Nacelle

A nacelle was an outboard housing structure that contained warp coils and other components that together made a starship's warp engine. In contrast Impulse nacelles of a sublight shuttlecraft housed the ship's impulse drive engines. ( display graphic). 
Many terms were used to describe these structures, including: warp nacelles, warp engine nacelles, warp field nacelles, power nacelles, energy nacelles, antimatter nacelles, warp drive pods, warp drive nacelles, or space/warp propulsion units. (; ) 
== Technical data == 
=== Operation ===
The warp coils in warp nacelles create a subspace displacement field, which "warps" the space around the vessel allowing it to "ride" on a spatial distortion, and travel faster than the speed of light. () While not always present on starships, warp nacelles were the most common component of warp flight, dating as far back as Zefram Cochrane's original warp ship, the Phoenix, circa 2063. () 
Aboard most warp-capable vessels, warp coils in the nacelles are fed by plasma conduits from the warp core reactor assembly. Venting the plasma from the nacelles made warp drive impossible until the plasma for the nacelles could be replenished. () Most starship designs feature two concurrently operating warp nacelles that act in tandem to generate a Warp field. Under emergencies, such vessels could operate with one nacelle disabled, but at reduced warp speeds. (; ) However, it was not uncommon for starships to employ one, three, or four warp nacelle configurations, depending on the role of the vehicle. (; ; ; ; )
Depending on starship design, nacelles may be separated from the rest of the ship by large pylons or may be housed directly in large cowlings within the main body on the ship, creating a more streamlined profile. Sometime by the 31st century, Federation starships began disconnecting warp nacelles via the use of programmable matter, which improved the starship's maneuverability and enabled her to be more efficient in flight. () 
On Federation starships, warp nacelles are usually built to house Bussard ramscoops at the fore end, primarily used for collecting hydrogen and other interstellar particles from open space to replenish fuel. (; ) Some Federation nacelles are designed to allow the warp field grills to open up, and channel energy directly back into the warp core, effectively "jump-starting" it in extreme emergencies. () 
=== Nacelle control systems ===
On older starships, such as the , the nacelles housed a large catwalk used as a service corridor for nacelle systems. In one documented case, the catwalks acted as a shelter for the ship's crew against certain types of radiation such as that created by neutronic storms. Nacelles aboard the NX-class were required to be polarized for warp travel to be possible. If one of the nacelles were to become depolarized, warp drive would be impossible until repolarization could take place. ()
On newer starships, a nacelle control room was built to house maintenance and monitoring systems for each nacelle's operation. Depending on ship size and layout, these rooms may be housed directly in the nacelles themselves, or nearby and are accessible through a Jefferies tube or standard service corridor. (; )
== Dangers and limitations ==
Due to the nacelle's function and design, extreme care needs to be taken to protect them from impacts from weapons fire, or space debris. Collision with an external object could spell disaster for a starship due to a feedback of energy throughout the vessel. ()
Also, it is noted that when a Class 2 shuttlecraft exceeded the speed of warp 9.7, tritanium depolarization created a velocity differential between the nacelles and fuselage. A depolarization matrix around the fuselage was required to avert the nacelles from tearing off due to subspace torque. ()
== Warp nacelle rings ==
Vulcan and Ni'Var starship designs were notable for often featuring a single ring-shaped warp nacelle at the rear of the ship, such as in the , and D'kyr type (22nd century), (24th century) and (32nd century).
== Appendices ==
=== Background information===
The use of the word "" in spacecraft design descends from its use for similar housing structures in air- and watercraft design. 
From the , "The nacelle control room and plasma injectors were a full-sized set designed by Richard James. The cavernous warp coils were a miniature built by Anthony Fredrickson and composited by visual effects supervisor David Stipes. The design of the coils was based on a drawing by Rick Sternbach in the Star Trek: The Next Generation Technical Manual. Warp nacelles were conceived by original series art director Walter M. "Matt" Jefferies, as part of his design for the original . Matt told us he felt that faster-than-light engines would be extremely powerful, and therefore potentially dangerous. For crew safety, he decided they should be housed separately, away from the inhabited part of the ship. He noted that this would also make it easier to replace the engines should it ever be necessary to upgrade them. This was done, years after the end of the original Star Trek, for the uprated Enterprise designed for Star Trek: Phase II and seen in ."
According to Star Trek Blueprints, while the Constitution-class nacelles are powered up, they produce dangerous levels of radiation, and crew members are not permitted to go up the Jefferies tubes that lead to the nacelles inside the nacelle pylons. 
According to Star Trek: Starship Spotter, there were several different types and designations of warp nacelles officially known as warp drive units. In Federation starships, the original configuration of the Constitution-class and the shuttles featured circumferential warp nacelles. The Constitution II-class and featured linear warp nacelles. Later starships featured advanced linear nacelles, whereas smaller ships featured compact versions of these. Klingon nacelles were known as dilithium conversion graf units and Romulan nacelles of the were known as quantum singularity energized warp drive units. The Jem'Hadar attack ships featured ion propulsion units as warp nacelles.
According to the Spaceflight Chronology (p. 139), a three-nacelle configuration gives a third more power to the warp drive, greater acceleration, and faster engagement. However, in the first experiments, the third nacelle accentuated discrepancies in the warp field causing warp vibrations. This created difficulties in steering and would have resulted in the ship shaking itself apart at higher warp speeds. It was however noted that if the design was constructed perfectly it could deliver what it promised.
The Star Trek: The Next Generation Technical Manual (pages 63, 65, and 66) states that the experiments with single and more than two nacelle designs, conducted in 2269, proved that having two nacelles was the optimal configuration for vessel control and power generation. On Galaxy-class starships, there was an emergency separation system for the nacelles. In the event the ship was damaged and unable to retain the nacelle safely, explosive latches separated the nacelle from the pylon and lifted it at thirty meters per second. If a nacelle was lost during warp flight, it would tear the ship apart, as the loss would cause different areas of the ship to travel at different warp factors.
===External link===
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Category:Propulsion technology
Category:Warp