A Terrifying Sight
On June 8, 1959, test pilot Scott Crossfield climbed into a North American X-15 for its first, unpowered flight. It turned out to be an intense ride to the dry lake bed at Edwards Air Force Base:
...he pulled the nose up to slow his descent. The nose came up too far, and he had to push it back down -- and now he knew, and watchers on the ground knew, that the airplane had entered a divergent oscillation, galloping along a sine wave that increased in amplitude as Crossfield descended. Another X-15 pilot, Milt Thompson, later wrote that it was "a terrifying sight." Crossfield couldn't stop it, but he managed to get the landing skid on the ground at the bottom of a cycle, saving the airplane and possibly his own life. The problem turned out to be due to a poorly adjusted pitch damper; it was easily corrected.
The image above shows an X-15 in a 1965 flight, being carried aloft by a B-52 and very nearly at 45,000 feet, at which the rocket-powered plane would blast off. Read more about the X-15 and its test pilots -- some of whom earned astronaut wings -- here.
Photo: NASA Dryden Flight Research Center Collection