NASA’s Quiet Supersonic Jet Prepares for Its First Noise Test

On August 21, the X‑59 — NASA’s experimental low‑boom jet — lifted off from the Armstrong Flight Research Center at Edwards, California, for its 25th flight. The two‑hour sortie saw the aircraft cruise at about Mach 1.2, climbing to roughly 49,000 feet while a loyal F‑15 chase plane trailed behind, its own sonic booms unintentionally drowning out any sound the X‑59 might have made.

That was fine for now, but the real moment is fast approaching. Later this year, NASA plans to strip away the chase‑plane cover and let the world hear exactly what the X‑59 sounds like when it zips past the sound barrier. In other words, the “quiet” part of the low‑boom concept will finally be put to the test.

The X‑59 isn’t just any supersonic aircraft. Its sleek, elongated nose and specially shaped fuselage were engineered to smooth out the pressure wave that normally creates a thunderous sonic boom. Instead, the designers hope to produce a gentle “thump,” a sound so soft that it could be acceptable over populated land — something that has been the holy grail of commercial supersonic travel for decades.

Since breaking the sound barrier for the first time on June 5, when it hit Mach 1.1 (about 713 mph), the aircraft has logged hundreds of minutes in the sky. “Each flight gives us more confidence,” says Cathy Bahm, project manager for the Low‑Boom Flight Demonstrator. “We’re refining our models, tweaking software, and learning how the plane behaves at real‑world speeds.” The only hiccup so far? A few nuisance alerts that the onboard computers mistakenly treated as caution warnings, which engineers corrected with a modest software update.

Now comes the acoustic validation phase, which NASA calls the “biggest benchmark” for the X‑59. Teams will deploy an array of microphones on the ground, airborne sensors, and even specially equipped drones to capture every nuance of the aircraft’s sound signature. The goal? To confirm that the aircraft’s pressure signature indeed translates into a faint thump instead of a boom, and to gather data that could shape the design language of future commercial supersonic jets.

Larry Cliatt, the acoustic‑validation lead for the Quesst mission, sums it up: “Building and flying a brand‑new aircraft is an extraordinary achievement, but the next phase is where the real research begins.” If the X‑59 passes this test, the findings could become part of the “DNA” of next‑generation airliners, finally making supersonic travel over land a realistic prospect.

In the meantime, pilots, engineers, and maintenance crews continue their routine of post‑flight debriefs, data crunching, and tiny tweaks to the control software. The aircraft has been remarkably stable — no major vibrations, no unexpected aerodynamic surprises — which bodes well for the upcoming noise campaign.

So, as the calendar turns toward the end of the year, the aerospace community watches with bated breath. Will the X‑59 deliver on its promise of a quiet supersonic thump? If it does, we might soon hear about commercial jets that can cross the Atlantic in half the time without waking entire cities.