According to numerous internet claims, the Saturn V rocket's acoustic power melted concrete and set grass on fire over a mile away. However, scientists disagree with this assumption. Researchers from Brigham Young University discovered that Saturn V could not melt concrete in a study published in the Journal of the Acoustical Society of America.
Does Saturn V Melt Concrete?
Scientists estimated the acoustic levels of Saturn V using a physics-based model and obtained a value of 203 decibels, which matched the very limited data from the 1960s. To put that number in context, commercial jet engines range from around 120 to 160 decibels.
According to BYU author Kent L. Gee, since decibels are logarithmic, an increase of 10 decibels corresponds to an order of magnitude. One hundred and seventy decibels is the equivalent of ten airplane engines. Two hundred machines equal 10,000.
Even though the Saturn V was incredibly loud, its power was insufficient to melt concrete or start a fire in the grass. If these reports are accurate, they are most likely caused by radiative heating from the plume or debris.
According to Gee, Saturn V has achieved legendary apocryphal status. He said they felt it was an opportunity to correct misinformation about the vehicle as part of the JASA special issue on Education in Acoustics.
Sound Power vs. Sound Pressure
Some of the misunderstandings stem from mixing up sound power and sound pressure. The former is analogous to the wattage of a light bulb. The latter is similar to the brightness of the same bulb: it varies depending on how far away you are. Calculation errors, changes to the decibel reference system, and spreading misinformation have all contributed to compounding mistakes.
Here's a more detailed explanation of the distinction between the two terms from Acoustical. According to the website, a sound power level is the acoustic energy emitted by a source that produces a sound pressure level at some distance.
While the sound power level of a source is constant, the sound pressure level is affected by the distance from the source and the acoustic properties of the area in which it is located.
NASA Johnson Space Center
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A sound source will generate more sound pressure in a small reflective reverberant room than in a large acoustically dead absorptive room or open space. The power of a heater can be measured in watts, while the temperature can be measured in degrees.
Similarly, the energy emitted by a sound source is measured in Watts, while the sound pressure produced is measured in Pascals.
How Was the Saturn V Sound Controlled?
NASA installed a sophisticated sound suppression system at Launch Pad 39A, according to Real Science, because the sound of powerful rocket launches can destroy not only living creatures but also mechanical structures, including the rocket itself. Approximately forty seconds after booster ignition, up to 300,000 gallons of water can be ejected from numerous nozzles onto the launch pad.
When sound waves collide with air bubbles in the torrent, they heat up, converting sound energy to heat energy. The system reduces the volume of gunfire directly in front of the barrel to around 142 decibels near the launch pad.
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