Levitation (energy technology)

Summary: Levitation refers to the elevated, stable floating of an object without any physical interference from gravity. Different technologies have been developed to produce the stable levitation of matter.

To overcome gravity, a vertically upward, vectored force equal to the gravitational force is presupposed. The related idea of antigravity refers to a place or object that is free from the force of gravity. At present, there is no technological demonstration of antigravity. However, the idea has led to several technological innovations.

Technological Methods

At the beginning of the 20th century, Sir Isaac Newton’s law of universal gravitation was superseded by the general theory of relativity, which describes gravity not as a force (as in Newton’s mechanics) anymore but as the result of alterations in the geometry of space itself. In this model, antigravity is considered very unlikely.

In 1923, O. Muck obtained a patent for electromagnetic levitation (EML). Magnetic materials and systems are able to attract or repel each other, depending on whether they carry the same charge (repulsion) or different charges (attraction). Samuel Earnshaw’s theorem demonstrates that by means of static ferromagnetism it is not possible to stabilize levitated objects, because the magnetic attraction decreases with cumulative distance, and the obverse is true. For a stable system with enabled movement of the levitated object, the opposite is necessary. Minimal movements should be pushed back to the equilibrium position, obtaining dynamic stability, as applied in servomechanisms, diamagnetic materials, superconductors, or systems involving eddy currents. Levitation techniques are useful tools in high-temperature, containerless melt property studies.

Diamagnetic substances repel magnetic fields, working in a fashion opposite to that of normal magnets. This is called electromagnetic suspension (EMS), which is caused by interaction with the screening currents. Earnshaw’s theorem does not apply. In practice, the position and speed of the levitated object are measured, and the electromagnets are continuously adjusted to stabilize the object’s motion, thus forming a servomechanism. Servo control keeps EMS maglev (from magnetic levitation) trains at a constant distance from the track. In very strong magnetic fields of about 16 teslas, even small live animals have been levitated, possibly because of the diamagnetic property of water in organisms.

Two physical phenomena related to conductors can be used to create magnetic repulsion. First is Lenz’s law: Upon bringing an electrical conductor, such as copper, aluminum, or silver, and a magnet close together, an induced current occurs in the conductor, creating an opposite field that repels the magnet. This is applied as electrodynamic suspension (EDS). Second is the Meissner effect, discovered by Walther Meissner and Robert Ochsenfeld in 1933: A normal conductor transmits a nearby electric magnetic field. In case the conductor is cooled below a so-called transition temperature for becoming a superconductor, any magnetic field will be blocked out.

EDS also occurs when an electromagnet is driven by an alternating-current (AC) electrical source, inducing a changing magnetic field. Magnetic levitation can be multiplied by means of Halbach arrays, instead of using single-pole permanent magnets.

In addition to using the methods discussed above, levitation can be simulated with pressurized gases. At high pressure, the density of gases, preferably noble gases (which have greatest stability because of their low reaction rates), can exceed that of some solids, thus providing the buoyancy to levitate objects.

In 1933, a method of acoustic levitation based on fixed ultrasound fields was discovered. This method is used for qualitative analyses in outer space under the influence of microgravity, allowing the precise placement of small assays contact-free in analytical tests. Forces due to the alternating pressure field of the fixed ultrasound waves act on the assay, placed at nodes of axial and radial forces.

Another example is gyroscopically stabilized levitation of a magnet by spinning it in a toroidal field created by a base ring of magnets. Although stable, this method is very unpractical, because it works only in a narrow region regarding space and the required rate of precession.

Applications and Research

Magnetic levitation is considered a promising propulsion technique, based on many super-conducting electromagnets using either EMS or EDS for lifting and propulsion. Maglev trains are much faster and quieter than wheeled trains, because the levitation of about 3.9 inches above the guideway avoids friction on guide rails. EDS allows larger gaps than EMS but requires support wheels for relatively low speeds (below 93 miles per hour), when levitation force is low.

In the late 1920s, Thomas Townsend Brown worked on high-voltage devices and obtained a British patent for a symmetric, parallel plate capacitor. Brown claimed his “gravitator” would produce a net thrust in the direction of the anode.

Between 1948 and 1967, the Gravity Research Foundation, formed by Roger Babson, was involved in research on gravity shielding. In 1956, the Institute for Field Physics was established by Bryce DeWitt at the University of North Carolina. The same year, the (later) Aerospace Research Laboratories (ARL) at Wright-Patterson Air Force Base in Dayton, Ohio, started research on gravitational and unified field theories. Also in the late 1950s, the Research Institute for Advanced Study (RIAS, founded by George S. Trimble of the Glenn L. Martin Company) developed nonlinear differential equations, providing the mathematical tools to understand general relativity. The Lefschez Center for Dynamical Systems began as a spin-off from RIAS.

Between 1996 and 2002, the National Aeronautics and Space Administration (NASA) funded the Breakthrough Propulsion Physics Program (BPP), studying antigravity-like designs for long-distance space propulsion, called diametric drive. The BPP program continues in the independent Tau Zero Foundation.

In the 2020s, scientists were experimenting with various materials to better understand levitation. Researchers at the Technical University of Denmark demonstrated how a magnet can be levitated by rotating another magnet of similar size near it. Experts at the Okinawa Institute of Science and Technology (OIST) were experimenting with materials such as superconductors that can float above magnets in hopes of learning how to develop advanced sensors for use by scientists and the public. Levitation was already being used in flywheels, high-speed machinery, and Maglev trains.

Bibliography

DeWitt, Bryce. Bryce DeWitt’s Lectures on Gravitation. New York: Springer, 2011.

Dume, Isabelle. "New Type of Magnetic Levitation Makes Its Debut." Physics World, 13 Nov. 2023, physicsworld.com/a/new-type-of-magnetic-levitation-makes-its-debut/. Accessed 7 Aug. 2024.

Hathaway, George, B. Cleveland, and Y. Bao. “Gravity Modification Experiment Using a Rotating Superconducting Disk and Radio Frequency Fields.” Physica C 4 (2003).

"Innovative Magnetic Levitation: New Material Offers Potential for Unlocking Gravity-Free Technology." Okinawa Institute of Science and Technology, 8 Apr. 2024, www.oist.jp/news-center/news/2024/4/8/innovative-magnetic-levitation-new-material-offers-potential-unlocking-gravity-free-technology. Accessed 7 Aug. 2024.

Moon, Francis C. Superconducting Levitation: Applications to Bearings and Magnetic Transportation. New York: Wiley, 1994.

Valoe, Thomas, ed. Electrogravitics Systems: Reports on a New Propulsion Methodology. Washington, DC: Integrity Research Institute, 2001.