Airlocks

A common airlock.

Airlocks are passages by which one moves between two different environments, without compromising the integrity of either.

The airlocks on cargo freighters and the like are generally provided so that a crew can go extra-vehicular without forcing everyone inside to put on environmental suits. Most are little more than two meters square.

In cases where cargo or personnel must be transferred from the ship in a vacuum, umbilical passageways are run from the adjacent ship or docking array to the ship's airlock.