Tractor Beam
A tractor beam is a piece of equipment that gives starships and space stations the ability to manipulate objects in space. Typically this will involve towing other vessels or holding sensor probes in place, but modifying the course of asteroids or space debris is also an option.
Tractor beams employ superimposed subspace / graviton force beams which focuses interference patterns on a remote object. This results in significant spatial stress being imposed on the object; by controlling the focal point and interference patterns of the beam it is possible to use this stress pattern to place either a repelling or attracting force on the object.
Power for the tractor beam emitters is provided by variable phase graviton polarity sources feeding sub-cochrane subspace field amplifiers. Phase accuracy of less than 2.7 arc-seconds per millisecond is required for precise control of a tractor beam. Use of a tractor beam can involve placing significant stress on both emitter and target, and vessels with low structural strength can be damaged by a tractor beam. Because of the potential damage to a vessel using a tractor beam, all Star Fleet tractor emitters are attached directly to the skeletal frame, and are protected by the structural integrity field system of the craft.
Most Federation vessels are equipped with a tractor beam emitter on the aft ventral hull, as it is the best location for towing objects. Vessels of Runabout size or above are fitted with more than one emitter - large starships having enough to ensure all-round coverage. Smaller tractor beams are installed within shuttlebays to assist in docking and landing maneuvers.
Tractor beams are generally only used at sub-warp velocities. There are, however a few instances where a tractor beam can be used during warp.
Using a Tractor Beam during Warp
To safely tow a vessel at warp speed, the target vessel's engines must be deactivated to avoid shearing forces against towing vessel. Using a tractor beam can be done at warp speed only if both vessels' speeds are exactly matched.
However, if a vessel's tractor beam is strong enough, its graviton field can reinforce the structural integrity of a target vessel, keeping its hull from succumbing to stresses normally exhibited by a tractor field.
When using a tractor beam to force another vessel out of warp speed, otherwise known as a "warp tow", both vessels must be matching velocity at the time of the tractor beam initiation. This brings tremendous risk to both vessels. However, if both vessels' hulls are strong enough to withstand the stress, they can both be brought out of warp with the tractor beam still engaged if the towing vessel carefully disengages the warp drive while engaging the impulse engines.
