The era of commercial supersonic flight could be just around the corner (again).
This November, residents will get to hear “quiet” sonic booms as military jets race above the skies of Galveston, Texas, said NASA.
Part of the Low-Boom Flight Demonstration program (LBFD), the space agency recently awarded Lockheed Martin’s Skunk Works a $247.5-million contract to design, build and flight test a low-boom X-plane that could produce a quiet supersonic aircraft in the next three to five years.
The experimental aircraft dubbed X-59 “QueSST,” is scheduled to take to the skies in 2021 with a top velocity of 1.5 times the speed of sound, or about 990 miles per hour at an altitude of 55,000 feet. The jet will only have room for a pilot, as it tests design principles that soften the sonic boom.
“It is super exciting to be back designing and flying X-planes at this scale,” said Jaiwon Shin, NASA’s associate administrator for aeronautics. “Our long tradition of solving the technical barriers of supersonic flight to benefit everyone continues.”
The news comes about four months after President Trump signed the federal budget deal, which funds the Low-Boom Flight Demonstrator (LBFD) program. In the budget proposal, the Trump administration noted that the X-plane “would open a new market for U.S. companies to build faster commercial airliners, creating jobs and cutting cross-country flight times in half.”
While the X-59 is more of a concept than reality, NASA will use McDonnell Douglas F/A-18 Hornets over Galveston to imitate the sonic profile of the X-plane while residents and sound recording sensors document the sonic booms overhead — if there are any.
During the tests this fall, F/A-18 Hornets will perform dives at supersonic speeds, making powerful sonic booms over the Gulf of Mexico and quieter booms over the coastal city. Simultaneously, a network of “audio sensors strategically placed around the city” will provide scientists with a decibel reading of how loud the sonic booms were, said NASA. About 500 local volunteers will be dispersed around the region to document their experience. The combination of audio sensors and the "human factor" will give scientists a better understanding if the LBFD program can produce “quiet” sonic booms.
According to NASA, the Gulf Coast city was selected because of its location near the Gulf of Mexico, allowing the F/A-18s to keep its louder sonic booms (near the dive point) out to sea, while sending muffled sonic thumps [X-59 supersonic profile] towards the city.
“We’ll never know exactly what everyone heard. We won’t have a noise monitor on their shoulder inside their home,” Alexandra Loubeau, NASA’s team lead for sonic boom community response research at Langley, Virginia, said in a statement. “But we’d like to at least have an estimate of the range of noise levels that they actually heard.”
The technology behind the X-59’s noise-reducing ability is its uniquely shaped structure, designed so that supersonic shockwaves do not build up into strong sonic booms.
“With the X-59 you’re still going to have multiple shockwaves because of the wings on the aircraft that create lift and the volume of the plane. But the airplane’s shape is carefully tailored such that those shockwaves do not combine,” said Ed Haering, a NASA aerospace engineer at Armstrong.
“Instead of getting a loud boom-boom, you’re going to get at least two quiet thump-thump sounds, if you even hear them at all,” he said.
“This is why the F/A-18 is so important to us as a tool. While construction continues on the X-59, we can use that diving maneuver to generate quiet sonic thumps over a specific area,” Haering added.
The X-59 is expected for delivery by the second half of 2021. Once the prototype is built and its “quiet” sonic booms confirmed, NASA stated it would conduct test flights across the United States.
Sonic booms have been a problem for aeronautical engineers for decades. In 1973, the U.S. banned commercial supersonic flights over the mainland for concern that sonic booms posed an extreme public nuisance. This was a significant challenge for the Anglo-French Concorde project to expand, which ultimately led to its retirement in 2003.
While commercial supersonic airliners have been around for decades, commercial flights were halted following the Year 2000 crash of Air France Flight 4590. However, the Trump administration is making a move to reintroduce these planes by the mid-2020 period. That is, assuming “quiet” sonic booms can be confirmed via NASA.
Meanwhile, the real test is about a decade later, because it is around early 2030 or mid-2030s when hypersonic airliners are expected to be introduced to the public domain. When that happens, and assuming commercial flight is cost-effective, it would spark the next "travel" revolution around the world.