Nacelle A nacelle was an outboard engine housing structure on a spacecraft . The nacelles in warp - capable shuttles and starship s housed the warp coil s of the vessel ' s warp drive . Warp nacelles were also sometimes known as power nacelles , antimatter nacelles , warp drive pods , or space / warp propulsion units during the 23rd century . ( ; ) Impulse nacelles of a sublight shuttlecraft housed the ship ' s impulse driver engines . ( " display graphic " ) The warp coils in warp nacelles created a subspace displacement field , which " warped " 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 were fed by plasma conduit s from the warp core reactor assembly . Venting the plasma from the nacelles made warp drive impossible until the nacelles could be replenished . ( ) Nacelles were separated from the ship by large pylon s , and usually housed a Bussard ramscoop at the fore end , primarily used for collecting hydrogen from space . On the large nacelles , the interior included a small control room , accessible in nominal conditions by a Jefferies tube that permitted maintenance and monitoring of the system ' s operation . ( ) Aboard the prototype 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 storm s . ( ) 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 . ( ) Most vessels typically had two nacelles . However , such vessels could operate with one nacelle disabled , but at reduced warp speeds . ( ; ) It was not unprecedented , though , for vessels to have had different nacelle configurations . For example , Federation , , , and the starships had only one nacelle . and in the prime reality " and starships in the alternate reality " had three nacelles . , , and starships had four nacelles . ( ; ; ; ; ) Even at sublight speeds serious impacts from weapon s or other objects could 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 collided with one of " Enterprise " s warp nacelles . " ( ) Some starship classes , such as the and the , possessed nacelles that were integrated into the ship ' s main structure without pylons . ( ; ) Alien vessels , such as the Dominion ' s Jem ' Hadar fighter s , also possessed nacelles . ( ) In 2374 , the crew of the had difficulty stabilizing the guidance thruster s on their port nacelle , forcing them to fall back from the position they were in as part of the Operation Return fleet . ( ) 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 . ( ) In 2377 , the expression " third nacelle " was analogous to " fifth wheel " . ( ) Background information . 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 " Star Trek Blueprints " , while the 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 " " , 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 refit - " Constitution " - 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 ( See : S - 2 graf unit ) and Romulan nacelles of the were known as quantum singularity energized warp drive units . The Jem ' Hadar attack ship s 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 was possible for it to deliver what it promised . The " " ( 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 nacelle safely , explosive latches separated the nacelle from the pylon and lifted it up at thirty meters per second . If a nacelle was lost during warp flight , it could tear the ship apart , as the loss would cause different areas of the ship to travel at different warp factor s . 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 art director Walter M . " Matt " Jefferies , as part of his design for the original " Enterprise " . 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 actually done , years after the end of the original " Star Trek " , for the uprated " Enterprise " designed for " " and seen in . " "