Douglas D-558-II Skyrocket
The Douglas D-558-II Skyrocket was a swept-wing research aircraft built by the Douglas Aircraft Company for the U.S. Navy and flown in a joint program by the NACA, the Navy-Marine Corps and Douglas from 1948 to 1956. Three aircraft were built, flying in jet, jet-and-rocket and all-rocket configurations. On 20 November 1953 the second Skyrocket, dropped from a Navy bomber and flown by Scott Crossfield, became the first aircraft to reach Mach 2. The program's data on swept-wing behavior and pitch-up informed the design of later fighters, and all three Skyrockets survive.
Why It Mattered
The Douglas D-558-II Skyrocket was one of the small group of research airplanes built just after the Second World War to explore flight at transonic and supersonic speeds. On 20 November 1953, the second Skyrocket, in all-rocket form and flown by NACA pilot Scott Crossfield, became the first aircraft to fly at twice the speed of sound, reaching Mach 2.005 in a shallow dive. The three Skyrockets were flown from 1948 to 1956 in a joint program of the National Advisory Committee for Aeronautics (NACA), the Navy-Marine Corps and the Douglas Aircraft Company. The data they returned on swept wings — on pitch-up, on wing and tail loads, and on stability and control — contributed to solutions to the pitch-up problem and aided the design of the century-series fighters that followed.
Design Notes
The Skyrocket was phase two of a three-phase program Douglas built for the Navy: phase one was the straight-wing, turbojet-only D-558-I, and a third phase, a mock-up of a combat aircraft using the results, was never built. Its wing was swept at 35 degrees, a choice the NACA urged after Robert Jones's research at Langley and captured German documents pointed the same way. To push the swept-wing aircraft past Mach 1, Douglas gave it both a Westinghouse J-34 turbojet and a Reaction Motors LR-8 rocket engine, which required a new fuselage; individual Skyrockets flew in jet-only, jet-and-rocket and all-rocket forms. The horizontal stabilizer sat high on the tail, was thinner than the wing and could be moved in flight, keeping pitch control when shock waves made the elevators ineffective. Rocket flights did not take off from the ground: a Navy P2B-1S, the Navy version of the B-29, carried the Skyrocket beneath its bomb bay and released it at about 30,000 feet.
Operational History
Douglas test pilot John Martin made the first flight on 4 February 1948; the early flights used the jet engine alone and took off from the lakebed at Muroc. The three aircraft flew 313 times in all: 123 flights by the first Skyrocket, 103 by the second and 87 by the third. The second Skyrocket began its career on jet power, but in 1950 Douglas replaced the turbojet with the LR-8 rocket engine, and Douglas pilot William Bridgeman flew it to Mach 1.88 and to 79,494 feet in August 1951, the latter an unofficial world altitude record at the time. Marine Lt. Col. Marion Carl then flew the same aircraft to 83,235 feet on 21 August 1953, a record in its day. For the attempt on Mach 2, NACA technicians fitted nozzle extensions to the rocket engine, chilled the fuel and waxed the fuselage; on 20 November 1953 Crossfield climbed to about 72,000 feet, pushed over into a shallow dive and reached Mach 2.005 as he passed through 62,000 feet — the only flight in which a Skyrocket flew that fast. The third Skyrocket kept both its jet and its rocket engine, and spent much of its career on the pitch-up investigation, testing wing fences, slats and leading-edge chord extensions, and later on the effect of external stores on transonic behavior. The program ended in 1956: the third aircraft flew its final mission on 28 August, and John McKay made the last flight of all on 20 December 1956.
Afterlife
All three Skyrockets survive in museum hands. The second aircraft, NACA 144, the one Crossfield flew to Mach 2, is held by the Smithsonian's National Air and Space Museum in Washington, D.C.; the museum's own page currently lists it as not on display, either on loan or in storage. It was transferred to the Smithsonian by the U.S. Navy Bureau of Weapons. The first Skyrocket, NACA 143, is in storage at the Planes of Fame Museum in Ontario, California. The third, NACA 145, stands on display in front of Antelope Valley College in Lancaster, California.