Magnetic Accelerator Cannon

''Were you looking for Mac, a Marine who served in the Harvest Campaign? Or maybe the large cannon at the Aszod drydock, referred to as a MAC gun in game?''

The Magnetic Accelerator Cannon, also known as Mass Accelerator Cannon, is a weapon delivery system employed by the UNSC for its warships and orbital platforms. Essentially a large coilgun, they are one of the few non-conventional non-nuclear weapons in the the UNSC arsenal capable of causing widespread destruction.

Operational design
The theory behind the operation of a Magnetic Accelerator Cannon is the same as that of a coilgun; the system consists a linear motor of magnetic fields coils which would accelerate a metal projectile through a barrel up to high velocity.

Firing operation
The firing process uses electromagnetism to fire a 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.

The weapon draws power from the ship's reactor and require a charge of the weapon's magnetic coils in order to be fired. The time it takes to bring the MAC's systems to full charge on a UNSC vessel is the deciding force in a conflict. Thus, while a vessel may not run out of ammunition for a long time (depending on the size/weight of the shots and the capacity of the ship), a captain or commander has to carefully analyze the situation of a battle and use his shots strategically. The weapon can be fired even when not at full charge, but the velocity of the projectile is greatly diminished.

By the time the slug is fired out the end of the barrel, it has been accelerated to a speed of approximately 30 kilometers per second for frigate-based MAC and around 12,000 kilometers per second for orbital platform-based MAC. 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.

Ammunition
Payloads used in the Magnetic Accelerator Cannon weapon delivery system alternates with the platform which the weapon is hosted; warship models tend to use ferric, ferrous, or depleted uranium cores whereas orbital platform models commonly use ferric tungsten rounds.

The standard frigate-based MAC fires a 600-ton slugs at around 30 kilometers per second; the high muzzle speed provides the 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. The standard orbital platform model on the other hand fires a 3,000-ton slug at nearly .04c, or around 12,000 kilometers per second, which is capable of piercing multiple obstacles before fully stopping the projectile if needed.

Aiming
The size of a Magnetic Accelerator Cannon is such that it is normally an integral component of a warship's structure. Orbital platforms are often built around the massive weapon for orbital defense. A dedicated targeting computer or an AI is typically required to aim or fire the cannon, as the projectiles are unguided.

Types
There are various variations of the Magnetic Accelerator Cannon system depending on the platforms it is installed in. Each variation performs and functions significantly different. The standard frigate is capable of carrying one MAC system whereas the standard destroyer is capable of possessing up to two MAC systems. Larger warships, such as the cruisers and carriers, can carry up to two MAC systems or more.

Frigate
A standard frigate-issued MAC system averages at 183 m. It can fire a 600-ton ferric-tungsten projectile with a depleted uranium core at 30,000 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 approximately 64 kilotons per shot, the standard Magnetic Accelerator Cannon is sufficient to destroy any human vessel or severely damage an unshielded Covenant vessel.

Specialized/Modified
The standard MAC can be further enhanced with booster capacitors which allows the weapon to be fired three times per charge rather than once per charge. This improved technology was only implemented into the prior to the Fall of Reach. The modified weapon was also noted to charge faster than the standard version, though this is likely due to the Pillar of Autumn 's advanced reactors. Also exclusive to the Pillar of Autumn along with the modified MAC were newer and lighter MAC rounds that had less dense ferrous core, but a harder outer layer of tungsten carbide.

"Super" Magnetic Accelerator Cannon


A UNSC orbital platform typically mounts larger and more powerful version of the standard Magnetic Accelerator Cannon, nicknamed "Super" MACs or the "big stick". At 802.2 m long, these cannons fire a 3000-ton ferric-tungsten round at .04c or 4% of the speed of light, impacting with a massive amount of relativistic kinetic energy, which is of equivalent to 51.6 gigatons of TNT. No known ship, UNSC or Covenant, has been shown to survive the impact of one of these rounds, with unshielded Covenant destroyers actually "exploding into glittering fragments" upon impact. 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 super 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.

Others
Although never explicitly elaborated upon, there may be many more different sizes of MAC weaponry based on the size 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. However destroyers and Marathon-class Cruisers 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.

M68 Gauss Cannon
The M68 Gauss Cannon is a UNSC weapon mounted on the M12G1 Light Anti-Armor Vehicle as well as on stationary turrets. It utilizes the same coilgun technology used in MAC weapon deliver system, but on a smaller scale.

M92 Principle Gauss Cannon
The M92 Principle Gauss Cannon is a weapon system of similar MAC mechanics that runs along the length of the Open Frame 92/Extra-Vehicular Activity.

M99 Stanchion Gauss Rifle
The M99 is a man portable anti-matérial and anti-personnel special application weapon using 5.4mm/.21 caliber rounds. Like the M68 Gauss Cannon, it utilizes the same coilgun technology as a MAC, only on an even smaller scale. Though smaller than conventional ammunition, these rounds are 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.

Mass drivers


The mass driver is a somewhat primitive United Nations Space Command orbital launch assembly designed to propel low-weight payloads into orbit, otherwise known as orbital lifting, or to deliver them across a planetary system. The operating principle of the mass driver is essentially the same as that of the Magnetic Accelerator Cannon: it is a large coilgun that magnetically accelerates a package consisting of a magnetizable holder containing a payload. While not a purpose-built weapon like the UNSC's Magnetic Accelerator Cannon, these platforms are still potent weapons of opportunity. While never formally incorporated as a weapon, mass drivers have been used at as defensive magnetic accelerator weapons at Harvest, the Rubble, and Reach.

MAC Blast
"Use the Spirit of Fire's awesome Mass Accelerator Cannon to incinerate enemy troops."

- In-game description.

In Halo Wars, the MAC Blast ability allows the player to use the 's MAC for pinpoint orbital bombardment. It is mainly used as a support weapon to help the UNSC penetrate heavy Covenant defenses and Covenant bases, and is a potent weapon against Scarabs.

In skirmish and multiplayer, the MAC Blast can only be used if Captain Cutter is selected as the player's leader character. In the campaign, the MAC Blast is available in several missions, most notably Dome of Light, during which the player is granted access to forty rapid-fire MAC rounds to destroy a Covenant base.

Trivia

 * The Magnetic Accelerator Cannon has been wrongly addressed twice in the Halo series. It is called the "Mass Accelerator Cannon" in Halo: Contact Harvest, and the "Mass Accelerated Cannon" in Halo Wars. The first reference may be a confusion between the MAC and the mass driver, which is a non-military application of similar technologies. The second reference may be a grammatical error also referring to the mass driver.
 * The 's MAC is unable to penetrate a Covenant citadel's shield in Halo Wars with one round. This could be because of the use of a less-powerful-than-normal rounds or lower-than-normal charge, or because of the high resistance of the shield. It may also be because the round loses kinetic energy and mass as it enters atmosphere from orbit. Another possibility is that the Spirit of Fire's MAC was designed for ground support and not ship-to-ship engagements, thus firing weaker rounds to avoid friendly casualties. The last theory might explain why the MAC cannon could fire multiple shots in quick succession. However, its weak power in Halo Wars may only be for gameplay purposes.
 * The total energy released from the impact of a MAC round fired from a UNSC Orbital Defense Platform releases a colossal 216 exajoules of energy (51.6 gigatons). To put this in perspective, this is about 3,428,571 times the energy released from the atomic bomb detonated over Hiroshima in World War II, which released a comparatively small 63 terajoules of energy (15.5 kilotons).

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Halo: Ghosts of Onyx
 * Halo 3
 * Halo: Contact Harvest
 * Halo: The Cole Protocol
 * Halo: Evolutions
 * Halo Legends
 * Origins
 * Halo: Reach