Vid The aircraft NASA hopes will usher in a new generation of transport that’s supersonic but also relatively quiet has fired up its engines for the first time as a test.
The X-59 Quiet Supersonic Technology (Quesst) airplane has been designed to generate what the agency refers to as a shaped sonic boom, or “sonic thump” [PDF] – rather than the sonic booms that have caused civilian supersonic flight over land to be banned in the US and most other countries. The X-59 is supposed to generate a brief burst of noise at 75 perceived loudness decibels (PLdB), compared to over 100 decibels generated by Concorde and military aircraft.
The noise level is described in NASA’s testing as comparable to a car door being slammed on the other side of the street, or the sound of distant thunder.
“The first phase of the engine tests was really a warmup to make sure that everything looked good prior to running the engine,” explained Jay Brandon, NASA’s X-59 chief engineer, this week.
“Then we moved to the actual first engine start. That took the engine out of the preservation mode that it had been in since installation on the aircraft. It was the first check to see that it was operating properly and that all the systems it impacted – hydraulics, electrical system, environmental control systems, etc. – seemed to be working.”
The aircraft – shown in the video below, and unveiled in January at Lockheed Martin Skunk Works in Palmdale, California – is designed to cruise at about Mach 1.4 (1,070 miles or 1,700 km per hour) at 55,000 feet (16.7 km). The high altitude will reduce the sound generated by going supersonic.
It uses a modified F414-GE-100 engine, similar to that in the F-18 Super Hornet, built on top of the plane to reduce ground noise, and rests on landing gear taken from an F-16 fighter. The rest of the airframe is custom made – a very odd design that doesn’t even allow the pilot a forward-facing windshield.
In order to minimize the sound generated by going supersonic, the nose of the aircraft stretches almost a third of the 99.7 foot (30 metre) length of the craft. This means the nose is too long for the pilot to see the ground, so external cameras – which NASA has dubbed the “eXternal Vision System” – provide a view for the enclosed operator.
Who are you calling big nose? … The X-59. Source: NASA
As you can imagine, this design poses considerable barriers to the X-59 design ever being scaled up to the size of a passenger jet. But it could provide ideas for startups seeking to get into supersonic aircraft, and have applications for military jets as well. One of NASA’s goals with the X-59 is to establish a standard for acceptable noise levels for supersonic flight over land, so that such travel might one day be viable.
The ban on supersonic flight over populated areas limited Concorde to relatively few inter-continental routes over water, which severely impacted its commercial potential.
Once the engine testing is done, NASA will try taxiing tests, then subsonic flight, before zooming up to Mach 1.4. Once that has been accomplished, the aircraft will be flown over six US communities to see how the sound is perceived in different geographical conditions. Local residents will be polled on the levels of noise.
“The success of these runs will be the start of the culmination of the last eight years of my career,” declared Paul Dees, NASA’s deputy propulsion lead for the X-59.
“This isn’t the end of the excitement, but a small stepping stone to the beginning. It’s like the first note of a symphony, where years of teamwork behind the scenes are now being put to the test to prove our efforts have been effective, and the notes will continue to play a harmonious song to flight.” ®
