Magnetic Accelerator Cannon

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"That MAC gun can put a round clean through a Covenant capital ship."

- Sergeant Johnson, talking to the Master Chief on board the Orbital Defense Platform Cairo.

The Magnetic Accelerator Cannon, also known as Mass Accelerator Cannon, or the MAC Gun or MAC Cannon, is a large coilgun that serves as the primary offensive weapon for UNSC warships.

A larger variant is in service aboard Orbital Defense Platforms. Within the UNSC arsenal, only nuclear ordnance exceeds the power of the MAC. The M68 Gauss Cannon used by UNSC ground forces mounted on some Warthogs may be regarded as a relative of the MAC, albeit on a much smaller scale.

Mounting
The size of a Magnetic Accelerator Cannon is such that it is normally an integral component of a warship's structure. Some types of Defense Stations are literally built around the massive weapon for orbital defense. A good example of this is Cairo Station. The MAC gun can be clearly seen protruding from the rest of the platform. After Cortana says, "I'm going loud", you can look outside and witness the cannon firing.

Ammunition
A typical ship-based MAC fires slugs of either ferric Tungsten or depleted uranium at thirty thousand meters per second. The high muzzle speed gives the 600 ton slug the kinetic energy and momentum necessary to damage a target and partially mitigates the unguided nature of the slug and its lack of maneuverability. Orbital Defense Platforms fire a 3,000 ton slug at nearly 50% of the speed of light about 150,000 km/s, enough to pierce the shield of a Covenant ship, destroy it and keep going (as seen in Halo: Uprising pt 4.) (similar to the Stanchion Rifle of Halo: Contact Harvest on how it pierced office buildings and its trajectory and velocity were unchanged). Hence demonstrating the ability of the MAC round to pierce multiple obstacles before fully stopping the projectile, if needed.

The Super MAC Slug can be seen on the level Cairo Station. To do this, go out of the elevator to the bomb and immediately turn left, then go into the hollow rail in the middle of the room, you will see the 3,000 ton slug being placed into the firing chamber. In other words, stare down the moving thing in the middle of the room. Consequently, walking into the firing chamber will result in the Master Chief being crushed by a slug as it is loaded into the chamber.

Aiming
The integration of the MAC to its hull means the entire warship or station must maneuver to aim the weapon. With the latest generation of 'Smart AI's', hitting a fleeing ship from 100,000km is more than possible. At a distance, one would have to aim where the target is going to be, a simple calculation for a Smart AI.

Firing
The firing process of a super MAC gun can be seen in the level Cairo Station. The process uses electromagnetism to fire a ferromagnetic-tungsten slug at high velocity. An extremely large amount of current is put through the first solenoid (coil of conducting wire) which creates a strong magnetic field which attracts the metal slug. As the slug passes into the solenoid, the solenoid is quickly turned off and the second solenoid, which is further up, turns on, which attracts the now high velocity metal slug just like the first solenoid, and the process is carried on. By the time the slug is fired out the end of the barrel it has been accelerated to a speed of approximately 40 - 50% of the speed of light (120 000 - 150 000 km/s). At the same time, a pair of thrusters on the bottom side of the station fire for a couple of seconds to counteract the acceleration imparted to the station. The process then repeats. It normally takes five seconds to recharge the capacitors as well as load the slug, which is why boarding craft have to be deployed to take the stations out.

Standard Magnetic Accelerator Cannon
The standard ship-mounted MAC fires a 600-ton ferric-tungsten projectile with a depleted uranium core at thirty thousand meters per second. The large amount of energy needed to fire the weapon is particularly onerous on a warship, and the extended recharge time is a significant factor in combat against Covenant warships as multiple MAC rounds are required to penetrate Covenant shields. At 1.17 Gigatons (Yield) per shot, the standard MAC is sufficient to destroy any human vessel or severely damage an unshielded Covenant vessel.

An experimental version of the MAC was developed to fire three successive rounds on a single capacitor charge. A prototype was mounted on the. This MAC was specially designed to fire the consecutive Tungsten-cored shots with an outer casing and a ferrous shell on top. Behaving like a normal assault rifle's shredder rounds, it gave the cannon three consecutive blows for one shot, which could supposedly down a Covenant ship with one charge.

The colony ship-turned-warship UNSC Spirit of Fire's MAC cannon is revealed to be unable to penetrate a Citadel's shield in Halo Wars in one hit. This might be the result of a weaker, earlier version of the Cannon, or that the Shield is simply very powerful. It is likely though that the Spirit of Fire, being a colony ship refitted for battle, had a weaker MAC gun. Alternatively, it may only be for gameplay purposes.



"Super" Magnetic Accelerator Cannon

 * Main article: Orbital Defense Platform

A UNSC Defense Platform typically mounts a much larger and more powerful version of the standard MAC, nicknamed "Super MAC" or "The Big Stick."

These cannons fire a 3000-ton ferric-tungsten round at nearly 50% the speed of light, impacting with a massive amount of relativistic kinetic energy, which at 50% of the speed of light is of equal power to 9.98 Teratons of TNT. No known ship, UNSC or Covenant, has been shown to survive the impact of one of these rounds. Against Covenant shield technology, the rounds possess enough kinetic energy to punch through shields, cut through the ship, and, upon exit, still retain enough energy to cripple or destroy a second ship. It is theorized that if a ship's armor or shields were to absorb all the kinetic energy of a MAC round, the release of thermodynamic energy would still vaporize the ship. By receiving power from ground-based power plants, orbital platforms could achieve recharge and reload times as short as five seconds.

M68 Gauss Cannon
The Gauss cannon is a UNSC weapon mounted on the Gauss Warthog and on the stationary Gauss Turrets. It uses the same coilgun technology a MAC uses, but on a much smaller scale. It is used as a light anti-armor weapon against the ground forces of the Covenant.

M99 Stanchion Gauss Rifle
The M99 is a man portable anti-material and anti-personnel special application weapon. Like the M68 Gauss Cannon, it utilized the same coilgun technology as a MAC, only on a even more still smaller scale, using 5.4mm/.21 caliber rounds. Though smaller than conventional ammunition, these rounds were accelerated to speeds fast enough to travel long distances with almost no change in trajectory, punch through any obstructing materials, hit their target, and still retain significant kinetic energy. Despite their effectiveness, production of this weapon ceased in 2521.

M92 Principle Gauss Cannon
The M92 Principle Gauss Cannon is one of the many weapons mounted on the Open Frame 92/Extra-Vehicular Activity, it is used primarily for attacks on Covenant vessels.

Mass Drivers
While never officially incorporated as a weapon, Mass Drivers have been used, most notably at the Rubble and Harvest, as MAC weapons. Their purpose is for drilling holes into asteroids and moving giant metal ingots to other in-system locations, but it can be a very powerful weapon. They use MAC technology to fire a large, dense slug across whatever distance necessary. It has been noted that they could launch a slug across the entire system of Hesoid. While not a purpose-built weapon like a MAC, these platforms are still potent weapons of opportunity. In 2525, Mack used two mass driver rounds to cripple the Brute controlled cruiser Rapid Conversion.

Railguns
While MAC's work on the principle of Gauss technology, railguns are a similar but separate type of projectile acceleration. Instead of using coils activated in sequence to accelerate a ferrous projectile, a rail gun uses two convective rails to accelerate a projectile (which is in between the two rails). A very large current is passed down one rail, through the projectile, and back through the other rail (completing a circuit). This current creates a strong magnetic field, and (by way of the Lorentz force) the projectile is propelled by the magnetic fields away from the back of the rails, accelerating the projectile out of the gun. The only known railgun in service in the UNSC was the LRG Rail Gun, mounted on the SP42 Cobra.

Other MAC Sizes
Although never explicitly elaborated upon, there may be many more different sizes of MAC weaponry based on the sizes of possible mounts. For example, one might extrapolate that a frigate would mount a smaller, less powerful cannon than a supercarrier or a, if only for power management issues. Conceivably, a 'large' ship could mount many 'small' MACs. However, the lack of such occurrences might suggest that the power of a MAC, once the mass and volume of all attendant components (i.e. capacitors) are accounted for, does not scale linearly. There is one known exception (destroyers), which are outfitted with two MAC cannons. The Pillar of Autumn had one large MAC cannon which could fire three 144 ton "shredder" rounds in succession on a single charge (see below).

MAC Location
Many believe that the MAC barrel is located near the underside of the ship, where there are three large plates. However, it is more likely that the barrel is located along the entire length of the ship.

Space Stations' MAC Location
Further along the hyper cargo elevator on Cairo Station, the player can look up and visibly observe the Super MAC platform in action. The slug travels through the entire length of the tower, and exits at the "top" of the further nozzle. Later in the level, the player can notice the loading zone of the slugs at the base of the firing chamber.

UNSC Usage
The following unit types mounted some form of MAC weaponry.


 * s
 * s
 * s (wartime refit)
 * Orbital Defense Platforms
 * UNSC Destroyers
 * UNSC Frigates

Trivia

 * The Magnetic Accelerator Cannon is twice mistakenly referred to as the "Mass Accelerator Cannon" in the Halo Universe - in Halo: Contact Harvest, and in Halo Wars, in which it is referred to as a "Mass Accelerated Cannon", which seems to be a simple typo as it does not make sense grammatically. It may be a confusion between the MAC and the Mass Driver, a non-military application of similar technologies.

Internal

 * M68 Gauss Cannon
 * MAC Blast

External

 * Bungie.org - MAC
 * Coilgun on Wikipedia

MAC