Magnetic levitation (maglev) or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational force and any other forces.
The two primary issues involved in magnetic levitation are lifting forces: providing an upward force sufficient to counteract gravity, and stability: ensuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized.
Magnetic levitation is used for maglev trains, contactless melting, magnetic bearings and for product display purposes.
https://en.wikipedia.org/wiki/Magnetic_levitation
https://en.wikipedia.org/wiki/Magnetic_field
Magnetic scalar potential, ψ, is a quantity in classical electromagnetism analogous to electric potential. It is used to specify the magnetic H-field in cases when there are no free currents, in a manner analogous to using the electric potential to determine the electric field in electrostatics. One important use of ψ is to determine the magnetic field due to permanent magnets when their magnetization is known. The potential is valid in any region with zero current density, thus if currents are confined to wires or surfaces, piecemeal solutions can be stitched together to provide a description of the magnetic field at all points in space.
https://en.wikipedia.org/wiki/Magnetic_scalar_potential
Superdiamagnetism (or perfect diamagnetism) is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of magnetic permeability (i.e. a volume magnetic susceptibility = −1) and the exclusion of the interior magnetic field.
Superdiamagnetism established that the superconductivity of a material was a stage of phase transition. Superconducting magnetic levitation is due to superdiamagnetism, which repels a permanent magnet which approaches the superconductor, and flux pinning, which prevents the magnet floating away.
Superdiamagnetism is a feature of superconductivity. It was identified in 1933, by Walther Meissner and Robert Ochsenfeld, but it is considered distinct from the Meissner effect which occurs when the superconductivity first forms, and involves the exclusion of magnetic fields that already penetrate the object.
See also[edit]
https://en.wikipedia.org/wiki/Superdiamagnetism
The Meissner effect (or Meissner–Ochsenfeld effect) is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state when it is cooled below the critical temperature. This expulsion will repel a nearby magnet.
https://en.wikipedia.org/wiki/Meissner_effect
Flux pinning is the phenomenon where a superconductor is pinned in space above a magnet. The superconductor must be a type-II superconductorbecause type-I superconductors cannot be penetrated by magnetic fields.[1] Some type-I superconductors can experience the effects of flux pinning if they are thin enough. If the material's thickness is comparable to the London penetration depth, the magnetic field can pass through the material. The act of magnetic penetration is what makes flux pinning possible. At higher magnetic fields (above Hc1 and below Hc2) the superconductor allows magnetic flux to enter in quantized packets surrounded by a superconducting current vortex (see Quantum vortex). These sites of penetration are known as flux tubes. The number of flux tubes per unit area is proportional to the magnetic field with a constant of proportionality equal to the magnetic flux quantum. On a simple 76 millimeter diameter, 1-micrometer thick disk, next to a magnetic field of 28 kA/m, there are approximately 100 billion flux tubes that hold 70,000 times the superconductor's weight. At lower temperatures the flux tubes are pinned in place and cannot move. This pinning is what holds the superconductor in place thereby allowing it to levitate. This phenomenon is closely related to the Meissner effect, though with one crucial difference — the Meissner effect shields the superconductor from all magnetic fields causing repulsion, unlike the pinned state of the superconductor disk which pins flux, and the superconductor in place.
https://en.wikipedia.org/wiki/Flux_pinning
Spin-stabilized magnetic levitation is a phenomenon of magnetic levitation whereby a spinning magnet or array of magnets (typically as a top) is levitated via magnetic forces above another magnet or array of magnets, and stabilised by gyroscopic effect due to a spin that is neither too fast, nor too slow to allow for a necessary precession.
The phenomenon was originally discovered through invention by Vermont inventor Roy M. Harrigan in the 1970s. On May 3, 1983 Harrigan received a United States patent for his original levitation device based upon this phenomenon he discovered.[1][2] Independent of Harrigan, a Pennsylvanian inventor named Joseph Chieffo made the same discovery in 1984 employing a flat base magnet, a geometry that proved a significant advance over his predecessor's dished-base design. Chieffo's design, publicized in a 1991 edition of the periodical "MAGNETS IN YOUR FUTURE",[3] further differed from Harrigan's in its incorporation of an un-weighted top.[4][5] Harrigan's technology, either entirely or in conjunction with Chieffo's flat-base innovation, provided the basis for the development of a mass marketed levitating toy top sold under the brand name, 'Levitron'.
In 2012[6] and 2014[7] Max Michaelis reported operating Levitron brand magnetic tops at inclination angles of 45° and 90° (i.e. with the spin axis, horizontal).
Physics[edit]
Earnshaw's theorem does not allow for a static configuration of permanent magnets to stably levitate another permanent magnet or materials that are paramagnetic or ferromagnetic against gravity. This theorem does not apply to devices consisting of a properly configured magnetic base and corresponding magnetic top, however, because the non-static nature of the spinning top acts as a gyroscope to prevent its magnetic field from fully aligning itself in the same direction as that of the primary supporting toroidal field of the magnetic base (i.e.: via the top flipping). In a vertical orientated configuration this gyroscopic property combined with the top's precession allows it to respond dynamically to the direction of the local toroidally shaped field of its base magnet(s) and remain levitating about a central point in space above the base where the forces acting on the top (gravitational, magnetic, and gyroscopic) are in equilibrium thereby allowing the top to rest in an energy minimum well.[8] (see: magnetic levitation)
In the laboratory, experimental setups are able to levitate tops for indefinite periods by measuring the spin rate and maintaining it using a drive coil. However, variations in temperature can affect the stability, and without ambient temperature control the top will eventually fall after hours or days due to the temperature coefficient of the magnets.[8]
The physics of the magnetic stability is similar to magnetic gradient traps.[8]
Inclined or horizontal axis levitation is accomplished by superposing a “macro-trap” on the precessional “micro-trap” first described by Sir Michael Berry[9] and Simon, Heflinger and Ridgway.[8] The macro-trap is generated by a combination of two magnetic “V”s as well as a puller magnet, situated directly above the Levitron. The puller acts like the string of a pendulum.
See also[edit]
https://en.wikipedia.org/wiki/Spin-stabilized_magnetic_levitation
A gyroscope (from Ancient Greek γῦρος gûros, "circle" and σκοπέω skopéō, "to look") is a device used for measuring or maintaining orientation and angular velocity.[1][2] It is a spinning wheel or disc in which the axis of rotation (spin axis) is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum.
Gyroscopes based on other operating principles also exist, such as the microchip-packaged MEMS gyroscopes found in electronic devices (sometimes called gyrometers), solid-state ring lasers, fibre optic gyroscopes, and the extremely sensitive quantum gyroscope.[3]
Applications of gyroscopes include inertial navigation systems, such as in the Hubble Telescope, or inside the steel hull of a submerged submarine. Due to their precision, gyroscopes are also used in gyrotheodolites to maintain direction in tunnel mining.[4] Gyroscopes can be used to construct gyrocompasses, which complement or replace magnetic compasses (in ships, aircraft and spacecraft, vehicles in general), to assist in stability (bicycles, motorcycles, and ships) or be used as part of an inertial guidance system.
MEMS gyroscopes are popular in some consumer electronics, such as smartphones.
https://en.wikipedia.org/wiki/Gyroscope
In accelerator physics strong focusing or alternating-gradient focusing is the principle that the net effect on a particle beam of charged particles passing through alternating field gradients is to make the beam converge. By contrast, weak focusing is the principle that nearby circles, described by charged particles moving in a uniform magnetic field, only intersect once per revolution.
Earnshaw's theorem shows that simultaneous focusing in two directions at once is impossible. However, ridged poles of a cyclotron or two or more spaced quadrupole magnets (arranged in quadrature) alternately focus horizontally and vertically.[1][2]
Strong focusing was first conceived by Nicholas Christofilos in 1949 but not published (Christofilos opted instead to patent his idea),[3] In 1952, the strong focusing principle was independently developed by Ernest Courant, M. Stanley Livingston, Hartland Snyder and J. Blewett at Brookhaven National Laboratory,[4][5] who later acknowledged the priority of Christofilos' idea.[6] The advantages of strong focusing were then quickly realised, and deployed on the Alternating Gradient Synchrotron.
Courant and Snyder found that the net effect of alternating the field gradient was that both the vertical and horizontal focusing of protons could be made strong at the same time, allowing tight control of proton paths in the machine. This increased beam intensity while reducing the overall construction cost of a more powerful accelerator. The theory revolutionised cyclotron design and permitted very high field strengths to be employed, while massively reducing the size of the magnets needed by minimising the size of the beam. Most particle accelerators today use the strong-focusing principle.
Multipole magnets[edit]
Modern systems often use multipole magnets, such as quadrupole and sextupole magnets, to focus the beam down, as magnets give a more powerful deflection effect than earlier electrostatic systems at high beam kinetic energies. The multipole magnets refocus the beam after each deflection section, as deflection sections have a defocusing effect that can be countered with a convergent magnet 'lens'.
This can be shown schematically as a sequence of divergent and convergent lenses. The quadrupoles are often laid out in what are called FODO patterns (where F focusses vertically and defocusses horizontally, and D focusses horizontally and defocusses vertically and O is a space or deflection magnet). Following the beam particles in their trajectories through the focusing arrangement, an oscillating pattern would be seen.
Mathematical modeling[edit]
The action upon a set of charged particles by a set of linear magnets (i.e. only dipoles, quadrupoles and the field-free drift regions between them) can be expressed as matrices which can be multiplied together to give their net effect, using ray transfer matrix analysis.[7] Higher-order terms such as sextupoles, octupoles etc. may be treated by a variety of methods, depending on the phenomena of interest.
See also[edit]
- Electron gun – uses cylindrical symmetric fields such as provided by a Wehnelt cylinder to focus an electron beam
- Maglev – has also been a suggested use of strong focusing
- Quadrupole magnet
- Sextupole magnet
- Nicholas Christofilos – the scientist who first conceived strong focusing
Accelerator physics is a branch of applied physics, concerned with designing, building and operating particle accelerators. As such, it can be described as the study of motion, manipulation and observation of relativistic charged particle beams and their interaction with accelerator structures by electromagnetic fields.
It is also related to other fields:
- Microwave engineering (for acceleration/deflection structures in the radio frequency range).
- Optics with an emphasis on geometrical optics (beam focusing and bending) and laser physics (laser-particle interaction).
- Computer technology with an emphasis on digital signal processing; e.g., for automated manipulation of the particle beam.
The experiments conducted with particle accelerators are not regarded as part of accelerator physics, but belong (according to the objectives of the experiments) to, e.g., particle physics, nuclear physics, condensed matter physics or materials physics. The types of experiments done at a particular accelerator facility are determined by characteristics of the generated particle beam such as average energy, particle type, intensity, and dimensions.
https://en.wikipedia.org/wiki/Accelerator_physics
https://en.wikipedia.org/wiki/Pyrolytic_carbon
https://en.wikipedia.org/wiki/Bismuth
An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode ray tubes (CRTs), used in nearly all television sets, computer displays and oscilloscopes that are not flat-panel displays. They are also used in field emission displays (FEDs), which are essentially flat-panel displays made out of rows of extremely small cathode ray tubes. They are also used in microwave linear beam vacuum tubes such as klystrons, inductive output tubes, travelling wave tubes, and gyrotrons, as well as in scientific instruments such as electron microscopes and particle accelerators. Electron guns may be classified by the type of electric field generation (DC or RF), by emission mechanism (thermionic, photocathode, cold emission, plasmas source), by focusing (pure electrostatic or with magnetic fields), or by the number of electrodes.
https://en.wikipedia.org/wiki/Electron_gun
A Hyperloop is a proposed high-speed mass transportation system for both passenger and freight transport.[1] The term was invented to describe the modern open-source project. Hyperloop is described as a sealed tube or system of tubes with low air pressure through which a pod may travel substantially free of air resistance or friction.[2] The Hyperloop could potentially move people or objects at airline speeds while being energy efficient compared with existing high-speed rail systems.[2] This, if implemented, may reduce travel times compared to train and airplane travel[2] over distances of under approximately 1,500 kilometres (930 miles).[3]
It has three major components: a tube, pod, and terminal.[1] The tube is a large sealed, low-pressure system that can be constructed above or below ground. A coach runs inside this controlled environment and is often referred to as a pod. The pod employs magnetic or aerodynamic levitation (using air-bearing skis) along with electromagnetic or aerodynamic propulsion to glide along a fixed guideway. The terminals arrivals and departures.[1]
The Hyperloop concept has its roots in a concept invented by George Medhurst in 1799 and subsequently developed under the names pneumatic railway, atmospheric railway or vactrain.[4] Elon Musk mentioned the Hyperloop in 2012, bringing it back to public attention.[5] His initial concept incorporated reduced-pressure tubes in which pressurized capsules ride on air bearings driven by linear induction motors and axial compressors.[6] The Hyperloop Alpha concept was first published in August 2013, proposing and examining a route running from the Los Angeles region to the San Francisco Bay Area, roughly following the Interstate 5 corridor. The Hyperloop Genesis paper conceived of a hyperloop system that would propel passengers along the 350-mile (560 km) route at a speed of 760 mph (1,200 km/h), allowing for a travel time of 35 minutes, which is considerably faster than current rail or air travel times. Preliminary cost estimates for this LA–SF suggested route were included in the white paper—US$6 billion for a passenger-only version, and US$7.5 billion for a somewhat larger-diameter version transporting passengers and vehicles.[7] However, transportation analysts expressed doubts that the system could be constructed on that budget, including some predictions that the Hyperloop would be several billion dollars over budget once construction, development, and operation costs are taken into consideration.[8][9][10]
https://en.wikipedia.org/wiki/Hyperloop
Electrodynamic suspension (EDS) is a form of magnetic levitation in which there are conductors which are exposed to time-varying magnetic fields. This induces eddy currents in the conductors that creates a repulsive magnetic field which holds the two objects apart.
These time varying magnetic fields can be caused by relative motion between two objects. In many cases, one magnetic field is a permanent field, such as a permanent magnet or a superconducting magnet, and the other magnetic field is induced from the changes of the field that occur as the magnet moves relative to a conductor in the other object.
Electrodynamic suspension can also occur when an electromagnet driven by an AC electrical source produces the changing magnetic field, in some cases, a linear induction motor generates the field.
EDS is used for maglev trains, such as the Japanese SCMaglev. It is also used for some classes of magnetically levitated bearings.
Types[edit]
Many examples of this have been used over the years.
Bedford levitator[edit]
In this early configuration by Bedford, Peer, and Tonks from 1939, an aluminum plate is placed on two concentric cylindrical coils, and driven with an AC current. When the parameters are correct, the plate exhibits 6-axis stable levitation.[1]
Levitation melting[edit]
In the 1950s, a technique was developed where small quantities of metal were levitated and melted by a magnetic field of a few tens of kHz. The coil was a metal pipe, allowing coolant to be circulated through it. The overall form was generally conical, with a flat top. This permitted an inert atmosphere to be employed, and was commercially successful.[1]
Linear induction motor[edit]
Eric Laithwaite and colleagues took the Bedford levitator, and by stages developed and improved it.
First they made the levitator longer along one axis, and were able to make a levitator that was neutrally stable along one axis, and stable along all other axes.
Further development included replacing the single phase energising current with a linear induction motor which combined levitation and thrust.
Later "traverse-flux" systems at his Imperial College laboratory, such as Magnetic river avoided most of the problems of needing to have long, thick iron backing plates when having very long poles, by closing the flux path laterally by arranging the two opposite long poles side by side. They were also able to break the levitator primary into convenient sections which made it easier to build and transport.[2]
Null flux[edit]
Null flux systems work by having coils that are exposed to a magnetic field, but are wound in figure of 8 and similar configurations such that when there is relative movement between the magnet and coils, but centered, no current flows since the potential cancels out. When they are displaced off-center, current flows and a strong field is generated by the coil which tends to restore the spacing.
These schemes were proposed by Powell and Danby in the 1960s, and they suggested that superconducting magnets could be used to generate the high magnetic pressure needed.
Inductrack[edit]
Inductrack is a passive, fail-safe magnetic levitation system, using only unpowered loops of wire in the track and permanent magnets (arranged into Halbach arrays) on the vehicle to achieve magnetic levitation. The track can be in one of two configurations, a "ladder track" and a "laminated track". The ladder track is made of unpowered Litz wire cables, and the laminated track is made out of stacked copper or aluminium sheets.
There are two designs: the Inductrack I, which is optimized for high speed operation, and the Inductrack II, which is more efficient at lower speeds.
Electrodynamic bearing[edit]
Electrodynamic bearings (EDB) are a novel type of bearing that is a passive magnetic technology. EDBs do not require any control electronics to operate. They work by the electrical currents generated by motion causing a restoring force.
https://en.wikipedia.org/wiki/Electrodynamic_suspension#Levitation_melting
Acoustic levitation is a method for suspending matter in air against gravity using acoustic radiation pressure from high intensity sound waves.[1][2]
It works on the same principles as acoustic tweezers by harnessing acoustic radiation forces. However acoustic tweezers are generally small scale devices which operate in a fluid medium and are less affected by gravity, whereas acoustic levitation is primarily concerned with overcoming gravity. Technically dynamic acoustic levitation is a form of acoustophoresis, though this term is more commonly associated with small scale acoustic tweezers.[3]
Typically sound waves at ultrasonic frequencies are used[4] thus creating no sound audible to humans. This is primarily due to the high intensity of sound required to counteract gravity. However, there have been cases of audible frequencies being used.[5]
There are various techniques for generating the sound, but the most common is the use of piezoelectric transducers which can efficiently generate high amplitude outputs at the desired frequencies.
Levitation is a promising method for containerless processing of microchips and other small, delicate objects in industry. Containerless processing may also be used for applications requiring very-high-purity materials or chemical reactions too rigorous to happen in a container. This method is harder to control than others such as electromagnetic levitation but has the advantage of being able to levitate nonconductingmaterials.
Although originally static, acoustic levitation has progressed from motionless levitation to dynamic control of hovering objects, an ability useful in the pharmaceutical and electronics industries. This was first realised with a prototype with a chessboard-like array of square acoustic emitters that move an object from one square to another by slowly lowering the sound intensity emitted from one square while increasing the sound intensity from the other, allowing the object to travel virtually "downhill".[6] More recently the development of phased array transducer boards have allowed more arbitrary dynamic control of multiple particles and droplets at once.[7][8][9]
Recent advancements have also seen the price of the technology decrease significantly. The "TinyLev" is an acoustic levitator which can be constructed with widely available, low-cost off-the-shelf components, and a single 3D printed frame.[10][11]
https://en.wikipedia.org/wiki/Acoustic_levitation
Aerodynamic levitation is the use of gas pressure to levitate materials so that they are no longer in physical contact with any container. In scientific experiments this removes contamination and nucleation issues associated with physical contact with a container.
Overview[edit]
The term aerodynamic levitation could be applied to many objects that use gas pressure to counter the force of gravity, and allow stable levitation. Helicopters and air hockey pucks are two good examples of objects that are aerodynamically levitated. However, more recently this term has also been associated with a scientific technique which uses a cone-shaped nozzle allowing stable levitation of 1-3mm diameter spherical samples without the need for active control mechanisms.[1]
Aerodynamic levitation as a scientific tool[edit]
These systems allow spherical samples to be levitated by passing gas up through a diverging conical nozzle. Combining this with >200W continuous CO2laser heating allows sample temperatures in excess of 3000 degrees Celsius to be achieved.
When heating materials to these extremely high temperatures levitation in general provides two key advantages over traditional furnaces. First, contamination that would otherwise occur from a solid container is eliminated. Second, the sample can be undercooled, i.e. cooled below its normal freezing temperature without actually freezing.
Undercooling of liquid samples[edit]
Undercooling, or supercooling, is the cooling of a liquid below its equilibrium freezing temperature while it remains a liquid. This can occur wherever crystal nucleation is suppressed. In levitated samples, heterogeneous nucleation is suppressed due to lack of contact with a solid surface. Levitation techniques typically allow samples to be cooled several hundred degrees Celsius below their equilibrium freezing temperatures.
Glass produced by aerodynamic levitation[edit]
Since crystal nucleation is suppressed by levitation, and since it is not limited by sample conductivity (unlike electromagnetic levitation), aerodynamic levitation can be used to make glassy materials, from high temperature melts that cannot be made by standard methods. Several silica-free, aluminium oxide based glasses have been made.[2][3][4]
Physical property measurements[edit]
In the last few years a range of in situ measurement techniques have also been developed. The following measurements can be made with varying precision:
electrical conductivity, viscosity,[5] density, surface tension,[6] specific heat capacity,
In situ aerodynamic levitation has also been combined with:
X-ray synchrotron radiation, neutron scattering, NMR spectroscopy
See also[edit]
Electrostatic levitation is the process of using an electric field to levitate a charged object and counteract the effects of gravity. It was used, for instance, in Robert Millikan's oil drop experiment and is used to suspend the gyroscopes in Gravity Probe B during launch.
Due to Earnshaw's theorem, no static arrangement of classical electrostatic fields can be used to stably levitate a point charge. There is an equilibrium point where the two fields cancel, but it is an unstable equilibrium. By using feedback techniques it is possible to adjust the charges to achieve a quasi static levitation.
https://en.wikipedia.org/wiki/Electrostatic_levitation
Optical levitation[edit]
In order to levitate the particle in air, the downward force of gravity must be countered by the forces stemming from photon momentum transfer. Typically photon radiation pressure of a focused laser beam of enough intensity counters the downward force of gravity while also preventing lateral (side to side) and vertical instabilities to allow for a stable optical trap capable of holding small particles in suspension.
Micrometer sized (from several to 50 micrometers in diameter) transparent dielectric spheres such as fused silica spheres, oil or water droplets, are used in this type of experiment. The laser radiation can be fixed in wavelength such as that of an argon ion laser or that of a tunable dye laser. Laser power required is of the order of 1 Watt focused to a spot size of several tens of micrometers. Phenomena related to morphology-dependent resonances in a spherical optical cavity have been studied by several research groups.
For a shiny object, such as a metallic micro-sphere, stable optical levitation has not been achieved. Optical levitation of a macroscopic object is also theoretically possible,[23] and can be enhanced with nano-structuring.[24]
Materials that have been successfully levitated include Black liquor, aluminum oxide, tungsten, and nickel.[25]
https://en.wikipedia.org/wiki/Optical_tweezers#Optical_levitation
A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley,[1][2] and patented in 1932.[3][4] A cyclotron accelerates charged particles outwards from the center of a flat cylindrical vacuum chamber along a spiral path.[5][6] The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying (radio frequency) electric field. Lawrence was awarded the 1939 Nobel Prize in Physics for this invention.[6][7]
Cyclotrons were the most powerful particle accelerator technology until the 1950s when they were superseded by the synchrotron, and are still used to produce particle beams in physics and nuclear medicine. The largest single-magnet cyclotron was the 4.67 m (184 in) synchrocyclotronbuilt between 1940 and 1946 by Lawrence at the University of California, Berkeley,[1][6] which could accelerate protons to 730 mega electron volts (MeV). The largest cyclotron of its kind is the 17.1 m (56 ft) multimagnet TRIUMF accelerator at the University of British Columbia in Vancouver, British Columbia, which can produce 520 MeV protons.
Close to 1500 cyclotrons are used in nuclear medicine worldwide for the production of radionuclides.[8]
https://en.wikipedia.org/wiki/Cyclotron
A launch loop, or Lofstrom loop, is a proposed system for launching objects into orbit using a moving cable-like system situated inside a sheath attached to the Earth at two ends and suspended above the atmosphere in the middle. The design concept was published by Keith Lofstrom and describes an active structure maglev cable transport system that would be around 2,000 km (1,240 mi) long and maintained at an altitude of up to 80 km (50 mi). A launch loop would be held up at this altitude by the momentum of a belt that circulates around the structure. This circulation, in effect, transfers the weight of the structure onto a pair of magnetic bearings, one at each end, which support it.
Launch loops are intended to achieve non-rocket spacelaunch of vehicles weighing 5 metric tons by electromagnetically accelerating them so that they are projected into Earth orbit or even beyond. This would be achieved by the flat part of the cable which forms an acceleration track above the atmosphere.[1]
The system is designed to be suitable for launching humans for space tourism, space exploration and space colonization, and provides a relatively low 3g acceleration.[2]
https://en.wikipedia.org/wiki/Launch_loop
Levitron is a brand of levitating toys and gifts in science and educational markets marketed by Creative Gifts Inc. and Fascination Toys & Gifts.[1]The Levitron top device is a commercial toy under this brand that displays the phenomenon known as spin-stabilized magnetic levitation. This method, with moving permanent magnets, is quite distinct from other versions which use changing electromagnetic fields, levitating various items such as a rotating world globe, model space shuttle or VW Beetle, and picture frame.[2] 750,000 units of the top were sold from 1994 through 1999.[1]
https://en.wikipedia.org/wiki/Levitron
Inductrack is a passive, fail-safe electrodynamic magnetic levitation system, using only unpowered loops of wire in the track and perslide magnets (arranged into Halbach arrays) on the vehicle to achieve magnetic levitation. The track can be in one of two configurations, a "ladder track" and a "laminated track". The ladder track is made of unpowered Litz wire cables, and the laminated track is made out of stacked copper or aluminium sheets.
There are three designs: Inductrack I, which is optimized for high speed operation, Inductrack II, which is more efficient at lower speeds, and Inductrack III, which is intended for heavy loads at low speed.
Inductrack (or Inductrak) was invented by a team of scientists at Lawrence Livermore National Laboratory in California, headed by physicist Richard F. Post, for use in maglev trains, based on technology used to levitate flywheels.[1][2][3] At constant velocity, power is required only to push the train forward against air and electromagnetic drag. Above a minimum speed, as the velocity of the train increases, the levitation gap, lift force and power used are largely constant. The system can lift 50 times the magnet weight.
The name inductrack comes from the word inductance or inductor; an electrical device made from loops of wire. As a Halbach magnet array passes over the loops of wire, the sinusoidal variations in the field induce a voltage in the track coils. At low speeds the loops are a largely resistive impedance, and hence the induced currents are highest where the field is changing most quickly, which is around the least intense parts of the field, thus little lift produced.
However, at speed, the impedance of the coils increases, proportionate to speed, and dominates the composite impedance of the coil assemblies. This delays the phase of the current peak so that induced current in the track tends more closely to coincide with the field peaks of the magnet array. The track thus creates its own magnetic field which lines up with and repels the permanent magnets, creating the levitation effect.[1] The track is well modeled as an array of series RL circuits.
When neodymium–iron–boron permanent magnets are used, levitation is achieved at low speeds. The test model levitated at speeds above 22 mph (35 km/h), but Richard Post believes that, on real tracks, levitation could be achieved at "as little as 1 to 2 mph (1.6 to 3.2 km/h)".[citation needed] Below the transition speed the magnetic drag increases with vehicle speed; above the transition speed, the magnetic drag decreases with speed.[4] For example, at 500 km/h (310 mph) the lift to drag ratio is 200:1,[5] far higher than any aircraft but much lower than classic steel on steel rail which reaches 1000:1 (rolling resistance). This occurs because the inductive impedance increases proportionately with speed which compensates for the faster rate of change of the field seen by the coils, thus giving a constant current flow and power consumption for the levitation.
The Inductrack II variation uses two Halbach arrays, one above and one below the track, to double the magnetic field without substantially increasing the weight or area of the arrays, while also reducing drag at low speeds.[6]
Several maglev railroad proposals are based upon Inductrack technology. The U.S. National Aeronautics and Space Administration (NASA) is also considering Inductrack technology for launching space planes.[7]
General Atomics is developing Inductrack technology in cooperation with multiple research partners.
https://en.wikipedia.org/wiki/Inductrack
A linear motor is an electric motor that has had its stator and rotor "unrolled" thus instead of producing a torque (rotation) it produces a linear force along its length. However, linear motors are not necessarily straight. Characteristically, a linear motor's active section has ends, whereas more conventional motors are arranged as a continuous loop.
A typical mode of operation is as a Lorentz-type actuator, in which the applied force is linearly proportional to the current and the magnetic field .
Linear motors are by far most commonly found in high accuracy engineering[1] applications. It is a thriving field of applied research with dedicated scientific conferences[2] and engineering text books.[3]
Many designs have been put forward for linear motors, falling into two major categories, low-acceleration and high-acceleration linear motors. Low-acceleration linear motors are suitable for maglev trains and other ground-based transportation applications. High-acceleration linear motors are normally rather short, and are designed to accelerate an object to a very high speed, for example see the coilgun.
High-acceleration linear motors are typically used in studies of hypervelocity collisions, as weapons, or as mass drivers for spacecraft propulsion.[citation needed] They are usually of the AC linear induction motor (LIM) design with an active three-phase winding on one side of the air-gap and a passive conductor plate on the other side. However, the direct current homopolar linear motor railgun is another high acceleration linear motor design. The low-acceleration, high speed and high power motors are usually of the linear synchronous motor (LSM) design, with an active winding on one side of the air-gap and an array of alternate-pole magnets on the other side. These magnets can be permanent magnets or electromagnets. The motor for the Shanghai maglev train, for instance, is an LSM.
https://en.wikipedia.org/wiki/Linear_motor#Rapid_transits_using_linear_motor_propulsion
A synchronous electric motor is an AC motor in which, at steady state,[1] the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current. The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field of any AC motor. A synchronous motor is termed doubly fed if it is supplied with independently excited multiphase AC electromagnets on both the rotor and stator.
The synchronous motor and induction motor are the most widely used types of AC motor. The difference between the two types is that the synchronous motor rotates at a rate locked to the line frequency since it does not rely on current induction to produce the rotor's magnetic field. By contrast, the induction motor requires slip: the rotor must rotate slightly slower than the AC alternations in order to induce current in the rotor winding. Small synchronous motors are used in timing applications such as in synchronous clocks, timers in appliances, tape recorders and precision servomechanisms in which the motor must operate at a precise speed; speed accuracy is that of the power line frequency, which is carefully controlled in large interconnected grid systems.
Synchronous motors are available in self-excited sub-fractional horsepower sizes[2] to high power industrial sizes.[1] In the fractional horsepower range, most synchronous motors are used where precise constant speed is required. These machines are commonly used in analog electric clocks, timers and other devices where correct time is required. In higher power industrial sizes, the synchronous motor provides two important functions. First, it is a highly efficient means of converting AC energy to work. Second, it can operate at leading or unity power factor and thereby provide power-factor correction.
https://en.wikipedia.org/wiki/Synchronous_motor
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