Long-Range Infrasound from Rockets

Abstract

Long-range infrasound from large rockets launched at Cape Kennedy have been recorded and studied since 1957 by a variety of low-frequency acoustic sensors. Dominant energy ranges from 0.1 to 2 Hz. Signals can be grouped into early (apparently supersonic) arrivals, normal acoustic arrivals, and late (apparently subsonic) arrivals. The normal acoustic signals detected in the eastern United States from rockets launched in the northeast quadrant from Cape Kennedy show two prominent wave groups generated by the launch and first-stage reentry. The origin of this long-range infrasound is shown to be acoustic energy radiated from the cone of shock waves. The data of early arrivals (supersonic waves) suggests an origin from coupling between normal acoustic waves and those in a higher-speed region. Late arrivals having apparently subsonic velocities are also detected less frequently than the supersonic arrivals.

A Study of the Infrasonic Wave in the Atmosphere

“…The distance between the volcano and infrasonic network (about 710 km) and the time lags of 35-39 min give the apparent speed of 303-338m/sec, which is a little less than the normal speed of sound at the ground level. Such subsonic speeds are reasonable for the infrasonic signals arriving after multiple reflections from the upper atmosphere (e.g., Kaschak et al 1970). As will be seen later, the ray tracing analysis shows that the computed travel time is in the range 35-39 min, for the signals propagating in the ducts below the stratopause.…”

Characteristics of Infrasonic Signals from Rockets

“…Infrasonic signals from rockets of frequencies from a few Hertz to fractions of a Hertz, have been reported by many investigators (Donn et al 1968;Kaschak 1969;Fehr 1968;Kaschak, Donn & Fehr 1970;Balachandran & Donn 1971). Signals have been detected at distances of the order of lo00 km from both the launch and re-entry stages of Saturn rockets launched at Cape Kennedy.…”

“…Signals have been detected at distances of the order of lo00 km from both the launch and re-entry stages of Saturn rockets launched at Cape Kennedy. This led Kaschak et al (1970) and Balachandran et al (1971) to conclude that the source of the signal is not the rocket engine, but rather that it is generated aerodynamically. A typical signal detected at Palisades, New York, from the Saturn V rocket launched from Cape Kennedy on 1967 November 9, is shown in Fig.…”

Preliminary Observations of 1-16 Hz Natural Background Infrasound and Signals from Apollo 14 and Aircraft

“…Recordings of infrasound following rocket launchings have been published by Donn et al (1968), Kaschak, Donn & Fehr (1970), and others. Generally, infrasound from Apollo launchings exhibits two distinct arrivals-the earlier, from the relatively close re-entry of the first stage; the later, from the relatively distant launch region.…”