When going ‘boom’ is a good thing
NASA using F/A-18 noise results in study for 2023 program
Jim Less, a test pilot with NASA’s Armstrong Flight Research Center, is part of a team researching sonic booms using F/A-18 aircraft based at Ellington Field.
When three loud booms akin to rolling, distant thunder sounded off in the distance, a group gathered to listen remarked on what they heard.
It was a blustery, unusually frigid afternoon in Galveston and the group of students from Texas A&M University stood in a circle in the parking lot at Kempner Park listening for an F/A-18 airplane breaking the sound barrier 10 to 20 miles south of the island over the Gulf of Mexico.
“It sounded just like a bass drum, but not loud. A calm bass drum,” said Maddie Hetlage, a doctoral student at Texas A&M’s aerospace engineering program.
“If I was inside I wouldn’t have noticed it,” said another student.
While these particular sonic booms were on the higher end of the “perceived decibel level” scale that NASA is testing, for some Galveston residents, the sonic booms being recorded on the island are noticeably softer, similar to the slam of a car door, officials said — good news for the agency as it works to bring supersonic flight back to commercial airline travel.
But those sounds may not even resemble what is emitted from the new experimental research plane, the X-59, being built to quietly travel faster than the speed of a sound, said Jim Less, a research test pilot flying these missions.
“Whether the sonic boom from the X-59 sounds like these thumps we’re doing, we’ll have to build it to find out,” Less said at a Tuesday news conference at Ellington Airport after describing the dive maneuver pilots do over the water to send a quieter “thump” over the island.
The Galveston test flights, which began last week, instead are more of a dress rehearsal for the real thing. Starting around 2023, NASA will fly the X-59 over U.S. cities to collect data on how the areas are impacted by the supersonic flights.
Until then, NASA is using the F/ A-18 flights in Galveston to perfect the process of soliciting community input before, during and after test flights. So far, fewer than 20 test flights have been conducted above Galveston, with NASA seeking input from 500 Galvestonarea residents about the noise.
The sound of the sonic booms are measured by “perceived” decibel level (PL). The target for the X-59 sonic thump is around 75 PL. By comparison, a typical gunshot registers at around 130 on the decibel level scale, and a balloon pop is around 105 PL.
When Charles Vicario, a Galveston resident, first heard the “quiet” sonic boom last week, he told the Houston Chronicle he thought someone had body slammed his roof.
“It sounded like something physical had came in contact with my house,” Vicario said. “Once I put two and two together and realized it was the sonic boom I was pretty impressed by how I was startled.”
Vicario knew the testing was taking place because of a Facebook post, he added, but decided not to reach out to NASA about it.
“They were actually pretty cool,” he said.
The group listening intently at Kempner Park on Tuesday echoed that sentiment. The Texas A&M students are part of a multidisciplinary team of researchers selected by NASA to receive a fiveyear, $10 million grant as part of NASA Aeronautics’ University Leadership Initiative (ULI) to supplement the agency’s efforts to perfect supersonic flight.
“It sounded like construction noise to me, incidental construction noise. But exciting,” said Chris Mabe, who accompanied her husband, James, a technical fellow for Boeing Research and Technology working with the ULI program in Galveston from College Station.
There have been some complaints, Larry Cliatt, principal investigator for NASA’s Quiet Supersonic Flights 2018 campaign said Tuesday, but the testing has been an overall success.
“We hope to take everything we’ve learned here — the community outreach, the recruitment process for the human subjects, the questions that we ask them, the feedback that they give us ... to the X-59 airplane once that’s flying,” Cliatt said.
The agency’s ultimate goal with the X-59 — which will never carry passengers — is to show the Federal Aviation Administration that it is time to develop new rules about supersonic passenger flights, which would cut cross-country, commercial flight times in half. Currently, the FAA bans these flights over land, in part because of concerns on how they would impact communities and infrastructure on the ground.
“We’re going to build the X-59 airplane and prove that we have the technology to make sonic booms so quiet that the FAA will change its regulations to allow over land supersonic flight,” Cliatt said.
Sound was a problem in the 1970s when the Concorde — an aircraft that could cross the Atlantic in just over three hours by traveling twice the speed of sound — was built by European manufacturers and began making transatlantic flights.
In March 1973, the FAA banned the Concorde — and any future supersonic civil aircraft — from flying over land after residents complained about the sonic boom, saying it was a nuisance and a safety issue, according to a February 2017 Washington Post article. The Concorde stopped flying in 2003.
Officials expect to be flying above the island community for another week or so. Cliatt said NASA has not picked another city for these F/A-18 flights to occur.