'We are talking about levels that people found unacceptable before.'
Last month's SpaceX Starship test launch marked another milestone for the world's largest and most powerful rocket. On October 13th, the launch and catch tower's "chopstick arms" successfully recaptured the Super Heavy booster stage during its landing, an achievement SpaceX described as "fundamental" to its "fully and rapidly reusable design." But additional data collected during the vehicle's fifth flight indicates Starship may be even more damaging to local communities and wildlife than critics previously feared.
According to datasets published on November 15th in JASA Express Letters, the 30-story-tall Starship's 33 engines generate anywhere between 105 and 125 decibels during its liftoff and landing. As The New York Times explained on Tuesday, another study authored by consultants hired by the nearby town of Port Isabel, Texas, additionally noted a peak sound pressure level of 144.6 decibels. Such events also include sonic booms powerful enough to potentially cause structural damage to buildings.
But researchers didn't record those sound levels directly adjacent to SpaceX's Starbase facility. Kent Gee, Brigham Young University Provo's chair of physics and astronomy, detected many of them roughly six miles away in Port Isabel.
"This is the largest rocket ever built. It would stand to reason that it would [also] be the loudest rocket ever built," Gee tells Popular Science.
Gee stresses that although researchers often measure audible noise using decibel levels, there exists no single metric for sound. For practical purposes, however, he believes it's best to assess Starship's loudness by comparing it to other understandable quantities. On the quieter end, Gee says Starship's liftoff may sound similar to an average rock concert or a chainsaw. At its loudest -- during the first stage booster's landing approximately 6.5 minutes later -- according to one study, that din is equivalent to hearing a close range gunshot, sustained over a longer period of time.
But there's that critical caveat: Starship is already this loud when standing as far as six miles away, and that still doesn't account for the rocket's lower frequencies. Even at that distance, Gee says the total amount of sound energy in a Starship launch is approximately equal to the sound created during the takeoff of a Boeing 747 or Airbus 380 -- while standing around 200 feet away from the plane.
"That should give people an appreciation of the significance of this sound event," he explains.
According to environmental engineer and compliance expert Eric Roesch, the "raw power output" from Starship's Super Heavy rockets has increased 30 percent since the FAA's initial risk review in 2019, an amount expected to grow over future launches.
Roesch, who previously brought attention to Starship's alleged environmental waste water regulation violations, also called past assumptions by the FAA and SpaceX "not only factually laughable based on an understanding of basic physics" but contradictory to NASA's decades of Acoustic Modeling Best Practice documentation. Like Gee, Roesch says that "extrapolating sound attenuation is a dangerous road to go down as a rule. But even so, Roesch believes Starship's din will be a disaster for local wildlife, much of which lives on federally protected land.
"No bird egg will survive that kind of impact," he offers as an example, adding that, "There is absolutely a radius of death for animals that is not accounted for in the FAA's risk assessment."
[Related: SpaceX accused of dumping polluted Starship wastewater in Texas for years.]
SpaceX's next Starship test launch is scheduled for no earlier than November 19th. During a press conference last week, SpaceX CEO Gwynne Shotwell expressed a desire to see upwards of 400 Starship launches over the next four years.
Gee declined to offer a personal opinion regarding SpaceX's ongoing Starship launch schedule, and believes humanity's future may require space travel. In the meantime, he hopes the new data will inform policy and regulatory decisions. He did, however, note that at six miles away, the launches are similar to the noise heard at ground level from Concorde supersonic jets while flying at their maximum altitude of around 11 miles.
"We are talking about levels that people found unacceptable before," he says.