Saturn IB

The Saturn IB (pronounced "Saturn one bee", also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It was an uprated Saturn I, replacing the S-IV second stage with the much more powerful S-IVB. The Saturn IB was able to launch a partially fueled Apollo command and service module (CSM) or a fully fueled Apollo Lunar Module (LM) into low Earth orbit for early flight tests before the larger Saturn V needed for the lunar flight was ready.