Impulse (Star Trek: Enterprise)

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Star Trek: Enterprise episode
Episode no.Season 3
Episode 5
Directed byDavid Livingston
Story byJonathan Fernandez
Terry Matalas
Teleplay byJonathan Fernandez
Featured musicDennis McCarthy
Production code305
Original air dateOctober 8, 2003 (2003-10-08)
Guest appearance(s)
  • Sean McGowan - Corporal Hawkins
Episode chronology
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Star Trek: Enterprise (season 3)
List of Star Trek: Enterprise episodes

"Impulse" is the fifty-seventh episode of the American science fiction television series Star Trek: Enterprise, the fifth episode of season three. The episode was written by story editor Jonathan Fernandez from a story by Fernandez and Terry Matalas. It first aired October 8, 2003 on the UPN network in the United States. The episode was described by Paramount Pictures as "as close to a horror show as Star Trek gets".[1]

Set in the 22nd century, the series follows the adventures of the first Starfleet starship Enterprise, registration NX-01. In this episode, while investigating the Delphic Expanse for a Xindi superweapon, the Enterprise responds to the distress call of a Vulcan ship. The crew on board have undergone the effects of exposure to Trellium-D, which turns Vulcans into violent zombie-like drones because it is a toxin. T'Pol is also poisoned and it begins to affect her, however Phlox is able to reverse the effects.


Captain Archer carries Sub-Commander T'Pol into sickbay, where he and Doctor Phlox strap her to a bed. She awakes and threatens to kill Archer, and Phlox sedates her. A day earlier, Enterprise receives a distress call from the Vulcan cruiser Seleya, and upon arrival, they find the ship adrift in an asteroid belt rich in Trellium ore. Archer decides to send in a shuttlepod as Enterprise is too big to maneuver among the asteroids. En route, T'Pol informs the other members of the away team that the Vaankara had been sent into the Expanse to find the Seleya, but the crew began to attack one another and the ship was destroyed. Meanwhile, Commander Tucker and Ensign Mayweather decide to mine some Trellium ore from an asteroid.

Lieutenant Reed, T'Pol and Archer board the Seleya and are attacked by zombie-like Vulcans. Soon T'Pol begins to show the same effects as seen on the other Vulcans. Archer and the away team then fight their way to Engineering, where they attempt to re-route the bulkhead controls on the ship so they can get back to their shuttle. They discuss a general override, which would unlock the bulkheads, but also shut down the containment on the warp core, and T'Pol accuses Archer of wanting to kill all the Vulcans.

Tucker and Mayweather retrieve the ore, but their shuttlepod is damaged in the process. After they return to Enterprise they begin repairs. Meanwhile, the Vulcan crew begins to gas Engineering, forcing Reed to activate the override. Archer's away team head back to the shuttle and arrive moments before the Seleya is due to explode, but find the docking clamps locked. Tucker and Mayweather then arrive on the second shuttle and destroy the clamps and the two shuttles depart, as the Seleya is destroyed. Tucker announces enough ore was recovered to shield the forward hull, but Archer orders it stored in a bio-hazard locker until a cure can be created.



Trellium-D is a fictional chemical substance from the Star Trek universe. It was introduced in the third season of Star Trek: Enterprise, and became an important recurring plot element throughout the season, exploring the subject of drug addiction.

Physical properties

Trellium-D was rare; a similar but less useful mineral called Trellium-A was more common. With the right equipment, Trellium-D could be synthesized in a liquid state, but it was then explosive, so the synthesizing procedures had to be followed exactly. Despite its volatility, Trellium-D was used in the mid-22nd century for starship insulation in the Delphic Expanse, as it offered protection against the region's dangerous spatial anomalies.

Physiological effects

It also had unusual properties affecting Vulcan physiology. In "Impulse," Trellium-D was revealed to be the cause of severe psychotic effects in that race, which led the crew of the Seleya to go insane and kill each other. Short-term exposure to the compound, which had been used by the Vulcan vessel as insulation, led to uncontrolled emotionalism for Enterprise science officer, T'Pol, and Archer determined that it was too dangerous to use to protect his own vessel from the effects of the Expanse.

T'Pol's addiction

T'Pol suffered side-effects and flashbacks from her exposure to Trellium-D, but over the next few months found herself desiring to access more of the new emotions she experienced while under its influence. She secretly devised a way of liquefying small amounts of the compound, which she injected directly into her bloodstream. The result was an increased level of emotion, which initially proved beneficial in her dealings with the crew. In the episode "Harbinger", T'Pol experience intensifies the negative emotion of jealousy, soon followed with engaging in a sexual encounter with Commander Tucker. In the episode "Azati Prime," T'Pol's emotions flare when she tells Captain Archer that she does not want him to die, and later is somewhat incapacitated as a commanding officer during an attack by four Xindi ships that kills 14 crewmembers and heavily damages Enterprise.

In the following episode "Damage," T'Pol's addiction to Trellium-D reached a breaking point when she nearly died trying to access some of the compound from a damaged part of the ship. She confessed her addiction to medical officer Doctor Phlox who treated her addiction and agreed not to reveal it to the captain. Long-term exposure to Trellium-D was said to be damaging to Vulcan brains, and T'Pol's injecting of the chemical caused her permanent damage, to the extent that she was expected to have some difficulty controlling her emotions for the rest of her life.

Reception and home media release[edit]

"Impulse" was first aired in the United States on UPN on October 8, 2003. It received a 2.8/4 percent share among adults. This means that it was seen by 2.8 percent of all households, and 4 percent of all of those watching television at the time of the broadcast. Enterprise was the sixth most watched program in the timeslot, behind Smallville on The WB. It was estimated that "Azati Prime" was watched by 4.17 million viewers, which was less than the previous episode, "Rajiin".[2]

Jamahl Epsicokhan at his website Jammer's Reviews described the episode as "sort of a guilty pleasure" due to the "superficial visual qualities".[3] He was positive about the visual qualities of the episode, but said that it lacked substance. He gave "Impulse" a rating of three out of four.[3] In 2017 this episode was noted as featuring scary and/or eerie Star Trek content.[4]

"Impulse" was released as part of the season three DVD box set, released in the United States on September 27, 2005.[5] The set included optional text commentary for "Impulse" from Mike and Denise Okuda.[6] The season was released on Blu-ray in the United States on January 7, 2014.[7][8][9]


  1. ^ "Production Report: Acting on "Impulse"". CBS Entertainment. August 22, 2003. Archived from the original on 2008-06-04. Retrieved 2011-03-17.
  2. ^ Krutzler, Steve (October 10, 2003). "Final Ratings: #6 "Impulse" Loses Viewers But Posts Gain in Household Figure". TrekWeb. Archived from the original on October 11, 2012. Retrieved October 16, 2013.
  3. ^ a b Epsicokhan, Jamahl. "Star Trek: Enterprise "Impulse"". Jammer's Reviews. Retrieved October 17, 2013.
  4. ^ "18 eerie, disturbing and downright scary Star Trek episodes". H&I. Retrieved 2019-06-05.
  5. ^ Douglass Jr., Todd (September 27, 2005). "Star Trek Enterprise – The Complete 3rd Season". DVD Talk. Archived from the original on March 4, 2016. Retrieved October 16, 2013.
  6. ^ Scultz, Paul (October 8, 2005). "DVD Review: Star Trek Enterprise - The Complete Third Season". The Trades. Archived from the original on November 10, 2006. Retrieved October 17, 2013.
  7. ^ "Enterprise Trekking To Blu-ray; Fans Helped Pick Covers". Star January 7, 2013. Archived from the original on March 30, 2016. Retrieved October 16, 2013.
  8. ^ Lambert, David (October 14, 2013). "Star Trek: Enterprise - 'Season 3' Blu-ray Announced: Date, Cost, Package, Extras". Archived from the original on October 16, 2013. Retrieved October 16, 2013.
  9. ^ "Star Trek: Enterprise - Season Three Blu-ray". Retrieved June 23, 2016.

External links[edit]