NASA’s silent supersonic aircraft test program, previously known as the Low-Boom Flight Demonstration mission, has progressed to the point that it has been awarded a coveted X-number by the U.S. Air Force. The X-59 QueSST name and number was bestowed on the $247.5 million Lockheed Martin Aeronautics project, which aims to build an aircraft that can fly over cities at supersonic speeds while suppressing the resulting sonic boom to little more than a “sonic thump.” 

That has been a goal of aircraft engineers since the 1960s when researchers first attempted to modify the noses of fighter jets to diminish the boom heard when the aircraft broke the sound barrier. Current regulations in the U.S. ban supersonic flight over land due to the noise.

The resulting X-59 aircraft is expected to take to the sky in 2023, and the test flight results will be presented to U.S. and international authorities to aid in crafting noise regulations for overland operations of future commercial civil aircraft.

The X-program began in 1947 with the rocket-powered X-1, in which pilot Chuck Yeager became the first person to fly faster than the speed of sound.