Electrostatic suspension

The image is an artist concept of Gravity Probe B spacecraft in orbit around the Earth. Credit: NASA/MSFC.

Electrostatic suspension can occur whenever a voltage difference exists between two locations and a charged mass is within the space separating the two locations, where the amount of charge is sufficient to allow suspension or prevent contact with either location. The potential gradient is the local space rate of change of the electric potential, usually in units of volts per meter (V/m). An electric field is an electric potential of opposite sign. The Earth, for example, has a natural electric field.

Charges

Charge polarization is often a stationary polarization of charge induced by a dc electric field to a polarization voltage (Vp) that polarizes the material of the mass, where the switch-on and switch-off time of the dc field is usually very slow.[1]

For some situations, the more positive the polarization, the greater the likelihood of electron transfer.[2]

The mass shape should be circular in front of the horizontal electrodes.[3]

Suspensions

Def. temporarily prevent from continuing is called suspend.

Def. hanging freely is called suspension.

Electrostatics

Def. the study of stationary electric charges or fields as opposed to electric currents is called electrostatics.

Vertical suspensions

This diagram describes the mechanical core of a torsion pendulum. Credit: E. Willemenot and P. Touboul.

"The upper electrodes are used to apply control voltages (228 V in nominal conditions). The lower electrode voltages are controlled to Vp [a dc voltage of about 10 V], so that no force attracts the mass toward the bottom."[3]

For a gap of 0.00206 m, a proof mass of 5.40 g is successfully suspended against 1 G (of gravity) with a field of 7.7 x 106 V/m. The voltage on the proof mass is nominally 10 V.[3]

A thin gold wire is attached at the bottom of the proof mass to allow charge or voltage to be added of removed from the proof mass. The mechanical core apparently including the proof mass is made of gold coated fused silica.[3]

Horizontal suspensions

The diagram displays the mechanism for horizontal suspension. Credit: E. Willemenot and P. Touboul.

Three horizontal axes can be used (two for translation x and y, and rotation φ).[3]

"The forces between the plates and the arm are proportional to the polarization voltage Vp of the proof mass [within the plate grid] and to the vertical V applied on the electrodes."[3]

The diagram on the right includes the thin gold wire which is used to bleed off or increase the potential (charge) on the proof mass.

Electrostatic stiffnesses

"In order to have electrostatic negative stiffness as low as possible on the three horizontal degrees of freedom (x, y, φ), the electrode arrangement and shapes have been chosen in order to have electrostatic forces that do not depend on the on the proof mass position, but only on control voltages."[3]

Parasitic forces

"[S]ome edge effects can [produce small] stiffnesses."[3]

Water droplets in an electric field

"In 1909, Robert Andrews Millikan began a series of experiments to determine the electric charge carried by a single electron. He began by measuring the course of charged water droplets in an electrical field. The results suggested that the charge on the droplets is a multiple of the elementary electric charge".[4]

A water droplet elongates in an electric field due to electrostatic pressure, and becomes unstable when a critical field limit is reached.[5]

Water droplets in an electric field become polarized through alignment of the polar water molecules with the external electric field and through redistribution of mobile charged particles or ions within the droplet.[6]

Rocky objects

A dusty plasma of fuel nanoparticles can be electrostatically suspended. Electrostatic particulate suspension (EPS) can be used for testing spark breakdown, ignition, and quenching characteristics of a small volume powder suspension.[7] Transient dust clouds are measured optically or assumed to have a uniform particulate distribution over a test volume so that particle concentration can be determined.[7]

Particle clouds can be trapped and manipulated by electrostatic suspension in a Millikan condenser.[7] Particles of opposite polarity can be kept apart and aggregation is induced by changing the electric field.[7]

Cluster growth into particles can occur that involves plasma negative ions and ion clustering with plasma species by electrostatic suspension and trapping.[8]

For a given charge to mass ratio there is, in principle, no limit on the size range of electrostatic control.[9]

When dust concentrations are high, there is a tendency for a reduction in individual grain charging due to collective effects.[10][11]

Moon

At lower latitudes on or very near the surface of the Moon is a twilight haze, associated with terminator passage (sunset and sunrise), that is believed to be due to small particles moving in electrostatic suspension within a few meters of the surface.[12]

There are also some gas clouds associated with terminator passage.[13] Since the terminator is always present in the polar regions, the local environment due to these particle and gas effects may be different.[13]

Dust grains and the lunar surface are electrostatically charged by the Moon's interaction with the local plasma environment and the photoemission of electrons due to solar ultraviolet and X-radiation.[14] Dust grains on the 0.1 µm-scale have been observed at ~100 km altitude above the Moon's surface.[14] These grains may be accelerated upward through a narrow sheath region by the surface electric field.[14]

Technology

An "electrostatically suspended induction motor (ESIM) [...] possesses the rotating ability of an ordinary electrostatic induction motor, in addition to providing contactless support by electrostatic suspension."[8]

Electrostatic suspension is used in several apparati, like the gyroscopes of the space mission Gravity Probe B, commercial gyroscopes, or space accelerometers.

Parasitic forces are associated with such a suspension.[3]

Original research

Hypothesis:

  1. Using the approximate charge separation between the ionosphere and Earth ground it should be possible to calculate how much charge is necessary to raise a 5,000 kg (kilogram) object above the ground between 70 m (meter) and 7000 m (meter).
  2. A supercapacitor or similar device can hold up to 3300 coulombs.

See also

References

  1. ↑ Gunnar Berg, Lars E. Lundgaard, and Nicholas Abi-Chebel (December 2010). "Electrically stressed water drops in oil". Chem Eng Process: Process Intens. 49 (12): 1229-40. doi:10.1016/j.cep.2010.09.008. http://www.sciencedirect.com/science/article/pii/S0255270110002345. Retrieved 2013-07-19.
  2. ↑ Kerry L. Sublette and Floyd L. Prestridge (September 4, 1984). "Electrically enhanced inclined plate separator". US Patent (4469582). http://www.google.com/patents?hl=en&lr=&vid=USPAT4469582&id=tsIrAAAAEBAJ&oi=fnd&printsec=abstract. Retrieved 2013-07-19.
  3. 1 2 3 4 5 6 7 8 9 E. Willemenot and P. Touboul (January 2000). "Electrostatically suspended torsion pendulum". Review of Scientific Instruments 71 (1): 310-4. http://www.mtl.mit.edu/researchgroups/mems-salon/sriram_torsion-pendulum.pdf. Retrieved 2015-01-12.
  4. ↑ "Robert Andrews Millikan, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. July 9, 2013. Retrieved 2013-07-19.
  5. ↑ G.M. Colver, S.W. Kim, and Tae-U. Yu (July 1996). "An electrostatic suspension method for testing spark breakdown, ignition, and quenching of powders". Journal of Electrostatics 37 (3): 151-72. doi:10.1016/0304-3886(96)00008-3. http://www.sciencedirect.com/science/article/pii/0304388696000083. Retrieved 2013-07-19.
  6. ↑ R. Vehring, C. L. Aardahl, E. J. Davis, G. Schweiger, and D. S. Covert (January 1997). "Electrodynamic trapping and manipulation of particle clouds". Review of Scientific Instruments 68 (1): 70-8. doi:10.1063/1.1147682. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4994503. Retrieved 2013-07-19.
  7. 1 2 Selwyn GS, Singh J, Bennett RS. "In situ laser diagnostic studies of plasma-generated particulate contamination". Journal of Vacuum Science and Technology A 7 (4): 2758-65. doi:10.1116/1.576175.
  8. ↑ Jong Up Jeona and Toshiro Higuchi (10 December 1998). "Induction motors with electrostatic suspension". Journal of Electrostatics 45 (2): 157-73. doi:10.1016/S0304-3886(98)00043-6. http://www.sciencedirect.com/science/article/pii/S0304388698000436. Retrieved 2015-04-11.

Further reading

External links

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