The Saturn I (pronounced "Saturn one") was a rocket designed as the United States' first medium-lift launch vehicle for low Earth orbit payloads. The rocket's first stage was built as a cluster of propellant tanks engineered from older rocket tank designs. Its development was taken over from the Advanced Research Projects Agency in 1958 by the newly-formed civilian NASA. Its design proved sound and flexible. It was successful in initiating the development of liquid hydrogen-fueled rocket propulsion, launching the Pegasus satellites, and flight verification of the Apollo command and service module launch phase aerodynamics.