For the initial start of the game the first thing you do is (in any order, making sure to keep water levels above minimum)
1, inspect water recycler (DO FIRST), ground floor door, generator.
2, repair generator and lift lockdown.
3, explore ground floor and workshop.
4, fill up on water pouches and inspection food synth.
At this point your limiting resource will be AIR and you should be able to get in the rover before that happens.