Like most technologies in the
Star Trek fictional 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 of
gravitons that can deflect beam and projectile weaponry. In
The Making of Star Trek, authors
Gene Roddenberry and Stephen Whitfield write that shields are
force fields similar in nature to the navigational deflector, while ''
Mr. Scott's Guide to the Enterprise further states that shields on post-refit Constitution-class vessels - of which the USS Enterprise
of Star 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. Shields may be unable to repel certain types of weapons; the phased polaron weapons used by the
Dominion - one of the primary antagonists of
Star Trek: Deep Space Nine - are initially unhindered by the shields of Starfleet ships. The
USS Defiant, introduced in the third season of
Deep Space Nine, was said to use
ablative armor in addition to shields; this technology also appeared in the alternate time line of the early 25th century shown in the
Star Trek: Voyager series finale "
Endgame", where it withstood repeated assaults by Borg weaponry and tractor beams. Another type of shield, the
navigational 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 using
Warp drive when even minute particles could cause serious damage. ==See also==