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Aperture Science Sentry Turret

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Aperture Science Sentry Turret
Production information

Aperture Science


Autonomous gun platform



Used by
Game information



Scott Klintworth[2]

Voiced by
"Are you still there?"
― Aperture Science Sentry Turret[src]

The Aperture Science Sentry Turret is a Personality Construct-based gun platform used throughout the Aperture Science Enrichment Center in Portal and Portal 2.

The Turrets are not only important testing track obstacles, but are also used to protect restricted areas of the facility as well as in the testing of Military Androids and the Portal Device.


The Aperture Sentry Turret has a single red eye, sleek appearance and predominately white color scheme common to most Aperture Science technology. Sentry Turrets are commonly seen serving as guards in the maintenance areas of the Enrichment Center, and when during testing it serves as an obstacle.

Sentry Turrets often speak in a sweet child-like, artificial voice similar to GLaDOS and a lavatory bowl within the Enrichment Center. They have a strangely polite demeanor, which is in direct contrast with their deadly behavior. They will even forgive Chell for knocking them over. In one scene in Portal 2, an Oracle Turret is seen stuck inside the Aperture Science Pipe Network, who attempts to get Chell and Wheatley's attention. At Wheatley's encouragement, Chell ignores it, but the Sentry Turret politely says "thanks anyway" with a hint of shattered hopes.

The Sentry Turrets are armed with two dual machine guns and can only be armed once a Test Subject approaches its range of sight. These weapons along with its antenna are normally hidden inside the body, during a Turret's "sleep mode". When the Sentry Turret is alerted, the machine guns will emerge, and fire at any visible targets (usually Test Subjects or intruders). When no targets are in range, the Sentry will scan back and forth across the area, and return to sleep mode after three seconds if no targets were found.

Aperture-Brand Resolution Pellets, the bullets for a Sentry Turret's guns, are simply dumped into its hollow body, called the Shell Redistribution Chamber; this allows for an unusually large supply of ammunition for such a small device. Aperture-Brand Resolution Pellets are the only type of ammunition that is recommended for use with a Sentry Turret. In addition, bullets are not "fired" in the traditional sense. They are propelled, shell and all, with a spring-loaded mechanism called the Projectile Acceleration Cylinder, which is guarded by the Aperture Turret External Barrel. Since the whole bullet is fired, this allows up to 65% more bullet mass per bullet, the extra mass adding to the stopping power of the bullet.

The Personality Core of the Sentry Turret is located within the outer shell, right above the guns. It is fitted with a Fire/No Fire Incident Resolution Chip, presumably to help the Turret distinguish when or when not to fire, an Empathy Generator and an Empathy Suppressor. Apparently, the Empathy Suppressor is of greater influence, as simply standing near a Sentry Turret may cause its Empathy Suppressor to accidentally activate, greatly reducing the Sentry Turret's feelings of empathy toward its foe.

The consumer version of the Sentry Turret is available in hundreds of different designer patterns and colors, including "Forest", "Desert", "Table", and "Evening at the Improv".[3]


Sentry Turrets, when idle, conceal their weapons under the two plates on either side of their body. When they spot a target it takes a moment to deploy its weapons to fire. A Sentry Turret's weapons are very powerful and are able to kill a human, such as Chell, after a few seconds of continuous fire. ATLAS and P-body, while sturdier than a human, still cannot endure lengthy sustained fire before falling apart.

However, Sentry Turrets can be easily spotted by the visible laser beam emitted from their eye at all times, making it easier to avoid them. When knocked over Sentry Turrets fire frantically in all directions before permanently deactivating. Like all other objects within the Enrichment Center, the Sentry Turret will disintegrate (and produce an unusual sound) if it passes through a Material Emancipation Grill.

In Portal, the primary method of defeating the Turret is to disable it via knocking it over (echoing the method used in Half-Life 2). This can be accomplished in various ways: by picking it up from behind and dropping it in an odd position, hitting it with another object (including another turret), shooting a portal at its feet, or directing a High Energy Pellet into it (the Pellet will not destroy the turret on impact, but it will impart enough force to knock it over). In some cases, a can of beans can be sufficient enough to knock a turret on its side, as evidenced in Test Chamber 16 of Portal. A Rattman den inside that chamber contains bean cans scattered around behind a broken wall. Picking one up with the "E" key and launching it with primary fire can knock a turret over. One must account for can drop, because the cans are not bullets. It is advised to aim the portal gun's crosshairs above the Sentry Turret's body for the can to hit its center mass.

Portal 2 introduces two means for the player to actually destroy the Turrets. One is to direct a Thermal Discouragement Beam onto it (usually via a portal and/or Discouragement Redirection Cube), causing it to heat up and explode. Another is to cover it in Repulsion Gel, causing it to bounce with increasing force until it either shatters or falls away.

Related Achievements[edit]

Portal hit turret with turret.png Friendly Fire (5G)
Knock down a turret with another turret.
Portal: Still Alive
Cameraaddstenpounds.jpg The Camera Adds 10 Pounds (5G)
Knock a turret over with a security camera.
Isanyonethere.jpg Is Anyone There? (20G)
Complete the game without ever taking a bullet.
Feelinglikefloating.jpg A Feeling Like Floating (5G)
Dissolve a turret.
Portal 2
LAUNCH TURRET.jpg Pturretdactyl (5G)
Use an Aerial Faith Plate to launch a turret.
NOT THE DROID.jpg Scanned Alone (5G)
Stand in a defective turret detector.
SAVE REDEMPTION TURRET.jpg No Hard Feelings (10G)
Save a turret from redemption.
YOU MONSTER.jpg Can't Touch This (10G)
Dance in front of a turret blocked by a hard light bridge in co-op. Reference to the song "U Can't Touch This" by MC Hammer.

Behind the scenes[edit]

According to Erik Wolpaw, at one point in Portal 2 Chell was to stumble upon a pile of abandoned turrets resembling a lost tribe one might find surviving on a forgotten island, and help them in some way. The Animal King would then marry off one of its turrets to her. Valve had even constructed a bride turret, which would follow Chell around for the rest of the game in a similar fashion to Watson in Sherlock Holmes Nemesis.[4]


  • In contrast to Portal, Portal 2 Sentry Turrets will not attempt to shoot at enemies if glass is between them, while still tracking the enemy with the laser pointer. A Hard Light Bridge will prevent the Turret from even detecting the enemy, making it go to sleep.
  • As stated in the "Investment Opportunity" video, the turrets "fire 65% more bullet per bullet". The video shows that, instead of igniting the powder behind the bullet, thus causing it to fire, they instead hit the bullet hard (but not igniting the powder) and launch the entire round. Most likely the bullet is covered in a flammable compound that ignites upon leaving the barrel, like a match on sandpaper. This would also explain the muzzle flash and bright look of the flying bullets[3]
    • In the same video, the turret taken apart more closely resembles the turrets in Portal rather than Portal 2, as only thin piping is taken out rather than the multitude of things seen inside of the Portal 2 model.
  • At the start of the Portal 2 chapter The Escape, three Turrets using a cut in half version of the model from Portal can be seen right before the drop onto the first operational conveyer.
    • Also in the chapter The Escape, Chell passes through the production line for the commercial version of the Aperture Science Sentry Turret. The developer commentary states that originally, they would have had the Sentry Turret built and boxed, then passed into a machine directly below. This machine would unbox and disassemble it, then recycling the parts, meaning that the Sentry Turrets are never actually shipped. They also would have included a massive pile of all the unrecycled packaging material, giving Aperture the most inefficient recycling system possible.
  • Some of the Sentry Turret's sounds were not used in the game, but can be found in Portal's Game Cache File, including "Hello" from Portal 2 teaser trailer and "Your business is appreciated," played when flushing the lavatory bowl in the Relaxation Vault.
    • The original Portal trailer also featured the Sentry Turrets using the same alarm sound effects as the Combine Sentry Gun, except the word "Searching," spoken with slightly modified voice from the final version. This was not used in the final version of the game.
      • In Portal 2, when Chell is ascending to the surface, the first stop involves four sentry turrets which do use the Combine Sentry Turret sound effects.
      • The Turret Wife Serenade also contains samples of the alarm.
  • In Portal 2, Sentry Turrets will fire at Wheatley's monitors, vital to getting the Smash TV achievement.
  • Portal 2 features numerous Defective Turrets, either missing their casings or assembled incorrectly.
  • The achievement, 'No Hard Feelings,' is earned by saving the Oracle Turret from the redemption conveyor belt leading to an incinerator (this turret will catch your attention by calling out, "I'm different"). If you do so, the turret will thank you and speaks several cryptic phrases, among them quoting Cave Johnson's 'Don't make lemonade' speech and mentioning Johnson's assistant Caroline. You will not be able to carry this turret with you very far, as a Material Emancipation Grill will bar it leaving the room.
  • Two unusual, non-defective turrets appear in Portal 2. The first is the "Animal King," used as part of a display to demonstrate some kind of non-human force dominating humanity. It also plays the bass tones during the opera at the end of the game. The second is the Soprano Turret, which sings the opera. The Soprano Turret is a common reference in the opera; "It's not over until the fat lady sings", in that the game is not over until the "fat turret" sings.
    • The Soprano Turret made a cameo appearance in the credits of the co-op campaign, after the name Matthew Russell comes up.
    • The Soprano Turret can also be seen in the elevator that leaves before Chell's in Test Chamber 11 of GLaDOS' test track.
    • Finally, in Test Chamber 16 of GLaDOS' testing track, a hidden room near the entrance leads to four turrets playing the Turret Wife Serenade while the Turret Wife watches. It can be accessed by using the Thermal Discouragement Beam in the room to destroy the turret guarding the grate.
    • There appears to have been more Soprano Turrets hidden in the Enrichment Center, as pieces of their components and remains are found nearing the Abandonment Hatch entrance to Test Shaft 09.
  • The Sentry Turrets are powered by a compact fusion core. It can be seen on the caseless Defective Turrets, on their back.
  • The turret box states that one of the blue turrets was bought on January 25, 2010 by a person with an unreadable name (possibly Tristan Reidford). The reference to Michael Jackson can be seen on the posters.
  • In Portal 2, turret boxes indicated that turrets inside are blue. However, the machines in Turret Manufacturing build and box white turrets.
  • Though Frankenturrets are able to move about with their legs, normal Turrets do not seem to be able to.
  • One of the Steam achievements in the game Blacklight: Retribution needs the player to destroy 10 enemy turrets. The name of the achievement is a reference to the Portal series' turrets; it's called "Are you still there...?".
  • In Half-Life: Alyx, graffitis depicting the turret could be found in multiple places, such as Fairview Junction. Those graffitis come in both colored and uncolored variants.



Portal 2[edit]



Half-Life: Alyx[edit]

Aperture Desk Job[edit]

List of appearances[edit]

Main games[edit]


See also[edit]


Aperture Science Sentry Turret
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