Thirty Thousand Volts and a Piece of Tin Foil

In 2002 I was working on the North Slope when a young man named Erich showed up on our job site. He worked for another outfit that had come over to do some work, and within about ten minutes of meeting him he started telling me about the things he had built.

He told me he had run his snow machine across a lake faster than a jet ski. I was deep into jet skiing at the time, and I thought, that is a load of it.

Then he told me he had built a cloud buster, and described how he made it. Then he told me he had converted his car to run on hydrogen. And then he told me he had built a little flyer out of tin foil, and that when he put thirty thousand volts to it, it flew. He had to tie it down to the table or it would take off.

By then I had him pegged. Nobody builds four impossible things.

So I asked him where he lived. Big Lake, he said, which is about ten minutes from my house. I asked him when he was going home. Wednesday, he said. I told him I went home Thursday, and I asked him whether he still had one of those flyers.

Yeah, he said. It's around the house somewhere.

I said I'd like to come see it. He said sure, come on over.

Now, understand what I was doing. I was giving that man every opportunity to back out. Every step of the way I opened the door for him to laugh and say he was pulling my leg. He never took it. I got off the plane Thursday and called him from the airport and told him I was on my way, one more chance to call it off, and he said come on out.

I grabbed a couple of buddies and told them where we were going and why. This guy says he has a device with no engine that flies on thirty thousand volts, and I am going out there to call bullshit on him to his face. We drove an hour and a half.

I walked into his garage and asked him where it was. He said it's right here.

On the table was a little frame with tin foil skirts hanging down off it and a very fine wire strung around the top, a few inches above the foil. It was wired to the back of an old computer monitor. Dental floss ran from the frame to a piece of tape on the tabletop.

I said, show me.

He turned the monitor on, and the thing came up off the table. It rose until the floss went tight and just sat there, holding in one place in the air. And you could hear it, a steady hiss.

I stood in that garage and looked at it, and it was the most amazing thing I had ever seen.

Then I turned around. There was a bulletin board on the wall behind me, and pinned to it was a newspaper article with a photograph of Erich on his snow machine, halfway across a lake. Open water. The thing I had laughed off on the job site was hanging in a clipping three feet from my face.

And then he said, hey, come out here and check this out. He took me outside to a little Ford Ranger. Under the hood was a bottle of water with a roll of plates and screen dropped into it and wires coming off it, plumbed toward the engine. He started the truck, and it ran. That truck is a whole story of its own, and I am going to tell it in a later issue with the chemistry laid out properly, because it deserves better than a paragraph on the way to something else.

What matters here is what I drove home knowing. I had gone out there to call a man a liar, and I had been shown three things in a row that I had said could not be done. Erich was not a bullshitter. Everything he told me he was doing, he was doing.

What I did next

I went home and spent about fifteen hundred dollars on balsa wood, tin foil, and old computer monitors.

Then I failed, over and over. It took me somewhere around thirty attempts, gluing frames together, getting the wire height right, getting the weight down, before I built one that would lift. The weight is the whole game. There is almost no margin. A little too much glue and it sits there hissing at you and never leaves the table.

But eventually I got one to fly, and I shot a little video of it and sent it to my dad.

What I actually had

Here is where I have to be straight with you, because I have had more than twenty years and a lot of reading to figure out what was on that table.

That device is called a lifter, and the effect is named the Biefeld-Brown effect after Thomas Townsend Brown and Paul Biefeld. For decades some people claimed it was doing something exotic, coupling electricity to gravity. It isn't.

What it does is this. The thin wire on top is at very high voltage, and the electric field right at the surface of a wire that fine is enormous. That field strips electrons off the air molecules around it. That is the corona discharge, and that is what you hear hissing. Those newly charged air molecules get driven away from the wire toward the foil skirt below, and on the way down they collide with ordinary uncharged air molecules and drag them along too. The result is a jet of air moving downward. The reaction to that jet is the lift. ¹

So the hiss was not a side effect of the thrust. The hiss was the thrust. I was listening to it work.

And that means the air is the propellant. Take away the air and you take away everything the machine has to push on.

This has been tested properly. In 1988 R. L. Talley ran Brown-style electrodes in a vacuum of about a millionth of a torr under direct current and measured no thrust at all. In 2004 Martin Tajmar hung the electrode assembly inside a box suspended on wires, so that any corona wind would be trapped and could not act on the outside world, and again measured no linear thrust. The conclusion in both cases was the same: what a lifter does is corona wind, a well-understood thing, and nothing more. ¹

The performance numbers are worth knowing, because they cut both ways. Jack Wilson at NASA in 2009 measured pin-based electrohydrodynamic thrusters reaching as high as fifty newtons per kilowatt, and Kento Masuyama in 2012 measured up to sixty-eight newtons per kilowatt for a single-stage lifter. ² Those are startling figures on a thrust-per-watt basis. The catch is that those ratios only hold at very small absolute thrust. You get a wonderful amount of push per watt, and the total push is still a few grams. Wilson's own conclusion was that the effect was not sufficient for manned vehicles. ²

I want to be plain about what that means for my garage. My flyer was not a spaceship engine, and it was never going to be. It was an air machine. In vacuum it is a paperweight.

But it was not a trick either, and this is the part I will defend. What I watched lift off that table was a machine accelerating charged particles with an electric field and taking the reaction. That is the working principle of every ion engine flying in the solar system right now. The difference between Erich's tin foil and a real ion drive is not the physics of the acceleration. It is where the particles come from.

What the real ones do

A real ion drive carries its propellant. Usually xenon: chemically inert, stores compactly, and the atoms are heavy, so each one you throw carries good momentum. ³ The engine ionizes the xenon, accelerates the ions through a charged grid, and shoots them out the back at speeds no chemical rocket can touch. It doesn't need air, because it brought its own atoms to throw.

The trade is brutal and beautiful. NASA's Dawn spacecraft, which went to Vesta and then Ceres, flew three NSTAR thrusters, using one at a time. Full throttle on one of those engines is ninety millinewtons of thrust. ⁴

Ninety millinewtons. That is about the weight of a couple of quarters sitting in your palm. That is the entire thrust of the main engine of an interplanetary spacecraft.

You would think that's useless, and it is, for about the first day. But the engine doesn't run for a day. It runs for years. Dawn carried 425 kilograms of xenon and the ion system delivered a total velocity change of nearly eleven kilometers per second over the mission. ^{4 5}

Stop on that number, because it is the one that matters. Eleven kilometers per second from the ion drive is comparable to what the entire three-stage launch vehicle gave it getting off the ground. ⁵ A thruster you could hold in one hand, pushing with the force of two quarters, eventually did as much for that spacecraft's trajectory as the rocket did.

That's what specific impulse buys you. Dawn's thrusters ran at a specific impulse of about 3,100 seconds, roughly ten times what a good chemical engine manages. ⁴ Deep Space 1, the first mission to fly NSTAR, carried about 81 kilograms of xenon, used 73 of it, and changed its own velocity by more than three and a half kilometers per second on 2.3 kilowatts of solar power. ⁶ And when NASA ran the follow-on NEXT thruster on a life test, it ran continuously for more than 48,000 hours, five and a half years, consuming about 870 kilograms of xenon. The same total impulse from conventional propellant would have taken over 10,000 kilograms. ⁷

That is the case for ion propulsion in one line: you can carry ten tons of chemical fuel, or you can carry most of a ton of xenon and be patient.

The limitation is just as blunt. Ninety millinewtons will never lift anything off a launch pad, or off the Moon, or out of a gravity well in a hurry. Ion drives are for the long haul between places, not for leaving them.

No propellant at all

If carrying less propellant is good, carrying none is interesting, and that's the light sail.

Sunlight carries momentum. Bounce it off a mirror and you get a push. It is a very small push. JAXA's IKAROS unfurled a 196 square meter sail in interplanetary space in 2010 on the way to Venus and became the first craft to be measurably accelerated by sunlight alone, confirmed that July. ⁸ The Planetary Society's LightSail 2 did it from a CubeSat in Earth orbit in 2019. ⁹

The numbers are humbling. A sail like that produces a fraction of a millinewton, and one worked example puts the zero-to-sixty time at around nine hours. ¹⁰ But there is no tank to run dry. IKAROS also did something clever that I like as an engineer: instead of using thrusters to steer, it changed the reflectivity of eighty liquid crystal panels around the sail's edge, so sunlight itself produced the steering torque. ⁸ No moving parts, no propellant, just changing how shiny the edges were.

And the same hardware scales to something wilder. Point a big laser array at a sail instead of relying on the Sun, and the push stops being limited by how far you are from a star.

And still, the chemical rocket

Every one of these things got where it was going on top of a chemical rocket, and that will stay true for a while.

Chemical rockets are the only propulsion we have that can pick a loaded vehicle up off the ground. They give you meganewtons for minutes. Ion drives give you millinewtons for years. Those are not competing products. They are different tools, and the reason spacecraft keep flying both is that you need the first to escape and the second to travel.

If I had to write the whole survey on one line, it's this: chemical to leave, electric to go, sails if you can wait.

The Harley

I said I sent that video to my dad.

He thought it was pretty cool, said he'd never seen anything like it, and he forwarded it to a friend of his, Mac Dorsey. Mac was an Air Force colonel working at DARPA at the time. He passed it along to a friend of his, Ed Friday, another scientist and engineer at DARPA.

Ed Friday had just bought himself a Harley. Then he saw that video, decided he wanted to see the real thing in person, and took the opportunity to ride the new bike from Manassas, Virginia, to Alaska to do it.

I took him out to my garage and turned it on for him. He said it was amazing.

Then he told me something I have never forgotten. He said if DARPA could get a device like that to fly on its own, untethered, no external power source, just lift off and go, they would spend a great deal of money on it, because that is exactly what an advanced propulsion program is looking for.

He went back and started setting up a workshop on it. He had done more digging and found other people on the internet building these flyers, and he wanted to bring them all together at DARPA for a small convention. I was invited.

Then, in March 2003, Iraq happened, and everything at DARPA that wasn't the war got shelved. The workshop never took place. I never made that trip.

I don't think we lost a spaceship engine in that shelved workshop. I've told you plainly what a lifter is and what it isn't, and I don't believe an untethered one was ever going to fly. But I think about that room anyway, because of who would have been in it: a couple dozen people who had each built the thing with their own hands and had each learned something the others hadn't, with no way to find each other. Whatever was going to come out of that room, we still don't know.

The question

So here it is, and I'd like to hear from you.

If you had DARPA's money and Ed Friday's question in front of you, where would you put it? Chase the high thrust-per-watt of an air-breathing electrostatic machine and try to make an atmospheric craft out of it, knowing it dies the moment you leave the air? Or pour it into ion engines and sails, which work in the only place that matters and just take forever?

And a second one, for anybody who has built a lifter: how many tries did it take you, and what finally made the difference? Mine was thirty and it came down to weight.

Write to hello@starboundmagazine.com.

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A note on where this comes from. I am not a metallurgist, a spacecraft engineer, or a degreed engineer of any kind. But I am a practical one, with more than forty years in heavy industrial construction: welding, millwright work, hydraulics, mining, and thirty-three years of electrical construction and commissioning on the North Slope of Alaska, in a place that punishes anything built wrong. Much of that time I have worked as a field engineer, which means I am the one standing in front of the equipment when the drawing turns out to be wrong, and the fix has to be made on the spot, with what is on hand, and has to work the first time. Anyone who has done that long enough learns that a lot of engineering gets corrected in the field by people with more experience than the people who drew it. That is the eye I bring to these subjects: not what should work on paper, but what actually gets built, and what breaks. The facts I take from other people are footnoted so you can check them and read further. The ideas built on top of those facts are my own, and I would rather see them knocked down by somebody who knows better than left standing because nobody looked.

Sources

1. "Biefeld-Brown effect," Wikipedia, summarizing R. L. Talley's 1988 vacuum measurements and Martin Tajmar's 2004 suspended-box experiment, both finding no linear thrust absent air. ↩
2. "An Examination of the Biefeld-Brown Effect and its Influence," Portland State University honors thesis, reporting Jack Wilson's 2009 NASA measurements up to 50 N/kW and Kento Masuyama's 2012 measurement of 68 N/kW for a single-stage lifter. ↩
3. NASA Science, "Ion Propulsion" (Dawn mission technology pages), on the choice of xenon and the 425 kg propellant load. ↩
4. "Dawn (spacecraft)," Wikipedia: NSTAR thrusters, 3,100 s specific impulse, 90 mN thrust, xenon allocations. ↩
5. Brophy et al., "The Dawn Ion Propulsion System," Space Science Reviews: total delta-v of nearly 11 km/s, comparable to that of the three-stage launch vehicle. ↩
6. "Deep Space 1" and "NASA Solar Technology Application Readiness," Wikipedia: 81 kg xenon load, 3.58 km/s velocity change, 2.3 kW. ↩
7. "Ion thruster," Wikipedia, NEXT life test: 48,000+ hours continuous, about 870 kg xenon consumed, equivalent to over 10,000 kg of conventional propellant. ↩
8. "IKAROS," Wikipedia: 196 m2 sail, JAXA confirmation of solar-pressure acceleration on 9 July 2010, attitude control via 80 liquid crystal reflectivity panels. ↩
9. Spaceflight Now, "LightSail team declares success in solar sail experiment," August 2019. ↩
10. ToughSF, "Riding Sunbeams with Solar Sails," worked example of sail acceleration. ↩

The 2002 North Slope encounter, the visit to Big Lake, the thirty build attempts, the video's route to DARPA, and Ed Friday's ride to Alaska are my own first-hand account. The video above is mine, shot at the time; the file is presented as recorded, resized for the web. Erich's other claims, the snow machine, the cloud buster, and the hydrogen conversion, are recorded as he told them and were never verified; only the flyer was witnessed.