This 1968 cutaway drawing illustrates the Saturn IB launch vehicle with its two booster stages, the S-IB and S-IVB. Developed by the Marshall Space Flight Center (MSFC) as an interim vehicle in MSFC's "building block" approach to the Saturn rocket development, the Saturn IB utilized Saturn I technology to further develop and refine the larger boosters and the Apollo spacecraft capabilities required for the marned lunar mission.