Variable geometry warp nacelles, were a type of warp nacelle used on Starfleet vessels in the 24th century. The nacelles were not fixed immobile to the hull of the starship, but rather would move into position when the warp engine was powered. This action lessened the harmful effect of warp travel on space and subspace. However, within a year of variable geometry nacelles being developed, conventional nacelles were upgraded to produce the same effect whilst immobile.