The tri-cobalt warhead is a high yield subspace device used for large scale destruction of stationary or slow-moving targets such as space stations or Borg cubes. Although the Federation is banned from using subspace weapons by the Khitomer accords, Starfleet vessels do carry tri-cobalt devices occasionally. In 2371 the U.S.S. Voyager used two of them to destroy the Caretaker's array in order to prevent it from falling into the hands of the Kazon. The Starfleet weapon has a programmable yield which can reach 20,000 Teracochranes, more than enough to destroy even a large station like the Caretaker's array. The tri-cobalt device creates a spatial rift for a short period of time, gravitational forces then pull anything in the vicinity apart, thereby destroying the objects. As shields are gravitational fields themselves tri-cobalt devices are ineffective against shielded targets, so a hole in an enemy shields needs to be opened before the tri-cobalt device can be used. The tri-cobalt device is larger than a standard torpedo and can only be fired from launchers that have been suitably modified to carry the weapon. It is also slower and can be avoided more easily by a moving target, making it ineffective against all but the biggest of starships, such as Borg vessels.