^Leave it nebulous so the fanboys have something to debate about in the coming years.
In the unfilmed Exeter
episode "The Atlantis Invaders" I deliberately didn't specify impulse or warp engines during a chase sequence because saying either raised questions that weren't important to the narrative (if they're at impulse, why not go to warp...if at warp, can you use phasers or transporters?). Furthermore, it left options open to the effects guys on how to portray it or whether to use any stock shots in the sequence. Sometimes being less specific is the right way to go.