Anyone who was near Florida’s Kennedy Space Center on November 16 would likely confirm that the first launch of NASA’s Space Launch System (SLS) was loud. Researchers, however, can now take it one step further: They’ve calculated exactly how loud the 32-story mega-rocket was when it sent the uncrewed Orion spacecraft into orbit around the moon for the Artemis 1 mission.
Their analysis suggests the launch was loud enough to cause ear pain or hearing loss, even from three miles away. At roughly one mile from the launch site (1.5 kilometers, to be exact), the rocket’s noise was 136 decibels, which is roughly equivalent to standing 100 yards from a jet engine. At a little more than 3 miles (5.2 km) away, it reached 129 decibels—about as loud as a chainsaw. Hearing loss can occur with less than two minutes of exposure to 110 decibels, and ear pain and injury can begin at around 120 decibels, per the Centers for Disease Control and Prevention.
SLS’s launch was so loud that it produced visible sound waves that were caught on video, per the scientists. The crackling sound produced by the rocket, from three miles away, was roughly 40 million times louder than the popping noises from a bowl of Rice Krispies cereal in freshly poured milk.
Scientists shared their findings in a new paper published Tuesday in the journal JASA Express Letters.
To figure out SLS’s maximum noise levels, researchers placed state-of-the-art microphones at five sites near the launch pad, then analyzed the data. But why go to all that trouble? Understanding the scientists’ motivations requires a little history lesson.
After NASA’s Saturn V sent astronauts to the moon in the late 1960s and early ’70s, rumors started circulating about the rocket’s extreme acoustical power. But those rumors turned out to be unfounded, at least according to a study published last year that modeled Saturn V’s noise levels.
“We hope these early results [from the SLS launch] will help prevent the spread of possible misinformation, as happened with the Saturn V,” says Kent Gee, an acoustics researcher at Brigham Young University (BYU) who led both projects, in a statement. “Numerous websites and discussion forums suggested sound levels that were far too high, with inaccurate reports of the Saturn V’s sound waves melting concrete and causing grass fires.”
Understanding the sound of rocket launches has present-day impacts, too. New spaceports are being built around the world, often close to wildlife areas and human communities, as Caroline Lubert, a rocket noise researcher at James Madison University who was not an author on this study, told Popular Science’s Eva Botkin-Kowacki in August. Such noise pollution might have impacts on wildlife, especially as rocket launches get more powerful, writes Inverse’s Doris Elín Urrutia.
When SLS lifted off from Florida last November, it became the most powerful rocket in the world to launch successfully. Its thrust—8.8 million pounds—was about 15 percent higher than that of the Saturn V, the previous most powerful rocket. And SpaceX last week fired the engines of Starship, a rocket that will blow even SLS out of the water with its 17 million pounds of thrust when it launches, perhaps as soon as next month.
SLS is what NASA describes as a “super heavy-lift rocket.” At 5.75 million pounds, it’s a big part of the space agency’s plan to eventually put astronauts back on the moon and, eventually, send people to Mars.
NASA engineers anticipated that SLS’s launch would be loud, so they dumped 450,000 gallons of water onto the launch pad to help dampen the sound. Even with the water, however, SLS produced noise levels that were higher than those NASA had predicted in a preliminary assessment. The noise roughly three miles from the launch site, for instance, was nearly 20 decibels higher than expected.
“This suggests a need to revisit and probably revise those [noise prediction] models,” says co-author Grant Hart, a rocket noise researcher at BYU, in the statement.
These models are important because rocket launch acoustics—particularly the vibrations caused by all that noise—can damage items and systems onboard the spacecraft.
“If you don’t understand the acoustics produced by the rocket, you can’t design payloads efficiently,” Gee told Popular Science.