The Saturn I was the first operational rocket from the Apollo program and was designed for launching heavy payloads. It was the first rocket to use staging, which is where multiple rocket engines are used in sequence to increase thrust. The Saturn I also had the largest diameter of any launch vehicle at 10 feet (3 meters). The first stage of the Saturn I consisted of eight Rocketdyne S-1C engines burning liquid oxygen and kerosene. The second stage had a single Rocketdyne S-IV engine burning liquid hydrogen and liquid oxygen. There were a total of three stages on the Saturn I.
The Saturn I was launched a total of 13 times between October 1961 and July 1965. It was used to test various aspects of the Apollo program including launch abort systems, heat shields, and navigation systems. The last launch of a Saturn I occurred on May 26, 1967 when it launched an uncrewed Apollo spacecraft into orbit around the Moon. This mission, known as AS-202, was designed to test the Apollo Command Module’s reentry capabilities.