Intrepid class at warp
The variable-geometry pylon is a feature first introduced to Federation starships around 2370.
The warp nacelles have the ability to be raised into position for warp speeds, then lowered into a more streamlined position when at slower-than-light speeds. The Template:ShipClass starships are equipped with this feature, an example of which is the USS Voyager. (VOY: "Caretaker")
The pylons were raised anytime a warp field was generated, even if the ship was not traveling at warp speeds. (VOY: "Learning Curve")
- No other class of starship to date incorporates this design.
Background
The first time the concept of variable-geometry warp nacelle pylons is mentioned anywhere is in the Star Trek: The Next Generation Technical Manual in the section dealing with preliminary concepts for future starships. The goal of these pylons is to improve engine efficiency by optimizing field stress when the ship travels extended journeys at warp 8+ velocity.
According to the unpublished VOY Season 1 edition of the Star Trek: Voyager Technical Guide, by Rick Sternbach and Michael Okuda, it was suggested that because of the variable-geometry pylons, warp fields may no longer have a negative impact on habitable worlds as established in TNG: "Force of Nature".
- While these Technical Manuals are not canon, they are both Memory Alpha permitted resources.