Editing Semi-Powered Infiltration armor

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[[File:Semi-Powered Infiltration.png|200px|thumb|right|A concept illustration of SPI armor from the ''[[Art of Halo 3]]''.<ref>'''[[The Art of Halo 3]]''', ''page 140''</ref>]]

The '''Semi-Powered Infiltration armor''' ('''SPI armor''') is a [[UNSC]] combat [[armor]] system designed with an emphasis on stealth through the use of [[photoreactive panel|special photo-reactive panels]].<ref name="goo14">'''[[Halo: Ghosts of Onyx]]''', ''page 14''</ref> Although early versions of the SPI system were tested by [[Orbital Drop Shock Troopers]],<ref name="g164">'''Halo: Ghosts of Onyx''', ''page 164''</ref> the armor was most prominently issued to the [[SPARTAN-III program|SPARTAN-III]] supersoldiers.<ref name="goo14"/>

Described as "part legionnaire mail, part tactical body armor, and part chameleon", the SPI armor features [[photoreactive panel]]s that mimic the surrounding textures, effectively being the UNSC equivalent to the [[Covenant]]'s [[active camouflage]] systems.<ref>'''Halo: Ghosts of Onyx''', ''page 16''</ref> The SPI armor features a full body armor with an enclosed helmet and [[heads-up display]]. The undersuit is equipped with a cushioning layer of liquid nanocrystals that provide more ballistic protection than three centimeters of [[wikipedia:Kevlar|Kevlar]] diamond weave, without the bulk.<ref name="goo171">'''Halo: Ghosts of Onyx''', ''page 171''</ref> The hardened armor plates, though advanced compared to standard UNSC infantry armor, can only take a few glancing blows before failing.<ref name="goo14"/>

Though more advanced than the [[Orbital Drop Shock Trooper]]s' [[ODST armor|body armor]], the SPI armor is less advanced and powerful than the [[MJOLNIR armor]] used by the [[SPARTAN-II program|SPARTAN-IIs]].<ref>'''[[Halo: Glasslands]]''', ''page 207''</ref> Its main benefit is that it is drastically cheaper to produce than MJOLNIR.<ref name="goo46">'''Halo: Ghosts of Onyx''', ''page 46''</ref> It is also not as bulky or as heavy as the MJOLNIR armor, making it easier to handle and transport.<ref>'''Halo: Glasslands''', ''page 40''</ref> The SPI suit does not enhance the user's physical performance (i.e. strength, speed, agility), unlike MJOLNIR;<ref>'''Halo: Ghosts of Onyx''', ''page 140''</ref> as a result, it can be worn by any individual and does not require special neurological, skeletal or muscular augmentation.<ref>'''Halo: Ghosts of Onyx''', ''pages 89, 94''</ref><ref name="g164"/> It is also made of a less durable, less dense alloy than MJOLNIR armor: [[Kelly-087]] dented a SPARTAN-III's chest plate with her fist when first encountering the SPARTAN-IIIs.<ref name="goo168">'''Halo: Ghosts of Onyx''', ''pages 168-169''</ref> It also lacks an [[energy shielding]] system, making the user far more vulnerable to enemy fire and was a major contributor to the high fatality rate of the SPARTAN-IIIs. The exception to this limitation could be found in the SPARTAN-III [[Headhunters]]: their experimental armor was known to be equipped with energy shields, due to their elite nature and value. However, power must be drawn from the energy shields to recharge the suit's active camouflage module.<ref name="head212">'''[[Halo: Evolutions - Essential Tales of the Halo Universe]]''', "[[Headhunters]]", ''page 212''</ref>

The Mark I was the first, experimental iteration of the SPI system used by the SPARTAN-IIIs of [[SPARTAN-III Alpha Company|Alpha Company]]. The featured photo-reactive panels gave the Spartans of Alpha Company a rough equivalent to active camouflage. The camouflage patterns, however, shifted irregularly and imperfectly, which made the photo-reactive panels inferior compared to the [[Covenant]]'s active camouflage technologies.<ref>'''Halo: Ghosts of Onyx''', ''page 85''</ref>

The Mark II was an improvement of the SPI Mark I, first used by the drill instructors of [[SPARTAN-III Beta Company|Beta Company]], and then by the Spartans of Beta and Gamma Companies.<ref name="goo89">'''Halo: Ghosts of Onyx''', ''page 89''</ref> The armor sports new photoreactive coating to boost its camouflaging properties. Although the new photoreactive coating can mimic a wide range of electromagnetic radiation, it is still sensitive to overload, making the wearer vulnerable for several seconds after a [[flashbang]] or [[plasma]] hit while the panels reset.<ref name="goo113">'''Halo: Ghosts of Onyx''', ''page 113''</ref>

The armor was proposed by [[Kurt Ambrose]] in [[2537]] for Alpha Company, but the request was denied because the armor was over budget.<ref>'''Halo: Ghosts of Onyx''', ''page 80''</ref> After Alpha Company's Pyrrhic victory in [[Operation: PROMETHEUS]], the Mark II was approved for mass production. After the augmentation of [[SPARTAN-III Gamma Company|Gamma Company]], small adjustments were installed into the Mark II SPI armor,<ref name="goo99"/> including experimental refits to the ballistic gel layers, upgraded software suites, and other functions, slated to be introduced to the systems prior to Gamma Company's deployment in [[2552]].<ref name="goo99">'''Halo: Ghosts of Onyx''', ''page 99''</ref> One minor improvement is that the armor is now hermetically sealed and contains an internal [[oxygen]] supply.<ref name="g251">'''Halo: Ghosts of Onyx''', ''page 251''</ref>

==Armor components==

;Helmet: The SPI helmet features a large, bulbous faceplate somewhat similar to that of the [[MJOLNIR Powered Assault Armor/V variant|MJOLNIR EVA variant]]. The visor is normally gold-mirrored in color<ref name="goo115">'''Halo: Ghosts of Onyx''', ''page 115''</ref> and can be depolarized.<ref name="goo168"/> The helmet supports a [[heads-up display]] with features similar to that of the MJOLNIR system, including TACMAP, TEAMBIO and [[COM|TEAMCOM]] interfaces as well as team status lights.<ref>'''Halo: Ghosts of Onyx''', ''pages 17, 22''</ref><ref name="g114">'''Halo: Ghosts of Onyx''', ''page 114''</ref> The visor suite features an automatic magnification and image enhancement system controlled by the wearer's eye movements. For example, if the wearer squints while looking at a particular spot the system will automatically zoom in.<ref>'''Halo: Ghosts of Onyx''', ''page 19''</ref> Both the image enhancement and the visor's internal polarization can also be controlled manually.<ref>'''Halo: Ghosts of Onyx''', ''page 268''</ref><ref>'''Halo: Ghosts of Onyx''', ''page 345''</ref> The helmet possesses tactical lights<ref>'''Halo: Ghosts of Onyx''', ''page 273''</ref> and a defogging vent to remove internal moisture.<ref>'''Halo: Ghosts of Onyx''', ''page 316''</ref>

;Bodysuit: The bodysuit of the SPI system contains a layer of ballistic liquid nanocrystal that is significantly more effective than traditional body armor materials such as Kevlar whilst being less bulky.<ref name="goo171"/><ref name="g114"/><ref>'''Halo: Ghosts of Onyx''', ''page 360''</ref> The suit comprises more than one component, including leggings.<ref name="g141">'''Halo: Ghosts of Onyx''', ''page 141''</ref>

;Photoreactive panels: While matte gray when inert,<ref name="g141"/> the photoreactive panels covering the SPI suit act as [[active camouflage]] when active,<ref>'''Halo: Ghosts of Onyx''', ''page 165''</ref> effectively blending the wearer with their environment.<ref name="goo14"/> Since the photo-reactive plates take time to recover after explosions such as a [[flashbang grenade]] and [[Plasma weaponry|plasma]] hits, the SPARTAN-III is visible until the plates recover.<ref name="goo113"/> With the exception of the [[Headhunters]]' suits, the SPI armor does not feature energy field-based active camouflage systems like those of the Covenant.<ref name="head212"/>

;Environmental controls: The suit possesses rudimentary environmental regulation system to maintain a comfortable temperature for the wearer.<ref>'''Halo: Ghosts of Onyx''', ''page 22''</ref> However, the system is not designed for extended use and it will become increasingly uncomfortable to wear if used continuously over long periods of time.<ref>'''Halo: Ghosts of Onyx''', ''page 254''</ref> As of 2552, the Mark II SPI armor is also fully sealed and contains an internal oxygen supply.<ref name="g251"/> The armor also has an efficient cooling system and is significantly difficult to detect even with thermal scanners.<ref name="goo89"/>

The SPI armor is referred to as "PR" twice in ''Halo: Ghosts of Onyx''.<ref>'''Halo: Ghosts of Onyx''', ''page 87'' (''"...the flaws in their Mark-I PR suits..."'')</ref><ref>'''Halo: Ghosts of Onyx''', ''page 141'' (''"...and pulled on the PR leggings."'')</ref> Since no context is provided for this alternate designation, it is possible that the suit was known as "PR" (likely an acronym for "PhotoReactive") in an earlier revision of the novel's manuscript and that the presence of the two mentions in the final book is an editing oversight.

File:SpartanIII.jpg|A Spartan wearing SPI armor.

File:Headhunters.png|Two Headhunters, [[Roland (SPARTAN-III)|Roland]] and [[Jonah]], wearing SPI armor. The former is wearing an unknown variant.

File:Headhunter SPI Armor.jpg|[[Jonah]] wearing his SPI armor.

File:HLL cover-Olivia full.png|[[Olivia-G291]] in SPI armor with her helmet removed.

*''[[Halo: Evolutions - Essential Tales of the Halo Universe]]''

*''[[Halo Online]]'' {{Mo}}

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