Aperture Science Sentry Turret

"This next test involves turrets. You remember them, right? They're the pale, spherical things that are full of bullets. Oh wait, that's you in five seconds. Good luck."

- GLaDOS, to Chell

The Aperture Science Sentry Turret, or simply known as sentries or turrets, 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.

Overview
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 during testing as an obstacle to the Test Subject.

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, which can only be armed once a target comes within visual sight. Upon visual acquisition of the target, the Sentry Turret will come to full alert, and the machine guns will emerge. They will began to fire at any visible targets (usually Test Subjects or intruders). When no targets are in visual range, the Sentry will scan the area in a sweeping motion with its laser targeting beam. Upon seeing that there are no more targets, the Sentry Turret will return to sleep mode after three seconds. These weapons, the machine guns, along with its antenna are normally hidden inside the body, during the Turret's "sleep mode".

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.

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", "Evening at the Improv", and "What Idiot Picked This?" (the latter three schemes being humorously named by Cave Johnson).

Detailed in a Portal comic strip, the inception of the Sentry's strange disposition for singing and using melodious tones came from Aperture Science consumer product testers using the weapon as a possible use for protecting children from criminals. The test is a success but the baby begins to cry every time so they decide to include soft tones and lullabies. The second test is then deemd a success with the sleeping child.

Tactics
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,knocking it over with a weighted cube, 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).

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

Trivia

 * 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.


 * During Portal 2's 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.


 * Sentry Turrets will fire at rockets fired from a Rocket Sentry. This is not seen in-game, as they normally never encounter each other.
 * Sentry Turrets will also fire at various NPCs, such as zombies and headcrabs, if they are spawned through the console.
 * 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. 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. This would indicate a usage modification which ultimately failed on Wheatley's part. However, turrets are able to fold their legs inside of themselves for storage. Frankenturrets, lacking the back leg, might be attempting this motion in a way that would drag themselves forward.


 * As also seen in the original trailer, turrets would stay in the position they were picked up in when held (i.e. picking up a turret upside-down would make you keep holding it that way, as opposed to the final game, where they rotate to upright).


 * When turrets are knocked over, they spin around wildly firing in all directions, this will cause them to deactivate themselves. If you can pick them up quick enough they wont deactivate.
 * Turrets, when on their sides, look similar to squid.
 * Despite the fact that the bullets fired from the aperture science turret are propelled using a spring, the guns produce a muzzle flash and a noise; this is unusual considering that there is no gunpowder, or explosive propellant being used.


 * When you see Turrets being made in Chapter 5, they are put together then packed into boxes, without being loaded with bullets. Maybe it says "Bullets not included" on the box.
 * Among the various Turret colors, are: Blue, Desert, Forest, Table.
 * In the Turret commercial, Cave Johnson says that the bullets are rammed into the Turret to have maximum functionality.

List of appearances

 * Portal
 * ApertureScience.com
 * Portal: Still Alive
 * Portal ARG
 * PotatoFoolsDay ARG
 * Portal 2: Lab Rat
 * Portal 2
 * The Final Hours of Portal 2