The Saturn INT-21 was a study for an American orbitallaunch vehicle of the 1970s.[1] It was derived from the Saturn Vrocket used for the Apollo program, using its first and second stages and capable of placing 115,900 kg (255,500 lb) to LEO, but lacking the third stage.[2] The guidance unit would be moved from the top of the third stage to the top of the second stage. The INT-21 was never flown.
A related variant was launched once, from the Kennedy Space Center, Florida carrying the Skylabspace station into orbit, at 17:30 UTC, on May 14, 1973.[3][4][5] As Skylab was built from an S-IVB stage, there was no need to move the guidance unit. This version was intended to be used for other flights in the Apollo Applications Program, and would have also been used to launch other American space stations,[5] including Skylab B.
This template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
Symbol † indicates past or current rockets that attempted orbital launches but never succeeded (never did or has yet to perform a successful orbital launch)