Rocket-powered and shrouded in secrecy, X-planes helped pave the way for the US space programme: Now they have another mission – taking the boom out of supersonic travel. In 1947, the first clue onlookers at Muroc Army Airfield, California, had that the sound barrier had been broken was a thunder-like sound, or bomb burst. It was the ninth powered flight of the experimental Bell X-1 aircraft, and onboard the pilot wrestled the controls as the aircraft's stability fluctuated as it's speed increased .

https://www.bbc.com/future/article/20230324-how-x-planes-may-solve-the-sonic-boom-problem

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