Transwarp coil

A transwarp coil was a propulsion device which allowed Borg vessels to generate a transwarp conduit. 

To generate a transwarp conduit the coil required a minimum input of thirty teradynes (three hundred meganewtons) of force from the ship's systems. On Borg vessels, the coils were protected by a protocol that damaged the coil beyond repair by fusing the field regulator when the vessel became critically damaged. 

In 2153, two scientists discovered a transwarp coil from the wreck of a Borg sphere that crashed in Earth's Arctic Circle. 

In mid-2375, after surviving a battle with a Borg probe, the crew of the USS Voyager managed to recover several Borg data nodes containing, among other information, long-range sensor telemetry and vessel movements for a radius of thirty light years. Utilizing this information, Voyager was able to locate a damaged Borg sphere and steal a working transwarp coil from the ship's transwarp chamber. The coil was fitted to both the Delta Flyer and Voyager itself, providing 20,000 light years of travel before giving out, shaving approximately fifteen years off Voyager's journey home.