TNG Enterprise, being a starship carrying families, has
the ability to separate into saucer and warp drive
sections in case of an emergency situation. When
separated, the saucer section is capable of only impulse
speed, while the warp drive section turns into a
formidable battle machine. The following are instances
where it has been shown:
at Farpoint” - While Worf takes the saucer section to
Farpoint Station, Picard takes the warp drive section to
meet up with the Q entity.
of Freedom" - Geordi takes the Warp Drive section in
order to destroy the defense device on Minos, while
Chief Engineer Logan takes the saucer section to safety.
of Both Worlds - Part II" - In order to retrieve Locutus/Picard,
the Enterprise separates into two sections, with Riker
in charge of the Warp Drive section, and Cmdr. Shelby in
command of the saucer section. While the Borg attack the
warp drive section, the rescue shuttle with Worf and
Data launches from the saucer section.
of the reason that we don't see more saucer seperations
is due to budget constraints.