In theStar Trekfictional universe,shields refer to a 23rd and 24th century technology that providesstarships,space stations, and entire planets with limited protection against damage. They are sometimes referred to asdeflectors,deflector shields, or (inStar Trek: The Original Series)screens. Types of shields includenavigational deflectors.

The term 'shields' first appears in theStar Trek episode "Balance of Terror", in which they were deployed, albeit to little effect, by aFederation outpost under attack from aRomulanWarbird. The first depicted use by a starship was in theStar Trek episode "Arena", in which theUSSEnterprise raises its 'screens' after being attacked by an alien warship although the term 'shields' is not used in this episode. Shields are not mentioned during the earlier seasons of theStar Trek: Enterprise series, starships instead using "polarized hull plating" to make their hull more resistant to damage.

Like most technologies in theStar Trekfictional universe, the exact operation of shield technology is never precisely described. Characters discuss its existence and manipulation, while only superficially describing its exact physics, which result in a field being projected around a ship or other body, deflecting or dispersing projectiles and energy weapons. Shields are not shown unless struck, and are then often shown briefly for dramatic effect as a translucent bubble of energy.

Shields are said to be made of a screen ofgravitons that can deflect beam and projectile weaponry.

InThe Making of Star Trek, authorsGene Roddenberry and Stephen Whitfield write that shields areforce fields similar in nature to the navigational deflector, whileMr. Scott's Guide to the Enterprise further states that shields on post-refit Constitution-class vessels - of which theUSSEnterprise ofStar Trek: The Original Series is an example - were generated by the subatomic scan and replication of an alloy known as diburnium-osmium, and then projected as a force field beyond a ship's hull along the shield grid. In "That Which Survives", the alloy of diburnium and osmium is stated to be the hardest alloy known to the Federation.

Shields can be weakened by attack, and are often shown to collapse after prolonged bombardment.^[1][2] Shields may be unable to repel certain types of weapons; the phased polaron weapons used by theDominion - one of the primary antagonists ofStar Trek: Deep Space Nine - are initially unhindered by the shields of Starfleet ships.

TheUSSDefiant, introduced in the third season ofDeep Space Nine, was said to useablative armor in addition to shields; this technology also appeared in the alternate time line of the early 25th century shown in theStar Trek: Voyager series finale "Endgame", where it withstood repeated assaults by Borg weaponry and tractor beams.

Another type of shield, thenavigational deflector (also known just as the deflector, the deflector array, the deflector dish, the main deflector, the nav deflector, or the parabolic dish), was a force beam generator, usually a dish on the front of a ship, that was primarily used to deflect objects that might collide with the ship specially when traveling usingWarp drive when even minute particles could cause serious damage.^[3]

• Force field (technology)

• Deflector shield atMemory Alpha
• Navigational deflector atMemory Alpha

• Star Trek devices

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