The race to build a working and dependable scramjet is happening all the world over — the United States, China, Australia and who knows who else all want one. DARPA's HTV-3X, also known as Blackswift, is an unmanned scramjet-powered plane that may take to the skies as soon as 2012, hitting speeds of up to Mach 6. Why the rush? Planes flying with scramjet engines would be able to fly from New York to Tokyo in two hours. Certainly more enticing to the nations of the world, a missile using a scramjet would be able to hit any target anywhere on the globe in a handful of minutes.
The fastest jet at the moment is the SR-71 Blackbird, which tops out at Mach 3.3. Scramjet engines have been tested at speeds of anywhere between Mach 6 and Mach 15. This amount of crazy acceleration is possible by sucking in air through the front of the engine, squeezing it into the thin sleeves of the combustion chambers until it superheats and subsequently igniting the fuel and generating thrust.