A warp core is a matter-antimatter reactor used to provide power for starships in Star Trek. Its primary purpose is to provide power for the warp drive, but "warp power" is also used to supply many other systems.
Inside a warp core, matter and antimatter are allowed to contact and annihilate each other within a magnetic containment field. Dilithium crystals are used to control the reaction, and their orientation affects the efficiency of the reaction. Energy from the reaction is collected in the form of plasma and piped around the ship to power various systems, especially the warp drive.
Warp cores are prone to excess reactivity, making them incredibly dangerous to operate. When operating, a warp core typically contains enough antimatter to destroy its ship if the magnetic field isolating the fuel from the containment vessel should fail.
Warp core safety systems, especially aboard Galaxy-class starships, are prone to failure themselves. In particular, the warp core ejection system -- a last-ditch option that launches the entire core into space -- has repeatedly failed to operate when needed.
For example, see the destruction of the Enterprise in TNG "Cause and Effect". Note that multiple "failsafe" systems to prevent the destruction of the ship fail: both an emergency shutdown of the warp core and an emergency ejection of the warp core.
- Enterprise, NX-01; destroyed in alternate timeline by a deliberate core breach
- Enterprise, NX-01 (Mirror Universe); destroyed in battle due to a jammed AM ejection system
- USS Enterprise, NCC-1701-D; destroyed multiple times in various timelines, permanently destroyed by core breach in Star Trek: Generations.
- USS Enterprise, NCC-1701-E; this breach was remotely triggered after core ejection
- USS Yamato; destroyed by an AM containment failure (TNG "Contagion")
- Farrakk's starship; sabotaged
- USS Orinoco; sabotaged
- TNG "Booby Trap"