# ISS: Airlocks between pressurized modules?

I was curious about whether interconnected pressurized modules (like Kibo and Harmony) had any airlocks between them in whatsoever.

There are two reasons why I think it would make sense if they did:

1. The Kibo module (STS-123 and STS-124) was most certainly installed after Harmony (STS-120) and anyway would have been too large to accommodate affixed to each other in the shuttle bay (Kibo is the largest pressurized module!). So the Harmony must have had an "exposed" side till the Kibo was installed, and installing it would have been difficult without an airlock.

2. In the case of an accidental decompression (hull breach, or of that sort) in a module, the airlock connecting it to the rest of the station could be sealed off, ensuring minimal loss of air.

Yet, in the visuals of the interior of ISS, everything seems to be seamlessly connected.

Question: do adjacent pressurized modules have airlocks between them?

This applies to the US side of the ISS.

They don't exactly have "airlocks" in the sense that an airlock = a compartment that can be decompressed and someone in the compartment can leave the vehicle.

Instead they have "vestibules" which are formed by the hatches on the end of each module and the small volume between the hatches encircled by the rings of the Common Berthing Mechanism (CBM).

Shamelessly cribbing from my previous answer:

The mechanical interface between a new module and the ISS is the Common Berthing Mechanism (CBM), which has been discussed on this site quite a bit. ...

The CBM forms a ring around the hatch, shown here.

.... The red A labels the hatch/CBM on the JEM and the red B labels the hatch/CBM on the ISS where the module will be attached.

Once the robotics/CBM magic happens and the JEM is mechanically installed, a "vestibule" has been created. I couldn't find a good schematic of this so I drew up a terrible one. This tries to show a view looking perpendicular to the long axis of the JEM

The linked answer is about the process of pressurizing the vestible so it's not really a duplicate, but I suggest you read it for more background on how the vestibules are used.

Incidentally, "Kibo" refers to the whole Japanese lab on the ISS, not just the large cylindrical module. From JAXA:

Kibo is a complex facility consisting of the following six major elements.

Major Component

Pressurized Module (PM)
Exposed Facility (EF)
Experiment Logistics Module-Pressurized Section (ELM-PS)
Experiment Logistics Module-Exposed Section (ELM-ES)
Japanese Experiment Module Remote Manipulator System (JEMRMS)
Inter-Orbit Communication System (ICS)


The large cylindrical module of Kibo is called the JEM by NASA and the PM by JAXA.

I was privileged to work on 2 of the 3 Kibo assembly missions including the one that brought up the JEM.

• Thanks for answering (and for your contributions to spaceflight)! – William R. Ebenezer May 9 '20 at 12:12