Z-4190 bubble shield

The Bubble Shield is a UNSC anti-artillery and personal defense device.

Summary
The Bubble Shield is a Human developed battlefield technology. The device projects a transparent, slightly yellow tinted defensive bubble dome that protects against bullets, lasers, flames, and other projectiles used primarily by the Marine forces of the UNSC and The Covenant. Covenant loyalists have been known to secure human weapons and equipment for their own ends, the bubble shield being one of the most common. The shield itself is a Geodesic dome (of sorts) made of tessellating hexagons. The bubble shield projects a defensive field around the user that, when deployed blocks all projectiles, plasma, explosions, and other forms of attack. Vehicles and players however, are still able to pass through it. After a significant amount of time has passed or the shield has taken enough damage, it will fade.

Development
Despite being UNSC technology, UNSC Marines rarely deploy it during the campaign, while Brutes deploy it often. At least one or two brutes in a covenant battle squad always have a bubble shield on hand. Brutes generally activate their bubble shields immediately following aerial insertion and when in large numbers.

General
Originally during Halo 3's development the bubble shield was intended to be the function of the X button, however the developers were not satisfied with the shield in general. It was only until the developers saw the Starry Night commercial that sold them on the idea of the bubble shield. Since that time the shield became a piece of equipment that the player would pick up over the course of gameplay. This also lead to the creation of the other pieces of equipment like the grav lift, power drainer, and the trip mine.

Is Quisnam Protero Damno" Multiplayer ViDoc
A player deployed this version while running from Battle Rifle fire. The shield successfully absorbed all projectiles and grenade explosions fired. It appeared to be a large sphere-shaped object. It could roll around while activated. It appeared much larger than its first appearance in the Starry Night commercial. This version of the Bubble Shield is seen used in the Alpha-stage Halo 3 footage for multiplayer. The Bubble Grenade rolls down a hill as the Spartan-II concealed in the sphere back-pedals away from an enemy. Information later released by Bungie, however, stated that the sphere would rest on the ground and the Spartan II would need to stand still to enjoy its effects.

Halo 3 Multiplayer Beta
The bubble shield appears and functions differently from both of its previous appearances. This version is similar to the Starry Night appearance. In the Halo 3 Beta the Bubble Shield is stationary and does not roll as it did in the ViDoc. The shield itself has remained the same otherwise. The Bubble Shield generator looks significantly different in the beta version than it does in both the commercial and the ViDoc. The generator has four legs and can be destroyed from within the shield, collapsing it prematurely.

Halo 3 Multiplayer
The Bubble Shield has changed since its appearance in the public multiplayer beta. The most noticeable being the shield effect itself. The shield now produces a yellow glow, making it more visible at longer distances. This was probably done since during the BETA, the shield was almost invisible and made players attack themselves. The shield generator itself, now produces a blueish glow once activated. The time in which the shield stays activated is about two seconds shorter.

Throughout all these physical changes, the shield itself has stayed the same with the hexagon patterns and transparency. Some of the other characteristics that have changed is the fact that a Spike grenade no longer sticks to it. During the BETA, the Spike grenade was able to stick to the bubble but now it just bounces off.

Trivia
Also the fact that slower objects may enter means that it acts like it, too.
 * Frankie has said that the shield is ONI tech..
 * This shield resembles the description of the Onyx Sentinel shields in the Eric Nylund novel Ghosts of Onyx.