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A tractor beam is a device that can attract one object to another from a distance. [1] The concept originates in fiction: The term was coined by E. E. Smith (an update of his earlier "attractor beam") in his novel Spacehounds of IPC (1931). Since the 1990s, technology and research have labored to make it a reality, and have had some success on a microscopic level. [2] Less commonly, a similar beam that repels is known as a pressor beam or repulsor beam. Gravity impulse and gravity propulsion beams are traditionally areas of research from fringe physics that coincide with the concepts of tractor and repulsor beams.
A force field confined to a Collimated beam with clean borders is one of the principal characteristics of tractor and repulsor beams. [3] Several theories that have predicted that repulsive effects do not fall within the category of tractor and repulsor beams because of the absence of field collimation.[ citation needed ] For example,[ clarification needed ] Robert L. Forward of Hughes Research Laboratories showed that 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. [4] [5] The mainstream scientific community has accepted Forward's work.[ citation needed ]
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. [6] 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.[ citation needed ]
The following are summaries of other notable experiments and theories that resemble repulsor and tractor beam concepts:
In July 1960, trade magazine Missiles and Rockets reported that Martin N. Kaplan, a research engineer at Ryan Aeronautical Company, had conducted experiments that could lead to an ability to direct an anti-gravitational force toward or away from a second body. [7]
In 1964, physicists Leopold Halpern of the Niels Bohr Institute and B. Laurent of the Nordic Institute for Theoretical Physics indicated general relativity theory and quantum theory allowed the generation and amplification of gravitons in a manner like the laser. [8] They showed, in principle, gravitational radiation in the form of a beam of gravitons could be generated and amplified by using induced, resonant emissions.
In 1992, Professor Yevgeny Podkletnov and R. Nieminen, of the Tampere University of Technology, discovered weight fluctuations in objects above an electromagnetically levitated, massive, composite superconducting disk. [9] Three years later, Podkletnov reported the results of additional experiments with a toroidal disk superconductor. [10] They reported the weight of the samples would fluctuate between −2.5% and +5.4% as the angular speed of the superconductor increased. Certain combinations of disk angular speeds and electromagnetic frequencies caused the fluctuations to stabilize at a 0.3% reduction. The experiments with the toroidal disk yielded reductions that reached a maximum of 1.9–2.1%. Reports about both sets of experiments stated the weight loss region was cylindrical, extending vertically for at least three meters above the disk. Qualitative observations of an expulsive force at the border of the shielded zone were reported in the Fall of 1995. [11] [ dubious – discuss ] Several groups around the world tried to replicate Podkletnov's gravity shielding observations. [12] [ further explanation needed ]
Italian physicist Giovanni Modanese, while a Von Humboldt Fellow at the Max Planck Institute for Physics, made the first attempt to provide a theoretical explanation of Podkletnov's observations. [11] [13] He argued that the shielding effect and slight expulsive force at the border of the shielded zone could be explained in terms of induced changes in the local cosmological constant. Modanese described several effects regarding responses to modifications to the local cosmological constant within the superconductor. [14] Ning Wu of the Institute of High Energy Physics (Beijing), used the quantum gauge theory of gravity he had developed in 2001 to explain Podkletnov's observations. [15] Wu's theory approximated the relative gravity loss as 0.03% (an order of magnitude smaller than the reported range of 0.3–0.5%).[ citation needed ]
C. S. Unnikrishan, Tata Institute of Fundamental Research, Mumbai, showed that if the effect had been caused by gravitational shielding, the shape of the shielded region would be similar to a shadow from the gravitational shield. For example, the shape of the shielded region above a disk would be conical. The height of the cone's apex above the disk would vary directly with the height of the shielding disk above the earth. [16] Podkletnov and Nieminen described the shape of the weight loss region as a cylinder that extended through the ceiling above the cryostat.[ citation needed ]
A team of scientists at the Australian National University (ANU) led by Professor Andrei Rode created a device similar to a tractor beam to move small particles 1.5 meters through the air. [17] Rather than create a new gravitational field, however, the device utilizes a doughnut-shaped Laguerre-Gaussian laser beam, which has a high-intensity ring of light that surrounds a dark core along the beam axis. This method confines particles to the center of the beam using photophoresis, whereby illuminated sections of the particle have a higher temperature and thus impart more momentum to air molecules incident on the surface. Owing to this method, such a device cannot work in space due to lack of air. Rode states that there are practical applications for the device on Earth, for example, the transportation of microscopic hazardous materials and other microscopic objects. [18] [19]
John Sinko and Clifford Schlecht researched a form of reversed-thrust laser propulsion as a macroscopic laser tractor beam. Intended applications include remotely manipulating space objects at distances up to about 100 km, [20] removal of space debris, [21] and retrieval of adrift astronauts or tools on-orbit. [22]
Functioning tractor beams based on solenoidal modes of light were demonstrated in 2010 by physicists at New York University. [23] The spiraling intensity distribution in these non-diffracting beams tends to trap illuminated objects and thus helps to overcome the radiation pressure that ordinarily would drive them down the optical axis. Orbital angular momentum transferred from the solenoid beam's helical wavefronts then drives the trapped objects upstream along the spiral. Both Bessel-beam and solenoidal tractor beams are being considered for applications in space exploration by NASA. [24]
In March 2011, Chinese scientists[ specify ] posited that a specific type of Bessel beam (a special kind of laser that does not diffract at the center) is capable of creating a pull-like effect on a given microscopic particle, forcing it toward the beam-source. [25] [26] The underlying physics is the maximization of forward scattering via interference of the radiation multipoles. They show explicitly that the necessary condition to realize a negative (pulling) optical force is the simultaneous excitation of multipoles in the particle. If the total photon momentum projection along the propagation direction is small, attractive optical force is possible. [27] The Chinese scientists suggest this possibility may be implemented for optical micromanipulation.[ citation needed ]
In 2013, scientists at the Institute of Scientific Instruments (ISI) and the University of St Andrews created a tractor beam that pulls objects on a microscopic level. [28] The study states that this technique may have potential for bio-medical research. Professor Zemanek said: "The whole team have spent a number of years investigating various configurations of particles delivery by light."[ This quote needs a citation ] Dr. Brzobohaty said: "These methods are opening new opportunities for fundamental photonics as well as applications for life-sciences."[ This quote needs a citation ] Dr Cizmar said: "Because of the similarities between optical and acoustic particle manipulation we anticipate that this concept will inspire exciting future studies in areas outside the field of photonics."[ This quote needs a citation ]
Physicists from ANU built a reversible tractor beam, capable of transporting particles "one fifth of a millimetre in diameter a distance of up to 20 centimetres, around 100 times further than previous experiments." According to Professor Wieslaw Krolikowski, of the Research School of Physics and Engineering, "demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists." [29] The work was published in Nature in 2014. [30] In the same year, Dr. Horst Punzmann and his team at ANU developed a tractor beam that works on water, which could potentially be used to contain oil spills, control floating objects, or study the formation of rips on beaches. [31]
In 2015, a team of researchers built the world's first sonic tractor beam that can lift and move objects using sound waves. [32] An Instructables webpage was made available with instructions to build a rudimentary device. [33]
In 2016, Rice University scientists discovered that Tesla coils can generate force fields able to manipulate matter through a process called teslaphoresis. [34]
In December 2016, researchers were able to manipulate the movement of bacterial cells using a tractor beam, thereby opening the possibility that tractor beams could have future applications in biological sciences. [35]
In 2018, a research team from Tel-Aviv University, led by Dr. Alon Bahabad, experimentally demonstrated an optical analog of the Archimedes' screw where the rotation of a helical-intensity laser beam is transferred to the axial motion of optically trapped micrometer-scale, airborne, carbon-based particles. With this optical screw, particles were easily conveyed with controlled velocity and direction, upstream or downstream of the optical flow, over half a centimeter. [36]
In 2019, researchers at the University of Washington used a tractor beam to assemble nanoscale materials in a process they describe as "photonic nanosoldering". [37]
Science fiction movies and telecasts normally depict tractor and repulsor beams as audible, narrow rays of visible light covering a small target area. Tractor beams are most commonly used on spaceships and space stations. They are generally used in three ways:[ citation needed ]
In the latter case, countermeasures can usually be employed against tractor beams. These may include pressor beams (a stronger pressor beam will counteract a weaker tractor beam) or plane shearsa.k.a.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 along the beam to its source.[ citation needed ]
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.[ citation needed ]
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 toward the planet, rather than vice versa. [3] [ better source needed ]
In Star Trek , tractor beams are imagined to work by placing a target in the focus of a subspace/graviton interference pattern created by two beams from an emitter. When the beams are manipulated correctly the target is drawn along with the interference pattern. The target may be moved toward or away from the emitter by changing the polarity of the beams. The range of the beam affects the maximum mass that the emitter can move, and the emitter subjects its anchoring structure to significant force. [38]
In theoretical physics, negative mass is a hypothetical type of exotic matter whose mass is of opposite sign to the mass of normal matter, e.g. −1 kg. Such matter would violate one or more energy conditions and exhibit strange properties such as the oppositely oriented acceleration for an applied force orientation. It is used in certain speculative hypothetical technologies such as time travel to the past and future, construction of traversable artificial wormholes, which may also allow for time travel, Krasnikov tubes, the Alcubierre drive, and potentially other types of faster-than-light warp drives. Currently, the closest known real representative of such exotic matter is a region of negative pressure density produced by the Casimir effect.
The Breakthrough Propulsion Physics Project (BPP) was a research project funded by NASA from 1996 to 2002 to study various proposals for revolutionary methods of spacecraft propulsion that would require breakthroughs in physics before they could be realized. The project ended in 2002, when the Advanced Space Transportation Program was reorganized and all speculative research was cancelled. During its six years of operational funding, this program received a total investment of $1.2 million.
Optical tweezers are scientific instruments that use a highly focused laser beam to hold and move microscopic and sub-microscopic objects like atoms, nanoparticles and droplets, in a manner similar to tweezers. If the object is held in air or vacuum without additional support, it can be called optical levitation.
Anti-gravity is a hypothetical phenomenon of creating a place or object that is free from the force of gravity. It does not refer to either the lack of weight under gravity experienced in free fall or orbit, or to balancing the force of gravity with some other force, such as electromagnetism or aerodynamic lift. Anti-gravity is a recurring concept in science fiction. Examples are the gravity blocking substance "Cavorite" in H. G. Wells's The First Men in the Moon and the Spindizzy machines in James Blish's Cities in Flight.
Laser propulsion is a form of beam-powered propulsion where the energy source is a remote laser system and separate from the reaction mass. This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle.
Levitation is the process by which an object is held aloft in a stable position, without mechanical support via any physical contact.
Eugene Podkletnov is a Russian ceramics engineer known for his claims made in the 1990s of designing and demonstrating gravity shielding devices consisting of rotating discs constructed from ceramic superconducting materials.
In theoretical physics, particularly fringe physics, polarizable vacuum (PV) and its associated theory refer to proposals by Harold Puthoff, Robert H. Dicke, and others to develop an analog of general relativity to describe gravity and its relationship to electromagnetism.
The gravitational interaction of antimatter with matter or antimatter has been observed by physicists. As was the consensus among physicists previously, it was experimentally confirmed that gravity attracts both matter and antimatter at the same rate within experimental error.
The Penrose interpretation is a speculation by Roger Penrose about the relationship between quantum mechanics and general relativity. Penrose proposes that a quantum state remains in superposition until the difference of space-time curvature attains a significant level.
The term gravitational shielding refers to a hypothetical process of shielding an object from the influence of a gravitational field. Such processes, if they existed, would have the effect of reducing the weight of an object. The shape of the shielded region would be similar to a shadow from the gravitational shield. For example, the shape of the shielded region above a disk would be conical. The height of the cone's apex above the disk would vary directly with the height of the shielding disk above the Earth. Experimental evidence to date indicates that no such effect exists. Gravitational shielding is considered to be a violation of the equivalence principle and therefore inconsistent with both Newtonian theory and general relativity.
A reactionless drive is a hypothetical device producing motion without the exhaust of a propellant. A propellantless drive is not necessarily reactionless when it constitutes an open system interacting with external fields; but a reactionless drive is a particular case of a propellantless drive that is a closed system, presumably in contradiction with the law of conservation of momentum. Reactionless drives are often considered similar to a perpetual motion machine. The name comes from Newton's third law, often expressed as: "For every action, there is an equal and opposite reaction."
Gravitational waves are transient displacements in a gravitational field – generated by the relative motion of gravitating masses – that radiate outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of electromagnetic waves. In 1916, Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime.
Mechanical explanations of gravitation are attempts to explain the action of gravity by aid of basic mechanical processes, such as pressure forces caused by pushes, without the use of any action at a distance. These theories were developed from the 16th until the 19th century in connection with the aether. However, such models are no longer regarded as viable theories within the mainstream scientific community and general relativity is now the standard model to describe gravitation without the use of actions at a distance. Modern "quantum gravity" hypotheses also attempt to describe gravity by more fundamental processes such as particle fields, but they are not based on classical mechanics.
American interest in "gravity control propulsion research" intensified during the early 1950s. Literature from that period used the terms anti-gravity, anti-gravitation, baricentric, counterbary, electrogravitics (eGrav), G-projects, gravitics, gravity control, and gravity propulsion. Their publicized goals were to discover and develop technologies and theories for the manipulation of gravity or gravity-like fields for propulsion. Although general relativity theory appeared to prohibit anti-gravity propulsion, several programs were funded to develop it through gravitation research from 1955 to 1974. The names of many contributors to general relativity and those of the golden age of general relativity have appeared among documents about the institutions that had served as the theoretical research components of those programs. Since its emergence in the 1950s, the existence of the related gravity control propulsion research has not been a subject of controversy for aerospace writers, critics, and conspiracy theory advocates alike, but their rationale, effectiveness, and longevity have been the objects of contested views.
Superfluid vacuum theory (SVT), sometimes known as the BEC vacuum theory, is an approach in theoretical physics and quantum mechanics where the fundamental physical vacuum is considered as a superfluid or as a Bose–Einstein condensate (BEC).
A gravity laser, also sometimes referred to as a Gaser, Graser, or Glaser, is a hypothetical device for stimulated emission of coherent gravitational radiation or gravitons, much in the same way that a standard laser produces coherent electromagnetic radiation.
Salvatore Cezar Pais is an American aerospace engineer and inventor, currently working for the United States Space Force. He formerly worked at the Naval Air Station Patuxent River. His patent applications for the US Navy attracted attention for their potential energy-producing applications, but also doubt about their feasibility, and speculation that they may be scams, pseudoscience, or disinformation intended to mislead the United States' adversaries.
Levitation based inertial sensing is a new and rapidly growing technique for measuring linear acceleration, rotation and orientation of a body. Based on this technique, inertial sensors such as accelerometers and gyroscopes, enables ultra-sensitive inertial sensing. For example, the world's best accelerometer used in the LISA Pathfinder in-flight experiment is based on a levitation system which reaches a sensitivity of and noise of .
Theoretical spacecraft propulsion refers to a series of theoretical spacecraft propulsion systems mainly proposed for interstellar travel.