Yesterday the Air Force tested a Boeing-built hypersonic "scramjet" called the X-51a "Waverider." It worked pretty well, apparently, tearing along at 5 times the speed of sound for three and a half minutes. They hoped to hit Mach 6, but a glitch interfered. Ah, well, one must walk before one can run, I suppose.
So what? This isn't the fastest machine ever built. Rockets have been going faster than that for years. On re-entry the Space Shuttle comes down at something like Mach 40 before burning off that speed in the upper atmosphere.
Ah, but the Waverider (which, I must admit, sounds like a high-tech surfboard) isn't a rocket. It's an air-breathing supersonic ramjet. Someday its remote descendants could be true "spaceplanes," taking off from a runway, accelerating to hypersonic speeds in the air before switching on rockets to climb into orbit. Its more immediate descendants could be awesomely powerful cruise missiles, zipping past defenses too quickly to be stopped.
If the Air Force is ever strapped for money to develop this further, I suggest putting in a passenger compartment and charging a million bucks or so for a ride.