Energy shielding

Several UNSC, Covenant and Forerunner vehicles, devices and armor systems make use of Energy shielding to protect users from harm. Energy shields consist of a field of energized particles that wraps around a surface, which deflects objects that attempt to impact the surface.

Human energy shielding
Humans started using energy shield technology with the production of the MJOLNIR Mark V powered assault armor, and has since been incorporated into all later models. This breakthrough was achieved through reverse-engineering the technology used in Kig-yar point defense gauntlets. Unlike the Covenant Elite Personal Energy Shield, when the human shield takes damage, it glows gold instead of blue.

Although the shields of MJOLNIR armor are very resilient, they can be stripped in seconds if the wearer isn't careful. Plasma weapons are especially effective against MJOLNIR and Elite Personal Energy Shield shields. Plasma Rifles, Plasma Pistols, and Plasma Cannons are all very good at depleting the MJOLNIR's shields.

One of the UNSC's most recent breakthroughs in energy shield development came with the creation of the YSS-1000 starfighter, which is the first human spacecraft known to use energy shields.

During the Fall of Reach, ONI utilized a prototype "drop shield" which had the protective abilities of the bubble shield and the healing abilities of a regenerator. Collapsing under continuous fire, the drop shield proved to be not as indestructible as the bubble shield, and not as fast a healer as the regenerator. The shield itself greatly resembles the bubble shield, even sporting its counterpart's comprising geometric shapes, but is instead blue in color.

Covenant energy shielding
The Covenant make extensive use of energy shielding technology. Nearly all Covenant starships larger than a Corvette use energy shields, and several ground-based structures, such as Covenant bases and Spires, use shields as well. Species such as Sangheili, Kig-yar, Jiralhanae, Huragok and high-ranking Yanme'e make use of personal energy shields of various types on the battlefield.

Also, the Covenant have discovered how to run Active Camo and Shielding at the same time. Even Tartarus and the Prophet of Regret were equipped with personal shields. Regret's shield, presumably projected by his Gravity Throne, was very similar to the Bubble Shield. It deflected all forms of projectile, plasma, and explosive weaponry and never depleted. It was also similar in that one could simply walk through the shield. It was this that allowed the Master Chief to kill Regret. Tartarus' shield is much different and seems to have to be actively turned on. His shield would deflect almost all attacks from the elites, even energy swords, and the only weapon really able to overload it was a beam rifle. It is implied that other Brutes do not have this type of shielding since Cortana says when first fighting brutes on the level Gravemind: "They don't have shield generators, but take them out before... it's berserking!".

The only Covenant vehicles to have shielding are the Locust and after an upgrade the Wraith and Ghost. It is odd that the Covenant do not have energy shields on any of their ground and aerial vehicles in the other Halo games (Halo: Combat Evolved, Halo 2, and Halo 3). Since they are able to make personal energy shields they should be able to have shields protecting their Wraiths, Banshees and Ghosts. It is likely that Bungie did not add shields to these vehicles in order to make them balanced. A shielded Wraith, for example, would be a significant challenge to the player.

Starship shielding
Nearly all Covenant vessels are protected by a highly resistant energy shield that can recharge over time. Covenant starship shields are light-gray/silver in color. The shields can take a vast amount of punishment, and can recharge very quickly. The only known flaw of starship shields is that when the vessel fires its Plasma weapons, the ship needs to drop a section of its shields for a fraction of a second. Otherwise, the Plasma Torpedo would detonate on the inside of the shields, damaging the ship itself. This weakness was demonstrated when a group of Spartans destroyed a Covenant ship in Halo: Fall of Reach, by going inside of the ship and planting an explosive. Additionally, when a Covenant ship unloads troops and supplies, it must lower its shields to let dropships out.

Shields can absorb almost all missile fire, including hundreds of Archer Missiles and even a Shiva nuclear missile (although Shiva nukes will usually deplete their shields, making them vulnerable to smaller weapons). The only UNSC weapons capable of penetrating a Covenant Starship's Shield are the MAC guns. Even then, ship-based MACs take multiple rounds to drop the shields; only a Super-MAC round from an Orbital Defense Platform can penetrate Covenant shields in one hit.

Plasma and other energy weapons, on the other hand, can relatively easily disable the shields, in much the same manner as Elite Personal Energy Shields. It must be noted that the size and class of a vessel determines the strength of its shields. Also, even though the shield can absorb a direct nuclear missile, if it detonates "inside" the shield, the blast will be magnified. It has been observed exploding inside the shield, and destroying the ship before the shields collapse. The pressure and heat released would bounce off the shields back into the ship to further damage it.

Another way to disable the shipboard energy shields is through an EMP, which would knock out the shields, but EMPs are only seen being used by Shivas when they explode, so it is a much more wasteful method of taking them out.

Forerunner energy shielding
Forerunner Sentinels are equipped with energy shields, implying that the Covenant's shielding technology was scavenged from Forerunner technology. The Enforcer is also shielded, and can absorb more damage than a normal Sentinel.

In the novel, Ghosts of Onyx, a group of Spartan-IIIs encounter a unique type of Sentinel. While other types of shielding are always on, the Onyx sentinel can actively turn on their shield just before contact in order to deflect fast-moving projectiles. However, this can be overcome by slow moving projectile such as rocks, and in one case, being boarded by a Spartan. Onyx sentinels can combine their shields to make the joint shield more effective.

The majority of Forerunner energy shields seem to consist of a translucent bubble composed of hexagonal patterns, as opposed to the wraparound shields typically used by the Covenant and UNSC. The Bubble shield also projects a similar shield, perhaps implying that it is an example of Forerunner technology.

Energy shields in-game

 * In Halo: Combat Evolved, the status of the energy shield is shown at the top-right corner of the screen above the health bar, in Halo 2, it is in the bottom-left above the motion tracker, in Halo 3, it is in the top-center of the screen, and in Halo: Reach, it is shown in the top-center of the screen above the health bar. They have been modified since Halo: Combat Evolved to charge faster and be more resistant.
 * Both in Campaign and Multiplayer shields protect you for a brief amount of time from small arms and weapons. However, in Multiplayer, you can have 50%, 100%, 200%, 300%, 400% (Halo: Combat Evolved), 500%, 1000%, 2000% shield, or none at all. Both Elites and Spartans have the same amount of shielding. A player's shields can be further augmented if they pick up an Overshield.
 * In Halo CE under standard game settings, energy shields begin regenerating 5 seconds after last being hit, and take 4 seconds to fully recharge from a total drain.
 * In Halo 2 and Halo 3 under standard game settings, energy shields begin regenerating 4.25 seconds after last being hit, and take 1.75 seconds to fully recharge from a total drain.
 * According to the E3 demo of the Halo: Reach campaign, energy shields begin regenerating 6 seconds after last being hit, and take 2.75 seconds to fully recharge from a total drain. Multiplayer regeneration may follow different numbers.
 * A Regenerator can be used to make your shields recharge very quickly after taking damage.
 * If a player deploys a Bubble Shield they will be protected from weapons fire by a spherical energy shield.
 * Activating the Deployable Cover will generate a stationary energy shield that regenerates after disabled by continuous damage.
 * Shield doors can be found on several maps and can be placed in all DLC maps in Forge.

The possibility of real life shielding
No devices of this kind currently exist in a practical form, although the University of Washington and the Rutherford Appleton Laboratory are exploring separate projects encasing satellites in a plasma "bubble", contained by wire mesh or electromagnetism, to vaporise debris before it can damage the satellite within. The possibility of Solid Light also fits the criteria. However, one known flaw of the plasma "bubble" would be that it isn't designed to protect any specific subject. As a result, the bubble would overheat and incinerate the occupant of the bubble since it is made out of charged, superheated gas that would rapidly gain heat as damage was received.

Another possibility in principle for some form of shielding would be a combination of technologies, such as combining certain nanotech techniques like carbon nanotubes, a "wall" of lasers, and a thin layer of superheated plasma above it. The carbon nanotubes would be constructed and arrayed into a lattice structure conforming to the shape of the object, and would be capable of withstanding considerable impact, due to the nanotube's great strength. It would also be invisible due to its nanoscale structure, while the grid of lasers would help vaporize incoming objects that the plasma sheath did not absorb.

Though the shield would work against solid impacts and particle weapons, it would not be able to stop lasers. It would need an ability called Photochromism, which is an ability in some materials to absorb certain parts of the electromagnetic spectrum, such as that possessed by sunglasses to deal with UV light. Though carbon nanotubes do not currently possess this ability, it may be possible to give them this capability. This shield would visually match the typical depictions of shields in science fiction. However, issues of flexibility, weight, energy requirements, heat dissipation, and similar considerations would make this far beyond most foreseeable technologies, though it is not impossible in principle. It should be noted that photochromism isn't an instantaneous process, it takes time to complete, during which enough radiation can penetrate successfully to accomplish the objective.

Trivia

 * Contrary to popular Fan and Halo community belief, the Energy Shield is always present, even while not under fire. However, under the stress and strain of projectile resistance when under fire, it glows blue/gold in an electrical design around the wearer's body, eventually giving way to heavy fire. The Energy Shield is marked as a constant, unwavering protection that covers a Spartan or Elite's entire body, safeguarding the player from any known projectile that isn't more potent than bullets or plasma.
 * In Halo: Combat Evolved, the shielding that Elites use is slightly stronger than that of a Spartan. Elites' shields only take 70% of the damage that projectile weapons deal out, whereas a Spartan's shielding tends to take full damage. (Case in point, the Spartan shield, with 75 hit points, only takes three shots from the M6D Pistol to break, whereas a Minor Elite's shield, which has 100 hit points, takes 8 shots from the same weapon.) Apparently this was changed in Halo 2 and 3 - in Halo 2, it takes four bursts from a Battle Rifle to break either a Spartan's shield or a Minor Elite's shield.
 * It is never fully explained what happens to the plasma bolts or bullets when they make contact with the Energy Shield; however, it is witnessed that most bullets disappear, plasma always following this, whilst some bullets will bounce off the armor, usually at a 1 out of every 7 ratio (except in Halo: Combat Evolved, which had far different gameplay from Halo 2 and 3, and the only shots that will bounce are that of the needler).
 * In Halo 3, in Campaign, the energy shields of Shielded Flood Combat forms do not flare when taking damage, like the Brute Power Armor. However, other Elite's shields still flare when taking damage.
 * In Halo 3: ODST, certain Drones are outfitted with personal shields.

Related Pages

 * MJOLNIR Armor
 * Elite Personal Energy Shield
 * Jackal Point Defense Gauntlet
 * Bubble Shield
 * Overshields
 * Regenerator
 * Stationary Shield Generator
 * Portable Shield Generator