How do airlock doors work?

Airlock doors work by creating a sealed chamber that can be pressurized or depressurized, allowing passage between areas with different air pressures. A typical modern airlock consists of a cylinder of steel plate with airtight doors located at both ends, one opening from the outside into the lock, the other from the lock into the compressed-air chamber, together with valves to admit or to exhaust compressed air.

Airlock Mechanism Explained

Airlocks are crucial for maintaining pressure differences, often used in environments like:

• Underwater construction
• Spacecraft
• Hyperbaric chambers

Here’s a breakdown of how they function:

1. Sealed Chamber: The airlock is essentially a small room or cylinder that can be completely sealed off from both the inner and outer environments.

2. Two Airtight Doors: An airlock always has at least two doors, one leading to the high-pressure environment and one to the low-pressure (or normal-pressure) environment. These doors are designed to be airtight when closed.

3. Pressurization/Depressurization: The key to an airlock’s function is its ability to control the air pressure inside the chamber. This is achieved through a system of valves.

   • Pressurization: To enter a high-pressure environment from a normal-pressure environment, the following steps occur:

     1. The user enters the airlock from the normal-pressure side.
     2. The door to the normal-pressure side is sealed.
     3. Valves open to allow compressed air to flow into the airlock, increasing the pressure inside the chamber.
     4. Once the pressure inside the airlock equals the pressure of the high-pressure environment, the door to the high-pressure environment can be opened.
     5. The user can then exit the airlock into the high-pressure environment.

   • Depressurization: To exit a high-pressure environment into a normal-pressure environment:

     1. The user enters the airlock from the high-pressure side.
     2. The door to the high-pressure side is sealed.
     3. Valves open to gradually release the compressed air from the airlock, reducing the pressure inside the chamber.
     4. Once the pressure inside the airlock equals the pressure of the normal-pressure environment, the door to the normal-pressure side can be opened.
     5. The user can then exit the airlock into the normal-pressure environment.

Example of Airlock Usage

Imagine divers working on an underwater construction project. They use an airlock connected to a diving bell to enter and exit the pressurized underwater environment:

1. The divers enter the airlock from the diving bell (already at high pressure).
2. The door to the diving bell is sealed.
3. The airlock is depressurized to surface pressure.
4. The door to the surface is opened, and the divers exit. The process is reversed for entering the underwater environment.