A tractor beam is defined as a device with the ability to attract one object to another from a distance. A similar beam that repels is called a pressor beamor repulsor beam. A form of tractor beam is used today to manipulate material and genetic components at a microscopic level. Gravity impulse and gravity propulsion beams coincide with the concepts of tractor and repulsor beams.
A force field confined to a well-collimated beam, with clean borders, is one of the principal characteristics of tractor and repulsor beams. Many theories that have predicted repulsive effects, do not fall within the category of tractor and repulsor beams because of the absence of field collimation. For example, Robert L. Forward, Hughes Research Laboratories, Malibu, California, showed general relativity theory allowed the generation of a very brief impulse of a gravity-like repulsive force along the axis of a helical torus containing accelerated condensed matter.
The mainstream scientific community has accepted Forward’s work. A variant of Burkhard Heim's theory by Walter Dröscher, Institut für Grenzgebiete der Wissenschaft (IGW), Innsbruck, Austria, and Jocham Häuser, University of Applied Sciences and CLE GmbH, Salzgitter, Germany, predicted a repulsive force field of gravitophotons could be produced by a ring rotating above a very strong magnetic field. Heim’s theory, and its variants, have been treated by the mainstream scientific community as fringe physics. But, the works by Forward, Dröscher, and Häuser could not be considered as a form of repulsor or tractor beam because the predicted impulses and field effects were not confined to a well defined, collimated region.