Acoustic signals from Apollo rockets at orbital altitude (188 km) appear to be explainable with the assumption that the exhaust plume serves as a conical body of large cross-section moving supersonically with the rocket. The presence of the surface signal (1.3 Hz and higher) implies that propagation in the upper atmosphere occurred as an N-wave shock cone without the strong attenuation to which an acoustic wave or even a saw-toothed (shocked) wave of similar frequency would be subjected. The shock cone does not attenuate because energy is continually resupplied along the shock cone from the vehicle and its plume acting as a piston. Calculated overpressures do not reduce to acoustic amplitudes until the wave is below 40km where acoustic attenuation becomes negligible. (Author)
Generation and Propagation of Shock Waves from Apollo Rockets at Orbital Altitudes
1971
14 pages
Report
No indication
English
Sound from Apollo Rockets in Space
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