The Tech Side #15 Airlocks

Airlocks – sci-fi is full of them. Virtually every sci-fi series or movie out there makes use of the airlock as a plot device or at least as a feature of the story – we’ve seen them in Star Trek, Event Horizon – and who can forget Sean Connery’s escapades with airlocks in Outland?

Airlocks are a safety buffer or transition zone between areas of unequal air pressure. They facilitate the transfer of personnel from one vessel to the other in a way that doesn’t endanger either. More plainly, they protect a ship from depressurizing if a crew member goes outside or comes back in again.

They’re hardly a new invention, airlocks have been around since at least 1830 when Sir Thomas Cochrane registered his patent for use in building underground constructions. Watertight doors (a form of airlock tech) appeared in oceanic ships in the late 19th century. Airlocks were added to submarines to allow submariners to leave the sub in shallow water since before the First World War. They’re used in ships and submarines today, as well as in space shuttles and the ISS in orbit around Earth – and even in medical applications at bio laboratories and at the CDC.

Today we take a closer look at the airlocks aboard Terran Space Fleet vessels.

Airlocks are not just there to keep the air inside a space ship while the crew go outside for a little exercise in a space suit – they’re really a lot more than that!

There are a lot of things that can threaten a starship crew, and not all of them come from outside the ship! One of the many varied things that can go wrong is contamination of the air. A ship is like a bottle – the air inside it at any time is confined and limited, and if the air became contaminated by any number of things, such as smoke or particles (from a fire), irradiated air, an airborne virus, or noxious gasses, the air aboard the entire ship would carry that same risk! Without airlocks to separate various parts of the ship from each other in the event of such a disaster, people on the bridge might be trapped or exposed directly to the airborne threat from somewhere else, even on the opposite end of the ship!

Airlocks play a vital role in limiting the effects of these risks on the rest of the ship.

Types Of Airlock

Let’s start by looking at the two different types of airlock aboard a starship – Ingress/Egress Airlocks and Internal Airlocks:

Ingress/Egress Airlocks

These allow bidirectional traffic to enter and leave a ship or space station. Naturally, that means they’re an entry point on the outside hull of the ship, and can be of two sub-types – an EVA (Extra Vehicular Activity) airlock, or the ship’s Main Airlock, which has an extendable docking tunnel and welcoming area in the event the ship docks with a space station or another ship.

Ingress/egress airlocks are definitively placed between the interior of the vessel and the outside environment – which may include the vacuum of space, the toxic atmosphere of an alien planet, a docked ship, space station or shuttle.

Internal Airlocks

These come in two different flavors – State A and State B – although they can be physically identical, the difference comes into their usage at a particular time, or their location on a ship in relation to a hazardous area.

State A) – the airlock allows bidirectional traffic to pass through it between two internal environments or compartments inside a ship or space station where the environments are the same and the doors may be normally open. These only activate during emergencies.

State B – the airlock allows bidirectional traffic to pass through it between two internal environments or compartments inside a ship or space station where the environments differ significantly, or where one compartment is compromised or a biohazard situation or radiation exists on the other side. This type is typically found at sickbays (infectious bio-hazards) and engine rooms (radiation) and may also be normally open (complete or partial – see modes).

Airlock Modes

Airlocks can be managed using different modes appropriate for their location and general use.

Normally Open (complete)

This mode keeps both doors open unless they are specifically required to be closed. This allows bidirectional traffic to pass through them unimpeded. Both doors only close under specific conditions such as a pressure failure, biohazard, contamination or security alert, in which case they act like the watertight doors on ocean-going ships of old – to retain as much atmosphere as possible until the emergency is over.

Normally Open (partial)

This mode keeps one door normally open, and only closes it under specific conditions such as a pressure failure, biohazard, contamination or security alert, while the other door remains normally closed. The normally closed door allows bidirectional traffic to pass through it, opening only open when personnel approach (proximity sensor), command it to open via a key-pad or voice command.

Normally Closed

This mode keeps both doors normally closed, and only opens them when personnel approach, command open, or manually open. This mode is typically used on external airlocks or at entrances to hazardous areas.

More Detail About Airlocks

The Main Airlock

A ship’s main airlock is generally used when the ship docks at a space station or with another ship. Most Terran ships are equipped with two main airlocks, one on either beam (port and starboard) so that it can dock with another ship or space station on either side, or even both at the same time.

While docked at a space station, Space Fleet regulations specify that one or more security marines is to be posted as sentries at the entrance of the airlock to maintain entrance control and security. The same protocol applies should the ship dock with a civilian vessel or any vessel other than another Space Fleet vessel.

A small welcoming area is often located right by the inner entrance of the main airlock which is sometimes used to greet dignitaries arriving or leaving by that route.

Terran ships dock with standardized and adaptive docking clamps at the end of a short docking tunnel which extends outward from around the outer main airlock door. They’re adaptive, because they may encounter alien or non-standard forms of airlock or docking mechanism, and an adaptive mechanism will overcome a range of challenges. Once a firm grasp and an air-seal are achieved using self-sealing forcefields to retain atmosphere, it is safe to open all main airlock doors simultaneously – but this is almost never done because of a) regulations and b) a cautious approach.

EVA Airlocks

Terran starships all have numerous airlocks situated around the ship. While the main airlocks are positioned on the sides of the ship out of necessity because of their docking function, EVA airlocks are positioned wherever convenient.

Unlike main airlocks, EVA airlocks are designed for crew members to conduct space walks or to perform maintenance tasks or repairs to the outside of the ship.

Further reading:

In Closing

That about covers it! I hope I’ve explained everything in a way that’s easily understood! I really enjoyed translating my original hand-drawn sketches into digital blueprint diagrams for this article, and I think they look pretty neat that way!

Feel free to email or message me via Facebook, Twitter or LinkedIn if you have any comments or questions!

Until next time,

Cheers! 🙂


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