The Space Launching System, or Space Launcher System, (SLS), was a 1960s-era design program of the

US Air Force The United States Air Force (USAF) is the Aerial warfare, air military branch, service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part ...

for a family of

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...

s based around a set of common components. After a series of studies in the late 1950s, the Air Force had concluded that the maximum efficiency would be gained by using only

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully l ...

fuel for upper stages, which demanded the use of boosters based on segmented solid fuel rockets. By combining one of three upper stages with three different diameters of solids built to any length needed, the SLS provided wide flexibility in launch capability. The SLS was one of two programs being designed at different divisions within the Air Force, with the ultimate aim of providing the launch services for the

X-20 Dyna Soar The Boeing X-20 Dyna-Soar ("Dynamic Soarer") was a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite mainten ...

crewed

spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes te ...

. Its competition was an upgraded version of the

Titan I The Martin Marietta SM-68A/HGM-25A Titan I was the United States' first multistage intercontinental ballistic missile (ICBM), in use from 1959 until 1962. Though the SM-68A was operational for only three years, it spawned numerous follow-on mode ...

with a new upper stage that produced the Titan C concept. In the end, neither SLS or Titan C would be developed, in its place the new

Titan III Titan was a family of United States expendable rockets used between 1959 and 2005. The Titan I and Titan II were part of the US Air Force's intercontinental ballistic missile (ICBM) fleet until 1987. The space launch vehicle versions contribu ...

was selected, combining the new missile of the Titan C with the solid boosters of the SLS. The SLS was also needed for the Lunex Project, a proposed human lunar landing in 1967. The replacing Titan III was more formally known as Program 624A (SSLS), Standard Space Launch System, Standardized Space Launch System, Standardized Space Launching System or Standard Space Launching System.

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SLS
on Astronautix Cancelled space launch vehicles Space launch vehicles of the United States Equipment of the United States Air Force {{Rocketry-stub

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