Auto-destruct
The auto-destruct system (also known as self-destruct or destruct sequence) was a starship system that allowed the total destruction of the vessel. This was typically activated as a last resort, usually to prevent a ship from falling into enemy hands. 

On Starfleet vessels, the activation sequence varied from class to class but usually required authorization with the use of command authorization codes. Once the countdown was activated, the ship's computer could give audio warnings and/or displayed countdown warning graphics on viewscreens and terminals, though this featured could be disabled when initiating the sequence. () In the 23rd century, self-destruct was also known as Starfleet Order 2005. ()

Known sequences

Constitution-class 

On  starships, the captain or admiral (including rear admiral) and two senior officers (chief engineering and science officers/acting science officer) were required to initiate the destruct sequence, using the following, concurrent codes: 

Each officer would state their name, rank and corresponding code:
 "Destruct sequence 1, code 1-1 A."
 "Destruct sequence 2, code 1-1 A-2B."
 "Destruct sequence 3, code 1 B-2B-3."

The computer would then reply:

"Destruct sequence completed and engaged. Awaiting final code for (time interval) countdown."

The commanding officer would then state:

"Code zero zero zero. Destruct. Zero."

The computer would than activate red alert and respond:
"Destruct sequence is activated."

The sequence could be aborted at any time until T-minus five seconds by the captain or highest-ranking officer, with the command "Code 1-2-3-continuity, abort destruct order." Beyond that, the destruct order could not be cancelled. (; )

Crossfield-class 
It was possible to set a remote auto-destruct for a  starship, allowing the crew to evacuate to another vessel. In 2257, Christopher Pike and Saru attempted this method with the , both of them providing handprint authorization. The crew was then evacuated to the , but the attempt failed due to the  data merging with the vessel's systems and protecting itself. ()

Galaxy-class 

Originally, the auto-destruct sequence aboard  starships required the authorization and palm-print identification of both the commanding and executive officers from main engineering. The sequence could be aborted from the bridge by voice recognition and palm print identification by the same officers. The time interval could not be adjusted and was preset for a five minute countdown. ()

By 2365, the time interval could be pre-selected and the countdown aborted without the need of palm-print identification. The activation of the auto-destruct sequence also triggered a red alert. ()

Upon providing palm-print identification, the captain would order the computer to initiate the auto-destruct. The computer would ask if the first officer concurred. Providing the first officer agrees, the computer would verbally confirm the order and begin the countdown with the appropriate time delay. Should the order be desired to be cancelled, the captain would order the computer to abort the sequence. The computer would question the first officer's agreement before cancelling the sequence. ()

Defiant-class 

The  sequence was activated from the bridge, requiring the captain and first officer's consent and palm-print identification to activate. The time delay was left to the captain's discretion. Upon activation of the destruct sequence, a red alert would be triggered and all bridge computer terminals would display the remaining time left in the countdown. Cancelling the sequence would require the captain and first officer's orders without the need of palm-print identification or computer clarification. ()

Intrepid-class 
Aboard the , auto-destruct required the captain's sole authorization. In addition to selecting the desired time interval, the captain also had the option of ordering a silent countdown – a single voice prompt would occur at the commencement of the sequence, with no further audio warnings made. () 

If the starship's secondary command processors were offline, the auto-destruct sequence could not be completed. ()

Sagan-class 
The  had an abbreviated, ten-second sequence activated with the old code "zero-zero-zero-destruct-zero".()

Sovereign-class 
The  required the authorization of the captain and two senior officers. Each would state their name and rank, confirming the sequence, and giving their authorization code. The captain would then select the destruct sequence type, sequence delay, and whether a silent countdown would be initiated.

"Computer, begin auto-destruct sequence, authorization Picard 4-7 Alpha Tango."	
"Computer, Commander Beverly Crusher. Confirm auto-destruct sequence, authorization Crusher 2-2 Beta Charlie."	
"Computer, Lieutenant Commander Worf. Confirm auto-destruct sequence, authorization Worf 3-7 Gamma Echo."	
(The computer would ask for the final code to start the sequence.)
"This is Captain Jean-Luc Picard. Destruct sequence Alpha-One. Fifteen minutes, silent countdown. Enable."

The auto-destruct need not be deactivated by the ship's captain, as Lieutenant Commander Data was able to deactivate the auto-destruct sequence by himself, however, this could be the result of Data hacking into main computer past normal operating parameters.

An "Omega" option for the auto-destruct was also available and only needed the captain's authorization to initiate.

"Computer, stand-by auto-destruct sequence Omega. Recognize voice pattern Jean-Luc Picard, authorization Alpha-Alpha 3-0-5."

If the ship was significantly damaged, the auto-destruct system could be rendered inoperable. (; )

Methods 
Klingon vessels, like the , could evoke their own self-destruction by causing a containment failure within the warp core. ()

Some 23rd century Klingon ships had scuttle systems that would trigger the self-destruct upon the slightest interaction with any onboard control, in circumstances where the crew was unavailable to trigger it directly. ()

Twenty-third century Romulan vessels used "old style" atomic weapons in their self-destruct system which were not integrated into the ship itself. These weapons could be removed and jettisoned into space as mines. () Romulan scout ships were equipped with an Auto-destruct sequencer. ()

During the Galen border conflict, Talarian observation craft equipped with self-destruct devices and subspace proximity detonators were responsible for 219 casualties over a three day period. ()

A Borg vessel's self-destruct mechanism forced the ship's power grid to feed back on itself, forcing an explosion that destroyed the ship. Lieutenant Commander Data was able to trigger such a destruction while being linked to the collective consciousness of the Borg ship that threatened Earth in 2367. The Borg Queen ordered the self destruction of several Borg ships that carried drones linked to Unimatrix Zero as well as a Borg tactical cube that had Captain Kathryn Janeway, Lieutenant Commander Tuvok, and Lieutenant B'Elanna Torres aboard. (; )

When a Borg vessel was critically damaged, all of its vital technology, such as the transwarp coils, self-destructed to prevent their use by other species. This process is autonomous and independent from the ship's self destruction. ()

Appendices

See also 
 Computer log
 Log buoy

External link 
 

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