D-558-II Skyrocket

D-558-2 #2 - Bureau No. 37974 NACA-144, 103 flights ca. 1950

The Douglas D-558-II "Skyrockets" were among the early transonic research airplanes like the X-1, X-4, X-5, and X-92A. Three of the single-seat, swept-wing aircraft flew from 1948 to 1956 in a joint program involving the National Advisory Committee for Aeronautics (NACA), with its flight research done at the NACA's Muroc Flight Test Unit in California. The Skyrocket made aviation history when it became the first airplane to fly twice the speed of sound.

The II in the aircraft's designation referred to the fact that the Skyrocket was the phase-two version of what had originally been conceived as a three-phase program, with the phase-one aircraft having straight wings. The third phase, which never came to fruition, would have involved constructing a mock-up of a combat-type aircraft embodying the results from the testing of the phase one and two aircraft.

The D-558 series of aircraft was developed by Douglas under the direction of Edward H. Heinemann for the U.S. Navy to explore transonic and supersonic flight. It was the first aircraft to fly Mach 2 with NACA pilot Scott Crossfield on 20 November 1953. It is on display at the National Air and Space Museum in Washington D.C. NACA 144 was powered by an LR-8-RM-6 rocket engine rated at 6,000 pounds-force (27 kN) static thrust. Its propellants were 345 US gallons (1,310 L) of liquid oxygen and 378 US gallons (1,430 L) of diluted ethyl alcohol. In its launch configuration, it weighed 15,787 lb (7,161 kg). The National Advisory Committee for Aeronautics (NACA, the predecessor to NASA), used this Skyrocket, the second one built, to explore the flight characteristics of swept-wing aircraft. It set several other speed and altitude records before the program ended in 1956.