Tractor beam

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WikiWorld comicstrip featuring the tractor beam.

A tractor beam is a hypothetical device with the ability to attract one object to another from a distance. Tractor beams are frequently used in science fiction books and movies. Less commonly, a similar beam that repels is called a pressor beam or repulsor beam. No real-world equivalents of these beams exist outside microscopic level (see optical tweezers). The exact specifics vary, but there are generalities.

[edit] Usage in fiction

Tractor beams are most commonly used on spaceships and space stations. They are generally used in two ways:

As a device for securing or retrieving cargo, passengers, shuttlecraft, etc. This is analogous to cranes on modern ships.
As a means of preventing an enemy from escaping, analogous to grappling hooks.

In the latter case, there are usually countermeasures that can be employed against tractor beams. These may include pressor beams (a stronger pressor beam will counteract a weaker tractor beam) or plane shears aka shearing planes (a device to "cut" the tractor beam and render it ineffective). In some fictional realities shields can block tractor beams, or the generators can be disabled by sending a large amount of energy back up the beam to its source.

Tractor beams and pressor beams can be used together as a weapon: by attracting one side of an enemy spaceship while repelling the other, one can create severely damaging shear effects in its hull. Another mode of destructive use of such beams is rapid alternating between pressing and pulling force in order to cause structural damage to the ship as well as inflicting lethal forces on its crew.

Two objects being brought together by a tractor beam are usually attracted toward their common center of gravity. This means that if a small spaceship applies a tractor beam to a large object such as a planet, the ship will be drawn towards the planet, rather than vice versa.

Tractor beams do not always work like this. In Star Trek, tractor beams are non-Newtonian. The target is always drawn toward the emitter, irrespective of mass, because the beam does not actually transmit a force across space. It functions similarly to the warp drive, manipulating space-time at the target's position.^{[citation needed]}

[edit] Appearances

Works containing well-known appearances of tractor beams include:

The Skylark of Space books by E. E. Smith (possibly the original appearance: 1929). The protagonist invents "attractor beams" and "repellor beams." Repellors can also be emitted isotropically as a sort of defensive Force field against material projectiles.
In Buck Rogers' first book, Armageddon 2419, (1928), by Philip Francis Nowlan the enemy ships used "repellor beams" for support and propulsion.
The Lensman books by E. E. Smith
Star Trek (TV series, movies, books, games)- However the USS Enterprise in the prequel series Enterprise does not employ tractor beams in favor of grappling lines.
Star Wars (movies, books, games)
Tom Swift - In the The New Tom Swift Jr. book Tom Swift and The Deep-Sea Hydrodome (1958), Tom invents the "repellatron." The device can be set to repel specific chemical elements. It was used to create a bubble habitat on the ocean floor, and as the propulsion system for his spacecraft Challenger.
Babylon 5 (TV series)
Buck Rogers comic strip - originally just repulsor beams; tractors appeared by 1970s
Galaga - used by the Galagas to steal the player's ship.
The "Grabber" in Doom 3: Resurrection of Evil (games)
The Salvage Corvette's "Salvage Field" in Homeworld (games)
The Honor Harrington books by David Weber
The Grapple Beam from the Metroid series (games)
The seaQuest DSV episode "Splashdown."
The Sector General books by James White The 1963 novel Star Surgeon is the source of the combined tractor/pressor beam weapon, the so called "Rattler." These weapons attract then repel the target (entire ship or a segment of the ship's hull) at 80 gs, several times a minute. The novel also featured a type of Force field called a "repulsion screen."
Starfire series - the combined tractor/pressor beam weapon
Starplex by Robert J. Sawyer
One Crystal Eres (magic spell) in Tales of Legendia and a magic spell in Tales of Phantasia (games) is named Tractor Beam, that launches the enemy in the air.
In Eve Online (game), tractor beams are modules that can pull wrecks or cargo canisters towards the ship in space.
The Trigger by Arthur C. Clark involves the development of tractor beams in the early part of the novel.
in Spaceballs, Spaceball 1 uses a tractor beam - referred to as a "magnetic beam" in the film - to intercept Princess Vespa's Mercedes space cruiser.
The Taelon mothership on Earth: Final Conflict used tractor beams on several occasions.
In The Incredibles, Syndrome uses zero-point energy.
In Time Crisis 4, Wild Dog uses a Tractor Beam at one point to direct crates and other heavy objects at the players.
In Austin Powers in Goldmember, Dr. Evil's evil plan involved using a tractor beam to crash a golden asteroid into the Earth, causing a torrential flood.
Archie Comics, where it is caricatured as a literal "tractor"
Ratchet and Clank: Going Commando, It is used as a Gadget to move marked objects from one place to another, often presenting a plot advance.
In Half-Life 2, Gordon Freeman is armed with a device called the Zero-Point Energy Field Manipulator or simply the "Gravity Gun", which can pick up, throw, and "punt" heavy or sharp objects with little or no effort. In the last mission, it is accidentally modified to manipulate biomatter, and can throw Combine soldiers to their deaths.
A similar gun to the one in Half-Life 2,, called the "Uplink", appears in TimeSplitters: Future Perfect, available to the player beginning with the second mission. In addition to a "gravity gun", the item also serves as a map and a time machine for the player's character, Sergeant Cortez.
Another similar gun to Half-Life 2's gravity gun called the "Capture gun" appears as the primary tool in the Wii video game Elebits, where it is used to manipulate objects and capture the titular creatures.
Yet another similar gun to Half-Life 2's, which is title the "Aperture Science Hand held Portal Device", can create a weaker zero-point energy field by simply lifting objects and carrying them, but cannot throw or pull in from a distance. These items can also be dropped through the portals it can create.
In Recess: School's Out a villain attempted to use a tractor beam to move the moon.
The anime Uchuu Senkan Yamato (known as Star Blazers outside Japan). In one episode, multiple tractor beams on planet Gamilon were used to drag the Yamato into a trap.
Pixar's 2006 short movie Lifted is based on an alien character who is in a tractor beam usage test.
In the Metroid prime series, the charged beam has a tractor beam effect.