>>10811653Neil proved his mettle by surviving (getting out of a bad situation on his own initiative) Gemini 8. That is the reason why he was given the first moon landing command. If anything had gone wrong at any point, no one had a better proven track record/better shot of fixing it than Neil.
>>10811649On a profile flight, the vehicle stack can really be thought of as ten pieces.
-The three rocket stages,
-the four components of the spacecraft, (command module/service module/lunar module descent stage/lunar module ascent stage)
-and another three bits: the first/second interstage ring, the launch escape tower, and the "SLA" (Spacecraft/Lunar module Adapter), the conical fairing which pops off when the CSM flies free for the first time, independently of the S-IVB to which the LM is still attached. This moment of separation was known as "SLA-sep".
starting at 30:20, this is all perfectly explained in a brief animation in Moonwalk One. In all, there's about 12-13 physical separation/docking events during a profile mission.
https://www.youtube.com/watch?v=9GVpoSrqMMgThe instrument unit, the Saturn V's onboard guidance computer, was assembled as part of the S-IVB (third stage). Although really a separate part (among millions), the Instrument Unit was part of the S-IVB for all practical purposes once a flight was underway. Likewise, the conical aft interstage assembly between the second stage and the third stage, was technically part of the third stage when built. However, during stack assembly it was permanently fixed to the second stage, so that the stage and the (front) interstage fell away as a single piece (depicted at 30:40 in the video). This was due partially to a clearance issue around aft rockets: since the third stage had only a single J-2 engine as opposed to the second stage's five J-2 engines, there was much more clearance (and thus less concern that the spent stage would bump the rockets during separation) at this staging event.