Atlas-Vega consisted of an Atlas booster with a storable propellant upper stage. It was planned by NASA at its inception for deep space and planetary missions before the Atlas Centaur was available. Work had already begun when NASA discovered that the CIA and the US Air Force had an essentially identical launch vehicle (Atlas-Hustler, later called Atlas-Agena) in development for the highly classified Corona reconnaisance satellite program. Atlas-Vega was accordingly cancelled.
After consultation and discussion with DOD, NASA formulated a national space vehicle program. The central idea of the program was that a single launch vehicle should be developed for use in each series of future space missions. The launch vehicle would thus achieve a high degree of reliability, while the guidance and payload could be varied according to purpose of the mission. Four general-purpose launch vehicles were described: Vega, Centaur, Saturn, and Nova. The Nova booster stage would be powered by a cluster of four F-1 engines, the second stage by a single F-1, and the third stage would be the size of an intercontinental ballistic missile but would use liquid hydrogen as a fuel. This launch vehicle would be the first in a series that could transport a man to the lunar surface and return him safely to earth in a direct ascent mission. Four additional stages would be required in such a mission.
NASA issues plan for development in next decade of Vega (later cancelled as too similar to Agena), Centaur, Saturn, and Nova launch vehicles. Juno V renamed Saturn I.