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"Lifters"
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Electrostatic lifters are fascinating devices that have become popular construction projects for experimenters all over the world. NASA's recent patent on a type of lifter design has only spurred interest in these devices. What is a lifter? The basic device merely consists of a lightweight (typically balsa wood) frame, to which is attached a wire and a sort of aluminum foil skirt. The photos below illustrate this. The wire is charged to approximately 30,000 volts by means of a power supply and very thin wire attached to the corona wire. The aluminum foil skirt is coneccted to ground by a thin wire as well. When the device is powered it developes downward thrust and levitates. How does it work? There are a few schools of thought on this. One holds that the assymmetry between the two electrodes creates a special type of electric field that developes thrust in a manner that is not fully understood. This is the so-called Biefeld-Brown effect, and a debate rages over its existence. Whether it exists or not is beyond the scope of this page, however it does not seem to be the prime motive force since lifters do not work in a vaccuum. Another school holds that the device levitates by simply creating an electrostatic "wind". This is caused as the thin positively charged corona wire ionizes the air surrounding it which is then repelled from the corona wire and pulled towards the negtively charged "skirt". The force of this ion wind combined with the impact of the moving ions on the surrounding air creates and upward thrust. This is essentially how some of the "ionic breeze" air purifiers work that you may have seen in catalogs. Various experimenters have sought to eliminate ionization by encapsulating the electrodes and noted that the the devices still prodced thrust. Clearly some other force is at work as well. A more thorough examination would have to include a well known effect called dielectrophoresis. This is an effect whereby dielectric material in an asymmetrc electric field becomes polarized and moves towards the larger electrode. In a fluid dielectric medium such as air or liquid, dielectrophoresis can cause a continuous flow of dieletric material from one electrode to another. The more intense the electric field the greater the effect. Dieletrophoresis is consitent with experiemental results shown by encapsulating the electrodes, as well as immersing a lifter in oil. It is likely that this is the primary motive force. |
 Lifter being powered by a 50kV DC supply operated at approximately 25kV. Not visible is the thin positively charged "corona wire" which is strung above, and parallel to, the flat negatively charged aluminum "skirt". |
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 Asymmetric electric field created by electrode geometry |
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