Astroengineering: Difference between revisions

Construction of these megastructures seems to be restricted to either [[Forerunner|Tier One]] or [[Covenant|Tier Two]] civilizations. Although listed as a Tier Three civilization, the [[UNSC]] has no known astroengineered structures.

The [[Forerunner]]s are renowned for their mimicry of natural environments, but it is their engineering achievements that stand as monuments to their extraordinary prowess, centuries after they have passed on. Their Halo Installations, Shield Worlds, and the [[Installation 00|Ark]] are all artificial habitats on a vastly larger scale than anything that either [[Human|humanity]] or the [[Covenant]] could have accomplished. All known [[Forerunner]] megastructures are a part of the [[Halo Array]].

[[Image:Delta Halo.jpg|thumb|200px|[[Delta Halo]], the second Halo discovered by the UNSC and the Covenant.]]

The Halo Installations are planet-sized artificial worlds, shaped like a ring. The interior surface contains a breathable atmosphere and seemingly natural terrain, including oceans, lakes, mountains, forests, and tundras. Underneath this is a support layer, upon which this terrain has been put in place, consisting of a vast grid network of metallic plates that provide the base. Though centripetal forces may provide at least some of a Halo installation's gravity, it also uses artificial gravity generators to generate [[Earth]]-like gravity.<ref>'''[[Halo: The Flood]]''', ''page 14''</ref>

The exact size of a Halo seems to vary. [[Alpha Halo]] has a diameter approximately equal to that of [[Earth]]<ref>'''[[Halo: The Flood]]''', ''page 13''</ref>, but [[Delta Halo]] was described as being only as large as a moon<ref>'''[[Halo: Ghosts of Onyx]]''', ''page 188''</ref>. Because these are the only two known Halo Installations, it remains to be seen whether these are standard sizes or whether each Installation is different in size and structure.

A variation of the concept also exists, built in a more conventional fashion. It's a structure whose surface is composed of an outer shell, with a hollow interior and a habitable inner surface, and a miniaturized artificial star in the center. The interior resembles a [[Dyson Sphere]], though on a far smaller scale.

The artificial planet [[Onyx]] was used as a cover for the [[Shield World]] in it's core. It was later colonized by the [[UNSC]], oblivious as to its true origins until [[2552]], when its [[Onyx Sentinel|Sentinels]] activated to defend the Shield World. It was later damaged by [[FENRIS Nuclear Warhead]]s, and destroyed as its Sentinels burst free and set up defensive stations around the Shield World portal.<ref>'''[[Halo: Ghosts of Onyx]]''', ''pages 377-378''</ref>

It was destroyed by the [[UNSC]] forces in [[2531]] when the overloaded [[Shaw-Fujikawa Translight Engine|Slipspace Drive]] of {{UNSCShip|Spirit of Fire}} sent the internal star to [[Supernova]] state.

The [[Forerunner]]s also constructed massive Dyson Spheres, with a diameter of 2 astronomical units<ref>'''[[Halo: Ghosts of Onyx]]''', ''page 380''</ref>, encapsulated them in a [[Slipspace]] field to protect them from the Halo Array as it activated. Essentially a sphere, with its habitable surface on its internal surface rather than external, Shield Worlds are also equipped with their own stars<ref>'''[[Halo: Ghosts of Onyx]]''', ''page 379''</ref>, providing warmth, light and energy to the installation. Originally intended as a way to circumvent the Halo effect, the Shield Worlds were not put into use by the Forerunners due to the rampant actions of one of their own [[Mendicant Bias|AI constructs]].<ref>'''[[Halo 3]]''', ''[[Terminals]]''</ref>

The only known structure resembling an Alderson disk constructed by the [[Forerunners]] is [[Installation 00]].  With a diameter of between 90,000 and 100,000 kilometers<ref>[http://carnage.bungie.org/haloforum/halo.forum.pl?read=871617 Carnage Bungie Forum]</ref>, and a larger total surface area than a [[Halo Array|Halo Installation]], it incorporates many similar elements, including [[Earth]]-like gravity and atmosphere and a rich and diverse ecosystem. Located in the center of the Installation is a small planetoid, presumably used for raw materials, and a star orbiting nearby despite its location: 2¹⁸, or 262,144 light years outside of the [[Milky Way Galaxy]], where stars cannot naturally form. It's possible that this is an artificial sun created by the Forerunners.<ref>'''[[Halo 3]]''', campaign level, ''[[The Ark (Level)]]''</ref>

[[Image:High charity and Alpha Halo.jpg|thumb|High Charity, next to the ruins of [[Alpha Halo]]]]

Though on a far smaller scale, the Covenant have been known to build super structures.

{{Quote|A Halo’s construction is executed by armies of Sentinels: some are the size of cities. Viewing the picture of the reconstituted asteroid material, you can see the process of skinning the Halo.  There are four huge terraforming factories moving across the face of the Halo.  They hold in the atmosphere which would leak out across the face, eventually pouring through the super structure, tugged into place by centrifugal force.|[[The Art of Halo 3]]<ref>'''[[Art of Halo 3]]''', ''page 117''</ref>}}

The exact methods used by the [[Forerunners]] to construct these artificial worlds is unknown. Presumably, large numbers of [[Constructors]] and [[Sentinels]] play a role in the construction process, laying down the initial structure. Over this is laid a vast network of scaffolding, over which the artificial environment is placed, including earth, rocks, and significant quantities of water.

[[The Ark]] plays a significant and noteworthy part in construction, and is the location where replacement Halo Installations are built and later transported, should one be destroyed by the [[Flood]] or opposing forces. Although the [[Ark]] constructs smaller installations, it is unknown how the [[Ark]] was initially built or if it is capable of repairing itself.