The Saturn V carried man to the moon and remains the most powerful rocket to be successfully launched into orbit. It captures the imagination, but sometimes it can capture a little too much imagination. Numerous claims on the internet about the acoustic output of the rocket suggest that it melted concrete and lit grass on fire more than a mile away.
Such ideas are undeniably wrong. In The Journal of the Acoustical Society of Americaresearchers from Brigham Young University used a physics-based model to estimate Saturn V’s sound levels. They got a value of 203 decibels, which matches very limited data from the 1960s.
To put that number into perspective, commercial jet engines range from about 120 to 160 decibels.
“Decibels are logarithmic, so every 10 decibels represents an order of magnitude increase,” said author Kent L. Gee of BYU. “One hundred and seventy decibels would equal 10 aircraft engines. Two hundred would equal 10,000 engines!”
While the Saturn V was extremely loud, that kind of power is nowhere near enough to melt concrete or start grass fires. If the reports of these phenomena are true, they likely stem from radiative heating via the plume or debris.
Part of the misunderstanding comes from confusing sound power and sound pressure. The first is like the power of a light bulb. The latter is like the brightness of the same light bulb: it depends on how far away you are. Miscalculations, changes to the decibel reference system, and the spread of misinformation have also led to compounding errors.
“The Saturn V took on this sort of legendary, apocryphal status,” Gee said. “We felt that, as part of JASA’s special issue on acoustic education, this was an opportunity to correct the misinformation about this vehicle.”
NASA’s Artemis 1 Space Launch System (SLS) is slated for launch in the fall of this year, when it will return humans to the Moon and surpass Saturn V in power and noise. The researchers used their framework to predict sound levels from SLS, and they plan to do acoustic measurements when it launches to help further refine the predictions.
The team also provided educational tools, such as homework assignments, to share their findings with college-level physics classes. They hope that the story of this rocket will show the importance of critical examination of data and scientific discussions online.
“Saturn-V Sound Levels: A Letter to the Redditor” is written by Kent L. Gee, Logan T. Mathews, Mark C. Anderson, and Grant W. Hart. The article will appear in The Journal of the Acoustical Society of America on August 23, 2022.
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Saturn-V Sound Levels: A Letter to the Redditor, The Journal of the Acoustical Society of America (2022). DOI: 10.1121/10.0013216
Provided by the American Institute of Physics
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