Saucer separation

Saucer separation is a maneuver where a Federation starship separates its primary hull from its secondary hull completely. This allows the crew to abandon one section of the ship for another in the event of an emergency. What was initially a one-time only event in the 24th century Starfleet started to design vessels were if a separation was performed the vessel could reconnect the two halves of the ship.

The USS performed a emergency saucer separation when it was trapped in a time causality loop in 2374. This was done to avoid the destruction of the whole ship by a warp core breach. However due to damage to the ship's systems many of the crew in the secondary hull were not made aware of this maneuver. In the end it proved a futile effort as the saucer section was also destroyed, resetting the loop.