I was interested to hear about NASA's unveiling on Friday of its experimental supersonic aircraft – the X-59. The aircraft has been in development for several years now, but last week a shiny new flight test model was revealed to a packed auditorium at a facility in California.
From its very beginnings in 2013 the X-59 was never designed to take passengers. Instead, it was intended to "pave the runway" for future supersonic passenger aircraft by showing that supersonic travel is possible without the very loud sonic booms suffered in the past. NASA is aiming to use the aircraft to gather data from communities to gauge whether the noise levels are acceptable and, NASA hopes, help lift the restrictions on supersonic commercial flights over land.
The X-59 is exciting because its developers Lockheed-Martin and NASA claim it should be able to reduce the sonic booms normally associated with supersonic air travel to a gentle thump – the equivalent of a car door being closed. Supersonic air travel over land has been banned by many countries including the US since the 1970s because of the excessive noise produced by the booms.
Concorde, the last commercial supersonic airliner, was retired in 2003 after more than 27 years in service. I remember fondly seeing its final flight over Bristol while at university there. By way of comparison, Concorde had a cruising speed of about Mach 2, whereas the X-59 is expected to fly at about Mach 1.4.
The X-59 includes a number of innovations that are designed to separate and "reshape" the shock waves occurring during flight, and so give the predicted noise reduction. These include: the very long and slender nose shape; its above-wing engine mounting; its smooth underside; and its lack of forward-facing cockpit window (high-resolution cameras and a 4K monitor will provide the pilot with the information needed).
The great advantage these aircraft designers have over Concorde's designers in the 1950s/60s and even more recent ones is that so much of the design (including the shockwave behaviour modelling) has been carried out on computer. In contrast to traditional aircraft design using wind tunnels, Lockheed claim to have developed code that allows them to generate the best shape of aircraft for the required boom level. They say they can actually control and virtually predict loudness of the boom. This capability was important to them winning the contract from NASA in the first place, and will be a powerful IP right that they will no doubt have protected with patents or other rights.
I look forward to seeing how the X-59 tests pan out, and whether in due course the decades-old restrictions on supersonic travel will be lifted.
"NASA will share the data and technology we generate from this one-of-a-kind mission with regulators and with industry. By demonstrating the possibility of quiet commercial supersonic travel over land, we seek to open new commercial markets for U.S. companies and benefit travellers around the world."
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