Turning sonic booms into combustion addresses a key, "fatal" flaw in scramjet designs.

A Chinese-made "sodramjet" engine has reached nine times the speed of sound in a wind tunnel test. The engine could power an aircraft to reach anywhere in the world within two hours, the makers say.

Scientists say the sodramjet (short for “standing oblique detonation ramjet engine”) could be the first real hope for hypersonic flight—many times the speed of sound, and something that would bring both global travel and space travel much closer to home.

"With reusable trans-atmospheric planes, we can take off horizontally from an airport runway, accelerate into orbit around the Earth, then reenter into the atmosphere, and finally land at an airport," the scientists, from the Chinese Academy of Sciences’ Institute of Mechanics, write in a new study published in the Chinese Journal of Aeronautics. "In this way, space access will become reliable, routine and affordable."

The idea is a decades-old theoretical variation on a scramjet, itself a variation on the ramjet, building on generations of work on high-speed flight.

Many commercial aircraft today have turbofans or, for smaller jets, turboprops. These have descended from the idea of the turbojet, and on the family tree of jet propulsion, the turbojet and ramjet are something like cousins.

The same way that, say, researchers continue to work on stellarators along with tokamaks and salt-cooled along with lightwater reactors, research on the lower profile idea of the ramjet has continued since the interwar period. Because of their design, turbojets, turbofans, and turboprops work better in the zone we’ve decided is right for passenger flight. For the most part, that’s subsonic flight within Earth’s atmosphere.

The sodramjet is the latest bleeding edge of a completely different use case. The ramjet led to the scramjet, which was designed to go as much as 15 times the speed of sound. Like the fastest combustion and even rocket cars, the secret is in dropping a great deal of weight from the craft—the scramjet scoops up oxygen from the air instead of in condensed form from a tank.

But that means a more fragile cycle of combustion that, it turns out, can be woofed out by the very sonic boom the engine creates. The scramjet just never reached its full potential.