EDWARDS AIR FORCE BASE, Calif -- Joseph A. Walker flew North American X-15 No. 3 serial number 55-6672 – destroyed during flight test No. 191 when X-15 entered a hypersonic spin while descending with Maj Michael Adams at the controls on 15 November 1967, to records of 347,800 feet (66.3 miles) and 3,710-miles per hour.
Joseph Albert Walker was an American World War II pilot, experimental physicist, National Aeronautics and Space Administration (NASA) test pilot, and astronaut. He was one of 12 pilots who flew the North American X-15, an experimental spaceplane jointly operated by the Air Force and NASA. In 1963 ,Walker made three flights above 50 miles, thereby qualifying as an astronaut according to the United States definition of the boundary of space. The latter two, X-15 Flights 90 and 91, also surpassed the Kármán line, the internationally accepted boundary of 62.14 miles. Making the latter flights immediately after the completion of the Mercury and Vostok programs, Walker became the first person to fly to space twice. He was the only X-15 pilot to fly above 62.14 miles during the program.
Michael James Adams was an American aviator, aeronautical engineer, and astronaut. On November 15, 1967, Adams flew X-15 Flight 191 aboard the X-15-3, one of three planes in the X-15 fleet. Flying to an altitude above 50 miles, Adams qualified as an astronaut according to the United States definition of the boundary of space. Moments later the craft broke apart, killing Adams and destroying the X-15-3. He was the first American space mission fatality by the American convention.