Chuck Yeager first broke the sound barrier in his rocket-powered X-1 in 1947, so it's staggering to think that just 23 years later, we stood poised to take our leisure travel supersonic as well.

Fans cooling the transmitter wailed with a sound like a high-powered leaf blower — and the thermometer inside the tube began to climb.

All he heard was the sound of the one engine that powered his plane. Hour after hour the same sound.