On the morning of November 20, 1953, A. Scott Crossfield became the first pilot to fly at twice the speed of sound, Mach 2. He accomplished this feat while flying the experimental air-launched rocket-propelled Douglas D-558-2 #2 Skyrocket. This sweptwing research plane attained Mach 2.005 (1,291 mph) while in a shallow dive at an altitude of 62,000 feet. Seconds afterward, the plane's XLR-8 rocket engine exhausted its fuel supply and shut down. Crossfield glided earthward to a smooth dead-stick landing on Muroc Dry Lake, at Edwards Air Force Base, California.
The D-558-2 #2 was just one of six different D558 research airplanes ordered by the U.S. Navy from the Douglas Aircraft Company for obtaining aerodynamic information at transonic and supersonic speeds. The Navy issued a letter of intent to Douglas on June 22, 1945, for construction of six Model D-558 aircraft, having straight, thin wing and tail surfaces, and turbojet propulsion. Development of the aircraft began under the direction of chief engineer Edward H. Heinemann. Subsequent analysis of captured data on wartime German sweptwing research, combined with sweptwing studies by American scientist Robert T. Jones, caused Douglas and the Navy to modify the D-558 contract by deleting three of the planned aircraft and replacing them with three sweptwing vehicles powered by both tu4bojet and rocket engines. The first three aircraft, each powered by a single General Electric TG-180 turbojet, became known as the D-558-1 Skystreak series. The last three, powered initially by a Westinghouse J-34 turbojet for low-speed flight plus a Reaction Motors, XLR-8 rocket engine for high-speed research, became known as the D558-2 Skyrocket series.
The D-558-1 and D-558-2 greatly differed from one another in detail design and there was little commonality between them. Both took off from the ground. Because of its engine type and airframe design, the D-558-1 was limited to approximately Mach 1, the speed of sound. The more powerful D558-2, using its 6,000-pound-thrust rocket engine fueled with liquid oxygen and diluted ethyl alcohol, could easily exceed Mach 1. The safety hazards of operating a heavily loaded rocket-propelled airplane from the ground later caused Douglas to modify the D-558-2 #2 and #3 for air launching from the bomb bay of a converted Boeing P2B-1S (Navy B-29) Superfortress. At the same time, Douglas modified the D-558-2 #2 to all-rocket propulsion, utilizing the space formerly taken up by its turbojet engine for additional rocket fuel. Thus modified, the D-558-2 #2 was capable of reaching Mach 2, which it did while being flown in a special high-speed flight
research program by the National Advisory Committee for Aeronautics (NACA).
The first D-558-1 Skystreak, bureau number 37970, completed its maiden flight on April 14, 1947, piloted by Eugene F. May. On August 20, 1947, Navy Cmdr. Turner F. CaIdwell set a new world air-speed record of 640.663 mph while flying the D-558-1 #1. Five days later, on August 20,. 1947, Marine Corps Maj. Marion Carl, while flying the second D-558-1, bureau number 37971 (NACA 141), broke CaIdwells record by reaching 650.796 mph. The NACA utilized the third D-558-1, bureau number 37972 (NACA 142), for extensive investigations of transonic aerodynamic phenomena and aircraft behavior, retiring this Skystreak in 1953. The D-558-1 #1 did exceed Mach 1 on September 29, 1948, while piloted by Eugene F. May and flown in a 35-degree dive. One Skystreak, the D-558-1 #2, crashed on May 3, 1948 during a takeoff accident following engine failure, killing Howard C. Lilly, a NACA research pilot.
The first D-558-2 Skyrocket, bureau number 37973 (NACA 143), completed its initial flight on February 4,1948, piloted by John F. Martin. The second Skyrocket, bureau number 37974 (NACA 144), went to the NACA, which used it to investigate the behavior characteristics of sweptwings. During this program, before its conversion to all-rocket propulsion, the D-558-2 #2 revealed the tendency of sweptwing aircraft to pitch up under certain aerodynamic conditions. After modification in 1950 to all-rocket configuration, the D-558-2 #2 attained Mach 1 .88 and an unofficial altitude record of 79,494 feet. while flown by Douglas test pilot William B. Bridgeman. Following delivery to the NACA, this Skyrocket extended its unofficial record altitude to 83,235 feet, while flown by Marine test pilot Marion Carl on August 21, 1953. Shortly afterward, NACA research pilot A. Scott Crossfield exceeded Mach 2 in the plane. The NACA utilized the third D-558-2, bureau number 37975 (NACA 145), in a program evaluating the effectiveness of wing slats and leading edge devices, and examined its behavior with external stores mounted beneath its wings. All three Skyrockets were retired from flight operations in 1956. At one point, Douglas considered developing a D-558-3 hypersonic research aircraft, upon request of the Office of Naval Research, but this aircraft remained a paper study.
The D-558-1 and D-558-2 were of mixed aluminum and magnesium construction. Both types featured jettisonable nose sections to serve as emergency escape capsules and both were designed to carry heavy instrumentation payloads for flight research purposes. The first two D-558-1 Skystreaks were bright glossy red overall, but the D-558-1 #3 and later D-558-2 Skyrockets were glossy white, which proved more desirable for optical tracking purposes. The historic Douglas D558-2 #2, NACA 144, the first Mach 2 airplane, is in the collection of the National Air and Space Museum.
