An Airlock was a device which permitted the passage of people and objects between a pressure vessel and it's surroundings while minimizing the change of pressure in the vessel and loss of air from it. The lock consisted of a small chamber with two airtight doors in series which did not open simultaneously.
Description and Role
An airlock may be used for passage between environments of different gases rather than different pressures, to minimize or prevent the gases from mixing. An airlock may also be used underwater to allow passage between an air environment in a pressure vessel and a water environment outside in which case the airlock could contain air or water. This was called a floodable airlock or an underwater airlock and was used to prevent water from entering a submersible vessel or an underwater habitat. Before opening either door, the air pressure of the airlock—the space between the doors—was equalized with that of the environment beyond the next door to open. This was analogous to a waterway lock: A section of waterway with two watertight gates in which the water level was varied to match the water level on either side.
A gradual pressure transition minimized air temperature fluctuations (See Boyle's law) which helped reduce fogging and condensation, decreased stresses on air seals and allowed safe verification of pressure suit and space suit operation.
Where a person who was not in a pressure suit moved between environments of greatly different pressures, an airlock changed the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness. This was critical in scuba diving and a diver may have to wait in an airlock for some hours, in accordance with decompression tables.
Stations with Airlocks
- The "airlock trouble" scene from Gravity was named 25 in a list of the 50 scariest movie moments of 2013 by TotalFilm.