Airlock

Airlocks can be open or closed without exposing a starship to the vacuum of space.
Airlocks can be detected with the sign text [airlock].
Right clicking the sign toggles the airlock by converting the iron bars to portal blocks and vice versa.
Airlocks can only be traversed when they are activated.
Note: Airlocks can be used by starships when activated.

Airlock

Airlock
Deactivated Activated
Properties
Resource Requirements
Invicon Iron Bars.png: Inventory sprite for Iron Bars in Minecraft as shown in-game linking to Iron Bars with description: Iron Bars2 Iron Bars 2
Iron Block 1
Any Sign 1

The normal Airlock is a simple version of the Expandable Airlock.

Expandable Airlock

Expandable Airlock
Deactivated Activated
Properties
Resource Requirements
Invicon Iron Bars.png: Inventory sprite for Iron Bars in Minecraft as shown in-game linking to Iron Bars with description: Iron Bars Iron Bars 1-5625
4 Iron Block 4-5
Any Sign 1
Invicon Any Slab.png: Inventory sprite for Any Slab in Minecraft as shown in-game linking to Any Slab with description: Any Slab2 Any Slab 2-300

The Expandable Airlock can be customized in height and width.
It has to consist of 4 corners made of Iron Blocks, with any Slabs connecting them.
The sign has to be placed on the left side of the frame and the slab the sign sits on needs to be replaced with an Iron Block.
The entire frame needs to be filled with Iron Bars.
Note: Despite the error message claiming the Slabs need to be double Slabs, it works perfectly fine with single Slabs.

Specific construction requirements

The sign has to be placed on an Iron Block on the left side of the frame. This Iron Block needs to be vertically connected to the bottom left corner using Slabs (This way the sign can the placed on the top left corner). The Iron Block can also be placed directly on top of the bottom left corner.
The bottom left corner then needs to be horizontally connected to the bottom right corner using Slabs. This specifies the width of the Airlock.
The bottom right corner needs to be vertically connected to the top right corner using Slabs. This specifies the height of the Airlock.
As the top left corner does not specify anything, it just has to be horizontally connected to the top right corner using Slabs. This connection can be any length. It can also be placed directly adjacently to the top right corner.
The top left and bottom left corner do not need to be connected.
The entire frame needs to be filled with Iron Bars.