This NASA document provides a historic perspective of supersonic cruise technology, beginning with the early NACA supersonic research and including efforts during the B-70 and SST phase. It also records technological progress made in the NASA SCR and VCE programs. Since every research result could not be detailed here, only the most critical technology issues and research findings are presented.NASA and its predecessor, the National Advisory Committee for Aeronautics (NACA), have participated since 1920 in efforts to develop the technology required for supersonic cruise flight. Preliminary work concentrated on developing rudimentary test facilities and methods that would permit the investigation of supersonic problems. This was accompanied by research for defining aircraft and propulsion concepts for flight at speeds greater than the speed of sound. These early investigations contributed to the development of the joint U.S. Air Force/Navy/Bell XS-1 airplane that was piloted on the first successful supersonic flight by Air Force Capt. Charles E. "Chuck" Yeager in 1947. Between 1956 and 1971, a strong research effort supported the USAF supersonic B-70 and commercial supersonic transport concepts. After neither of these programs resulted in a production aircraft because of technical and political problems, NASA was given the responsibility of establishing the technology base for a viable supersonic cruise airplane. This latter effort, known as the NASA Supersonic Cruise Research (SCR) program, was conducted from 1971 to 1981. The NASA Variable Cycle Engine (VCE) program, a propulsion offshoot of SCR, was conducted from 1976 to 1981.1 Introduction * 2 Setting The Stage For Supersonic Cruise Technology * The Sound Barrier * The First Supersonic Cruise Aircraft * The Next Logical Step * After the U.S. Supersonic Transport Program * 3 NACA Preliminary Supersonic Cruise Technology (?-1956) * Mounting an Attack on the Sound Barrier * Breaking the Sound Barrier * 4 NACA/NASA