NASA is preparing to publicly unveil an experimental aircraft designed to reach supersonic speeds without the disruptive 鈥� and sometimes destructive 鈥� sonic booms associated with current faster-than-sound aircraft. test flights of the X-59 could 鈥渂ring a return to supersonic air travel over land鈥�.
Many military aircraft are capable of breaking the sound barrier, but since the retirement of Concorde in 2003, only a small clutch of civilian craft can do the same. Some former military jets now in private hands can easily reach supersonic speeds, and can in certain circumstances.
Once an aircraft passes the speed of sound 鈥� around 343 metres per second, though the exact speed can vary with temperature and altitude 鈥� it begins to overtake the sound waves it creates. This produces a shock wave cone behind the craft that is not perceptible to people on board, but can be heard from the ground as a short, percussive boom.
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Because sonic booms startle humans and animals, and can even shatter windows and set off car alarms, pilots are forbidden from breaking the sound barrier over land. When flying at an altitude of 15,000 metres, Concorde would create a sonic boom along a 100-kilometre-wide path.
NASA is developing the X-59 as part of its Quiet Supersonic Technology (Quesst) project, which aims to investigate ways to minimise sonic booms. It plans to fly the X-59 over US cities at around 1510 kilometres per hour and an altitude of 16,800 metres to test its effect at ground level.
The space agency says those on the ground will hear a 鈥渟onic thump鈥�, rather than a sonic boom 鈥� around the same volume as a car door being slammed nearby. People living below will be surveyed about the experience and the data will be passed to the Federal Aviation Administration (FAA) to inform future legislation.
If sonic booms can be minimised, the FAA could begin to allow some aircraft to break the sound barrier over US land in order to reduce journey times, despite . Reintroducing supersonic travel could also lead to , a NASA report found in 2021.
The X-59 is relatively small, but its design is dramatically elongated in order to prevent shock waves from its nose from coalescing with those produced towards the rear of the aircraft. Its 9-metre wingspan is smaller than an F-16 fighter, but at 29 metres in length, it is almost twice as long.
The aircraft has been in development by Lockheed Martin鈥檚 secretive Skunk Works in Palmdale, California, since 2016, and was delivered to NASA for testing in 2021. Artists鈥� impressions of the X-59 have been revealed before, and an unpainted craft was seen in , but the plane is due to be publicly unveiled for the first time on 12 January.
As an experimental plane, its design borrows elements from existing aircraft where possible to keep costs and development time down. Its cockpit, ejection seat and canopy are all taken directly from the Northrop T-38 training plane also used by NASA. However, the pilot will not be able to see through the canopy because of the elongated nose, meaning they will need to rely on a video feed from a nose-mounted camera.
