The Biefeld–Brown effect is an electrical occurrence first observed by inventor Thomas Townsend Brown in the 1920s. This effect happens when high voltage is applied to the electrodes of an uneven capacitor, creating a pushing force that moves toward the smaller electrode. Brown thought this force might be related to anti-gravity and called it electrogravitics, a term combining electricity and gravity. Later experiments in vacuum chambers could not repeat Brown's findings, and further research showed the force was likely caused by corona wind from electrical discharge.

Overview

The Biefeld–Brown effect is often believed to create an ionic wind that moves its momentum to nearby neutral particles. This effect describes a force that appears on an asymmetric capacitor when high voltage is applied to its electrodes. After being charged to high DC voltages, a thrust is created at the negative terminal, pushing it away from the positive terminal.

Using an asymmetric capacitor, where the negative electrode is larger than the positive electrode, allows more thrust to be created in the direction from the low-flux to the high-flux region compared to a regular capacitor. These asymmetric capacitors are called Asymmetrical Capacitor Thrusters (ACT). These devices are found in ionocrafts and lifters, which use this effect to create thrust in the air using electrical power without needing any burning or moving parts.

History

In the 1920s, Thomas Townsend Brown, while still in high school, studied X-ray tubes during experiments. When he placed a Coolidge tube on a scale and applied a high voltage electrical charge, he noticed changes in the tube’s mass depending on its position. This suggested a possible net force was acting on it. Brown believed this might mean he had discovered a way to influence gravity using electricity. In 1927, he applied for a patent titled "Method of Producing Force or Motion," describing an invention that used electricity to control gravity and create movement. In 1929, he wrote an article for the magazine Science and Invention, explaining his work and introducing an invention called the "gravitator." This device, he claimed, could move without using electromagnetism, gears, propellers, or wheels, instead relying on a concept he called "electro-gravitation." Brown also suggested that unevenly shaped capacitors could create fields that interacted with Earth’s gravity, and he imagined future uses, such as propelling ships and spacecraft.

The phenomenon later became known as the "Biefeld–Brown effect," a name Brown may have used to associate himself with Paul Alfred Biefeld, a physics professor at Denison University. Brown attended Denison for one year but left before completing his studies. There is little evidence that Biefeld was involved in Brown’s experiments, and Denison University has no records of their collaboration.

In 1960, Brown filed a patent titled "Electrokinetic Apparatus," linking the Biefeld–Brown effect to the field of electrohydrodynamics (EHD). He also referred to the effect as "electrogravitics," suggesting it could produce an anti-gravity force. However, there is limited evidence to support these claims. In 1965, Brown patented a device that claimed to generate force in a vacuum, but experiments have not confirmed these results.

In 1988, R. L. Talley tested electrodes similar to those used by Brown in a vacuum and found no thrust under direct current. However, he observed a force during electrical breakdown. In 2004, Tajmar tested the same setup in a vacuum, enclosing the device to eliminate effects from air movement. No linear thrust was detected, suggesting the Biefeld–Brown effect is likely related to a known phenomenon called corona wind.

Effect analysis

This effect usually happens because of something called corona discharge. This process allows air molecules to become charged near sharp points or edges. Typically, two electrodes are used, with a high voltage between them. The voltage can range from a few thousand volts up to millions of volts. One electrode is small or sharp, and the other is larger and smoother. The best distance between the electrodes happens when the electric field strength is about 10 kilovolts per centimeter. This is just below the voltage needed to make air break down between two sharp points, which is called the saturated corona current condition. This creates a strong electric field around the smaller, positively charged electrode. Near this electrode, air molecules lose electrons, which are pulled away by the electrode's charge.

This leaves a group of positively charged particles in the air. These particles are pulled toward the larger, negatively charged electrode by Coulomb’s law, where they become neutral again. This creates an opposite force on the smaller electrode. This effect can be used for movement (like in EHD thrusters), moving fluids, and cooling systems. The speed achieved by these systems depends on the momentum of the charged air. However, this momentum is reduced when charged particles collide with neutral air molecules. A theoretical explanation of this force has been proposed (see the external links provided).

This effect works whether the small electrode is positive or negative, as long as the larger electrode has the opposite charge. Some experiments show that the small electrode produces more force when it is positively charged. This might be because of differences in the energy needed to create ions and the energy released when ions form in air.

When air pressure is reduced, several factors lower the force and momentum in the system. There are fewer air molecules near the charged electrode, which reduces the number of charged particles. At the same time, charged and neutral particles collide less often. Whether this increases or decreases the maximum momentum of the charged air is not usually measured. However, the force on the electrodes decreases until the system reaches a glow discharge state. The force also decreases because lower voltages are needed between the electrodes, which reduces the force from Coulomb’s law.

In the glow discharge state, air becomes a conductor. Even though electricity moves almost as fast as light, the movement of the conductors is very slow. This results in a Coulomb force and momentum change so small they are nearly zero.

Below the glow discharge state, the voltage needed to make air break down increases again. At the same time, fewer ions are available, and collisions between charged and neutral particles are less likely. Some experiments have found evidence of force at very low pressures, while others have not. It is likely that experiments using very high voltages at low pressure show force because the limited number of air molecules is more likely to become charged, and each charged particle creates more force from Coulomb’s law. However, the force observed in these cases is usually much smaller than in experiments done at normal air pressure.