Saturn INT-21

Intermediate-21 INT-21 Saturn V 2-stage

Mission Profile

The Saturn INT-21 (Intermediate-21, Saturn V 2-stage) was a proposed two-stage American super-heavy launch vehicle concept in the Saturn family, essentially a Saturn V without the S-IVB third stage, studied for large payload delivery under the Apollo Applications Program. Standing approximately 81 m tall with a 10.1 m core diameter, it would have used the S-IC first stage and S-II second stage. Conceived around 1965, the Saturn INT-21 configuration was actually used for the Skylab launch in May 1973, when a modified Saturn V without its third stage lofted the space station into orbit in a single launch.