Early S-IVb cutaway art art, history, projects, rockets, spacecraft Add comments Jul 012013 NASA art depicting the third stage of the Saturn V. A bit different from what actually got built. Date uncertain… probably ca. 1963. LordJim Why is it called the S-IV if it is the third stage? mikej An early plan for Saturn was to have it eventually be a five-stage rocket, with stages called the S-I, S-II, S-III, S-IV, and S-V, but with additional, smaller configurations using only some of the stages. (There were even earlier plans, where existing missiles such as Atlas or Titan stages would be used as Saturn upper stages.) Keeping with the ABMA’s “building block” approach, they decided to initially build Saturn with a live S-I and dummy S-IV and S-V stages (SA-1 through SA-4), eventually replacing the dummy S-IV with a live one (SA-5 through SA-10). Of course, plans changed, and eventually Saturn evolved into a 3-vehicle family, with the S-I stage becoming the S-IB for Saturn IB and the S-IC for Saturn V. The second stage selected for the Saturn IB (which, slightly modified, would be used as the third stage for the Saturn V) was considered close enough to the original S-IV stage that they slapped a “B” to the end of the stage’s name and sole-sourced it to Douglas (the manufacturer of the S-IV), without putting it out for bid. The Saturn V was the first vehicle to have an S-II stage, which look nothing at all like some of the early S-II concepts (when it would be used with the original S-I stage). The early chapters of “Stages to Saturn” (http://history.nasa.gov/SP-4206/ch2.htm) have more detailed history.