Z-4190 bubble shield

The bubble shield is a personal defense device. The technology involved with it is owned by UNSC's Office of Naval Intelligence branch.

Design details
The bubble shield projects a translucent, slightly white/gold tinted protective sphere around the user. The shield itself is similar to a geodesic dome, made of tessellating hexagons. The shield protects against bullets, explosions, lasers, plasma, flames, grenades, and other projectiles. Vehicles and personnel, however, are still able to pass through it. After approximately 20 seconds has passed, the shield will collapse and the generator will self-destruct.

An early form of the bubble shield was used in the original teaser trailer for Halo 3. It is shown being used by John-117 to protect him from an incoming Wraith mortar. In the teaser trailer, the bubble shield looked like a type of grenade, leading to rumors that it would be one of the new grenade types.

Deployment
UNSC Marines are never seen deploying it during Campaign, while Brutes deploy it often, however they have been seen using human equipment in the past. At least one or two Brutes in a Covenant pack always have a bubble shield on hand. Brutes generally activate their bubble shields immediately when taking fire or when feeling threatened.

Unlike the multiplayer "shield doors", vehicles are able to pass through the bubble shield. Damaging the shield generator itself in the bubble's enclosure will cause it to explode, and the shield will collapse upon detonation. Upon reaching its energy limit, bubble shields will make a high-pitched sound prior to overloading and exploding.

Disadvantages

 * Enemies can enter the shield freely.
 * The bubble shield only lasts about 20 seconds. In combat, however, this is more than enough time to regroup and recover.
 * If either the player or an enemy throws a grenade inside the bubble shield, it stays inside and will more than likely kill almost everyone in the shield at that time. This strategy is most effective with spike grenades, as the spikes will bounce around and shred anything inside the shield.
 * The generator is very delicate, and if shot from the inside, it will quickly explode and destroy the bubble shield.
 * Vehicles can also enter bubble shields. Therefore, you can run somebody over while they are still in the bubble shield.
 * The bubble shield can be affected by other equipment if thrown within the shield's proximity. For example, if an opponent throws in a Portable Gravity Lift near the generator, the Gravity Lift can raise the shield generator up, leaving anyone previously inside the shield defenseless. Additionally, effects from equipments can also be limited in the shield; if a Regenerator is thrown inside the bubble dhield, only those within the shield are affected. Likewise, if a power drain is thrown inside an active bubble shield, the disabling effects of the power drain are contained within the bubble shield.
 * The bubble shield can be knocked away by throwing a power drain or radar jammer at the generator, causing both objects to roll, and leaving anybody previously inside the shield exposed.

Origin
Oddly, the manufacturer of the bubble shield has never been explicitly stated. It has primarily been seen deployed by Covenant forces in the later years of the war, suggesting it is of Covenant design. However, it has been stated that the technology involved with it is owned by ONI.

The device itself bears little in common aesthetically with devices used by either faction. However, the geometric angles of the device vaguely resemble those used in Forerunner technology. In addition, the shield it generates is spherical and made of tessellating hexagons, which is similar to shields used by Sentinels and Protectors. As such, the bubble shield may be Forerunner technology reverse-engineered by the Covenant, which the UNSC then acquired for research. This would fit with the description of the similar drop shield, which is an "evolution of bubble shield technology."

Trivia

 * The original bubble shield was smaller than the finished bubble shield, as seen in the Starry Night video. It stuck into the ground rather then just stood on top of it; it was also originally in a grenade form, seemed more like a personal device and looked similar to Invincibility, another piece of equipment.
 * In the Beta version of Halo 3, the bubble shield looked and rolled like the power drain, did not glow gold, had orange lights, and was able to protect players against the turrets guarding the outer perimeter of the Multiplayer map Snowbound.
 * If you look closely at the bubble shield, you can see that there are actually two layers of shields that comprise it.
 * In Halo Wars, a Shield Protector will deploy a bubble shield-like object onto selected friendly units.
 * Although it appears in Halo 3: ODST, it cannot be used by the player or by other allies; only Brutes. This may be because of its extreme weight, weighing in at 20.5kg. This may also be the reason why Marines are not seen using it in Halo 3 and Halo 3: ODST. In fact, it may never had been intended for personnel-deployment purposes.
 * The bubble shield is replaced by the drop shield in Halo: Reach. It is a combination of the bubble shield and the regenerator. The bubble shield is much stronger than the drop shield, which could only take one Wraith shot.
 * The Covenant artillery is one of the few weapons powerful enough to destroy a bubble shield.
 * If one looks closely at the deployed bubble shield, you can see it "pulses" as though the shield were breathing.
 * The bubble shield is capable of negating the effects of a Kill Ball, allowing players to go inside the ball.

List of appearances

 * Halo 3
 * Halo Wars
 * Halo 3: ODST
 * Halo Legends
 * The Package
 * Odd One Out
 * Halo: Spartan Strike