Tau cannon

The tau cannon (AKA the gauss gun) is a particle weapon developed at the Black Mesa Research Facility. Although it is quite small, it is an accurate and devastating weapon, when used correctly.

Operation

The weapon works by using by electromagnetically accelerating negatively charged tau particles at high velocities, which to the human eye this appears as a bright-yellow or -orange beam.

The kinetic and electrical energies of the particles are dispersed into the target on impact, causing large amounts of damage. It can be shot in quick bursts, which do moderate damage, or a shot can be charged up to do much higher damage. If the bursts of tau particles hit a solid wall at an acute angle, they can ricochet off along a new path.

Prototype

The original Black Mesa prototype of the tau cannon was a powerful, but unstable weapon. It was, unusually, fuelled by a miniature fission reactor, developed at Black Mesa, that used depleted uranium (The same device was also used to power the Black Mesa developed gluon gun and displacer) and two household batteries. This was, no-doubt, unnerving to the wielder, who had to carry a nuclear reactor.

Firing Modes

The primary firing mode shot small, inaccurate blasts in quick succession and was only effective on light targets at short to medium range.

The secondary firing mode was much more impressive. The gun could be charged to fire a single, powerful and very accurate blast. At full power, this blast had the ability to shoot through all but the strongest and thickest of armour and even through solid walls. When the particles emerged at the other side of the wall, their energy would be dispersed in all directions, dealing damage to anything surrounding the point of exit.

Charging a shot was deadly to the uncareful. If the trigger was held for too long the gun would “overcharge” and disperse its energy outward, dealing, possibly fatal, damage to the operator and those surrounding him. Furthermore, the powerful recoil of the weapon could throw a user to his death if he was standing in front of a high ledge.

Acrobatics

The gun’s large recoil was also put to unusual use by some users. A wielder would charge the gun up to full strength and shoot directly downwards while jumping. This would allow the user to leap otherwise impossible heights and distances. With the right timing the gun could also be used to slow one’s descent while falling, avoiding grave injuries.

City 17 Resistance

The dune buggy with attached tau cannon

The Combine-resistance movement developed their own, weaker, but more efficient and reliable, tau cannon. Although the weapon can still be charged, its maximum strength is lower and can no longer penetrate walls and heavy armour.

Despite its weakness, this version of the gun also has a few advantages: It uses much less power than the prototype and the primary fire is much more accurate, making it useful at greater ranges. It is also more reliable; it will not overcharge no matter how long the trigger is held and the recoil is not as great.

The only known resistance tau cannon was confiscated by the Combine shortly before the City 17 rebellion, along with the buggy to which it was attached (and from which it received its power). Any Combine developement of the weapon in unknown.