Halo Array

A human ship approaches a Halo still under construction. Portions of the Ark (see below) are visible at bottom.

Halos are fictional megastructures and superweapons in the Halo video game series. They are alternately referred to as "Installations" by their AI monitors, and are collectively referred to as "the Array" by the installations' creators, the Forerunners. The series' alien antagonists, The Covenant, refer to the structures as the 'Sacred Rings', believing them to form part of a greater religious prophecy known as 'The Great Journey'. According to Halo's fiction, the Forerunners built the rings to contain and study the Flood, an infectious alien parasite. The rings also act together as a weapon of last resort; when fired, the rings kill any sentient life capable of falling prey to the Flood, starving the parasite of its food. The installations play important roles in Halo: Combat Evolved and its sequels and adaptations.

The Halos are massive ringworlds, which feature their own wildlife and weather. The constructs resemble Larry Niven's Ringworld concept in shape and design, while they are closer to Iain M. Banks' Culture Orbitals in terms of scale and structure, the latter of the two being the inspiration for the Halo rings. The structure that Combat Evolved takes place on was initially to be a hollowed-out planet, but was changed to its ring design later in development; a staff member provided "Halo" as the name for both the ring and the video game after names such as Red Shift were suggested.

Design

Originally, before the title for Bungie's next project was announced and development of the game that would become Halo was in its early stages, the megastructure that Combat Evolved took place on was instead a massive, hollowed-out planet called "Solipsis". The planet was eventually changed to a ringworld, which some Bungie staffers felt was "ripping off Larry Niven", according to Bungie artist Paul Russel. Russel himself ended up suggesting that the game's name be 'Halo' after titles such as The Crystal Palace, Hard Vacuum, Star Maker, Star Shield, and The Santa Machine were suggested; 'Halo' became the ring's name as well.

The wildlife of a Halo installation is something of a mystery. Installation 04 features moth-like creatures, as well as distant animal calls indicating other species, but nothing else. Halo 2 features a variety of animals, though none that the player can directly interact with, besides the bird-like creatures that can be shot at. In the E3 2000 video showcasing an early build of Halo, there are dinosaur-like creatures that roam Halo's surface, as well as another creature (referred to as the "Blind Wolf") intended for use as a vehicle for the player. A "Doberman Gator" was also mentioned in the Halo 2 documentary. The animals were removed for both technical and conceptual reasons; there were difficulties in A.I. interaction and the designers felt that removing the animals would make the appearance of the Flood more terrifying and unexpected.

Installations

Installation 04

Installation 04, also known as Alpha Halo, is first encountered during the events of Halo: Combat Evolved. The majority of gameplay takes place in areas on or near this installation.

Installation 04 is managed by the Monitor known as 343 Guilty Spark, who has been doing so for 101,217 local years, a local year being the amount of time it takes Threshold to orbit its star. In an interview with Joe Staten of Bungie Studios, Staten confirmed that the previous firing, to which Guilty Spark alludes in the game, occurred around 100,000 years previous to the events in year 2552 at Installation 04.

Installation 04 is located in the Soell system, orbiting a gas giant known as Threshold. Its orbit is at Lagrange point L1, directly between the gas giant and one of its moons, Basis, but closer to the latter. At the Lagrange point L1 the gravity of Basis and Threshold partially cancel out, giving Halo the same orbital period as Basis despite being in a closer orbit. All three bodies revolve with the same angular speed around their common center of gravity, which is inside of Threshold, but not exactly at the center of gravity of the star. Their common center of gravity revolves around the star. In contrast to the Lagrange points L4 and L5, the Lagrange points L1, L2 and L3 are metastable positions, similar to a marble placed on the center of a saddle. This indicates that Halo would have to stabilize its position actively (if real laws of physics applied to it), so as not to fall onto either Threshold or Basis. Using Halo's game data for scale, the gas giant Threshold measures about 214,604 kilometers in diameter. Threshold's moon, Basis, measures at 23,848 km in diameter, and features a breathable atmosphere. Following the events of Halo: Combat Evolved, debris from Installation 04's destruction litters the lunar surface, and among the pieces of this debris is a temporary base camp set up by the Heretic forces, who later relocate to Threshold's gas mining facility. Halo 2's multiplayer mode also has a map based on this debris called Burial Mounds.

Installation 04 is destroyed at the end of the game by the Master Chief and Cortana, who overload the fusion reactors of the Pillar of Autumn, triggering a massive nuclear explosion that destroys enough of the ring to allow the installation's momentum and rotation to over-stress the remainder of the structure, causing it to tear itself apart. Following the destruction of the ring, the remaining segments were baked to an almost molten state. Only two significant pieces of the ring are still in their original orbit (in a molten and clearly uninhabitable state), and debris from Installation 04 still rains down on Basis. 343 Guilty Spark escapes the destruction of his installation, relocating to Threshold's gas mining facility and eventually Installation 05.

A replacement for Installation 04 is found partially built within the Ark during the events of Halo 3. Despite having only been under construction for a period of a few months, it contains a functional main weapon, along with atmosphere and climate controls. However, as it is incomplete, the firing of the main weapon causes it to self-destruct. As the facility was intended to replace his destroyed installation, 343 Guilty Spark considered it "his" and violently objected to the Master Chief's intentions to destroy it, even though doing so breaches primary protocol, which is to contain the Flood out-break with the purpose-built installation 04; the AI was destroyed in the ensuing battle, but not before fatally wounding Sergeant Major A.J. Johnson.

Installation 05

Installation 05, also known as Delta Halo, is the subject of Halo 2, but unlike the first game, it is not the sole location of gameplay. Similar to the first game, the main focus of activity on Installation 05 is the attempt to retrieve its Index, which the various factions in the series seek for different reasons. This installation remains intact following the end of the game, though as a result of its near-activation, every other Halo installation is primed to fire.

"Delta Halo" is the title of a specific group of levels in the Halo 2 campaign set on the eponymous second Halo installation. Although Installation 05 is known as Delta Halo, it is uncertain if this is the official UNSC designation for the installation.

Installation 05 is managed by the Monitor 2401 Penitent Tangent, a red-glowing counterpart of 343 Guilty Spark. However, following the events of Halo 2, 2401 Penitent Tangent is in the custody of Gravemind, a Flood intelligence who now commands limited control over the ring's systems. Installation 05 orbits a blue gas giant called Substance; though not named in-game, texture files for the planet are named as such.

In Halo 2, when the High Prophet of Regret flees New Mombasa, East African Protectorate, he sets up a base of operations on Installation 05 and attempts to activate it. The Master Chief follows the Prophet and kills him, preventing the installation's activation. After the High Prophets and Brutes betray the Elites (a major plot point in Halo 2), the Brutes set up a base of operations in the control room of this Halo and engage the activation sequence. The Arbiter and a number of Elites launch an offensive against the Brute encampment, and manage to kill the Brute Chieftain, Tartarus, with the assistance of Sergeant Major Avery Johnson and Commander Miranda Keyes. Keyes is instructed by 343 Guilty Spark on how to shut the weapon down, but in doing so activates a fail-safe, priming the remaining Halo installations via subspace beacon for remote activation by the Ark.

The Ark

Installation 00, also known as the Ark, was first mentioned at the end of Halo 2 and serves as a control station for the Halo network. When one Halo is activated but kept from firing, a subspace signal primes the remaining installations to be fired remotely by the Ark. A gateway leading to the Ark is buried inside Kenya, East African Protectorate, between Mount Kilimanjaro, Voi, and Mombasa. It creates a massive portal upon activation, leading to the Ark. The Ark itself is an immense, starfish-shaped structure located outside the Milky Way galaxy. According to 343 Guilty Spark, it is 2¹⁸ (262,144) light years from the galactic core; the maximum range of the Halo network is roughly 250,000 light years. The Ark serves as the main setting for the events of the second half of Halo 3. It is discovered that the Ark has the ability to build Halos, and that it has nearly completed construction of Installation 04 when the Master Chief and allies decide to activate the new ring to destroy the local Flood infestation. The Ark is damaged when the Halo is fired, and the slipspace portal it creates collapses, stranding the Master Chief and Cortana in deep space.

Scientific analysis

The five Lagrangian points in a two-body system. Threshold is the yellow circle, Basis is the blue circle, and Installation 04 is positioned at L1.

References

• Trautmann, Eric (2004). The Art of Halo. New York: Del Ray Publishing. ISBN 0-345-47586-0.