A nacelle pylon was part of a starship or shuttlecraft's structure that supported the warp nacelles.

The nacelle pylon could be mounted on the primary or secondary hull, and housed the power transfer conduits, and turbolift shafts and/or jefferies tubes so the crew could gain access to the nacelle. The pylons' exterior could be mounted with various features such as emergency flush intakes and vents, sensor arrays, phaser arrays, deflector grids, transporter emitter, impulse engines and exterior pennants. (TOS reference: Mr. Scott's Guide to the Enterprise; TNG reference: Star Trek: The Next Generation Technical Manual; ST reference: Starship Spotter))

In the event that a pylon was damaged to the point that it could no longer safely hold a nacelle, ejection systems were often put in place. Consisting of explosive bolts, once activated the system would propel the nacelle up and away from the vessel. (TOS episode: "The Apple" and TNG reference: Star Trek: The Next Generation Technical Manual)

During the refit of the Constitution-class USS Enterprise it was discovered that the existing pylons were not wide enough to house the plasma conduits, nor would they be able to bear the weight of the new nacelles. As a result, the pylons were replaced on the Enterprise and other refit Constitution-class vessels. (TOS reference: Mr. Scott's Guide to the Enterprise)

External link[]

• Nacelle pylon article at Memory Alpha, the wiki for canon Star Trek.