Editing AS-201 (section)

===Launch vehicle===
{{Main|Saturn IB}}
The Saturn IB was the uprated version of the [[Saturn I]] rocket flown in ten earlier Apollo missions. It featured an upgrade of the first stage (S-IB-1) engines to increase total thrust from {{convert|1,500,000|lbf|kN|abbr=on}} of thrust to {{convert|1,600,000|lbf|kN|abbr=on}}, and replacement of the second stage with the [[S-IVB (rocket stage)|S-IVB]]. This stage used a new [[liquid hydrogen]]-burning [[J-2 (rocket engine)|J-2 engine]] which would also be used on the [[S-II]] second stage of the [[Saturn V]] lunar launch vehicle. A modified version of the S-IVB, with an in-space restartable J-2, would also be used as the third stage of the Saturn V. It also used a new model of the guidance and control system known as the [[Saturn V Instrument Unit|Instrument Unit]], which would also be used on the Saturn V.