Like many people, going through university followed an intense career building period was a dry spell in terms of making things. Of course things settled down and I finally broke that dry spell to work on what I called “non-conventional propulsion”.
I wanted to stay away from the term “anti-gravity” because I was enough of a science nut to know that such a thing was dubious. But I also suspected that there might be science principles yet to be discovered. I was willing to give it a try anyway, and did for a few years. It was also my introduction to the world of high voltage… DC. Everything came out null though, meaning that any effects could be accounted for by some form of ionization or Coulomb force. At no time did I get anything to actually fly, though there was a lot of spinning things on rotors or weight changes on scales and balances due to ion propulsion.
So when a video appeared in 2001 from a small company called Transdimensional Technologies of a triangle shaped, aluminum foil and wire thing called a lifter that actually propelled itself off the table, I immediately had to make one. I’d had enough background by then to be confident that it was flying using ion propulsion. And in fact, given my background I was able to put an enhancement in my first version that others came up with only later.
For those who’ve never seen a lifter, it’s extremely simple. Think of it as a very leaky capacitor. One electrode is an aluminum foil skirt, in the shape of a triangle. Spaced apart from that around an inch or so away, usually using 1/6″ balsa wood sticks, is a very thin bare wire (think 30AWG) also shaped as a triangle. High voltage is applied between the foil skirt and the wire. The result is that a downward jet of air is created around and through the middle of the triangle and the lifter flies up off the table. But that is just the barest explanation of how it works. We must go deeper!
The Unsteady Lightweight
For a lifter to succeed it has to be extremely lightweight. There’s no chance of carrying the power supply along. A typical lifter with 4″ (100mm) sides weighs in at just 0.07 ounces (2 grams).
If you’ve ever seen one lift off while the voltage is gradually turned up you’ll have noticed that its flight path is highly erratic until the voltage is sufficiently high that it appears to hover. The truth is, the flight still is erratic, or would be, if it weren’t for three threads tied to the legs, tethering each corner down. Typically the propulsion produced by the three sides of the triangle is not even and so to get it stable, all three sides have to be propelling enough to lift their respective sides. That means that the strongest side is propelling more than it needs to and the weakest side is propelling just as much as it needs to. The threads holding it down make it look stable at that point.
It wasn’t long after the first lifter was flying that variations were also being made: multiple triangles connected together, spirals instead of triangles, even foil tubes in place of the straight sided skirts.
I recall one from Asia (I seem to remember it was in Japan but am not sure) that was room sized and flew in a large garage or warehouse. The documented record for payload is a 98 gram hexagonal shaped lifter lifting a 102 gram payload using 40kV from a specially made 1000 watt power supply. This isn’t the answer to how to fly like Iron Man.
How It Works
The lifter flies using ion propulsion. The key is that one electrode acts as a sharp point and the other acts as a smooth edge. The thin wire is the sharp point. Mine is usually positive. Any sharp point at sufficiently high voltage in air ionizes the air around it. That’s due to the strong electric field there. The foil skirt is the smooth edge and is at the opposite polarity, negative and connected to ground in my case. Having a large surface area, the electric field there is weaker and so there’s less ionization. The enhancement I made in my first version was to make the edge of the foil closest to the wire be rounded, resulting in an even weaker electric field. When I tried following the plans of others without the rounding, it was more difficult to get it to lift off. Having an asymmetric electric field as created by sharp and smooth electrodes is essential to this form of ion propulsion.
The positive ions are attracted to the negative skirt. Some get to the skirt and are neutralized, and some collide along the way with neutral air molecules and impart momentum to them. The neutral molecules then continue in a generally downward direction. The resulting downward flowing jet is made up of these neutral molecules, though I’ve found some evidence that a few positive ions also make it past the skirt. The momentum is passed from the ions to the lifter through the electric field during the collisions. Think of the electric field as arms and hands that are physically a part of the lifter and the ions as balls. A ion colliding with a neutral atom is analogous to the ball in your hand smacking into another ball. When the balls smacking together it pushes your hand in the opposite direction. The same happens to create ion propulsion.
Electrons also play a part but with the wire being positive in my example they play more of a part in creating the positive ions than in transferring momentum.
Smoke And Vacuum Tests
Smoke tests show the large mass of air rapidly moving downward through and around the middle of the triangle. I’ve tested this using smoke from an incense stick. Not only did that clearly show the moving air mass, but as you can see in the last photo, I captured a glowing piece of the incense break off and be rapidly carried away in the moving air mass.
While there have been a mix of results in vacuum chambers with lifters and sharp object/smooth object arrangements, any resulting movement is always tiny compared to a flying lifter. Sometimes the experiment is a device suspended along a torsion wire with a small twist produced in the wire. A larger twist is achieved by turning the power supply on and off in time to the movement, but the resulting larger twist is simply the result of resonance, the same as happens when you apply force to a swing at just the right point in its arc to make it swing higher yet.
Tips And Tricks
A lot of people who try to fly a lifter fail because their power source isn’t powerful enough. The original video by Transdimensional Technologies showed a Van de Graaff generator with a dome of approximately 14″. I tried with my own 14″ dome VDG and judging by the bluish ionization it came up woefully short, even for a 2″ lifter.
To make a 0.07 ounces (2 grams) lifter fly requires 25kV and somewhere above 250 microamps (the analog meter I was willing to sacrifice topped out at 250 microamps.) I’ve read of a 0.18 ounce (5 gram) lifter requiring 37kV and 1.7 milliamps. For that you’re talking about a wall powered Cockcroft-Walton voltage multiplier power supply. An old CRT PC monitor has that and is easily adapted to fly lifters. Some sparks can contain enough current to cause damage to some power supplies, especially PC monitor power supplies. To protect against that use around 240 kiloohms of at least 2 watt rated resistance in series with the input to the lifter. I usually put it on the ground side since that doesn’t have as many issues with leakage.
Note that I once tried flying a lifter from a dusty floor and it didn’t work. I suspect that the dust was getting positively charged by positive ions getting past the skirt. That would result in the positively charged floor attracting the negative skirt down. So stay away from dusty surfaces.
But the best tip for getting a lifter to fly is to do it in total darkness — while taking all safety precautions. In darkness the corona that is the ionization is visible as a bluish glow. This way you can tell which sides of the triangle are contributing to the lift. Often you’ll find it’s just one side. After turning on the lights and turning off and discharging the power supply and the lifter, try moving the wires on the other sides closer to the foil skirt, or the ionizing one further away. If you get sparks then you’ve moved the wires too close. Sparks are the enemy of ion propulsion since they are a shorting out of the electric field that produces the ions.
And that’s a brain dump from my experience with lifters. Have you done any ion propulsion in any form? Perhaps you’ve done the much simpler spinning needle form in school? We’d love to hear about your experiences. Let us know in the comments below.