High Quality Content by WIKIPEDIA articles! The Saturn IB (pronounced "one B", alternatively known as the Uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for use in the Apollo program. It was an uprated version of the Saturn I rocket, which replaced its S-IV second stage with the much more powerful S-IVB, which gave it enough payload capability to allow it be used for early testing of the Apollo spacecraft while the larger Saturn V needed to send Apollo to the Moon was still being developed. Unlike the earlier Saturn I, it could launch either the partially fueled Apollo Command/Service Module (CSM), or the fully fueled Lunar Module (LM) into low Earth orbit.