Ion-propelled aircraft

For other meanings of "lifter", see Lifter.

The Lifter is an electrokinetic, or electrohydrodynamic device. The term "Lifter" dates back to the 1960s, an era in which EHD experiments were at their peak. In its basic form, it simply consists of two parallel conductive electrodes, one in the form of a fine wire and the other a foil skirt with a smooth round surface, which when powered by high voltage in the range of a few kilovolts, produces thrust. It forms part of the EHD thruster family, but is a special case in which the ionisation and accelerating stages are combined into a single stage.

The Lifter can be used as a science fair project for students, but requires many safety precautions due to the high voltage required for operation and the risk of lung and throat cancer from long term inhalation of its ionised air product. A large subculture has grown up around the Lifter phenomena and its physics are now known to a much better extent.

What it is

File:Lifter with power supply.jpg

A Lifter, in flight, with its power supply

The Lifter is a propulsion device thought to be based on electrokinetic propulsion that works without moving parts, flies silently, uses only electrical energy and is able to lift its own weight plus an additional payload, with the future prospect of its power supply. The principle of ionic air propulsion with corona-generated charged particles has been known as from the earliest days of the discovery of electricity, with references dating back to 1709 in a book titled Physico-Mechanical Experiments on Various Subjects by Francis Hauksbee. However, its use for propulsion was first given serious thought by Thomas Townsend Brown in 1928 and later on by Major Alexander Prokofieff de Seversky, who contributed much to its basic physics and construction variations in 1960. In fact, Major De Seversky patented a very similar device known as the Ionocraft in 1964, also part of the EHD thruster family. The basic external design of the Lifter was first described in a 1960 patent filed by Thomas Townsend Brown, titled "Elektrokinetic Apparatus". Biefeld-Brown effect.

Lifter construction

The Lifter can be easily constructed by anyone with a minimal amount of technical knowledge. The Lifter shape was defined by Transdimensional Technologies as an equilateral triangle with sides generally between 10 and 30 cm. Lifters basically consist of three parts, the corona wire (or positive electrode/anode), the air gap (or dielectric), and the foil skirt (also collector, ground electrode/cathode). The roles of cathode and anode can be reversed. All of this is usually supported by a lightweight balsawood or other electrically isolating frame so that the corona wire is supported at a fixed distance above the foil skirt, generally at 1 mm per kilovolt. The corona wire and foil should be as close as possible to achieve a saturated corona current condition which results in the highest production of thrust. However the corona wire should not be too close to the foil skirt as it will tend to arc in a spectacular show of tiny lightning bolts which has a twofold effect.

It degrades the thrust as it is shorting the device and there is current flow through the arc instead of the ions that do the lifting
It can destroy the power supply or burn the balsa structure of the Lifter.

Parts of a Lifter

The corona wire:

The corona wire is usually, but not necessarily the anode part of the Lifter. It is made from a small gauge conductive wire such as copper.

The corona wire is named because of its tendency to emit a purple corona like glow while in use. This is simply a side effect of ionization. Excessive corona is to be avoided, as too much means the electrodes are dangerously close and may arc at any moment, not to mention the associated health hazards due to excess inhalation of ozone and NOx produced in the corona.

The air gap:

The air gap is simply that, a gap of free flowing air between the two electrodes that make up the mass of a Lifter.

The air gap is a vital necessity to the functioning of a Lifter as it is the dielectric used during operation. Best results have been observed with an air gap of 1 mm to every kV.

The foil skirt:

The foil skirt is usually, but not necessarily, the cathode part of the Lifter. It is made from cheap, lightweight kitchen aluminum foil found at any supermarket in the world.

The foil skirt is named simply because it is shaped much like a skirt, and is made from aluminum foil. It is by far the most fragile part, and must not be crumpled to work properly. Any sharp edges on the skirt will degrade the performance of the thruster.

Reversing the polarities of the corona wire with that of the foil does not alter the direction of motion. Thrust will be produced regardless of whether the ions are positive or negative.

How it works

The Lifter effect is a form of electrokinetics or, in modern terms, electrohydrodynamics propulsion. In its basic form, the Lifter is able to produce forces great enough to lift up a few grams of payload, but its use is restricted to a tethered model. Lifters capable of payloads in the order of a few grams usually need to be powered by power sources and high voltage converters weighing a few kilograms, so although its simplistic design makes it an excellent way to experiment with this technology, it is unlikely a fully autonomous Lifter will be made with the current construction methods. Further study in electrohydrodynamics, however, show that different classes and construction methods of EHD thrusters and hybrid technology, put no limit to shape, size, payload or thrust-to-power ratio. Thus, a fully autonomous EHD thruster is theoretically possible, and possibly already conceived.

When the Lifter is turned on, the corona wire becomes charged with high voltage, usually between 20 and 50 kV (20,000 and 50,000 volts). The user must be extremely careful not to touch the Lifter at this point, as it can give a nasty shock. At extremely high current, well over the amount usually used for a lifter, contact could be fatal. When the anode is charged with approximately 30 kV, it causes the air molecules nearby to become ionized by stripping the electrons away from them. As this happens, the ion is strongly repelled away from the anode but is equally strongly attracted towards the cathode, causing the majority of the ions to begin accelerating in the direction of the cathode. These ions travel at a constant average velocity termed the drift velocity. Such velocity depends on the mean free path between collisions, the external electric field, and on the mass of ions and neutral air molecules. If this were the only effect present, there would be no movement; as the ions impact the second electrode, they create another equal and opposite force that cancels out the initial movement.

The fact that the current is carried by a corona discharge (and not a tightly-confined arc) means that the moving particles are diffusely spread out, and collide frequently with neutral air molecules. It is these collisions that create a net movement. The momentum of the corona ions is partially imparted onto the neutral air molecules that they collide with, which, being neutral, do not eventually migrate back to the second electrode. Instead they continue in the same direction, creating an ionic wind. As these neutral molecules are ejected from the lifter, there are, in agreement with Newton's Third Law of Motion, equal and opposite forces, so the Lifter moves in the opposite direction with an equal force. There are hundreds of thousands of molecules per second ejected from the Lifter, but the force exerted is comparable to a gentle breeze. Still, this is enough to make a light model lift off its own weight. The resulting thrust also depends on other external factors including air pressure and temperature, gas composition, voltage, humidity, air gap, and Lifter mass.

The air gap is very important for the function of this device. Between the electrodes there is a mass of air, consisting of neutral air molecules, which gets in the way of the moving ions. This is air mass is impacted repeatedly by excited particles moving at high drift velocity. This creates resistance, which must be overcome. The barrage of ions will eventually either push the whole mass of air out of the way, or break through to the cathode where electrons will be reattatched, making it neutral again. The end result of the neutral air caught in the process is to effectively make the ion more massive, causing more force to be exerted, both on the ion and on the Lifter. The heavier and denser the gas, the higher the resulting thrust.

Patents and publications

Below are patents and publications related to lifters, electrokinetics, electrohydrodynamics, and the Biefeld-Brown effect.

American patents

U.S. patent 1,974,483 — Electrostatic motor — T. T. Brown
U.S. patent 2,949,550 — Electrokinetic apparatus — T. T. Brown

U.S. patent 2,022,465 — Electric vacuum pump — C. W. Hansell
U.S. patent 2,182,751 — Electronic pump — R. W. Reitherman
U.S. patent 2,282,401 — Electric vacuum pump — C. W. Hansell
U.S. patent 2,295,152 — Fluid movement with precipation — W. H. Bennet
U.S. patent 2,460,175 — Ionic vacuum pump — R. C. Hergenrother
U.S. patent 2,636,664 — High vacuum pumping method, apparatus, and techniques — E. A. Hertzler
U.S. patent 2,765,975 — Ionic wind generating duct — N. E. Lindenblad
U.S. patent 3,018,394 — Electrokinetic transducer — T. T. Brown
U.S. patent 3,022,430 — Electrokinetic generator — T. T. Brown
U.S. patent 3,071,705 — Electrostatic Propulsion Means — W. J. Coleman, Et. al.
U.S. patent 3,095,163 — Ionized boundary layer fluid pumping system — G. A. Hill
U.S. patent 3,177,654 — Electric aerospace propulsion system — V. Gradecak
U.S. patent 3,187,206 — Electrokinetic apparatus — T. T. Brown
U.S. patent 3,196,296 — Electric generator — T. T. Brown
U.S. patent 3,120,363 — Flying apparatus — G.E. Hagen
U.S. patent 3,223,038 — Electrical thrust producing device — A. H. Bahnson., Jr.
U.S. patent 3,130,945 — Ionocraft — A. P. DeSeversky
U.S. patent 4,663,932 — Dipolar force field propulsion system — James E. Cox

Non-American patents

GB300311 — A method of and an apparatus or machine for producing force or motion — T. T. Brown

Journals and articles

Talley, R .L., "Twenty First Century Propulsion Concept". PLTR-91-3009, Final Report for the period Feb 89 to July 90, on Contract FO4611-89-C-0023, Phillips Laboratory, Air Force Systems Command, Edwards AFB, CA 93523-5000, 1991.

External links