The X-59 quiet supersonic experimental aircraft has completed 25 test flights, clearing the way for a new phase of acoustic evaluation at supersonic speeds.
The aircraft performed its 25th flight on August 21, taking off from NASA’s Armstrong Flight Research Center in Edwards, California, for a 72-minute sortie. It climbed to Mach 1.2 and 49,000ft, accompanied by a chase plane whose own sonic booms masked any noise from the X-59.
Years of design and analysis preceded the aircraft’s construction, and the team is now seeing predictions made using computer models and wind tunnel tests confirmed in flight. One tool used to track progress is a real-time digital twin, which compares live flight data against simulated predictions.
So far, the X-59’s real-world flight characteristics have matched the simulations closely, said NASA. The aircraft has shown agreement across its flying qualities, its stability margin and the flight loads acting to bend and twist the airframe, with no unexpected instability or excessive vibration.
Cathy Bahm, project manager for NASA’s Low Boom Flight Demonstrator project, said, “Through our ongoing flight tests with the X-59, we’ve gained invaluable insights into both the aircraft’s performance and the challenges of the aircraft design. Each test point has validated our models and predictions, and it has strengthened our confidence in the aircraft’s performance.
“Every flight brings us closer to transitioning to the next phase where we will demonstrate the X-59’s quiet supersonic flight capabilities.”
Early flights had simple objectives, such as flying and landing safely while demonstrating stability, before the aircraft reached supersonic speeds and worked up to its target cruise speed of Mach 1.4 (924mph/1,486km/h) and 55,000ft relatively early in the schedule. NASA test pilot Nils Larson has described the flights as “exciting but uneventful”.
Much of the remaining work has focused on checking performance across the flight envelope — the speeds and altitudes where the aircraft can safely operate — including at the low and slow end.
Individual components have met each challenge as it arose. The top-mounted inlet feeding the aircraft’s single GE F414 engine has performed as expected across a range of maneuvers and conditions.
Attention now turns to the acoustic validation phase, expected later this year, in which the team will fly the X-59 while using ground- and air-based tools to measure and characterize its sonic thumps. It marks the point at which the effort moves from proving the aircraft flies as designed to testing whether it sounds as intended.
Data gathered from the acoustic testing will feed into the creation of regulations for the use of supersonic commercial aircraft over land.
Larry Cliatt, acoustic validation technical lead for NASA’s Quesst mission, said, “This is the phase we’ve been working toward. Building and flying a brand-new aircraft is an extraordinary accomplishment, but the next phase is where the real research begins.”
The X-59 is the centerpiece of NASA’s Quesst mission, which aims to help enable commercial supersonic flight over land.
