Warp coils, also known as warp field coils, warp drive coils, or warp field generational nacelle coils, were an integral part of a starship's warp drive. Mounted within the warp nacelles, the primary and secondary warp coils used the plasma generated by the warp core to create a subspace displacement field that allowed faster-than-light travel.
Warp coils were typically composed of cast verterium cortenide surrounding a core of densified tungsten-cobalt-magnesium. (VOY: "Investigations")
The material was first mentioned in the Star Trek: The Next Generation Technical Manual.
When matter and antimatter on an NX-class starship collided together, it created an extreme amount of energy within a warp core which was then transferred to conduits, leading to the nacelles outside the ship which contained the warp coils, thus creating a subspace displacement field around a ship, allowing it to travel at warp speed. (ENT: "Cold Front") Though technological details evolved, this process primarily remained the basic propulsion system for most warp-capable ships of the Federation, Starfleet and many other cultures for centuries.
Around a kiloton of gallicite, a mineral, was enough to refit the warp coils of an Intrepid-class vessel. (VOY: "Blood Fever")
A Class 2 shuttle could generate a dielectric field with its warp coils to protect itself from turbulence within a planet's atmosphere. (VOY: "Innocence")
A teraphasic coil was a type of warp coil utilized by the Xyrillians in the mid-22nd century. Enterprise NX-01 encountered a Xyrillian starship with damaged teraphasic coils in 2151. (ENT: "Unexpected")
In 2152, a group of Mazarite criminals chased Enterprise on Mazarite ships at warp 4.9 in order to capture Ambassador V'Lar before she could testify against them. In order to sustain their warp velocity, the ships released drive plasma to keep their warp coils from overloading. (ENT: "Fallen Hero")
Later, the automated repair station asked Jonathan Archer what he could compensate it with to repair Enterprise after it was severely damaged in an encounter with a Romulan mine. The station then told Archer he could supply it with three warp coils, five deuterium injectors, or two hundred liters of warp plasma. (ENT: "Dead Stop")
Later that year, Commander Charles Tucker III asked Ensign Travis Mayweather if he could re-polarize the warp coils in Enterprise's starboard nacelle, since he was shorthanded with his engineering staff. (ENT: "The Crossing")
In 2153, after discovering debris of a Borg sphere destroyed in 2063 by the USS Enterprise-E that crashed in the Arctic Circle, the scientist Rooney speculated that a Borg transwarp coil she found might be some kind of warp coil. (ENT: "Regeneration")
In an alternate timeline, Captain T'Pol crashed a Xindi-Reptilian warship that was docked with Enterprise into another, causing massive damage to Enterprise's starboard nacelle. Commander Tucker told her that half the warp coils in the nacelle were fused. Tucker told T'Pol he would have to rebuild the coil assembly from scratch, which would take him a minimum of six months. (ENT: "Twilight")
In 2154, after awakening from an induced coma for three days, Commander Tucker complained that it would take him days to realign the warp coils on Enterprise after Phlox slightly damaged the ship while trying to take it to warp inside a nebula in the Delphic Expanse. (ENT: "Doctor's Orders")
Later on, Enterprise's primary warp coil was destroyed in the fierce battle of Azati Prime, making warp speed impossible for the starship. Captain Jonathan Archer, with no other options to restore warp capability to Enterprise, stole a primary warp coil from the Illyrians in order for the ship to intercept the Xindi weapon in time to save Earth. (ENT: "Damage")
Curiously, this reference seemed to indicate that a warp coil was a small, portable device built directly into the warp core much like a Borg transwarp coil. However, in the episode, it was specifically referred to as a "primary warp coil."
Shortly afterwards, T'Pol suggested to Commander Tucker that she could order him to go to sleep, since he had not slept for two days. Tucker told her he couldn't, since Enterprise was full of holes and the only thing allowing them to travel at warp speed was a stolen warp coil. (ENT: "The Forgotten")
Later, while attempting to capture Dr. Arik Soong and his Augments in Klingon space, Commander Tucker had Enterprise's warp coils realigned, so the ship would appear to be a Klingon battle cruiser to Klingon sensors. (ENT: "The Augments")
In the mirror universe in 2155, Commander Trip Tucker, when seeing the USS Defiant, mentioned that the size of the ship's warp coils could allow the ship to travel at speeds faster than warp 7. (ENT: "In a Mirror, Darkly")
In 2366, a Romulan D'deridex-class vessel exceeded its maximum warp speed by thirty percent in an effort to reach Gomtuu before the USS Enterprise-D. It ended up causing permanent damage to its warp coils. (TNG: "Tin Man")
In 2367, while in a simulation created by Barash, Admiral Jean-Luc Picard told Captain William T. Riker that peace between the Romulans and the Federation occurred after Riker saved a Romulan battle cruiser that had its warp coils and life support fail on them. (TNG: "Future Imperfect")
Later that year, the warp coils on the Klingon starship IKS Bortas, commanded by Gowron, were damaged after a Klingon Bird-of-Prey opened fire on the Bortas in orbit of Qo'noS, plunging the Klingons into a Civil War. (TNG: "Redemption")
Wesley Crusher once stated that his first friend was a warp coil. (TNG: "The Game")
William T. Riker, in 2368, considered the warp coil the most important invention of the past two hundred years. Before the coils were invented, "Humans were confined to a single sector of the galaxy". (TNG: "A Matter Of Time")
Later that year, after the computer systems of the Enterprise-D were disrupted by a energy wave from a Satarran starship, Geordi La Forge accessed the basic system directories of the Engineering Department. According to the department, the nacelle coils were off-line. (TNG: "Conundrum")
Much later that year, the Enterprise-D's starboard warp coil suffered from a minor fluctuation, as reported to Captain Jean-Luc Picard by his chief engineer, Geordi La Forge. (TNG: "Ethics")
In 2369, Captain Edward Jellico told Lieutenant Commander Geordi La Forge that he found the efficiency of the Enterprise-D's warp coils unacceptable shortly after taking command. (TNG: "Chain Of Command, Part I")
The USS Hera used trionic initiators in the warp coils, which had the reputation of creating strange side effects, such as warp bubbles and subspace deformations. (TNG: "Interface")
In 2372, a subspace inversion in the Bajoran wormhole damaged the USS Defiant and its warp coils were locked into a feedback loop. (DS9: "The Visitor")
In an alternate timeline, Lieutenant Lasca asked Harry Kim if he brought the schematics for the USS Yellowstone's warp coil with new plasma flow equations for their meeting with Admiral Strickler to show they had solved the dilithium fracture problem with the ship. Kim did not bring it with him, however. (VOY: "Non Sequitur")
Later that year, the USS Voyager required polyferranide to help seal its warp coils. Voyager was able to obtain a small amount from the Sky Spirits' homeworld. (VOY: "Tattoo")
Later, Lorrum, a Kazon, asked Crewman Michael Jonas to sabotage Voyager's warp coils, so the Kazon-Nistrim would be able to commandeer the ship. (VOY: "Lifesigns")
When Voyager was severely damaged by proton bursts, Lieutenant Tuvok reported that the warp coils on both of Voyager's nacelles were fused and inoperable. (VOY: "Deadlock")
In 2374, Lieutenant Tom Paris and Neelix bribed an alien in the Delta Quadrant with a spare warp coil from Voyager, so he would provide him with information on Tau, who stole many important items from the ship, which the crew were intending to get back. (VOY: "Concerning Flight")
Later that year, Voyager's warp coils were in need of maintenance after the ship narrowly escaped from the Hirogen and a black hole. (VOY: "Hunters")
In a holographic simulation of Voyager's crew created by Seven of Nine, Neelix suggested that re-phasing the warp coils would increase power to the nacelles. (VOY: "One")
In 2375, the crew of Voyager stole a transwarp coil from a Borg sphere and used it in place of its warp coils to generate a transwarp corridor propelling the ship at much faster speeds than a regular warp coil could. The transwarp coil ended up taking Voyager 20,000 light years closer to the Alpha Quadrant before eventually giving out. (VOY: "Dark Frontier")
In 2377, USS Voyager landed on a planet for a maintenance overhaul. Among the repairs was the removal and maintenance of several warp coils using Class 2 shuttles. (VOY: "Nightingale")