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 a capacitor that is not symmetrical, creating a force that pushes toward the smaller electrode. Brown thought this force might be related to anti-gravity and called it electrogravitics because it involves electricity and gravity. Later studies in vacuum chambers did not find the same results, and further research suggests the force was caused by corona wind, which is air movement from electrical discharge.
Overview
The Biefeld–Brown effect is believed to create an ionic wind that moves its motion to nearby neutral particles. This effect is seen when a high voltage is applied to an asymmetric capacitor, which has two electrodes of unequal size. When the capacitor is charged to very high DC voltages, a force is created that pushes the negative electrode away from the positive electrode.
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 smaller area to the larger area compared to a regular capacitor. These capacitors are called Asymmetrical Capacitor Thrusters (ACT). These devices are used in ionocrafts and lifters, which use electrical power to create thrust in the air without needing fuel or moving parts.
History
The "Biefeld–Brown effect" was the name given to a phenomenon observed by Thomas Townsend Brown during the 1920s. At the time, Brown was still in high school. He was experimenting with X-ray tubes, specifically a type called a Coolidge tube. When he placed the 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 the tube. Brown believed this might mean he had found a way to influence gravity using electricity. This idea led him to design a propulsion system based on the phenomenon. On April 15, 1927, he applied for a patent titled "Method of Producing Force or Motion." The patent described an electrical method that could control gravity to create movement. In 1929, Brown wrote an article for the magazine Science and Invention, which explained his work. The article also described an invention called the "gravitator," which Brown claimed could produce motion without using electromagnetism, gears, propellers, or wheels. Instead, it relied on a concept he called "electro-gravitation." Brown also stated that unevenly shaped capacitors could create fields that interacted with Earth's gravity. He imagined future uses, such as propelling ocean ships and space vehicles.
At some point, the phenomenon became known as the "Biefeld–Brown effect," likely named by Brown to credit Paul Alfred Biefeld, a physics professor at Denison University. Brown studied at Denison for a year before leaving, and records of his connection to Biefeld are unclear. Brown claimed he worked with Biefeld on experiments, but Denison University has no evidence of such experiments or a relationship between Brown and Biefeld.
In his 1960 patent titled "Electrokinetic Apparatus," Brown described the Biefeld–Brown effect as "electrokinesis" and linked it to a field called electrohydrodynamics (EHD). He also believed the effect could create an anti-gravity force, which he called "electrogravitics." However, there is little evidence to support his claims about anti-gravity. In 1965, Brown filed another patent stating that uneven capacitors could produce a net force even in a vacuum. Yet, no strong experimental evidence confirms these claims.
In 1988, R. L. Talley tested electrodes similar to those Brown used in a vacuum with low pressure. He found no thrust from the electrodes under direct current, but he did observe a force during electrical breakdown. In 2004, Tajmar tested the same setup in a vacuum, enclosing the electrodes in a box to prevent interference from air movement. No linear thrust was detected, suggesting the Biefeld–Brown effect is actually a known phenomenon called corona wind.
Effect analysis
The effect is generally believed to depend on corona discharge, a process that causes 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, while the other is larger and smoother. The most effective distance between the electrodes occurs when the electric field is about 10 kV/cm, which is just below the voltage needed to cause a spark between two sharp points. This condition is known as the saturated corona current. At this point, a strong electric field forms around the smaller, positively charged electrode, causing air molecules to lose electrons. These electrons are pulled away by the electrode’s charge, leaving behind positively charged ions in the air.
These positively charged ions are attracted to the larger, negatively charged electrode due to Coulomb’s law, where they combine with electrons and become neutral again. This creates an opposing force on the smaller electrode. This effect can be used for propulsion (like in EHD thrusters), fluid pumps, and cooling systems. However, the speed achieved by these systems is limited by how much force the charged air can create, which decreases when charged particles collide with neutral air molecules. A theoretical explanation of this force is available in external resources.
This effect works regardless of the polarity of the electrodes. The smaller electrode can be either positive or negative, while the larger electrode must have the opposite charge. Some experiments show that the thrust is slightly stronger when the smaller electrode is positive, possibly because of differences in the energy needed to create ions in air.
When air pressure decreases, several factors reduce the force and momentum in the system. Fewer air molecules are present near the electrode, leading to fewer charged particles. At the same time, there are fewer collisions between charged and neutral particles. Whether this increases or decreases the maximum force is not usually measured, but the overall force on the electrodes decreases until the system enters a glow discharge region. In this region, the breakdown voltage of air drops, requiring lower voltages between the electrodes, which reduces the force from Coulomb’s law.
During the glow discharge phase, air becomes conductive. Although the voltage and current move nearly as fast as light, the movement of the conductive air is very slow. This results in a Coulomb force and momentum change so small they are nearly zero.
Below the glow discharge region, the breakdown voltage increases again, while the number of potential ions decreases and collisions become less likely. Experiments at very low pressure have shown mixed results. Some found a small force when using very high voltages, which increases the chance of ionizing the limited air molecules and creates more force per ion. However, experiments with lower voltages showed less ionization and weaker force. In all cases, the force observed at very low pressure is much smaller than at normal air pressure.