Editing MJOLNIR Powered Assault Armor/Mark IV

{{Era|UNSC|HCW}} 
[[File:Mark_IV_schematic.jpg|thumb|200px|right|Schematic of the baseline Mark IV platform in 2535.]]
{{quote|You're the only ones who can use them, Petty Officer. Who else could we give them to?|[[Catherine Halsey|Dr. Catherine Halsey]]}}
The '''Mark IV MJOLNIR Powered Assault Armor''' was the fourth version of the [[MJOLNIR Powered Assault Armor]] series. The suit was issued to [[SPARTAN-II Program|SPARTAN-II commandos]] on [[2525#November|November 27th, 2525]],<ref>'''[[Halo: The Fall of Reach]]''', ''page 113'' ''page 136'' (2010 edition)</ref> and was in service until [[2551|November 24th, 2551]], when it was replaced by the [[MJOLNIR Powered Assault Armor/Mark V|Mark V]].<ref>[http://www.bungie.net/News/content.aspx?type=topnews&link=BWU_012910 '''Bungie.net''': ''Bungie Weekly Update: 01.29.10'']</ref><ref group="note">''Halo: The Fall of Reach'' states that the Mark V was issued on August 29, 2552. However, the aforementioned Weekly Update, supported by Dr. Halsey's personal journal, retcons this, clearly stating that the Mark V was issued on November 24, 2551; the test performed by John-117 was intended to gauge the pairing of the Mark V suit with a piggy-backed AI, not to observe the suit's performance ''per se''. ''Halo Waypoint''<nowiki>'</nowiki>s ''MJOLNIR Project 2'' video erroneously presents the date given in the novel as valid.</ref> 

==Introduction==
[[File:MarkIV model.jpg|200px|thumb|The first iteration of the MJOLNIR platform.]]
Developed parallel to the SPARTAN-II Program<ref name="Sybex">'''Sybex [[Halo PC]] Strategy Guide''', ''page 5''</ref> by the [[Office of Naval Intelligence]]'s [[Materials Group]], the MJOLNIR powered assault armor was a radical redesign from previous large bulky exoskeletons, streamlining their design into a compact suits of armor, practical for use in the field. The brainchild of Dr. Catherine Halsey, the fourth iteration of the MJOLNIR armor represented her vision of creating a slim powered exoskeleton capable of taking full advantage of the physical capabilities of a SPARTAN-II.<ref name="Sybex"/> Planning and research for the revised MJOLNIR battlesuit began in 2511<ref name="halsey1">'''[[Dr. Halsey's personal journal]]''' ''July 30th, 2511 entry''</ref> along side the SPARTAN-II project, and over the course of 14 years its development gave birth to many new technologies that would later see major adoption throughout the military. 

Completed, the MJOLNIR battlesuit is a multilayer suit constructed in overlapping layers. It is a sealed system, capable of [[extra-vehicular activity]] or operations in toxic atmosphere and vacuum. It is hardened against [[Electromagnetic pulse|EMP]] and radiation, and has filters that are completely effective at removing toxins and bacteria from local atmosphere.<ref name="xbox">'''[http://www.xbox.com/en-US/games/h/halo/spotlight2.htm Master Chief's Armor: An Overview]'''</ref><ref group="note">The reference, ''Master Chief's Armor: An Overview'', was posted on xbox.com before the release of ''Halo: Combat Evolved''. It is an official excerpt from the Halo Story Team. However, the article has been removed from xbox.com and there are few websites that have re-posted the article, including the old ''Halo'' timeline that article can be viewed [[Xbox.com/Halo|here]].</ref><ref name="FoR120">'''Halo: The Fall of Reach''' ''page 120'' ''page 143'' (2010 edition)</ref>

The armor's outer shell is composed of a multilayer alloy of remarkable strength which has been augmented with a refractive coating capable of dispersing a limited amount of Covenant [[Directed energy weapon|energy weapon]] strikes.<ref name="xbox"/><ref name="FoR">'''Halo: The Fall of Reach''' ''page 114-115'' ''page 137'' (2010 edition)</ref> Underneath the alloy shell is a thick black armored titanium nanocomposite bodysuit. Underneath that layer is a gel-filled layer. The gel layer regulates temperature and can re-actively change its density in a few seconds.<ref name="xbox"/><ref name="FoR"/> The inner skinsuit is made of a moisture-absorbing synthetic material linked to an environmental control computer and the occupant's UNSC-issue [[neural interface]].<ref name="xbox"/><ref name="FoR"/> An [[Command Neural Interface|upgrade]] to the standard neural interface is issued to all high ranking officers; another [[SPARTAN neural interface|modified neural lace]] is issued to all SPARTAN-IIs in the UNSC as well. This network translates electrochemical signals to digital code and routes them through an interface connection at the rear of the skull.<ref name="xbox"/> Through this interface, the user's thoughts commands the armor's movement and weapons and input from the on board sensors comes directly to the user's mind.<ref name="xbox"/> The synthesis of machine and mind is so fast that it is almost impossible to chart the reaction time. Unfortunately, the system is so reactive that normal human beings cannot use the suit without injuring or even killing themselves.<ref name="for115">'''Halo: The Fall of Reach''', ''page 115'' ''page 138'' (2010 edition)</ref> Only humans who have undergone carbide ceramic ossification, a bone-strengthening treatment from the SPARTAN-II augmentation program, have been shown to safely operate the suit.

Sandwiched between the external armor and the internal padding is the most devastating weapon the suit carries: a layer of [[polymerized lithium niobocene]], a form of reactive metal liquid crystal.<ref name="xbox"/> Woven by molecular tools into a superdense layer, this layer is amorphous, yet it amplifies force, doubling lifting capability and increases reaction time by a factor of five.<ref name="Sybex"/> Such technology did not exist when work began on the Mark I prototypes.<ref name="Sybex"/><ref>'''Halo: The Fall of Reach''' ''page 70'' ''page 89'' (2010 edition)</ref>

Because of these advancements, the design is more akin to an actual suit of armor, as opposed to a powered exoskeleton; the user moves the suit, and in return the suit moves the user. This allows for an incredibly compact design when compared to other combat systems. The armor contains numerous features including an integrated computer system which continuously monitors weapons, biological functions, and a limited function motion sensor system. The suit also contains a built-in oxygen re-breather system that can provide air for up to ninety-minutes.<ref name="FoR120"/> The suit's helmet also features imaging and video recording, and thermal sensors among other features.

In its final phase the MJOLNIR armor weighs half a ton,<ref>'''Halo: The Fall of Reach''' ''page 2'' ''page 16'' (2010 edition)</ref> or 1,000 pounds, is a fully neural-linked system and is currently the most advanced piece of tactical military hardware in human hands.<ref name="xbox"/>

==Armor platforms==
[[File:H4FUD-MasterChief-MkIVArmor.png|thumb|185px|A secondary design of the original MJOLNIR platform, worn by John-117.]]
Throughout the Human-Covenant War, the Mark IV saw several generational design changes and became a testbed for new technologies and hardware to help improve its integrity and efficiency in certain combat conditions.<ref name="mjolnir">'''[http://halo.xbox.com/en-us/intel/theuniverse/tech/video/the-mjolnir-project-1/cf313a1a-e1e5-4be8-a9a2-7071eda6ca8f Halo Waypoint: The MJOLNIR Project Part 1]'''</ref> While some of these variants are rumors and have never been witnessed in the field, some have become common knowledge.<ref name="eync8889">'''[[Halo Encyclopedia]]''' ''pages 88-89''</ref> By [[2535]], fourteen variants had already been developed.<ref name="journal">'''Dr. Halsey's Personal Journal''' ''January 7th, 2535 entry''</ref> Mark IV went through multiple external design iterations,<ref>[http://halo.xbox.com/blogs/Headlines/post/2012/07/19/The-Halo-Bulletin-71812.aspx ''The Halo Bulletin: 7.18.12'']</ref> and variants designed for a specific purpose tend, by necessity, to look different from the contemporary core model.<ref name="way-mjol"/> However, each generational Mark is categorized by its internal components and software suit, not by its superficial design: therefore, while a first-generation Mark IV suit may look drastically different from a third-generation suit, they are still essentially the same model.<ref name="way-mjol">'''[http://halo.xbox.com/en-us/intel/related/video/the-mjolnir-project-2/46e89c1a-f619-41e2-ad7f-ab65c61ca2df Halo Waypoint: The MJOLNIR Project Part 2]'''</ref>   

<!--Please do not add Mark IV into the titles below as the Mark categorization was not mandated until 2535.--> 
===Functional prototype===
The Materials Group developed this prototype to test the technologies that were being developed for the MJOLNIR battlesuit. In February 2525, this model was sent to [[UNSC Special Forces|Naval Special Warfare]] for evaluation and final testing. Over the next four months the model was tested to ensure proper function and evaluate its capabilities. The prototype was built and fine-tuned for the SPARTAN-II supersoldiers. A test was conducted to see if a normal human could operate the suit. Because of an override in the prototypes safe mode to prevent unintended use, the subject was killed by his own muscular twitch.<ref name="hals2">'''Dr. Halsey's Personal Journal''' ''June 30, 2525 entry''</ref><ref name="for115"/> A short time after the failed demonstration, limited production of the MJOLNIR battlesuit was approved.<ref name="hals2"/>

===Initial production model===
Five months after production began,<ref name="hals2"/> the MJOLNIR PAA entered service. Although highly advanced, the suit entered service in an accelerated state due to the Covenant threat. As such, upgrades to the suit were already in the works when it was issued to the Spartans. The first-issued model was bulky, angular, and restrictive in mobility. Due to its design philosophy being centered around a human insurrection, this model was not adequately prepared for dealing with advanced alien technology and weapons. By [[2531]], the suit had been replaced by a generational upgrade to better combat the alien threat.<ref name="journal"/><ref name="mjolnir"/><ref name="original" group="note">''[[Halo: Fall of Reach - Covenant]]'' and ''[[Scanned]]'' show that the first version of MJOLNIR to be issued was the one featured in ''Halo Wars'' and ''[[Origins]]''. In ''Halo 4: Forward Unto Dawn'', set in [[2526]], John-117 wears the version featured in ''[[The Package]]'' and Fred-104 wears a suit almost identical to the later Mark V [B]. Presumably, multiple variants of the first-generation suit had already been created by this time; as previously mentioned, external components are irrelevant to the suit's internal design. Though the suit featured in ''Forward Unto Dawn'' and the suit featured in ''The Package'' share external components, they are presumably quite different internally, as eighteen years elapse between the web series and the short.</ref>

===Final production model===
By 2535 the MJOLNIR system, (intended as a continuous, pioneering effort to shatter technological barriers), had become the single most expensive item ever produced by the UNSC.<ref>'''Halo: Ghosts of Onyx''' ''page 45''</ref> With each suit costing as much as a [[UNSC destroyer|destroyer]] to manufacture,<ref>'''Halo Legends''', ''Halo: The Story So Far''</ref> the budgetary commission overseeing the MJOLNIR project mandated a simplified generational system to categorize, prioritize, and serialize development neatly into fiscal-year budgets. Thus, the "Mark" system was added to MJOLNIR, with the current version being designated "Mark IV" to suggest continuity with the powered exoskeleton program that had preceded MJOLNIR's development.<ref name="hals3"/>

With the adoption of the "Mark" categorization, an updated model of the suit that had entered service four years earlier was adopted as the standard-issue suit. Its design would inform all future "Mark" generations. The third-generation suit included numerous improvements not available at the beginning of the war, including a standardized vacuum survival system, standard fusion power, and a new radar sensory package.<ref name="hals3">'''Dr. Halsey's personal journal''' ''January 7, 2535 entry''</ref>

==Armor variants==
===Advanced Hardware Program===
The MJOLNIR advanced hardware program refers to the development and furthering of hardware and technologies for testing, evaluation, and incorporation into later versions of the MJOLNIR armor. The goal of the program is to produce new technologies to aid the SPARTAN-IIs in the war against the Covenant,<ref name="eync8889"/> such as the prototypical [[energy shielding]] tested by [[Red Team]] in [[2531]].<ref>'''Halo: The Essential Visual Guide''', ''page 119'': ''"Energy shielding was a key feature of Mark V, although other Spartan squads had field-tested prototypes of this technology as early as 2531."''</ref><ref group="note">According to [[Ensemble Studios]] representatives, ''Halo Wars''<nowiki>'</nowiki> portrayal of the Mark IV with energy shields was intended to be a liberty made for the sake of gameplay, as stated [http://www.halowars.com/news/devblog/archive/2009/08/25/Lessons-Learned.aspx here]. However, this portrayal was canonized by ''[[Halo: The Essential Visual Guide|The Essential Visual Guide]]'', which provides that the shielding feature saw in-the-field prototyping as early as 2531; this implicitly refers to Red Team, as the Grenadier variant did not enter service until 2535. Furthermore, the version of the Mark IV seen in ''The Package'', (set in 2544), displays a shield bar on its HUD, (which may be a misrepresented health bar), though it does not possess the distinctive shielding lights of later Marks. In ''Halo 4: Forward Unto Dawn'', the same suit clearly possesses shielding lights but shows no sign of a shield when shot.</ref> Any changes in appearance of the armor are for research and development of future MJOLNIR components.<ref name="eync8889"/>

===Mark IV MJOLNIR Powered Assault Armor/Air Assault [AA] variant===
{{Main|MJOLNIR Powered Assault Armor/AA variant}}
The Air Assault variant was developed as an improvement of the ODST helmet and entered service in 2535. The helmet features specialized optics and can provide real-time satellite imagery and enemy signature allocation. The helmet offers key advantages during airborne deployment scenarios.<ref name="EVG">'''[[Halo: The Essential Visual Guide]]''' ''page 4''</ref>

===Mark IV MJOLNIR Powered Assault Armor/EVA [V] variant===
{{Main|MJOLNIR Powered Assault Armor/V variant}}
The MJOLNIR Mark IV Extra Vehicular Activity variant was developed to focus on increasing exo-atmospheric endurance and improving mobility in zero gravity. The movement could be controlled with the use of a [[T-PACK]], or Thruster Pack, attached to the armor. This was not without dangers however; in case the T-PACK would malfunction, the wearer would be propelled into deep space where a rescue would be nearly impossible. The V variant of the MJOLNIR armor contains a reverse-angle camera on the helmet to allow for better view of anything behind the wearer. The helmet also contains a single-beam laser TEAMCOM system for communications. The only limitation of this variant is the mobility of the wearer is a fraction of normal movement.<ref>'''Halo: Ghosts of Onyx''', ''pages 49-50 and page 57''</ref> Technologies developed for the Mark IV EVA variant were later applied for the V Variant of the Mark V and Mark VI armor. However, this version was able to maneuver in vacuum without the original use of thruster packs.

===Mark IV MJOLNIR Powered Assault Armor/Commando [K] variant===
{{Main|MJOLNIR Powered Assault Armor/K variant}}
The Mark IV version of the Commando variant's design differs greatly from the Mark V version. Its ability to improve a Spartan's tactical awareness on the battlefield led to its frequent use during the Human-Covenant War.<ref>'''Halo: The Essential Visual Guide''', ''page 33''</ref>

===Mark IV MJOLNIR Powered Assault Armor/Security [M] variant===
{{Main|MJOLNIR Powered Assault Armor/M variant}}
The Mark IV [M] was manufactured at the [[Misriah Armory|Misriah Armories]] facility on [[Mars]] in [[2528]]. 

===Mark IV MJOLNIR Powered Assault Armor/EOD [E] variant===
After the MJOLNIR PAA was activated in 2525, the [[Damascus Materials Testing Facility]] on [[Chi Ceti IV]] began working on a variant of MJOLNIR armor that would improve the survivability of the user in close proximity to an explosion. The result became known as the Explosive Ordnance Disposal variant MJOLNIR armor, entering service in [[2531]].<ref name="armor">'''Halo: Reach''', ''The Armory''</ref> The EOD variant is speculated to have been developed in response to the death of [[Samuel-034]] in November of 2525.<ref name="way-mjol"/>

===MJOLNIR Powered Assault Armor/CQC [C] variant===  
{{Main|MJOLNIR Powered Assault Armor/CQC variant}}
Entering service in [[2548]],<ref name="armor"/> the CQC was the predecessor to the MJOLNIR Powered Assault Armor/C variant, or "CQB". The main advantage of the CQC variant over its successor is that its design is less rigid, allowing field upgrades to be easier. The CQC variant is standard equipment for missions involving close-quarters combat, including boarding actions and urban operations.<ref name="armor"/>

===Mark IV MJOLNIR Powered Assault Armor/Grenadier [G] variant===
{{Main|Mark IV(G) MJOLNIR Powered Assault Armor}}
The Mk. IV [G] variant is an up-armored prototype based on the baseline Mark IV that was used as a testbed for incorporating [[energy shielding]] technology into the MJOLNIR program.<ref name="armor"/> Although these tests proved unsuccessful, the data gained in addition to continued research of stolen Covenant technology paved the way for later successes.<ref name="hals3"/> Despite the unsuccessful attempt to incorporate energy shield technology, the [G] variant continued to served as the basis for all subsequent supplemental armor development programs.<ref name="armor"/>

==Inner armor components==
*'''Inner skinsuit:'''
The inner skinsuit is made of a moisture-absorbing synthetic material linked to an environmental control computer and the occupant's neural interface. It controls the suit's temperature and actively changes how the suit fits the user.<ref name="for115"/>

*'''[[Hydrostatic gel]]:''' 
On top of the inner skinsuit is a gel-filled layer, which regulates the temperature of the suit and can change its density to conform to the wearer's shape. The temperature inside the suit is controlled by the moisture absorbing cloth suit underneath the hydrostatic layer. The hydrostatic gel layer can also be pressurized to various levels to potentially save the wearers life should the wearer be subjected to high G forces or a high velocity impact; however, over-pressurizing this layer can cause nitrogen embolisms.<ref>'''Halo: First Strike''' ''page 13'' ''page 20'' (2010 edition)</ref><ref>'''Halo: Ghosts of Onyx''' ''page 36''</ref> 

*'''[[Polymerized lithium niobocene|Liquid metal crystal piezoelectric layer]]:'''
Fitted in between the outer plates and the inner padding, is a layer of liquid crystal within a piezoelectric material that deforms along a preferred axis when exposed to a electric charge.<ref name="journaljul">'''Dr. Halsey's Personal Journal''' ''July 11th, 2511 entry''</ref> This layer acts as a sheath or a suit artificial muscle; this reactive piezoelectric effect increases the strength, reaction time, mobility, speed, and all around physical performance of the suits user.<ref name="journaljul"/> The material is amorphous, which circumvents a major obstacle in its design: custom fitting millions of the polygonal pieces under the second armor layer.<ref name="journalsep">'''Dr. Halsey's Personal Journal''' ''September 1st, 2525 entry''</ref> Knitted together at a molecular level the liquid crystal material is merely "poured" into a multilayered Sierpinski capillary system where microelectric fields can direct crystallization geometries.<ref name="journalsep"/> The only downfall is the materials production, which involves classified super-toxic precursor materials and requires a zero-gravity environment.<ref name="journalsep"/> As such this layer accounts for over eighty percent of the MJOLNIR armors cost of construction and materials.

*'''[[Pressure seal]]:'''
The Pressure Seal is a vital component to the MJOLNIR system, it keeps the system airtight, underwater or in space. The seal is very strong but will only break under extreme pressure, such as in a high velocity impact or when the Hydrostatic Gel has been over-pressurized. 

*'''Titanium nanocomposite bodysuit:'''
Sandwiched between the external armor and the internal padding is a thick black armored bodysuit. This suit has numerous functions, small but vital to the safety and survival of the wearer. The bodysuit is made of a titanium-based material, making it very strong and yet very flexible. It also serves as another layer of protection against ballistics attacks and is coated with a heat resistant material to disperse heat from plasma weapons.<ref name="enyc"/>

*'''Lock-down system''': The lock-down system protects muscles and joints from traumatic, high-impact injuries by seizing the suit into a rigid posture through modifying the density of the hydrostatic gel layer.<ref>''Halo 3'', level ''[[Arrival]]''</ref><ref>''Halo Encyclopedia'', page 91</ref><ref>'''Halo: Reach''', level ''[[Tip of the Spear]]''</ref><ref>[http://www.youtube.com/watch?v=eLmtVh_bmhs '''Youtube''': ''Halo Reach Legendary Edition'' developer commentary, part 4]</ref><ref group="note">No source has stated that the MJOLNIR Mark IV was equipped with a lock-down system. However, this article assumes that the Mark IV did possess such a system, due in part to [[Jorge-052]] being able to lock his upgraded Mark IV/G armor in the level ''Tip of the Spear'' in ''Halo: Reach''.</ref>

==Outer shell and components==
The outer shell of the MJOLNIR armor is comprised of a fairly thick titanium alloy. This alloy is very resilient, can take significant punishment, and is nearly impervious to small arms fire. While enough shots from armor piercing rounds will breach the outer shell, the suit can take a few glancing blows from them without compromising the armor. The outer shell of the MJOLNIR suit is covered with a refractive coating to help disperse the heat experienced from Covenant energy weapons. However one or two direct hits from any plasma weapon will compromise the armor plating.<ref name="enyc">'''Halo Encyclopedia''' ''page 90''</ref>  

*'''Integrated Communications Helmet:'''
The MJOLNIR helmet is one of the most vital aspects to the MJOLNIR armor system. It is made of [[titanium]] and features a [[heads-up display]], that links to the brain and hands, and can identify equipment and display information about it when it is picked up by the wearer. A environmental control unit that includes filters to remove toxins from the atmosphere, and a rebreather to automatically supply oxygen to the wearer during EVA. In addition the helmet is packed with thermal and motion sensors, communications, solar-powered lighting, and imaging and video gear.<ref name="hals3"/>

The most important feature though, is the direct neural interface system which connects to a SPARTAN-IIs neural implants. Two core processor chips are implanted into the subjects skull in the rear of the head. This is essentially comparable to an on board computer using parts of the human brain for processing - when the connector at the rear of the subjects head and receptors in the brain link to the helmets on board sensors it creates the neural link needed to move the MJOLNIR suit.<ref name="hals3"/>

*'''Titanium alloy outer shell/chest:'''
The titanium chest plating provides maximum ballistics protection in both generational versions of the Mark IV. The older generation consists of wide plating to allow for free rotation of the head and neck; the external mic is located below the collar area and below that an environmental control unit. The earlier generation also had large arm sockets, and the waist area consists of free rotating bearings which lock into the lower body or jumper armor section. Later versions of the chest plates are more angular and are joined via a hinge system on both the central brace and the shoulder connectors, allowing them to rise and fall with the user's movements.<ref name="hals3"/>

*'''Titanium alloy outer shell/arms:'''
The earlier versions of the soldier and arm plating consisted of an organic shape with larger shoulder area for ample protection the upper assembly piece sits flush inside the upper-arm armor. The elbow armor was hinged sit flush with one another when arm is straight, making hyperextension impossible without ample force to destroy the armor. The forearm armor is the same with locking pieces to prevent overrotation, the lower portion is attached to the handguard. The range of motion is adequate for firearm use and hand-to-hand combat, however the guard prevents hyperextension of the wrist. Later revisions to this armor discard this for more nanofabricated pieces and more mobility focused plating. The pauldrons are mounted at a downwards diagonal angle at the upper edge of the shoulder, independently of the armor below them. This allows the lower arm pieces to slide and rotate beneath them, and when the arms are raised, the angled pauldrons move with them.<ref name="hals3"/>

*'''Titanium alloy outer shell/waist:'''
The MJOLNIR armor's torso plating is connected to the upper-torso plating by free-rotating waist connectors the waist plating contains ammunition/utility pouches. The lower-abdomen plate connects into a track for upper torso bending, the codpiece is connected to the femoral-artery armor.<ref name="hals3"/>

*'''Titanium alloy outer shell/legs:'''
The MJOLNIR PAA's leg armor consists of two major plating sections, with a third piece protecting the knees. The earlier version of the armor consisted of the thigh armor which is actually two sections held together by two locking collars, the knee pads are secured on the sides. The lower leg contains reinforced pezioelectric bladders which secure ankle and lower legs to prevent impact injury from high-elevation jumps. The boots consist of 15mm-thick soles, which are secured by a foot covering hinge locking bolt.<ref name="hals3"/>

*'''Magnetic weapon holder strips:'''
Available on updated outer armor components of the Mark IV the magnetic strips are very small yet powerful magnets placed on the legs, waist, and back of the suit and is used to hold any equipment with a magnetic property. The suit also contains a magnet system on the boots of the MJOLNIR suit that allow its wearer to stay attached to a metal surface in Zero-G environments and can be toggled on or off by the wearer. In addition to the magnetic holders, the default Mark IV is also equipped with utility pouches on the waist and a clip for a holster capable of accommodating most UNSC sidearms.<ref name="journal"/><ref name="hals3"/>

*'''[[Biofoam|Biofoam injector port]]:'''
The biofoam injectors on the Mark IV is a port where a direct supply of biofoam or other medicines, must be administered from a standard military first aid kit when the wearer is injured, as the suit does not hold or generate its own supply inside the suit.

*'''Fission reactor:'''
Integrated in the limited production model of the MJOLNIR PAA the nuclear fission reactor was the MJOLNIR armors source of power, the reactor was built into the suit and allowed for unlimited power. However because of the delicacy and radioactive nature of the fission reactor its use was limited until it was replaced with a micro-fusion plant in the final production model in 2535.<ref name="hals3"/><ref>'''Halo: Ghosts of Onyx''' ''page 45''</ref>

*'''Microfusion reactor:'''
Integrated in the final production model in 2531, the microfusion cell is the most vital component to the MJOLNIR system, as it provides power to all components of the MJOLNIR armor. The reactor is built into the suit and allows for nearly unlimited power. The fusion reactor in all versions of the MJOLNIR armor is half the size of a normal fusion pack that conventional marines carry around.<ref>'''Halo: The Fall of Reach''' ''page 114'' ''page 137'' (2010 edition)</ref>

*'''[[MJOLNIR power supply control unit|Power supply control unit]]''': 
The power supply control unit is integrated into the miniature fusion reactor located on the back of the MJOLNIR suit. It provides power distribution to the suit's functions and can be overloaded when too much power is allocated to one function or all functions for long periods of time.

*'''[[Fail-safe detonation system]]''':
This system functions as a self-destruct mechanism in order to prevent a dead Spartan's armor from being compromised by hostiles. It is activated by a series of digits that only the Spartans know. When engaged, it produces a reactor overload that burns everything within a ten-meter radius, then produces a large blast.<ref>'''Halo: First Strike''', ''page 315''</ref>

==Trivia==
{{Linkbox|gallery=yes|gallerypage=Images of MJOLNIR Mark IV}}
*In ''Halo Legends'', many elements are portrayed with considerable artistic license; as such, their visual appearances may not be considered canon. For example, in the episode ''Homecoming'', [[Daisy-023]] is depicted as wearing a helmet that resembles that of the MJOLNIR CQB variant during the [[Harvest Campaign]] in [[2531]]. However, the CQC variant, the precursor to the CQB variant, entered service in 2548 and was developed using feedback from the [[Battle of Jericho VII]], which occurred in 2535; thus, it is impossible for the CQB variant to have been in use seventeen years earlier.
**The director's commentary for the episode reveals that the armor's appearance is largely an aesthetic concession to the studio to allow for some visual variety for the character, and as a nod towards multiplayer fans who use armor permutations, such as the CQC variant. The same is true for the armor's color, though this is also representative of an effort to camouflage the suit. This means that other than the suit's color, the armor's appearance is non-canon.<ref>'''Halo Legends:''' ''Homecoming'', director commentary.</ref> At the end of the episode, John-117 is depicted in a Mark IV suit that has greatly exaggerated features, more closely resembling the Mark VI; this is clearly another instance of non-canonical imagery.
*The sketches of the limited-production Mark IV in [[Dr. Halsey's personal journal|Doctor Halsey's journal]] are almost identical to [[:File:Masterchief sheik.png|an early concept]] for the MJOLNIR armor, apart from the helmet.
*In 2526 Kelly and Fred are seen in MJOLNIR Mark IV suits that that are visually very similar to the first generation of the MJOLNIR Mark V armor worn by NOBLE team in 2552 (Fred's armor being almost identical to that of the MJOLNIR Mk. V [B]). This is because the actors were using repainted Mark Vs made for the ''[[Deliver Hope]]'' commercial.

==Gallery==
<gallery>
File:H4L Awakening 1.jpg|[[John-117]] being equipped with his original MJOLNIR armor.
File:H4L Awakening 2.jpg|Technicians securing the back section of John's MJOLNIR.
File:The Covenant - MJOLNIR.jpg|John-117 in his newly issued MJOLNIR armor.
File:Mjolnir MkIV.png|A Spartan in the first-generation MJOLNIR armor.
File:MarkIV render.png|[[Jerome-092]] in his first-generation suit.
File:John117FOReach.png|John-117 wearing the same armor.
File:The Babysitter Cal-141.jpg|[[Cal-141]]'s obsolete first-generation armor circa [[2540]] or later.
File:H4FUD-MasterChief-John117.png|John wearing a superficially distinct variant of the original model.<ref name="original" group="note"/>
File:FUD-Fred-Helmet.jpg|[[Fred-104]] wearing another variant of the original suit. The helmet closely resembles the later [[MJOLNIR Powered Assault Armor/Mark V(B)|Mark V [B]]].
File:HaloLegends-MasterChief.png|John wearing a later-generation suit with the same external components he used on [[Circinius IV]].
File:The Package poster.jpg|Three Spartans wearing the previous suit with MOS-specific modifications.
File:CP armor.png|[[Gray Team]]'s Mark IV model.
File:XHW - unscunit.jpg|An early model of the MJOLNIR in ''Halo Wars'' alongside a [[Hellbringer]].
File:Halo Wars - Mark IV.png|Another early design of the MJOLNIR in ''Halo Wars''. This version is featured in the game's [[Halo Wars announcement trailer|announcement trailer]].
File:XHW - spartan03.jpg|A later pass on the MJOLNIR design from ''Halo Wars''.
File:HWunit Spartan.png|In-game model of a Spartan's armor in ''Halo Wars''. The pauldrons are symmetrical in-game.
File:1775194-gallery.png|Concept art of the Mark IV version featured in ''The Package''.
File:Ih mjolnir 3.jpg|Concept of the Mark IV armor for ''Halo: Reach''.
File:VanityMkV.png|Visually the same armor, the Mark V is essentially a Mark IV armor platform upgraded to function with the MJOLNIR's new shielding technology.
</gallery>

==Notes==
<references group="note"/>

==Sources==
{{Reflist|2}}
{{SPARTAN Armor}}
{{armor}}
[[Category:MJOLNIR Armor]]