. The accompanying expansion wave may approach and eventually collide and recombine with the shock wave, creating a process of destructive interference. The sonic boom associated with the passage of a supersonic aircraft is a type of sound wave produced by constructive interference.  Unlike solitons (another kind of nonlinear wave), the energy and speed of a shock wave alone dissipates relatively quickly with distance. When a shock wave passes through matter, energy is preserved but entropy increases. This change in the matter's properties manifests itself as a decrease in the energy which can be extracted as work, and as a drag force on supersonic objects; shock waves are strongly irreversible processes.



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