A sentry gun is a gun that is automatically aimed and fired at targets that are detected by sensors. The earliest functioning military sentry guns were the close-in weapon systems point-defense weapons for detecting and destroying short range incoming missiles and enemy aircraft first used exclusively on naval assets, and now also as land-based defences.
Fictional sentry guns have appeared in science fiction since the 1940s. Video games have provided a fertile ground for fictional visions of sentry guns. Fictional examples of automatic sentry guns have appeared since the 1980s, in films such as Aliens (1986) and the television series Æon Flux (early 1990s).
The Samsung SGR-A1 is a South Korean military robot sentry designed to replace human counterparts in the demilitarized zone at the South and North Korea border. It is a stationary system made by Samsung defense subsidiary Samsung Techwin.
In 2007, the Israeli military deployed the Sentry Tech system along the Gaza border fence with pillboxes placed at intervals of some hundreds of meters. The 4-million USD system is supposed to be completed by the end of the summer. Initial deployment plans call for mounting a .50-caliber M2 Browning automated machine gun in each pillbox. Connected via fiber optics to a remote operator station and a command-and-control center, each machine gun-mounted station serves as a type of robotic sniper, capable of enforcing a nearly 1,500-meter-deep no-go zone. The gun is based on the Samson Remote Controlled Weapon Station.
Super aEgis II
In December 2010, the South Korean firm DoDAAM unveiled the Super aEgis II, an automated turret-based weapon platform that uses thermal imaging to lock onto vehicles or humans up to 3 km away. It is able to function during nighttime and regardless of weather conditions. The system gives a verbal warning before firing, and though it is capable of firing automatically, the company reports that all of its customers have configured it to require human confirmation. It is used at various facilities in United Arab Emirates, Abu Dhabi, and Qatar, among other places, and has been tested in the Korean Demilitarized Zone.
A simple sentry gun is used to pin down a group of rebelling colonists in Robert A. Heinlein's 1949 novel Red Planet. Michael Crichton's 1969 novel The Andromeda Strain, uses sentry guns firing tranquillizer darts at pests in the underground facility elevator shaft. Later, in 1980, Crichton wrote about a more advanced vision of sentry guns in his book Congo.
Video games have provided a fertile ground for visions of sentry guns. The Team Fortress mod for QuakeWorld solidified the sentry gun's position in gamers' vocabularies. Two relatively early games that featured sentry guns were GoldenEye 007 on the Nintendo 64, and its spiritual successor, Perfect Dark. Various games, including Duke Nukem, Fallout 2, Dune 2, Metal Gear, and Worms 4: Mayhem had several versions. Sentry guns play an important role during gameplay and puzzles in Portal where, mainly due to comic effect, sentry guns are equipped with a voice synthesizer, and upon a player getting in the field of view, plays a phrases such as "I see you!" and "Could you come over here?" in a childlike voice. Team Fortress 2 features sentry guns capable of being upgraded, a cylinder shaped ammunition box, with minigun like barrels. Bioshock features sentry guns that may be hacked to target enemies instead of the player. Unturned features sentry guns as a piece of craftable and placeable equipment, extremely valuable when it comes to defending bases or locking down checkpoints, as they may be fitted with the same variety of weapons that can be used by the players, from small handguns to more powerful light machine guns and high caliber rifles, thus making it a very versatile defense tool, with the disadvantage of constantly needing manual ammunition reloads and to be powered by a generator with a limited fuel supply. The Unturned incarnation of the sentry gun comes in three different variants, each with its own behavior and level of hostile towards enemy, passive and ally players and AI entities.
Many near-future and mid-future games make heavy use of sentry guns, often to fulfill level designer objectives: in the Modern Warfare series, they were used to slow the player's advance at key points and build tension, while in many other games sentry guns, often unseen, are used to constrain the player within a map area. Sometimes these become objectives in and of themselves, such as disabling their power supplies to allow the player to proceed, while in other cases they are permanent and serve to prevent the player from exiting the game world or map.
Film and television
Fictional examples of automatic sentry guns also appeared in the Special Edition version of Aliens. In the film, marines who were surrounded by Xenomorphs barricaded themselves into a sick bay facility, and deployed sentry guns to block access points to the sick bay. The weapons successfully repelled the alien adversaries until they ran out of ammunition. All references to this sequence were deleted from the theatrical print of the film, though Alan Dean Foster's 1986 novelization of the movie contained this scene. The sentry gun sequence was reinstated for the extended Special Edition cut of the film, released initially on Laserdisc in 1991 and much later on DVD. In Star Trek, Independence Day, and other action movies, sentry guns are used on some ships or sites.
Congo depicts a fictional laser-sighted remote sentry unit, which was used to repel the enemies. The science fiction television series Æon Flux depicted accurate sentry guns in multiple episodes. In the show, these guns, along with concrete walls, are depicted as a series of Fortifications separating two nations.
- Robo-Snipers, "Auto Kill Zones” to Protect Israeli Borders Noah Shachtman, Wired.com, June 4, 2007
- Lethal Robotic Technologies: The Implications for Human Rights and International Humanitarian Law Philip Alston, Journal of Law, Information and Science, 2012
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- Killer Robots: The Soldiers That Never Sleep
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