On the pathway to the Moon, there were more small steps than Neil Armstrong’s off the Lunar Module on July 20, 1969. NASA also had to step its way up to the Saturn V rocket. One of those steps was called the Saturn IB.

On Feb. 26, 1966, the first Saturn IB launch vehicle lifted off from Cape Canaveral, Florida. The Apollo-Saturn 201 (AS-201) uncrewed suborbital flight set out to test the new Saturn IB rocket along with the Apollo command and service modules.

Primary objectives of the mission included evaluating the heat shield for the Apollo command module and testing the structural integrity and subsystem operations of the launch vehicle.

The flight lasted 37 minutes, reaching an altitude of 303 miles and traveled 5,264 miles downrange. The command service module was recovered by the U.S.S. Boxer in the South Atlantic two and a half hours after splashdown.

The historic flight accomplished many firsts.

It marked the first flight test of a Block I Apollo spacecraft. It also marked the first flight of the Saturn IB launch vehicle with the S-IB first stage and the S-IVB second stage. It was the first test flight of the J-2 engine in the S-IVB stage which utilized liquid-hydrogen/liquid-oxygen rocket propellant. It marked the first non-orbital flight separation of the launch vehicle and spacecraft in the Saturn IB configuration. The AS-201 mission also saw the first use of Historic Mission Control in Houston for the Apollo program.

Despite being hailed as a success, three problems did arise after launch. These setbacks were detailed in a NASA publication titled, “Chariots for Apollo: A History of Manned Lunar Spacecraft.” The first involved the service propulsion system, which only operated correctly for 80 seconds. NASA attributes this to helium ingestion in the oxidizer chamber. There was also an issue with the electrical power system. This resulted in a rolling reentry attributed to a loss of steering control. Lastly, NASA documents that a short circuit led to the distortion of flight measurements. While the mission didn’t go perfectly according to plan, it did achieve all its primary objectives.

Smaller than the Saturn V, the Saturn IB provided NASA an interim rocket relatively fast. It provided NASA the capability to train for the later Moon missions via crewed and uncrewed Earth orbital flights. This includes the first crewed flight of the Apollo program, the Apollo 7 mission.

However, its usefulness extended well beyond Apollo. The Saturn IB rocket was also used to carry three crewed missions to Skylab and again as part of the Apollo-Soyuz Test Project. The Saturn IB rocket may have been smaller than the mighty Saturn V, but it still played a monumental role in spaceflight history.

The same year this flight test was conducted, Neil Armstrong flew aboard Gemini 8. Just three years later he would become the first person to step foot on the surface of the Moon with the Apollo 11 mission. The uncrewed AS-201 flight was a precursor to the later crewed Apollo missions which would do the impossible, put an American on the Moon by the end of the decade.