Vault

A Vault is a type of a subterranean installation designed by Vault-Tec. Officially, they were designed for the sole purpose of sheltering up to one thousand dwellers from a nuclear holocaust.

History
Commissioned by the United States government as part of Project Safehouse, Vault-Tec built 122 such Vaults over the country. However, when the storm of nuclear war came in 2077, the Vaults were sealed without many of their dwellers due to the Cry Wolf effect training drills had on the populace.

The first Vault was built in Los Angeles, intended to demonstrate the viability of such a facility. The demonstration Vault was built beneath the city, within its limits and unlike other Vaults, wasn't part of the experiment. Most Vaults were completed by 2063, except for Vault 13, which was the last one to be completed.

Before Project Safehouse was privatized, ODYSSEUS, an extremely advanced AI was designed with the intent to coordinate and operate all of the Vaults.

True purpose
Officially, the Vaults were nuclear shelters designed to protect the American population from nuclear holocaust. However, with a population of almost 400 million by 2077, the U.S. would need nearly 400,000 Vaults the size of Vault 13, while Vault-Tec was commissioned to build only 122 such Vaults. The real reason for the existence of these Vaults was to study pre-selected segments of the population to see how they react to the stresses of isolationism and how successfully they re-colonize Earth after the Vault opens.

The shadow government, the Enclave, responsible for the experiment, have considered themselves prime candidates for recolonizing the world after a nuclear holocaust and to this end commissioned the construction of their own shelters, isolated from the Vault network. The purpose of the Vault experiments was to help prepare the Enclave for either re-colonizing Earth or colonizing another planet if Earth turned out to be uninhabitable by unmutated humans.

The total number of vaults is a government secret and has been lost; there were the aforementioned "public" vaults, which numbered 122 and an undisclosed number of "private" vaults. Information on whether Vault-Tec was an international corporation and were there vaults made by them in other parts of the world, or were they strictly U.S. based, cannot be released due to Vault-Tec and US Government regulations

Overview
The Vaults were one of the most expensive shelters in the pre-War world, as according to the Vault Dweller's Survival Guide for Vault 13 (otherwise known as the Fallout manual), the intended budget for that particular installation was 400 billion dollars, and by the end of its construction reached 645 billion. The Vaults were located in various locations, and little information is available as to why those particular sites were chosen. For example, Vaults 13 and 15 were located in rather remote locations, far from population centers, while Vaults 12 and 101 lay near or in cities themselves.

Each Vault was designed to hold one thousand occupants at any given time, although hot bunking was required at maximum capacity, and equipped with all facilities and supplies needed by them to survive in isolation for the designated time. The facilities and supplies included complete construction equipment, hydro-agricultural farms, a water purification system, defensive weaponry to equip 10 men, communication systems and surface monitors, social and entertainment files (for total duration) as well as one or two G.E.C.K.s, intended to help the inhabitants repopulate the post-nuclear world after the All Clear signal is sent following the conclusion of the social experiment. Different types of power sources were utilized for the Vaults. Vault 13 relied primarily on geothermal energy, with backup power available from a General Atomics Nuclear Power generator, and could sustain one thousand inhabitants for two hundred years. Vault 8 on the other hand, relied on an unspecified type of reactor, which, while enough for Vault City to emerge, could only support a relatively small, highly advanced settlement, and in 2241 was nearing its capacity, after which further growth would be impossible.

All Vault Dwellers wore blue-and-yellow jumpsuits, although the design varied between different Vaults.

It should be noted that due to scaling, the size of Vaults in games shouldn't be taken at face value - after all, Vault 13 in-game couldn't possibly hold 1000 people, despite it's stated capacity.

Entrance
The entrance houses the Vault's only connection to the outside world - the airlock. Closed from the inside by a reinforced high-security door and from the outside by a massive, four yard thick blast door, it's the only means of leaving the Vault. Security codes are required to both leave and enter the Vault, and they are usually only known to a handful of people within the facility.

Most Vaults use a single, universal model of the blast door to secure the airlock, however, some older Vaults (such as Vault 101) use a different, more crude blast door model. Vault 8, the control Vault, had also a second, much larger, blast door built, that secured the entry hallway leading to the entrance to the Vault.

In addition, the Entrance level also houses the Emergency Medical Lab complete with an AutoDoc. A Vault medic was required to be present at the EML 24 hours a day. The lab had the equipment to treat nearly all injuries and illnesses, ranging from simple bruises to irradiation.

Living Quarters
Standard pre-War design of the living quarters was that of a single room with a sanitary annex. Vault 13 had one hundred living quarters, and at maximum capacity, ten people would be assigned to a single living quarter, in a hot bunking system.

Command Center
The heart of the Vault, the command center was where the Overseer's seat was located. Equipped with dual 5mm miniguns, the Overseer's command post can be considered the last line of defence in case the Vault security is breached. The operations center, apart from the seat of power, included the computer lab, where the water purification system was located, and an armory, where the Vault's arms were stockpiled. A security guard was posted in the command center at all times, to ensure that the armaments are properly secured, and handed out only to people possessing the proper clearance from the Overseer.

Apart from that, the level also contained the computer core, housing data processing units, a library playing an important role in educating Vault Dwellers and information, a meeting room for the dwellers and the primary store room, where the most important supplies would be stored.

Differences

 * Vault 29 (Van Buren) was outfitted with a ZAX AI, which replaced the Overseer.
 * Vault 12 had its Overseer's room sealed due to unknown reasons.
 * East Coast Vaults (92, 101, 106, 108, 112) use a different, older door mechanism.

Appearances
Fallout: The other Vaults present in this article were mentioned in Chris Avellone's Fallout Bible or Penny Arcade's comic strips.
 * Vault 12, Vault 13, Vault 15 and the LA Vault appeared in Fallout 1
 * Vault 8, Vault 13 and Vault 15 appeared in Fallout 2
 * A malfunctioning Vault with unknown number and location appeared in Van Buren tech demo
 * Vault 69 advertisement appeared in the Van Buren concept art.
 * Vault 29 and Vault 70 were to appear in Van Buren, the cancelled Fallout 3 project by Black Isle (year 2253).
 * Vault 101 appears in Fallout 3 alongside Vault 87 Vault 92 Vault 106 Vault 108 Vault 112 and the DC demo Vault (year 2277).

Spin-offs:
 * Vault 0 appeared in Fallout Tactics, but the idea did not really fit the Vault experiment.
 * A secret Vault-Tec Vault dedicated to FEV research appeared in Fallout: Brotherhood of Steel, but is considered non-canon.

Behind the scenes
The vault experiment was an idea created by Tim Cain during the initial stages of Fallout 2 development.

Cut content
The developers intended for the player to first encounter information about the Vault Experiment as they read the Vault 8 records in Fallout 2. They could discover a classified file (opened with a successful Science skill roll) explaining the purpose of Vault 8 was to be a "control Vault," designed to hold 1000 people and open at a designated time. This file was intended to foreshadow the discovery of the true and sinister purpose of the Vaults.

The player was also intended to apply his Science skill to the central computer in Vault 13 to obtain a history of Vault 13, the Overseer's involvement in the Vault Dweller's expulsion, and even worse, the true purposes of the Vaults. The Overseer was conscious of the true purpose of the Vaults as social experiments on a grand scale, and consequently drove out the Vault Dweller because of fear he would ruin the experiment... or uncover it.