[Animats]

What if the command module pilot became incapacitated but was still alive?

That's why one of the mission planning decisions was that the astronaut tasked with operating the orbiter must have previous time in space.

[Breza]

And they made him fly acrobatics in a jet shortly before the mission. ("Made" might be too strong a word since Collins thought it was fun.) NASA thought that might help train the inner ear to avoid the dreaded space sickness.