Even before the launch of Sputnik, Wernher von Braun's team in Huntsville, Alabama, recognised the need for a heavy launch vehicle. Initially, the idea was to combine the Jupiter rocket and Redstone missile to create a two stage booster known as Juno 5.

By 1959, the design had evolved somewhat and the rocket was now called Saturn. As U.S. President John F. Kennedy had not yet called for a mission to the moon, just what exactly this rocket would be used for hadn't been determined, but, wisely, work went on anyway that gave the Apollo project a good headstart.

The first version of the Saturn I was the Block I design. Something of a frankenstein creation, the first stage used a lengthened Jupiter rocket tank surrounded by a cluster of eight lenghthened Redstone missile tanks. Eight liquid oxygen and kerosene burning H-1 engines provided thrust. The second and third stages were dummies and so the Block I could not enter orbit. This model was used to prove various Saturn technologies during four missions from October 27, 1961 to March 28, 1963. The Block I was 21.4 feet in diameter and stood 165.3 feet high.

The Block II model used a live second stage known as the S-IV (predecessor of the S-IVB stage used in manned Apollo missions). The S-IV stage used six RL-10 engines which burnt liquid oxygen and hydrogen. Other improvements were made to the first stage, most noticeably the addition of stabilizing fins.

The first Block II flight was on January 29, 1964 and placed a third stage consisting of some navigation and guidance equipment and a lot of sand ballast into orbit. Subsequent flights carried dummy Apollo capsules or satellites.

All the Block II's flights were flawless and paved the way for the manned Apollo missions on board the Saturn IB and Saturn V. The last flight was July 30, 1965. The Block II was 164 feet high and 29.1 feet in diameter.