Engineering news
Jock Lowe, who flew the iconic aircraft for British Airways, made the comments to Professional Engineering after the US space agency awarded Lockheed Martin a $247.5m contract to build a new experimental “X-plane”.
The agency hopes the X-plane’s sharp design will send shockwaves away from the aircraft, rather than coalescing at the nose and tail and creating two “distinct and thunderous” booms.
Instead, bosses say the craft’s profile will result in the much weaker shockwaves reaching the ground still separated, sounding like “a quick series of soft thumps… if anyone standing outside notices them at all.”
The project, known as the Low-Boom Flight Demonstrator, could run test flights over a handful of US cities between 2022-25 to gauge public acceptance before the Federal Aviation Administration and International Civil Aviation Organisation develop new regulations.
However, Lowe raised doubts over widespread support even if the X-plane’s design partially reduces the noise impact at ground level. The pilot, who said Concorde was “always a joy to fly” despite facing four times as many system failures as other commercial planes, said he often had to change routes because of noise concerns caused by ‘secondary booms’, shockwaves which bounce back to the ground after reflecting from the upper atmosphere.
“We had to change our flight plan in winter coming into London and in summer coming into New York, because that secondary boom was still not acceptable – it was equivalent to slamming a car door at 50 yards away on a quiet night,” said Lowe. “In the end, just too many people complained about it.”
The former pilot said he was unconvinced that the X-plane’s primary sonic booms will be quieter than Concorde’s troublesome secondary booms.
Despite Lowe’s concern, NASA said its confidence in the X-plane’s design was “buoyed” by recent research using wind tunnel testing, advanced computer simulations and flight testing.
The plane’s configuration will be based on a preliminary design by Lockheed Martin, published last year. The proposed aircraft is 29m long with a wingspan of 9m, and a fully-fuelled weight of almost 15,000kg.
At a cruising altitude of 16.7km, the X-plane could fly at Mach 1.42, or 1,753km/h. NASA said its top speed will be Mach 1.5. A single General Electric F414 engine, used by F18 fighters, will power the craft.
“Supersonic commercial travel is on the horizon,” Lockheed Martin wrote on Twitter. “We’re thrilled to continue working with @NASAaero to make supersonic commercial travel a reality!”
Another flight project involving Lockheed Martin, Aerion Supersonic, could stand the best chance of efficient travel at above Mach 1, Lowe claimed. The concept uses thin wings and a horizontal stabiliser rather than the delta wing shape of the X-plane and Concorde. The design could reduce friction over the wing by 70%, reducing overall drag by 20%.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.