The Tri-Cobalt Device is a high-yield subspace device used for large scale destruction of stationary targets such as space stations.

The Tri-Cobalt Device was the first torpedo weapon in Starfleet. These weapons proved very effective against unshielded targets, but rather ineffective against shields. The torpedo also lacked the range Starfleet wanted, thus, they began developing the Photon torpedo. Once the Photon torpedo was in service, the Tri-Cobalt torpedo was removed from Starfleet ships. A few were left aboard ships and used primarily as demolition weapons. Currently in its 26th version, the Tri-Cobalt is a very powerful weapon when used against unshielded targets. With a maximum yield of 22,000 TeraCochranes, the device is powerful enough to tear subspace (this can be done with a yield of 18,000 TeraCochanes or higher). However, Starfleet doesn't consider these subspace weapons, which are banned by the Second Khitomer Accords. With the recent conflicts with the Borg and Dominion, Tri-Cobalt Devices are again becoming a standard part of Starship torpedo inventories, even though their arsenals are more impressive then ever with Photon and Quantum Torpedos standard on all ships, with some also carrying powerful and Hellfire and Transphasic Torpedos.

Starfleet vessels do carry Tri-Cobalt Devices occasionally. In 2371 the USS 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 design of the Tri-Cobalt device is thoroughly unique in the Alpha Quadrant. It uses a three-tier warhead: one compartment is loaded with antimatter; one with around 14 Quantum filaments; and another with the appropriate amount of Tri-Cobalt. Upon impact, a number of particle collisions and energy reactions occur within the warhead. Firstly the Quantum filaments are released into the Tri-Cobalt chamber creating a cascade reaction, mixing the Tri-cobalt into a highly volatile mixture. A millisecond later the magnetic containment field around the antimatter is released and the active Tri-Cobalt and antiproton bundle mix together creating a lethal explosion.

• Range Limit: 10 km - 2 500 000 km (from starships at warp)
• Warp Speed: 110% of warp factor of firing ship
• Sublight Speed: up to a 70% higher velocity (maximum velocity = initial velocity + .70 × initial velocity/ c {or Vmax = Vi + .70 Vi/c}
• Developed: 2174
• Operational Since: 2180
• Yield: 22,000 TeraCochrane (maximum for Mark XXVI)