Mach 5 hypersonic engines will revolutionize air travel

It utilizes a combined jet engine and ram jet engine design. As explained, a conventional jet engine cannot go at such speeds because the air gets too hot for the engine to handle. To get around that problem, there will be a precooler that will cool down the incoming air so that the conventional engine can get up to mach 3, which is the speed that ramjets require in order to run efficiently.

By the way, the Skylon SSTO concept uses a precooler as well. But it is a rocket engine that is also breathable, meaning that it doesn't need as much oxidizer as a conventional rocket engine. I'm wondering if an SSTO could be built using this design as well. The complexity would be too great to combine them all, so perhaps the breathable engines could give way to rocket engines after Mach 5.

But these are intended for military applications first. In perhaps a decade, there will be a passenger craft version available.   More info here.     And here...