The X-15 is the only vehicle so far that has been flown by a pilot (rather than a computer) into space and back, routinely surviving re-entry temperatures. The X-15 was also the fastest airplane ever built, over twice as fast as the SR-71 Blackbird! It was also the highest-flying aircraft ever to take to the skies, in it five Air Force pilots became astronauts taking the X-15 into near-space. Nineteen years before the Space Shuttle, the small, black, rocket-powered, bullet-shaped X-15 showed it was possible to fly into and out of space. There had never been anything like the X-15; it had a million-horsepower engine and could fly twice as fast as a rifle bullet. The X-15 set records that stood for years. Hypersonic is the most extensively researched history of the X-15 programme yet produced. Written with the co-operation of surviving X-15 pilots as well as many other programme principals it is based on six years of research in Air Force, NASA, and North American archives. The book describes the flight programme in detail,. This includes the most authoritative flight log ever assembled; derived from the original flight data recordings.
The book also describes each of the experiments that were flown aboard the X-15 late in its career when it became the workhorse of the space programme, carrying such things as startrackers destined for the Apollo programme and missile detection systems that would later be sent into orbit on satellites.