In At the Edge of Space, Milton O. Thompson, a pilot active in the X-15 program from beginning to end, tells the dramatic story of one of the most successful research aircraft ever flown. Initiated in the 1950s by the National Advisory Committee for Aeronautics (later NASA), the U.S. Air Force, and the Navy, the X-15 program tested the survivability of rocket-powered aircraft at hypersonic speeds and at the outermost limits of the earth`s atmosphere. Nine phases of the program tested engine capabilities, altitude and speed capacity, and pilot ability, as well as experiments unrelated to the aircraft itself. Achieving hypersonic speeds, the X-15 aircraft also yielded design and materials data integral to the subsequent Apollo and space shuttle missions. The first full-length account of the X-15 program, At the Edge of Space profiles the twelve test pilots (Neil Armstrong, Joe Engle, Scott Crossfield, and the author among them) chosen for the program. Thompson has translated a highly technical subject into readable accounts of each pilot`s participation, including many heroic and humorous anecdotes and highlighting the pilots` careers after the program ended in 1968.