Nacelle

Inside an Template:ShipClass warp nacelle

File:Shuttlepod type-15.jpg

Impulse nacelles of a type 15 shuttlepod

File:USS Enterprise (alternate universe) nacelle.jpg

The opening nacelle fin of the alternate reality Template:ShipClass

The four nacelles of a Template:ShipClass starship

Inside a Template:ShipClass warp nacelle

A graphic of Galaxy-class warp nacelles

A nacelle is an outboard engine housing structure on spacecraft.

Impulse nacelles of a sublight shuttlecraft house the ship's impulse driver engines. (TNG: "In Theory", "Descent" display graphic) The warp nacelles in warp-capable shuttles and starships house the warp coils, necessary components of warp drive. The warp coils 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. (ENT: "Cold Front") While not always present on starships, warp nacelles are the most common component of warp flight, dating as far back as Zefram Cochrane's original warp ship, the Phoenix, circa 2063. They were also sometimes known as power nacelles or warp drive pod during the 23rd century. (Star Trek: First Contact; TOS: "The Doomsday Machine")

Aboard most warp-capable vessels, warp coils are fed by plasma conduits from the warp core reactor assembly. Venting the plasma from the nacelles will make warp drive impossible until the nacelles can be replenished. (ENT: "Civilization") Nacelles are usually separated from the main structure of the ship because of radiation generated by the nacelles; when at optimal levels, the radiation could be deleterious to the safety of ship and crew. ^{(citation needed • edit)} Nacelles are separated from the ship by large pylons, and usually house a Bussard ramscoop at the fore end, primarily used for collecting hydrogen from space.

A nacelle's interior also includes a small control room, accessible in nominal conditions by a Jefferies tube that permits maintenance and monitoring of the system's operation. (TNG: "Eye of the Beholder") Aboard the prototypical Template:ShipClass Enterprise of the 22nd century, a long catwalk spanned the length of each nacelle and, in emergency situations, acted as shelter for the ship's crew against certain types of radiation such as that created by neutronic storms. (ENT: "The Catwalk", "The Crossing") Nacelles aboard Enterprise 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. (ENT: "Fight or Flight")

Most vessels typically have two nacelles. However, such vessels can operate with one nacelle disabled, but at reduced warp speeds. (VOY: "Year of Hell"; ENT: "Twilight") It is not unprecedented, though, for vessels to have different nacelle configurations. For example, Federation Template:ShipClass, Template:ShipClass, Template:ShipClass and the Template:ShipType starships have only one nacelle. Template:ShipClass and Template:ShipType starships, in the alternate reality, have three nacelles. Template:ShipClass, Template:ShipClass and Template:ShipClass starships had four nacelles. (Star Trek II: The Wrath of Khan; Star Trek; TNG: "The Battle", "The Best of Both Worlds, Part II"; VOY: "Message in a Bottle")

Two additional nacelles deployed from the saucer section of Template:ShipClass starships when they entered multi-vector assault mode; these were not active during normal operation. In an alternative future, depicted in TNG: "All Good Things...", a refit version of the USS Enterprise-D was equipped with three nacelles.

Even at sublight speeds serious impacts from weapons or other objects can spell disaster for a ship because of a feedback of energy throughout the vessel. The Enterprise-D was destroyed by such an impact in an alternate timeline when the USS Bozeman collided with one of Enterprise's warp nacelles. (TNG: "Cause and Effect")

Some starship classes, such as the Template:ShipClass and the Template:ShipClass, possess nacelles that are integrated into the ship's main structure without pylons. (Star Trek: Deep Space Nine; Star Trek: First Contact)

Alien vessels, such as the Dominion's Jem'Hadar fighters, also possess nacelles. (DS9: "Sons and Daughters")

In 2374, the crew of the USS Cortez had difficulty stabilizing the guidance thrusters on their port nacelle, forcing them to fall back from the position they were in as part of the Operation Return fleet. (DS9: "Favor the Bold")

In 2377, the expression "third nacelle" was analogous to "fifth wheel". (VOY: "Inside Man")

Background

The use of the word nacelle in spacecraft design descends from its use for similar housing structures in air and water craft design.

According to the Spaceflight Chronology (page 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 creates 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 is possible for it to deliver what it promises.

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 is the optimal configuration for vessel control and power generation. On Template:ShipClass starships, there is an emergency separation system for the nacelles. In the event the ship is damaged and unable to retain a nacelle safely, explosive latches separate the nacelle from the pylon and lift it up at thirty meters per second. If a nacelle is lost during warp flight, it can tear the ship apart, as the loss would cause different areas of the ship to travel at different warp factors.