The bird finally has wings!
By bird, I mean that lawn-dart of a rocket plane, NASA's X-15. Until yesterday, that sleek black vehicle, designed to probe the edges of space from underneath, had been a work in progress. The X-15 had already flown 25 times, zooming at faster than Mach 3 and climbing to a height of 40 kilometers. But its engines, a pair of Reaction Motors XLR11s, were an old set of training wheels: virtually the same rockets that pushed Chuck Yeager's X-1 past the sound barrier in 1947.
Together, these engines gave the plane a thrust of 32,000 lbf (pounds of force--or the force of Earth's gravity on one pound of matter). That's nothing to sneeze at, but it was always an interim solution. Yesterday, veteran test-pilot Scott Crossfield took the X-15 for a spin with the engine it was always meant to have: the Reaction Motors XLR99.
(find out how the flight went at Galactic Journey!)