The X-59 supersonic aircraft is under construction

Lockheed Martin’s Skunk Works division is already building the machine, which will produce a low bang instead of a sonic boom: it is expected to be little louder than the noise of a vacuum cleaner.

The history of Lockheed Martin’s Skunk Works division dates back to the 1940s, when representatives of the United States Army approached Lockheed with an important request: they wanted America’s first fighter jet built as soon as possible, so they would no longer have to fear the Messerschmitt Me 262 fighter jet, the supercopter under development by the Germans. Kelly Johnson quickly assembled a small team and got to work, even though the official contract had not yet been signed and in 143 days the XP-80, the first prototype of what would go down in history as the P-80 Shooting Star, was born.

The name Skunk Works was inspired by a top-secret workplace and a popular comic book: one of the engineers was a big fan of Li’l Abner, which featured a mysterious factory called Skonk Works, where workers brewed drinks from all sorts of questionable ingredients, and the name, initially used as a joke, eventually stuck. And Skunk Works is now the name of another revolutionary and eagerly awaited technological innovation, the X-59 QueSTT supersonic aircraft, which could be the first aircraft capable of speeds above the speed of sound without sonic booms.

Other companies are working on developing silent supersonic machines, but there are relatively few who are trying to develop the technology and even fewer who are getting anywhere with it. Aerion Supersonic, which was to have experimented with Boomless Cruise technology on the AS2, pulled the plug in May: for financial reasons they stopped further work, and General Electric also stopped development of the Affinity gas turbine jet engine that would have powered the vehicle.

Spike Aerospace is still in the race to build quiet supersonic jets in the US, and the company has already presented its visual designs for the future S-512, but so far they have not yet reached the prototype stage, although, according to news in March, they plan to fly the first flight in 2022. Spike’s plane is smaller and greener than its competitors’ models, and the 18-seater, which will have displays instead of windows in the cabin, will be powered by a hybrid, then liquid hydrogen, propulsion system.

But the company that is actually building a prototype in the workshop and is the most advanced of the companies is Skunk Works, who are working with NASA to build the X-59, so the model is already starting to take the shape of a real aircraft, according to NASA.

David Richardson, Lockheed Martin’s programme director, said the assembly process is similar to that of a lego, as the parts are placed together using pre-drilled holes, which significantly reduces assembly time. More details about the structure were revealed, including things that were already known, such as the fact that in the cockpit the pilot will not look out over the landscape through the windscreen, but through a monitor. The shape of the plane is too narrow and too long for a conventional cockpit, so cameras above and below the 9-metre nose section will provide a view of the outside world. The wings, also just under 9 metres long, contain the fuel and most of the control system, while the tail section houses the GE F414 engine, which is located in the upper section of the structure.

The design of the structure: the particularly long fuselage of 30 metres, the positioning of the engine similar to that used in fighter aircraft, the special wings, all serve a single purpose: to eliminate the sonic boom so that the quiet plane can be licensed to fly over populated areas.

This is the drawback of supersonic aircraft and the bottleneck of faster-than-sonic-speed air travel: the sonic boom that is generated when the speed of sound is exceeded and reaches ground level is so disturbing to the inhabitants and all living creatures in the vicinity of its path that it is only allowed to fly outside populated areas, over oceans and seas, except for testing. This allows only extremely limited operations, as it means that large parts of cities cannot be served by the planes, and their superpower, which could provide much faster travel than at present, cannot be fully exploited.

Supersonic flight without sonic booms is possible because the sound waves that normally condense along the long structure after the speed of sound has been exceeded, which produce the shock waves and the accompanying loud noise when they reach the ground, remain separated and cannot combine to form the powerful shock wave that causes the explosion.

According to Lockheed Martin, the noise generated would be little louder than the sound of a vacuum cleaner, and would be equivalent to about 75 decibels (PLdB, or decibel level). Levels above 85 decibels, which are considered to be damaging to the ear and harmful to health after prolonged exposure, are usually set by experts, so the X-59 will not cause any problems for the general public, but this will need to be tested before it can be proven, and this should be sometime next year.