Tau Cannon

The Tau Cannon
 * Weapon category: 4
 * Range: Medium to Long
 * Primary attack: Fully-automatic, 20 pts/beam
 * Secondary attack: Charged-up shot, between 10 and 130 pts/beam
 * Ammunition: Depleted uranium
 * Capacity: Ammo reserve of 100 units

A prototype for the assault rifle of the future, the tau particle cannon is an experimental weapon developed by scientists at Black Mesa. Its advanced technology allows it to use depleted uranium as fuel. Furthermore, you do not have to worry about reloading the gun – it taps directly into your ammo reserve. The depletion uranium ammunition is shared by the gluon gun. The tau cannon is also known by many as the ‘gauss gun’, as many of the Half-Life game files refer to the weapon as the ‘gauss’, though this is simply a relic of Half-Life’s alpha development stage.

The tau cannon is a type of experimental weapon that fires beams of tau particles. The weapon has two different fire modes. The first shoots tau particles rapidly, visible as yellow beams in the air; each beam damages a target with its negative charge and its bullet-like kinetic energy. Though very inaccurate, these rapid discharges can quickly gun down un-armoured targets. The alternate fire mode charges up the weapon to fire more powerful white-hot beams; these can shoot through multiple targets or penetrate walls, causing a devastating explosion-like blast of particles on the far side. ''In multiplayer this means that it can be safer to jump around in the open than duck behind cover if your opponent is armed with a tau cannon. Furthermore, in multiplayer the recoil from the weapon’s secondary attack is greatly increased, and if you fire at the ground the recoil will throw you backwards high into the air, allowing you to propell yourself up to a high location. This technique is commonly known as ‘gauss jumping’.'' The tau particle beams can reflect off walls if they are hit indirectly, and in fact can be reflected several times. This aspect can be useful as it can be used to hit targets when there is no clear shot, but as with bullet ricochets there is also a danger of friendly fire or self-harm. Tau cannons are compact and light enough to count as small arms, despite the fact that a blast from a charged-up tau cannon can penetrate or destroy armoured vehicles. Originally developed at the Black Mesa Research Facility, the prototype design somehow survived the facility’s destruction and years later the tau cannon was utilised by the Resistance, including a version that was mounted on the buggy that was given to Gordon Freeman.

The tau is the most massive member of the lepton family of elementary particles; like electrons, tau particles are negatively charged, but tau particles have more than three thousand times as much mass. This would explain the tau cannon’s powerful penetrating power, as well as its significant recoil. Though the early tau cannon prototypes used normal household batteries as an initial power source for the particle accelerator, a micro-fission reactor generated the deadly particle beam. This advanced nuclear device, developed at Black Mesa, was capable of using inexpensive depleted uranium as fuel rather than an enriched isotope. (The same technology was put to use in the experimental gluon gun that was developed during the same period.) When the tau cannon alternate fire mode was used the reactor would be fed more depleted uranium fuel without being fired, and the energy would be stored in a set of spinning capacitors. Although these prototype capacitors could store a vast amount of energy they could not hold a charge for long, and if the tau cannon’s capacitors were fully charged-up the weapon would have to be fired within ten seconds to prevent a catastrophic discharge that could and kill the user of the weapon.

The vehicle-mounted tau cannon used during the time of the rebellion against the Combine is a more advanced model. It uses an alternative fuel source that gives it seemingly unlimited ammunition, and the capacitors can hold a full charge indefinitely. The weapon is devastating against Combine soldiers and alien life-forms, but useless against Combine vehicles as their advanced armour is designed to reflect energy weapons.

Behind the Scenes
The tau cannon is also known by many as the ‘gauss gun’, as many of the Half-Life game files refer to the weapon as the ‘gauss’. The weapon’s recoil is exaggerated in multiplayer, giving players the ability to launch themselves into the air by firing the weapon in the opposite direction; this ability is commonly known as ‘gauss jumping’.

A gauss gun (or coilgun) is a device that uses electromagnetism to accelerate projectiles, and has some similarity to a railgun. Early during Half-Life’s development Valve intended the weapon to be a hypervelocity projectile weapon, but later changed their minds and made it into a particle beam weapon, but did not feel there was any need to change names of the game’s data files to reflect this. The weapon uses the same ammunition as the gluon gun, which is obviously an energy weapon, giving further evidence to the weapon not being a true gauss gun. The evidence for the weapon’s real name can be found in a game of Half-Life Deathmatch: in the game console a kill from the weapon is recorded as being a death by ‘tau_cannon’. When the Opposing Force: Capture the Flag multiplayer game was released the key configuration menu included the option to bind keys to particular weapons; here the weapon in question is listed as the Tau Cannon.

Name Confusion/Confirmation
In Half-Life 2 the player receives a buggy that has a version of the weapon mounted on it; a resistance member actually refers to the weapon by name, calling it a Tau Cannon, thereby officially confirming the name of the weapon. Since the tau cannon is a particle accelerator, it is possible that is uses an electromagnetic acceleration technique similar to what might be found in a gauss gun, therefore the gauss gun term could still be applied to the tau cannon as long as it is remembered that the weapon fires particle beams rather than more conventional projectiles.