Developed at MSFC under the direction of Dr. Wernher von Braun, the SA-5 incorporated a Saturn I, Block II engine. Launched on January 29, 1964, SA-5 was the first two stage (Block II) Saturn with orbital capability and performed the first test of Instrument Unit and successful stage separation. Block II vehicles had two live stages, and were basically in the two-stage configuration of the Saturn I vehicle. There were marked changes between the Block I and II versions. The Block II S-I stage had eight fins added for greater aerodynamic stability in the lower atmosphere. All Block II H-1 engines had a thrust of 188,000 pounds each for a combined thrust over 1,500,000 pounds. The Block II second stage (S-IV) had six RL-10 hydrogen-oxygen engines, each producing a thrust of 15,000 pounds for a total combined thrust of 90,000 pounds. A motion picture camera capsule loated on stage I was successful recovered.

The launch of the SA-5 on January 29, 1964 was the fifth Saturn I launch vehicle. The SA-5 marked a number of firsts in the Marshall Space Flight Center-managed Saturn development program, including the first flight of Saturn I Block II vehicle with eight aerodynamic fins at the bottom of the S-I stage (first stage) for enhanced stability in flight. This also was the first flight of a live S-IV (second or upper) stage with the cluster of six liquid hydrogen-fueled RL-10 engines. the first successful second stage separation, and the first use of the Launch Complex 37.

Marshall Space Flight Center (MSFC) Director Dr. Wernher von Braun (left) with Kennedy Space Center (KSC) Rocco Petrone prior to the January 29, 1964 launch of SA-5, the first Block II configuration of the Saturn I launch vehicle. Petrone played key roles at KSC in the development of Saturn launch facilities before becoming director of launch operations in 1966.

The Saturn I (SA-3) flight lifted off from Kennedy Space Center launch Complex 34, November 16, 1962. The third launch of Saturn launch vehicles, developed at the Marshall Space Flight Center (MSFC) under the direction of Dr. Wernher von Braun, incorporated a Saturn I, Block I engine. The typical height of a Block I vehicle was approximately 163 feet. and had only one live stage. It consisted of eight tanks, each 70 inches in diameter, clustered around a central tank, 105 inches in diameter. Four of the external tanks were fuel tanks for the RP-1 (kerosene) fuel. The other four, spaced alternately with the fuel tanks, were liquid oxygen tanks as was the large center tank. All fuel tanks and liquid oxygen tanks drained at the same rates respectively. The thrust for the stage came from eight H-1 engines, each producing a thrust of 165,000 pounds, for a total thrust of over 1,300,000 pounds. The engines were arranged in a double pattern. Four engines, located inboard, were fixed in a square pattern around the stage axis and canted outward slightly, while the remaining four engines were located outboard in a larger square pattern offset 40 degrees from the inner pattern. Unlike the inner engines, each outer engine was gimbaled. That is, each could be swung through an arc. They were gimbaled as a means of steering the rocket, by letting the instrumentation of the rocket correct any deviations of its powered trajectory. The block I required engine gimabling as the only method of guiding and stabilizing the rocket through the lower atmosphere. The upper stages of the Block I rocket reflected the three-stage configuration of the Saturn I vehicle. During the SA-3 flight, the upper stage ejected 113,560 liters (30,000 gallons) of ballast water in the upper atmosphere for "Project Highwater" physics experiment. The water was released at an altitude of 65 miles, where within only 5 seconds, it expanded into a massive ice cloud 4.6 miles in diameter. Release of this vast quantity of water in a near-space environment marked the first purely scientific large-scale experiment.