Starfleet Academy. Courses. Warp Theory. Nacelles. Nacelle control systems: On older starships, such as the NX-class Enterprise NX-01, the nacelles house a large catwalk use as a service corridor for nacelle systems. In one documented case by Starfleet Command, 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 nace