Quiet Supersonic - NASA Chases Fleeting Booms

One way to get to a quiet supersonic transport sooner rather than later would be to design an aircraft flies at a combination of speed and altitude at which its shockwaves do not reach the ground because of atmospheric refraction. That speed is around Mach 1.2 and, with the absence of  a sonic boom allowing supersonic flights over land, would be usefully faster than today’s fastest civil aircraft...