Editing Deflector Shields (section)

==Operation and Use==

Deflector shields operate by creating a layer of energetic distortion containing a high concentration of [[Graviton]]s around the object (ship, city, etc.) to be protected. Shield energies can be emitted from a localized antenna or "dish" (such as a ship's navigational deflector), or from a network of "grid" emitters laid out on the object's surface (such as a ship's hull). On modern starships, deflector shields are essential equipment. They are raised to full power in anticipation of environmental hazards or in combat situations.

Neither matter nor highly-concentrated energy (i.e., weapons fire) can normally penetrate a shield. When shields are "up," or energized at a high level, most matter or energy that comes into contact with the shields will be harmlessly deflected away. In contemporary starship combat, shields are essential for hull protection. When shields are up, only minor hull damage can be expected during combat. Without deflector shields, modern weapons are capable of causing catastrophic damage to starship hulls almost immediately. (Star Trek II: The Wrath of Khan, Star Trek VI: The Undiscovered Country, Star Trek Generations)

Continuous or extremely powerful energy discharges can progressively dissipate the integrity of a shield to the point of failure. Shield capacities vary according to many variables, from the power available to environmental concerns (such as nebulae), making definitive and universal calculations of how much damage they can take difficult to estimate (there is no way to know exactly how many phaser hits will cause a failure, for instance). Therefore, during combat, tactical officers continually report on shield strength. Usually, the officer reports shield strength as a percentage of total effectiveness, with 100% meaning that the shields are at full capacity, and lower percentage scores indicating weaker shield conditions. Often, specific sections of the shield grid (e.g. aft or starboard) will take more damage than other sections, so tactical officers will report on the health of any section that needs reinforcement with additional power reserves. Shields are said to be "holding" if damage is not sufficient enough to allow a compromise, while if the shields are "buckling" or "failing," then a total loss of shield protection is imminent. (Star Trek VI: The Undiscovered Country)

Shields operate within a range of shield frequencies to allow certain specific types of energy and matter to pass through, or to make them more effective at blocking them. The frequencies of shields are not usually discernible without examining the controls on board the ship deploying them, meaning that it is very difficult to tune weapons to the exact frequency of an opponent's shields to bypass them. (DS9: "The Jem'Hadar"; Star Trek Generations)

In combat situations, starships match their own shield and weapon frequencies so their shielding does not interfere with their own weapons. Some weapons technologies, including those commonly used by the [[Borg]], have rapidly adjustable frequencies, meaning that they will more rapidly penetrate shields with static frequencies. An effective counter is to repeatedly and randomly alter the shield nutations to minimize the effectiveness of the weapon's retuned frequencies. (Star Trek Generations; TNG: "The Best of Both Worlds")

It takes time to activate a deflector shield. A refit [[Constitution Class]] starship needs exactly 13.5 seconds to lower and raise its shields when taking a shuttlecraft onboard via its tractor beam, though this includes the time required to tractor in the shuttle during an automated docking; flying the shuttle in manually reduces this time significantly. (Star Trek V: The Final Frontier)

Shields on a [[Nova Class]] starship can be fully recharged after charging the shield emitters for 45 seconds. This task requires the shields to be dropped. (VOY: "Equinox")

Normally [[Transporter]]s are not capable of penetrating shields. (TOS: "Arena") Older Federation starships, such as the Constitution-class USS Enterprise, could not even transport through their own shields, but later starships such as the [[Intrepid Class]] and [[Sovereign Class]] vessels could transport personnel and objects freely to and fro without having to lower their shields.

There are at least two different shield configurations commonly used by starships. One type projects an ellipsoid shield bubble around the ship in addition to a relatively large region directly adjacent to the ship. In the other shield configuration, a contour-conforming shield layer is projected a few meters outside the main hull.

The ellipsoid shield configuration isn't shown until the 24th century. Though shield harmonics can be adjusted to change the shape of shields of the 24th century, it is unclear if ships could produce both shield configurations. 

Certain starships have a shield system advanced enough to allow protection of only specific areas of the ship while leaving other areas unprotected. This is useful in times when power reserves are low. Lowering portions of the shields also allows usage of transporters without completely sacrificing the protection that shields provide.

This was also useful to Captain Janeway on the USS Voyager when she wished to extract information from a renegade crewman concerning the whereabouts of Captain Ransom in 2375. In this instance, she lowered the shields around a cargo bay, with the crewman inside, to allow the nucleogenic lifeforms to attack him.

Shields may be "extended" to encompass another vessel, which is often accomplished by matching the ships' shield emitter frequencies. (TOS: "Mudd's Women"; TNG: "The Defector"; VOY: "Equinox, Part II"). While the extended shielding can provide some protection in the event of a shield failure on one ship in a convoy, this technique can put a strain on ship systems, and the overall strength of the extended shields is generally not as strong as two independent shield systems.

Shield strengths seem to vary from time to time, making an exact calculation of how much damage they can take impossible. However, there are some examples:

*A [[Constitution Class]] starship's shields could take the equivalent of 90 [[Photon Torpedo|Photon Torpedoes]] at once. (TOS: "The Changeling") 

*The type of deflector shield used by the Lysian Central Command had an output of 4.3 kilojoules and could have easily been taken out with a single photon torpedo. (TNG: "Conundrum") 

To give further perspective to the Federation's 24th century encounter with the Lysians, the phase cannons found on the Enterprise NX-01 were rated at 500 gigajoules, suggesting that the 24th century Lysians were significantly behind even 22nd century Starfleet technology. (ENT: "Silent Enemy")