Supersonic low-boom aircraft progress

Garrett Reim at aviationweek.com.

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NASA unveiled its X-59 Low Boom Flight Demonstration aircraft at a ceremony at Lockheed Martin’s Skunk Works facilities.

The experimental aircraft, which was designed and built by prime contractor Lockheed Martin, promises to dampen sonic booms into a mere thud—about 75 perceived dB. It was formally presented to the public in a rollout ceremony on Jan. 12.

Despite problems that had delayed the program from its scheduled flight debut in 2021, there are now no obvious obstacles in the way of the X-59 flying for the first time in the late spring or early summer of this year, says David Richardson, Lockheed Martin program director for the X-59. Lockheed Martin is looking at engine runs in March and taxi tests in April, with first flight coming perhaps sometime in May or June, he says.

One of the issues that had bedeviled the aircraft was stray solder within a flight computer that was causing a short circuit, Richardson says. “There had been some strange behaviors,” he says, noting that it took nine months to find the root cause of the problem. “But we’re back in the saddle again and going forward.”

The X-59 is designed to break up shockwaves that typically cause a sonic boom when an aircraft passes the speed of sound. One way it does that is with a long nose that measures about a third of the aircraft’s 100-ft. length. To reduce shockwaves coming from a protruding cockpit canopy, the X-59 also does not have a conventional transparent windscreen. Instead, NASA developed the eXternal Vision System, a series of high-resolution cameras and a 4k monitor that allow the pilot to see forward and below the nose of the aircraft.

The Low Boom Flight Demonstration aircraft is designed to fly at speeds up to Mach 1.4 (the Concorde had a maximum speed of Mach 2.04) and at an altitude of about 55,000 ft. It is powered by a GE Aviation F414-GE-100, a derivative of the jet engine that powers Sweden’s Saab JAS 39E Gripen fighter. Because NASA plans to fly the X-59 so regularly above the sound barrier, it expects the engine will limit the lifespan of the aircraft to about 1,000 hr.

“Fighters are usually in afterburner for maybe seconds. We stay there for minutes,” Richardson says. “We're actually burning the life out of this engine.”

The X-59 is part of NASA’s overarching Quiet Supersonic Transport (Quesst) mission, an initiative to develop predictive tools for sonic booms and measure the reaction of people on the ground to a dampened sonic boom. NASA is planning 2-2.5 years of flight tests of the X-59 above five different representative populations in the U.S. to gauge the public reaction to the aircraft’s sound, says Peter Coen, Quesst integration manager for NASA.

NASA aims to gather enough data by 2031 for the International Civil Aviation Organization’s Committee on Aviation Environmental Protection (CAEP) to craft noise regulations for supersonic flights, Coen says. “That’s when CAEP has told us they would like to bring the standard to the full committee for a decision,” he says.