Saturn A-1, studied in 1959, was projected to be the first version of Saturn I and was to be used if necessary before the S-IV liquid hydrogen second stage became available.

[1] It was designed as a three stage vehicle.

The S-I first stage (initially proposed for the Juno V rocket and eventually used on Saturn I) would propel the Saturn A-1 into space, continuing the flight with a Titan I[2]: 3–6  missile based second stage.

Finally a Centaur[2]: 3–6  C high-energy double-engine third stage could send a payload into its final Earth orbit or to other planets.

The Saturn A-1 never flew, but all proposed stages were used on different launch vehicles.