The 1959 conceptualization of the National Aeronautics and Space Administration (NASA) lunar program, codenamed Apollo, envisioned manned lunar exploration in the 1970s when NASA expected large boosters to be available. Nova was the largest of the four planned boosters, powerful enough to send a manned spacecraft directly to the moon. The second stage of the multistage Nova was to be powered by the liquid hydrogen M-1 engine. Aerojet-General Corporation began development work on the M-1 on 30 April 1962 and, after the Nova direct ascent mode was dropped in favor of lunar orbit rendezvous with the smaller Saturn booster, continued as a program to develop a post-Saturn launch vehicle. The M-1 program was canceled in August 1965 with the indefinite postponement of the vehicle program, at which time most of the major components had undergone testing, although the complete engine had not.