Editing Constitution Class (section)

===Physical arrangement===

The Constitution-class featured the saucer section-engineering section-warp nacelle layout common to most Starfleet vessels. (TOS: "The Cage", Star Trek: The Motion Picture, etc.)

Various science labs, numbering fourteen in all, (TOS: "Operation -- Annihilate!") were located in the primary hull in the class' original configuration. An officer's lounge and dining area would be located in the aft superstructure beneath the bridge after the 2270s refit. (Star Trek: The Motion Picture)

The modular design of the Constitution-class allowed for component separation in times of crisis. The primary and secondary hulls could separate where the connecting "neck" joined the saucer, allowing either section to serve as a lifeboat if the other was too badly damaged. If an emergency was confined to the warp engine nacelles, it was possible to eject them while keeping the bulk of the vessel intact. (TOS: "The Apple", "The Savage Curtain")

Though not an aerodynamic craft, in emergencies, Constitution-class vessels were able to break orbit and enter a Class M planet's upper atmosphere (and maintain attitude control while passing through it) for a limited period of time, conditional on the ship's ability to re-achieve escape velocity. (TOS: "Tomorrow is Yesterday")