The X-1's were joined in the quest to expand the high-speed and stratospheric frontiers by the Navy-National Advisory Committee for Aeronautics (NACA)- Douglas D-558-II Skyrocket. The Douglas D-558-2 "Skyrockets" were among the early transonic research airplanes like the X-1, X-4, X-5, and X-92A. The mission of the D-558 II program was to investigate the flight characteristics of a swept-wing aircraft at high supersonic speeds. Particular attention was given to the problem of "pitch-up," a phenomena often encountered with swept-wing configured aircraft. The Skyrocket made aviation history when it became the first airplane to fly twice the speed of sound.
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 CA, redesignated in 1949 the High-Speed Flight Research Station (HSFRS). Also partners in the flight research were the Navy-Marine Corps and the Douglas Aircraft Co. The HSFRS became the High-Speed Flight Station in 1954 and is now known as the NASA Dryden Flight Research Center.
Shortly after the D-558 I Skystreak research project was started, the contract was modified to include investigation of sweptback wings in addition to the straight wings of the Skystreak. In August of 1945, the decision was reached to split the program into a Phase 1 that was a straight-wing aircraft and a Phase 2 that was a swept-wing airplane. The redesigned aircraft was named D-558 II Skyrocket. 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.
Three D-558 II "Skyrockets" were built by Douglas Aircraft. The three airplanes flew a total of 313 times--123 by the number one aircraft (Bureau No. 37973--NACA 143), 103 by the second Skyrocket (Bureau No. 37974--NACA 144), and 87 by airplane number three (Bureau No. 37975--NACA 145). Skyrocket 143 flew all but one of its missions as part of the Douglas contractor program to test the airplane’s performance.