By Jan Tegler
January 1, 2021
One of the great remaining accomplishments of flight would be creating an operational aircraft that can fly hypersonically, defined as Mach 5 or above, by gleaning oxygen for combustion from the air, just as conventional jets do. The U.S. has tested air-breathing hypersonic engines but not of the size required for aircraft that would carry passengers, weapons or intelligence equipment. Jan Tegler looks at the challenges of scaling up.