Clarification: I'm talking about the INNER airlock door.

Keeping the airlock closed in-between spacewalks sounds safer:

  • In case of accidental puncture of the outside of the module, this has no effect on the rest of the station.


  • This removes a (little bit) of livable space for the astronauts
  • It will need to be actually opened up again once you'll want to depart.

So what do they actually do ?

  • 1
    $\begingroup$ While I really know nothing about the subject, it seems like using the airlock as "livable space" would not be a good idea... $\endgroup$
    – Steve
    Commented Sep 13, 2016 at 14:51
  • $\begingroup$ @Steve Could be a good place to read a book when the coupla is crowded $\endgroup$
    – Antzi
    Commented Dec 5, 2016 at 16:43

2 Answers 2


The configuration between EVAs is - Inner hatch open, Outer Hatch closed, Inner hatch equalization valves closed.

Reference: ISS EVA Checklist

Look at the POST EVA steps. The first few actions configure the hatch and valves. There are no further steps in POST EVA reconfiguring the hatches or equalization valves.

Here is a screen shot of the first page of the procedure.

enter image description here


Since the airlock acts as a buffer between "inside pressure" and "space pressure", I assume you would always want it to be at one of these pressure levels. By keeping a door open, you are sure that the airlock doesn't get its own third pressure level.

It's like avoiding floating potentials when building an electronic circuit.

  • 2
    $\begingroup$ We're not looking for assumptions but answers that can be backed up by references. $\endgroup$ Commented Dec 5, 2016 at 16:25
  • $\begingroup$ This is however, a very good comment. $\endgroup$
    – Antzi
    Commented Dec 5, 2016 at 16:41
  • 1
    $\begingroup$ Sorry about that, that was my first contribution here. Next time I will put my assumption in the comments. $\endgroup$
    – McFabulous
    Commented Dec 13, 2016 at 20:03

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