The X-59 aims to solve the last difficult problem of supersonic air travel: noise.
NASA’s new X-59 supersonic research aircraft is poised to crack the most vexing problem of commercial faster-than-sound travel: Sonic boom. The unique shape of the aircraft manages shockwave formation and is anticipated to reduce the window-rattling noise of sonic booms to a thump no louder than the slamming of a car door. If it works, a new generation of supersonic commercial airliners may be free of current FAA restrictions over supersonic operations over populated areas.
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Episode Transcript:
In commercial aviation, many argue that this airplane represents the peak of human achievement: the Concorde. It was the first, and so far only, commercial airliner to operate in scheduled airline service across transcontinental ranges carrying passengers at over twice the speed of sound.
By 1970, it was widely expected that aircraft like the Boeing 747 would be replaced by supersonic transports, and Boeing itself designed the 2707 to compete with Concorde. The actual future of air transport switched from speed to size, for two reasons: firstly, the operating economics of supersonic aircraft using 1960s technology, like Concorde, showed very high fuel burn for relatively few passengers carried. The second, less well-known reason is that all supersonic aircraft generate an objectionable environmental impact: Sonic boom.
Other forms of noise pollution can be abated by active and passive means. Engines can be muffled. Noisy equipment can be encased in sound absorbing materials. Active noise cancellation can be used to emit out-of-phase frequencies to reduce perceived noise. But none of these strategies work with supersonic aircraft, because the loud and potentially damaging shockwaves that create the “sonic boom” are generated by the motion of the airframe through the air itself, a little like the way a wake is created from the hull of a speedboat.
This has been an academic challenge for decades, and in a step towards a solution, NASA has introduced the latest in their storied series of experimental X-planes, the X-59. Rolled out by NASA in a high-profile live event similar to a major movie premiere, the X-59 was built by Lockheed Martin’s famed Skunk Works, and it is radically different from any experimental aircraft before it.
A third of the fuselage length is taken up by the aircraft’s nose, and the pilot sits in a cockpit with no windshield in the conventional sense of the word. The aircraft is shaped like none other in the world, for a reason: the airframe is optimized to manage shockwaves, with the goal to reduce the sonic boom to a mild, 75 dB “thump” heard by a ground-based listener. That’s significantly less than the window-rattling 105-plus dB sonic boom levels of Concorde.
That long nose results in an aircraft that is 100 feet long, despite its slender 30-foot wingspan, creating the classic problem for builders of supersonic aircraft: pilot visibility in low-speed flight, particularly during approach and landing.
Even if a conventional cockpit windshield was possible aerodynamically, 30 feet of nose would require a near zero angle of attack during approach and landing, which would have necessitated heavy and complex devices to enhance low-speed lift. There are technologies available to achieve this, such as the tilting wing device on the F8 Crusader jet fighter, but NASA has come up with a simpler solution: eliminate the windshield.
The pilot will use a NASA developed external vision system with a 4K forward facing camera, combined with a Collins-supplied multispectral imaging system under the nose for landing. Enhanced forward vision using multispectral devices already gives pilots better situational awareness in landing, particularly in bad weather, and has been offered commercially since 2001 with Gulfstream.
Periscope-based systems were tested in the 1950s as part of the Republic XF-103 interceptor program, and no serious problems were reported with flying aircraft this way, and NASA expects the pilots to have no problem with the X-59 either.
Why does sonic boom matter? It resulted in regulations prohibiting supersonic flight over populated areas by airframes like the Concorde, severely limiting their total addressable market in airline service. Today’s technology addresses the fuel burn problem of supersonic airliners with efficient engines that allow super cruise, flight above Mach 1 without afterburners, but the sonic boom issue must be resolved to make a market case for mass production of supersonic airliners.
If the X-59 works as advertised, expect that long, long nose to be the look of high-performance airliners in the future.
