Planet killer The " planet killer " was an informal name given by Spock in 2267 to an automated , self - propelled doomsday machine capable of destroying entire planet s . This robot was encountered by the Federation starship s and . Its origins were unknown , but based on its apparent trajectory , it was believed to have come from a galaxy other than the Milky Way . Discovery . On or about stardate 4202 . 1 the " Constellation " , under the command of Commodore Matt Decker , encountered massive destruction in system L - 370 – all seven planets had been utterly destroyed . Proceeding to system L - 374 ( stardate 4202 . 3 ) , the ship found three intact planets , and a fourth in the process of breaking up . Orbiting the fourth planet was the planet killer , firing a pure antiproton beam at the planet and consuming the planet ' s rubble as fuel . As the " Constellation " approached , it was attacked by the planet killer . The ship ' s deflector shield s were quickly overwhelmed by the onslaught . The machine proved completely invulnerable to counterattack because its hull was composed of pure neutronium . The " Constellation " sustained heavy damage . The main bridge was destroyed , the phaser banks were exhausted , the warp drive was destroyed and the impulse drive was severely damaged . In addition , the machine projected a powerful dampening field which cut off all communications with Starfleet Command . The field also deactivated the " Constellation " s antimatter fuel and left the ship nearly powerless . Unable to continue the attack or escape , Decker ordered the crew to evacuate to the third planet in the system . Decker himself remained aboard as the last man . However , having finished consuming the fourth planet , the machine then turned towards the third planet . Decker tried to beam his crew back up , but the machine attacked again , damaging the transporter . He could only watch helplessly as the machine consumed the planet below and killed his entire crew of 400 men and women . A short time later , the " Enterprise " , under the command of Captain James T . Kirk , received a faint and garbled distress signal . Unable to make out any words aside from " Constellation " , she entered system L - 374 and found her sister ship drifting and abandoned , with Commodore Decker the sole survivor aboard . Assessing the situation using the " Constellation " s sensor records taken by science officer Masada , Spock projected the weapon ' s origin . He also determined , based on its present course , that it would enter the most densely populated regions of the Alpha Quadrant , including the nearby Rigel system . Decker became determined to stop the threat posed to the Federation by the planet killer . The Battle . As the " Enterprise " held alongside the " Constellation " , it was suddenly and swiftly attacked by the planet killer . Although the " Enterprise " was more maneuverable , the weapon was extremely fast and gaining on its target . In the first volley , the " Enterprise " took heavy damage , with shields almost exhausted and transporters and communications damaged . While Captain Kirk was trapped with the boarding party aboard the " Constellation " , Spock ordered evasive action . Commodore Decker , taken aboard the " Enterprise " for medical treatment , exercised his authority to assume command under Starfleet General Order 104 and countermanded Spock ' s orders to avoid the machine and seek a clear space to warn Starfleet . With a combination of seeking retribution for the loss of his ship and crew , and the presumption that the nearby Rigel colonies would be the next target of the machine , Decker ordered an immediate attack on the weapon . However , the " Enterprise " was overwhelmed as quickly as the " Constellation " had been , and soon trapped by a tractor beam which was pulling the ship towards the planet killer ' s maw . Meanwhile , on the " Constellation " , Chief Engineer Montgomery Scott managed to effect partial repairs to the impulse engine s and a single phaser bank . Kirk launched a diversionary attack on the Planet Killer that allowed both ships to escape . The planet killer apparently had a relatively simple and straightforward defensive computer program that only allowed it to engage single targets within a specific range . The immediate danger past , Captain Kirk ordered Decker relieved of command of the " Enterprise " . As the two Starfleet ships withdrew , the planet killer returned to L - 374 and resumed consuming the planetary debris , taking in additional fuel . When Decker gave indications he was going to continue to press the attack despite narrowly avoiding disaster in the previous engagement , he was relieved of command by Spock under direct orders from Kirk on the basis that to continue to press the futile attacks would be indication he was suicidal , and was ordered to report to sickbay for a psychological examination . Suffering from a mental break - down brought on by extreme stress and the loss of his ship , crew and command , Commodore Decker escaped custody and stole a shuttlecraft from the " Enterprise " , piloting it on a suicide course directly into the weapon ' s maw , where it was quickly destroyed . However , the " Enterprise " sensors detected a small drop in the power output of the planet killer – the shuttlecraft ' s explosion , however small , had in fact caused some minor damage to the weapon from the inside . Based on this data , Captain Kirk proposed detonating the " Constellation " s main impulse engines inside the Planet Killer , creating a much bigger explosion and hopefully causing major damage to the weapon , if not destroying it outright . As the " Enterprise " held position near the Planet Killer , outside of weapons range , Kirk piloted the " Constellation " on a direct course toward the weapon . Beaming out at the last second , he detonated the " Constellation " s engines directly inside the weapon ' s maw , bypassing the neutronium hull , and effectively dropping its power output to zero ( in essence completely disabling the machine ) . It should be noted that due to the presence of the seemingly impenetrable neutronium hull , the hulk ( or " corpse " ) of the planet killer was left intact , floating lifelessly in space . Following the battle , Captain Kirk noted in his log that Commodore Decker gave his life in the line of duty . ( ) Appendices . Background information . Norman Spinrad was displeased with the model used for the planet killer . As he told Allan Asherman in " The Star Trek Interview Book " , he envisioned the planet killer bristling with all sorts of evil - looking weapons . The " planet - eater " was proposed , by J . Michael Straczynski and Bryce Zabel , to appear in a new " Star Trek " TV series they proposed in . In a fourteen - page treatment which outlined their plans , Straczynski and Zabel supposed , " " What if we discover that the device was a left - over piece of warfare tech from the race our characters are pursuing ? Do they allow the planet - sized weapon to destroy a sparsely populated colony world if in doing so , they gain the time to get information that could save billions of lives elsewhere ? " " The " Star Trek Concordance " refers to the device as the " " or " planet - eater " ; the reference book " The Monsters of Star Trek " also used the berserker moniker in describing the weapon . It is also of note that the sketch of the berserker , titled " doomsday machine " , that appeared in the " Concordance " was sketched by future franchise staffer Greg Jein . The " Ships of the Line " book states that that the Planet Killer once " had " been the monster Norman Spinrad envisioned , boasting a " complete arsenal of weaponry " , but centuries of combat had taken their toll so that , by the time the " Constellation " encountered it , only the main weapon remained . Apocrypha . The " planet killer " was featured in several non - canon productions . Peter David ' s novel " Vendetta " featured another " planet killer " that was believed to have originated as an ancient race ' s ( perhaps the Preservers ) last resort weapon against the Borg . According to David ' s story , the planet killer encountered by the " Enterprise " was an automated prototype , sent on a course that would have eventually carried it to Borg space , had the " Enterprise " not stopped it . Its basic design – destroy planets already assimilated by the Borg for use as fuel – coupled with an indestructible neutronium hull and antiproton beam ( against which there was little or no defense ) , made it an ideal weapon against the Borg . This planet killer is much larger and also has the much more menacing appearance Spinrad initially imagined . During the novel ' s climax , in an engagement with three Borg cube s , the Borg fire weapons powerful enough to actually hurt the machine , revealing a secondary hull of rodinium beneath the neutronium , and an inorganic coolant fluid running through its conduits that causes the planet killer to appear to " bleed " when it is sufficiently damaged . It is finally " destroyed " when the planet killer ' s pilot attempts to take it up to Warp 10 , trapping herself in an infinite time loop where she will always keep trying to reach Borg space but never succeed . In the novel ' s prologue , a young Cadet Jean - Luc Picard presents a history report on the planet killer to his class , noting that Captain Kirk ' s report was somewhat short on details , and so Picard interprets his statement that Commodore Decker died in the line of duty as meaning that Decker , not Kirk , piloted the " Constellation " into the weapon ' s maw . He also notes that the planet killer ' s need for planets as fuel meant that it could not have come from that far outside the galaxy , as there would be no planets for it to ' eat ' in the inter - galactic void and it could not have passed through the galactic barrier through sheer inertia . The WildStorm Comics " Star Trek " comics included a " " miniseries , " " , with another doomsday machine . In this encounter , it was revealed that the machine was the creation of an extinct species designated by the Borg as Species 4672 . After attempts to destroy the machine by repeating Kirk ' s trick with the " Constellation " fail using a ship belonging to a new ally , they are able to shut it down by coating The Doctor ' s mobile emitter with neutronium and using the " Delta Flyer " to transport him inside the machine and inject it with Borg nanoprobe s designed to " infect " it with a " virus " . In Kevin Lauderdale ' s short story " Devices and Desires " ( in " Constellations " ) , the doomsday machine was taken to The Yard , a top secret facility where the alien technology Starfleet acquired was stored and studied . One of its researchers was Dr . Pad – a reference to Peter ( Allen ) David , above . This idea for the fate of the original doomsday machine was used for its return appearance in " Before Dishonor " , a partial sequel to the " Vendetta " storyline , when a new , upgraded Borg cube led by an assimilated Admiral Kathryn Janeway , now a new Borg Queen , attacked Earth forcing the crew of the to travel to the ship " museum " where the original machine was placed after its destruction . Spock , Geordi La Forge , and Seven of Nine subsequently reactivated the machine and used it to destroy the cube once and for all . A third planet killer was featured in the novel " Armageddon ' s Arrow " ; with the original planet killer established as a prototype for the one that featured in " Vendetta " , the " Enterprise " - E discover a prototype to the original planet killer on a moon in an unexplored region of space , which has been discovered by the Golvonek , a race inhabiting the planet Urphrel who are at war with their local neighbors . The Golvonek use this crashed version as a template to create their own , more primitive version of the planet killer , capable of destroying planets with a particle weapon but requiring a degree of active crew operation and suffering various operating problems . When the Golvonek planet killer travels back from the future to be discovered by the " Enterprise " in the present , it is eventually destroyed when its surviving crew crash it into its own past self to convince their worlds to seriously consider peace , while the proto - planet killer is salvaged by Federation scientists for future study . In the game " " , in the level " From Hell ' s Heart " , the doomsday machine appeared and was trying to destroy the Klingon homeworld in the Mirror universe . In the PC game " " , the Terran Empire from the mirror universe attempted to unleash a fleet of doomsday machines on our Earth . The player is able to destroy them by beaming prototype mines into the maws of the devices , shutting them down . In the Gameboy game " " , the entire game plot resolved around a doomsday machine that was discovered heading into Federation space . The player must find scattered parts to a protomatter fusion disruptor , that was built to combat the planet killer . In " Star Trek Online " , Ambassador B ' Vat ' s faction of Klingons rediscovered a planet killer , and managed to modify and reactivate it for use as a weapon against the Federation . The player has to destroy the Klingon remote control systems and destroy the planet killer with an experimental Klingon torpedo , the Hargh ' Peng . Two more planet killers are introduced in the " Agents of Yesterday " expansion . One of them causes the Galorndon Core to be inhospitable when it sucks up a Na ' kuhl ship and it crashes to the planet . Another is fought over between players and Klingon of the 23rd century .