US rocket, originally designed and built in 1946 as an intercontinental missile for the US Air Force but subsequently adapted for space use.

The rocket used a ‘balloon tank’ construction with thin stainless steel sections that had to be pressurized by helium gas when not fuelled, to prevent their collapse. Atlas rockets, using a liquid oxygen fuel, launched US astronauts into orbit during the Mercury project (1961–3).

Upper stages added at a later date created the Atlas–Agena and Atlas–Centaur rockets. The addition of an Agena rocket as the upper stage on an Atlas rocket was used by the US Air Force to launch spy satellites. The Atlas–Agena rocket launched the Mariner spacecraft, and in 1965 and 1966 the Atlas rocket placed the Agena rocket in orbit as a docking target for Gemini spacecraft.

The addition of a Centaur rocket to the Atlas rocket created a more powerful launch vehicle, which could lift 4 670 kg. The combination sent the Surveyor spacecraft to the Moon and was also often used by the US Air Force, forming the basis of a commercial Atlas fleet.