Labels:sky OCR: MIL ESTONES X-15 DEVELOPMENT APRIL 1952 NACA INITIATES STUDIES OF SPACE FLIGHT PROBL EMS JULY 1954 NACA COMPL ETES STUDIES AND PRESENTS X-15 PROPOSAL TO AIR FORCE AND NAVY DEC 1955 NORTH AMERICAN AVIATION GIVEN "GO AHEAD" FOR THREE 15'S. OCT. 1958 ROLLOUT AND DELIVERY FLIGHT TEST STUDIFS
