Space Launching System

{{Short description|1960s-era design program of the US Air Force}}

{{about|the 1960s USAF rocket project|the 21st-century NASA launch vehicle|Space Launch System|the Turkish satellite launcher|Space Launch System (Turkey)|the general topic|space launcher}}

The Space Launching System, or Space Launcher System, (SLS), was a 1960s-era design program of the US Air ForceAnn Beardsley, C. Tony Garcia, Joseph Sweeney, Historical Guide to NASA and the Space Program, p. 220, Rowman & Littlefield, 2016 {{ISBN|1442262877}}. for a family of launch vehicles 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 fuel for upper stages, which demanded the use of boosters based on segmented solid fuel rockets.Robert Godwin, Dyna-Soar: Hypersonic Strategic Weapons System, pp. 141-142, Apogee Books, 2003 {{ISBN|1896522955}}. 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 crewed spaceplane. Its competition was an upgraded version of the Titan I 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 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.{{Cite web|url=https://nsarchive2.gwu.edu/NSAEBB/NSAEBB479/docs/EBB-Moon04.pdf|title=Lunar Expedition Plan: Lunex|date=12 July 1961}}{{Cite web|url=http://www.astronautix.com/s/sls.html|archive-url=https://web.archive.org/web/20161228024707/http://astronautix.com/s/sls.html|url-status=dead|archive-date=December 28, 2016|title=SLS|website=www.astronautix.com|access-date=2018-10-15}}

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.{{Cite journal|last=BLEYMAIER|first=JOSEPH|title=The Titan III Standardized Space Launch System |date=1963-12-11|url=https://arc.aiaa.org/doi/abs/10.2514/6.1963-1407|journal=Heterogeneous Combustion Conference|language=en-US|location=Reston, Virginia|publisher=American Institute of Aeronautics and Astronautics|doi=10.2514/6.1963-1407|url-access=subscription}}{{Cite report|date=1962-11-01|title=PROGRAM 624A. PROGRAM DOCUMENTATION REQUIREMENTS GENERAL SPECIFICATION.|url=https://apps.dtic.mil/sti/citations/AD0431109|archive-url=https://web.archive.org/web/20220415145902/http://www.dtic.mil/docs/citations/AD0431109|url-status=live|archive-date=April 15, 2022|language=en}}{{Cite book|url=https://books.google.com/books?id=HxU-9UeDCI0C&pg=PA496|title=Military Space Systems|publisher=New Scientist|date=September 6, 1962|language=en|access-date=February 7, 2023}}