X-planes: Are they needed in the new era of drones?
There's a weird and wonderful jet flying over the US. It has the nose of anteater, parts cannibalised from other planes and a cockpit so far back the pilot depends on a camera to see where he's going. The X-59's owes its eccentric design to the problem of sonic booms. The shockwave created by a jet breaking the sound barrier restricted Concorde to flights over the sea and barred it from lucrative routes across the US. Now Nasa is working around that problem using the X-59's elongated snout to flatten supersonic booms into tolerable bumps in the background. On top of its bizarre appearance the X-59 boasts a remarkable lineage. It's the latest in a series of experimental Nasa aircraft dating back to 1947 and the first plane to break the sound barrier, the Bell X-1. Peter Coen, a 43-year Nasa veteran who manages the programme, explains the thinking behind 80 years of X-planes. "Our approach is to pick small goals we aim to prove with flight data and we construct an airframe for that one task." The X-plane philosophy is to "minimise goals, the more goals you have the more expensive it gets." For the X-59 it's about suppressing sonic booms on a budget and nothing else. In the case of the X-1, flown through the sound barrier in 1947 by the legendary test pilot Chuck Yeager, Nasa knew a .50 calibre bullet travelled faster than the speed of sound. So the stumpy little aircraft was shaped like a bullet with wings added. A mere 20 years later the X-15 rocket plane, a cylinder with tiny wings dropped from a B-52 bomber, flew to 6.7 times the speed of sound (4,520 mph) and the edge of space, paving the way for heat-resistant materials vital to the Space Shuttle. Nasa is flying the X-59 in conjunction with community surveys to assess what people think when a supersonic boom is bent by the planes stretched nose and hushed up. "We want to figure out what level of boom is acceptable to people on a regular basis," says Coen, who reckons his machine will sound "like a car door being closed across the street" when it flies past Mach 1, around 660mph at airline cruising altitude. With its cockpit and ejector seat taken from a T-38 training jet, its landing gear from an F-16 fighter and engine courtesy of the F-18 this jigsaw of an aircraft was assembled by Lockheed Martin for Nasa. A camera feeding a screen in front of the pilot relies on instantaneous computer processing to get round the lack of forward vision. It first flew in 2025 and is now breaking the sound barrier over chosen US towns.