The X-15 rocket plane flew at Mach 6.72 and at altitudes above 67 miles -- at the threshold of space! The men who flew this amazing plane became the USAF's first astronauts. Powered by an XLR-99 engine capable of producing 70,000 pounds of thrust at peak altitude, the X-15 pushed the envelope for manned aircraft past the post office. Notably, both Apollo commander Neil Armstrong and Space Shuttle commander Joe Engle piloted the X-15. Originally highly restricted, the manual was recently declassified and is here reprinted in book form. This affordable black and white facsimile has been reformatted. Due to the historic nature of this text, image quality can vary. Care has been taken however to preserve the integrity of the text.