An Inaudible Sonic Boom, Visualized

The company’s XB-1 “Baby Boom”—a demonstrator that is about one-third the size of Overture, a supersonic, SAF-powered airliner it is developing for 64 to 80 passengers—is the first independently built jet to break the sound barrier. Retired in February, it eclipsed Mach 1 six times across two test flights. But you wouldn’t be able to tell from the ground.

That’s because microphones stationed along XB-1’s flight path confirmed the sonic booms did not reach the ground. Boom’s analysis of NASA data confirmed that assessment, it said Monday. The firm relied on a physics concept called Mach cutoff, which engineers have long considered feasible but been unable to achieve. And with NASA’s specialized photography, Boom believes it could make “boomless cruise” the norm for supersonic flight over land, which is prohibited under FAA regulations. Boom conducted its test flights under a special flight authorization.

“Basically, [the rule] says, ‘Thou shalt not exceed Mach one,’” Blake Scholl, founder and CEO of Boom, told FLYING in February. “And what it should say is, ‘Thou shalt not make loud noises.’”

NASA teams on the ground used specialized telescopes to deploy the Schlieren photography technique, which captures changing air densities around a supersonic aircraft as it eclipses the sun to visualize shockwaves. NASA computed waypoints, while Boom devised avionics software that guided Brandenburg to the exact spot he needed to hit. The maneuver also required precise timing and conditions.

“This image makes the invisible visible—the first American made civil supersonic jet breaking the sound barrier,” Scholl said in an update Monday. “Thanks to Geppetto’s exceptional flying and our partnership with NASA, we were able to capture this iconic image.”

According to Boom, the partners’ analysis “estimated a very high likelihood of operating at Mach cutoff.” The data collected from the effort, the firm said, will help it add boomless cruise capability to Overture, planned as the company’s successor to the famed Concorde.

Fifty-six years ago on Sunday, Concorde made its maiden voyage. It was retired in 2003. But Boom hopes to bring supersonic commercial flight back by the end of the decade—including operations over land.

The company claims boomless cruise has the potential to reduce U.S. coast-to-coast flight times by 90 minutes, if the FAA can be swayed to change its rules. Regulations prohibit all supersonic flights over land, boomless or not. But having demonstrated Mach cutoff, Scholl believes it will be “pretty easy” to convince regulators the provision is outdated. The Boom CEO said those efforts are already underway.

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