"Phaser" is an acronym for PHASed Energy Rectification. All phasers release an energy beam. Personal phasers can stun or kill an enemy. The stun setting can also be used for crowd control. Ship-mounted phasers can damage shields or other systems or even cut a vessel's hull.
Phasers are based on the Rapid Nadion Effect, whereby energy is passed through a special phaser crystal resulting in a discharge of nadion particles (often, the detection of nadion discharges is a key sign that a battle has recently taken place). Nadion particles have varying effects on the subatomic bonds of particles with which they interact, largely depending on the mass of the atom in question. To wit, dense starship hulls are more resistant to nadion discharges than is a humanoid lifeform. The disruptive effects of nadion discharges can be moderated to produce varying effects (discussed below), ranging from benign to extremely destructive.
Personal phasers come in three types. Phaser type-1s (hand phasers) are small and can be concealed easily. Phaser type-2s are larger and handheld. They have a similar emitter but have a longer handgrip, or a pistol grip, depending on the model. Phaser type-3s are also known as "phaser rifles." They have a longer barrel, a double-handed grip, and a stock. These weapons can fire beams or phaser pulses. Over centuries of use, there have been many models of the lightweight and effective phaser rifle.
Beyond these, phasers are usually mounted devices, such as the phaser type-4 used on Starfleet shuttlecraft and other small vehicles, all the way up to the phaser type-10 mounted in arrays on the hulls of Galaxy class starships.
Phasers can be made to overload, either deliberately or by sabotage. About sixty seconds after the overload started, the weapon would expend all of its remaining energy in an explosion capable of doing considerable damage to its surroundings. In 2266, Lenore Karidian attempted to murder James T. Kirk by hiding an overloading phaser in his cabin. In 2269, Kirk, McCoy, and Sulu were almost killed while on the Kalandan outpost planet, when its defensive computer fused the controls on Kirk's phaser, causing it to overload.
Since early times, human beings have endeavoured to create less lethal weapons. Although often good intentioned, these weapons have to be used with care and can often be abused or used for toture.
An example of this is the stun setting of the 23rd and 24th century phaser. Although mostly harmless when used at a low setting, phaser stuns can result in injury and death. This risk increases with the strength of the setting and the duration of use. A phaser on high stun used over a long duration can be used as a means of murder and will not be detected as easily as a phaser blast at a 'kill' setting would be. Star Trek VI: The Undiscovered Country
Phaser type-1s have eight settings:
- Light stun - Can cause minor injury in humanoids; target may be rendered helpless for short period; usually non-lethal even with long duration blast.
- Stun - Short duration blast can render humanoid helpless or even unconscious; risk of injury is serious for long duration blasts.
- Heavy stun - Humanoids are usually knocked unconscious from short duration blast; can cause serious injury; can kill when used for long duration.
- Potentially lethal - extensive neural damage and skin burns to humanoids; causes metals to retain heat if applied for over five seconds; short duration blast can kill humanoids.
- Low lethal - severe skin burns to humanoids; can penetrate simple personal force fields; short duration blasts are usually deadly.
- Lethal - matter disassociates and deeply penetrates organic tissue; can heat objects; any contact by humanoids is usually lethal.
- Heavy lethal - kills humanoids; disruption becomes widespread
- Maximum setting - vaporizes humanoid organisms; chances of survival slim even from short duration blast.
24th century phaser type-2s have at least 16 settings. (TNG:"Chain of Command, Part II") It should be noted that this does not neccessarily mean that hand-phasers of that era are twice as powerful. More than likely, its settings are simply finer than previous models.
The phasers mounted aboard starships are considerably more powerful than those used by Starfleet personnel, owing to the increased power reserves available. Early phasers were mounted in banks of one or two emitters, firing in either pulses or beams. This phaser design was retained on Starfleet ships until the Ambassador-class, at which point phasers were installed in arrays of several (sometimes hundreds!) emitters. These arrays enhanced both firing arcs as well as overall phaser output, the design benefitting from force-coupling all of the emitters in the array for the final composite beam. With the launch of the Defiant-class, phasers were again redesigned to fire pulses, though this time benefiting from the advances made with phaser arrays. Pulse phasers typically discharge several emitters internally to emit the final composite nadion burst.
- Phasers are often seen vaporizing or disintegrating matter. However, if vaporization were, in fact, occurring, a tremendous amount of heat would be liberated by the sudden conversion of a great deal of biomatter to vapor. For instance, if a person were instantly vaporized into carbon-dioxide, enough heat would be released to seriously injure or destroy objects within a radius of several meters. The nadion effect may result in matter-neutrino conversion, resulting in exotic particles. This is one possible explanation for the varied effects phasers seem to have on their targets (particularly the Klingon soldier who is thrown through the air by Kirk's phaser blast in Star Trek III).
- In TOS the phaser was often seen vaporizing people when set to kill. This is likely because the visual effect was cheaper to do than to show the victim with a serious burn injury to his or her body.