An airlock is a device which permits the passage of people and objects between a pressure vessel and its surroundings while minimizing the change of pressure in the vessel and loss of air from it. The lock consists of a small chamber with two airtight doors in series which do not open simultaneously.
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 the water environment outside, in which case the airlock can contain air or water. This is called a floodable airlock or an underwater airlock, and is 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--is equalized with that of the environment beyond the next door to open. This is analogous to a waterway lock: a section of waterway with two watertight gates, in which the water level is varied to match the water level on either side.
A gradual pressure transition minimizes air temperature fluctuations (see Boyle's law), which helps reduce fogging and condensation, decreases stresses on air seals, and allows safe verification of pressure suit and space suit operation.
Where a person who is not in a pressure suit moves between environments of greatly different pressures, an airlock changes the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness. This is critical in scuba diving, and a diver may have to wait in an airlock for some hours, in accordance with decompression tables.
Airlocks are used in
This article may contain minor, trivial or unrelated fictional references. (March 2020)
A four-door airlock (with three interior chambers) was proposed by science fiction writer H. Beam Piper in his novel Uller Uprising. The atmosphere inside the fictional structure was human-breathable, while the outside atmosphere was highly toxic. Only one door of the airlock opened at a time, and the middle chamber of the three would always contain a vacuum to minimize traces of the exterior atmosphere reaching the habitat.
In the 1979 spy film Moonraker, James Bond dispatches the villain Hugo Drax aboard his own space station by first shooting him in the chest with a cyanide dart, then pushing him out an airlock into space ("Take a giant leap for mankind.").
In the 2014 science-fiction film Interstellar, airlocks are featured several times, beginning with the initial journey into space. In the film's climax, Dr. Mann attempts to maroon Cooper and Brand by stealing their spacecraft, the Endurance. When Mann tries docking his own ship onto the Endurance, he does so imperfectly. Despite this, he decides to board the Endurance from his own spacecraft regardless of the circumstances. In the midst of an arrogant monologue, he opens the airlock door. Due to the pressure change caused by the vacuum of space, the airlock explodes, killing Mann and critically damaging the Endurance. As a result of this, Cooper and Brand are forced to pursue the damaged Endurance in their own ship, as it is their only chance of survival. Due to the explosion, the circular ship is spinning out of control toward the stratosphere of a nearby planet. In a last ditch effort to save the mission, Cooper attempts to match the RPM of the Endurance with that of his own spacecraft. Due to the intense g-forces being subjected to Cooper and Brand, they must rely on their versatile AI known as TARS to accurately dock the ship with the Endurance while spinning.
In the 2015 science-fiction film The Martian, airlocks are used in the Hab, a habitat and base of operations on Mars, as well as on space-faring vessels. Mark Watney, an astronaut stranded on Mars improvises a farm in the Hab where he is living. Subsequently, the failure of an airlock and the depressurization of the environment kills the potato crops he was growing. Additionally, the crew of the Hermes vessel tasked with rescuing Watney deliberately breached an airlock to produce reverse thrust, in order to slow their vessel down enough to intercept Watney's capsule.
In Star Trek, Star Wars and some other works of fiction, conventional airlocks may be replaced by forcefields which hold in air while allowing solid matter like spacecraft to pass through. Airlocks of this type usually have pressure doors as a backup.
Airlocks are commonly used in science fiction as a form of execution, often referred to as "spacing" or "airlocking". Battlestar Galactica, Babylon 5, The Expanse and the Honorverse make frequent use of or reference to it.
Airlocking is also used as a means of expelling an antagonist or some object into space. In the film Alien the Xenomorph XX121 or Internecivus raptus is ejected from the Nostromo's lifeboat when Ripley opens its airlock. In an episode of the television series Space: 1999, "The End of Eternity", the alien Balor is swept out of Moonbase Alpha when Commander Koenig lures him to an airlock which unexpectedly opens. In the episode "Eyes" of the TV series Space: Above and Beyond an enemy bomb is jettisoned out of a USMC shuttlecraft just before exploding.
Airlocks are also used in the following video games:
Media related to Airlocks at Wikimedia Commons