A group in England called the Manpowered Aircraft Group assembled itself and began working on it on a very low level, hobby basis. One of the stalwarts in that group was the head of one of the companies that the British industrialist Henry Kremer had. He would ask this person how that program was coming. One time after one of the divisions of his empire had been sold and Kremer was having a three-martini lunch, he asked how it was going. It wasn’t going very well. “Well, how can you get it moving?” “Well, maybe a prize would be a good idea.” And Kremer said, “Well, I’ll put up a prize.” It was just done like that. Kremer was pretty far-sighted and was an enthusiast for physical conditioning, but I don’t think it had huge deliberation in it. It really was a very important event to take place, to put up a prize which eventually became a very significant prize.

All of us have known power — big power, available cheaply — our whole lives. You always have a 100-horsepower or 200-horsepower car and all the heat you need in your house, and so on. It’s hard to realize that just 200 years ago, all our ancestors were getting by for transportation on biological power — walk, run, whatever, use a horse. Then occasionally, you’d use windmills for some things, and water power, and there’d be sailboats. Basically, we got by on those puny powers, and now we can’t even conceive of how we would do it. So here is this Britisher who, in effect, said, “Go back to the power that we were using — but use modern technology — and fly. Fly on a third of a horsepower.” That was an amazing challenge of great value — to think of biology and nature at the same time that we are thinking of technology, and also to think about how little energy and materials we could get by with. This challenge was not just another ordinary one; it had great value. We can see that challenge produced our — and the significant prize — produced our Gossamer Condor, without which there would not have been the Gossamer Albatross, without which there would not have been the Solar Challenger or the Pterodactyl. Without all of these, there wouldn’t have been the Sunraycer, the solar-powered car that won the race across Australia in ‘87. And without that, there would not have been the Impact battery-powered car that now is going into mass production. As you look back in roots, you realize that was a pretty important lunch that took place many, many decades ago.

Paul MacCready: I had guaranteed a relative’s loan at a bank for roughly $100,000 for him to start a company, which didn’t succeed. He couldn’t pay the money back, and as guarantor of the note, I was obligated to pay the money back. Because of some peculiar circumstances, where I thought I had some liquid assets around, they had evaporated while all this was going on. So I was stuck with the debt, which was rather annoying. There wasn’t anything I could do about it. I didn’t have any special plans on what to do. I couldn’t figure out how to handle it. I was going on this vacation trip in the summer of 1976, having time to just daydream, let the mind dawdle around on what it wanted to think about — nibbling away on little old memories and new thoughts and making connections that I otherwise would not have made. I did recall, with no special emphasis, this £50,000 prize that Henry Kremer had put up 17 years earlier. And then, one day I happened to notice that at that time the pound was worth just two dollars. And suddenly, this great light bulb just glowed over my head — the prize was $100,000! My debt was $100,000! There just may be some interesting connection between these two. My interest in human-powered flight suddenly zoomed up to high level. I fussed away at it, and eventually it worked.

Paul MacCready: Well, first of all, I realize, looking back, that for me, right at that time, with my particular skills, strengths, and weaknesses — which all helped with it — it was almost as though the Kremer Prize was designed for me. At that stage, there wasn’t anybody in the world as well-situated to handle it — with knowledge of aerodynamics but no knowledge of structure, so I could more flexibly deal with new methods there. Living in Southern California, where all the aerospace technologies are around, if you need some tubing, you just go buy it. If you need it chemically-milled, you take it someplace else, they chemically mill it. You couldn’t do this in the middle of some other state in the United States or some other country — and where you can get a good airport and an empty hangar if you hunt around for it. And the weather is gentle. And so many things — it almost seemed like this was the perfect spot to win that prize.

In this case, what I was doing was just a fun little scientific hobby. I realized on a vacation trip that you could figure out the flight speed and the turning radius of birds flying around in circles — just soaring in circles like you see a hawk do or a turkey vulture — by noting the time to do a turn and estimating the bank angle at which the bird was operating. From those two numbers, you can immediately calculate the flight speed and turning radius, and you can do it with essentially no tools, just your wristwatch and estimating the bank angle. You have to write a formula and use a little calculator for it. So we were doing this on this vacation trip and comparing the black vulture with the turkey vulture, which flies slower, in smaller thermals, and can take off earlier in the day when the thermals are smaller.

We began to be more interested in how one bird compares with the other, and I found myself thinking about “How does this compare with a hang glider? Can it fly at the same turning radius? What about sailplanes? How much power does each take? What about the power per pound?” I was doing the scaling laws for all of these different flight devices, natural and artificial, in my mind. The scaling laws are pretty simple. While working on that, I thought back about human-powered flight and realized, why yes, there was a very simple, straightforward way of doing it, which is merely that you can take any airplane conceptually — keep the weight the same, but let the size just get bigger and bigger and bigger in all dimensions, and the power goes down. And conceptually, you can make it big enough so it can get by on the tiny power that a person puts out.

When you work out numbers, you realize if you take a hang glider, sort of a 30-foot span, and keep the weight the same — sort of 50 pounds, 70 pounds, something like that — and swell it up to a 90-foot span, and the chord, increase also, the power goes down to one-third of what it was, and that brings it down to about point-four horsepower, which a person — a good athlete — can put out for some number of minutes. You didn’t need an elegant sailplane-like aircraft. You could have an ugly, dirty-looking hang glider-type plane, quick to build, as long as you made it giant without the weight going up.

That was the basic idea. There is one other idea that was essential, which was how to make something that big without the weight going up. The gimmick was that you did not need a structural safety margin that you need in a regular hang glider, which is going to fly at high altitudes, so if it breaks, somebody is going to get hurt. This was only going to fly at ten-feet altitude at ten miles an hour. If it broke, who cared? Nobody would get hurt at all. You could have it just on the very edge of breaking — no safety margin at all. Instead of cables, you use thin piano wire as a structural element. And so, with that idea and the basic idea of “large and light,” the problem was solved. I knew there would be a bunch of grunt work, engineering, to actually win the prize, but the idea that assured that the prize could be won was then in possession.

Paul MacCready: What we really went back to is what birds have been doing for a hundred million years, so who thought of it first is a question. One of the blind alleys that we went up in this development of the Gossamer Condor was — I was picturing that because the flight was so slow and the turns were fairly large, you could just have a wing that always had the same shape and you could gently get around the turn. But when we were having huge problems with the turn and with other aspects of stability and control, I finally sat down and really did some calculations and realized the huge increase of angle of the tack you get in the one wing versus the other wing and that it was necessary — in order to maintain lift —well, a big change of speed, I should say — in order to maintain lift, you have to change the angle of the wing. You just plain have to twist the wing, and when you finally began twisting the wing, it suddenly began working pretty well. But there were a lot of other problems to the stability and control part — but the need to wing twist was important, and I should have figured that out ahead of time and incorporated it right into the very first vehicle. But because I have mental blinders like everybody else, I went off on what I thought was a simpler approach. I tried to do everything on this project as simply as possible, assuming that the simple answer would work. You knew it wouldn’t always, but that saves you a lot of time so when you get to a troublesome thing, you can then spend some time with it.

We figured that one out. Then, by some ingenious tests with a little model that only took an hour to build, pushed around in a swimming pool — just a couple of slabs of balsa wood — we got some final insights about what some computer programs were trying to tell us. The computer programs, a rather elegant technology, were correct, but they didn’t give you any insight. This swimming pool event did give us the insight, and we figured out how to complete all the stability and control problems and came up with a final version that worked.

Paul MacCready: After that prize was won, this prize of Henry Kremer’s that had stood for 18 years no longer existed, and so he didn’t have a prize out. About four months later or so, he put up the new prize for a flight across the English Channel, which is a 22-mile flight across a dangerous body of water. I think he thought it was probably going to take another 18 years for somebody to do that because it was so much longer than this first one-mile flight. We realized that if we just cleaned up the Condor and made a plane that was more elegantly fashioned — a more accurately contoured wing, many more ribs, better foam to help contour the wing, and so on, focused on structure, didn’t pay any new attention to aerodynamics because that had all been solved in the previous one — this new plane, which we would call the Gossamer Albatross, could get by on maybe a third less power. A bicyclist can put out a little less power for a much longer period of time. And so Bryan Allen, our pilot, should be able to fly this new plane for literally hours if we got it properly all cleaned up. So we built it. I guess it was built by mid-spring of the next year.

Paul MacCready: Well, the event was perhaps one of the most exciting things certainly that I will ever live through or that any of the people involved with it would live through, but it doesn’t mean it’s something we’d want to go do again. Maybe the pilot was tired, but the 100 other people who were all in boats going along with him, trying to use psychokinesis to lift him up mentally, were certainly exhausted by the time the thing was over. The big pressure was organizing this thing. You had to predict the previous day, by three o’clock, whether you were going to do a flight the next day. And none of the weather forecasts you got ever agreed — or ever agreed with the weather that subsequently materialized. It’s a very difficult area to get good weather forecasts. I’d actually have to ride over on a bike — and a broken foot at the time and a cast on — and I’d have to ride over from the airport to a pay phone and find the weather forecasts and then turn on, or not turn on, the whole project. And once the project was turned on, which it was for this day, about 100 people, journalist types, were converging from all over Europe — and all the team, the DuPont people. It was about like operating D-Day out of a pay telephone booth. It had pressure, and the usual pressures: we were running out of money and the weather wasn’t right. But finally, we thought, “Okay, let’s try it.” There was really zero chance of it working right the first time, and the first plane was considered sort of a sacrificial plane. We didn’t know what was going to go wrong, but we knew some of the 100 things that could go wrong would go wrong. So we assembled the plane on a thing called The Warrens, where one of the early tunnels was starting to be dug from England to France. It’s an acre of concrete just in the right place for us.

As to Bryan, we only felt that he could keep the plane up for two hours. Prior tests had shown his stamina at the amount of power the plane required. We only gave him enough water to avoid dehydration for two hours. Any extra water would have added weight, and he couldn’t have lasted the two hours even. Unfortunately, a headwind cropped up that meant that after two hours, he was still nowhere near the French coast. He still had many miles to go. He was all out of water, and the increased wind also made more turbulence in the air, which made the power required a little bit higher for the plane. And finally, he just had to give up and signal for a tow. A little rubber boat with several people in it went around under him and, with a fishing pole, was trying to snag a line onto a little ring on the plane and provide a tow, to tow it to either one coast or the other. But during the maneuver, he had to move up higher, and he found that the air was a lot calmer up there, in the stable air, and the turbulence was damped out, and it took a little less power up high. Usually it takes a little less power down low; there is a ground effect that helps you. But here there was turbulence that was bad down low. When he got up high, it took a little less power, and so he decided that even though they were trying to catch the plane all the time, he kept dodging, and finally he said — the radio wasn’t working then, but he signaled that he didn’t want to be hooked up, and he decided to continue for five more minutes and give it a try, and the five minutes became ten, became 15, became 20.

Some of the time, he was down low. For a while, he was down really just six inches above the water, in the changing winds. Somehow he struggled along as his left leg cramped from the dehydration. He pedaled mostly with his right. Then his right leg would cramp, and he would pedal mostly with his left. Towards the end, both legs were cramped, but he somehow just got that last little bit. And there was extra turbulence that was almost beyond the capability of the plane to handle its controls in just that last bit, 50 meters offshore. But finally, he made it. It was almost a three-hour flight — beyond all odds, just impossible for human stamina to have kept going that long, but he did.

If it had been high tide, I think he wouldn’t have made it because he would have had to go an extra 100 meters to reach the shore. It was that close. He had worked for the last several months before the flight with a full-time exercise physiologist, Professor Joe Mastropaolo, who helped him train to build up his stamina. Bryan was a good bicyclist but hadn’t been doing Olympic training, but he worked at it very hard. Mastropaolo, I think, gave him the real spirit, the attitude, that you just don’t quit. It doesn’t matter how impossible, how painful, if you are conscious, you are still pedaling. And somehow this sunk into Bryan, and what he did then is just so beyond reasonable human stamina, I’ve never seen anything else like it.

Paul MacCready: Those are the lightest. You can’t get any non-toy wheels that are down to the two-ounce, three-ounce category. This was about five inches in diameter. It was only going to be used once on the flight, for a few seconds on takeoff. The rest of the time, it was just dead weight. So you don’t want it good and reliable; you want it just strong enough to handle that. We found that on little toy trucks you could find such wheels, so that’s what we used. The idea of this whole project, and the previous Gossamer Albatross project, the only goal was to win the prize, and it wasn’t to have fun, it wasn’t to make a museum piece, it wasn’t to make something that was ever going to fly a second flight. It was just to win the prize. With the Gossamer Condor, we never even drew plans until after the prize was won. Because you didn’t need plans with the way we were doing it. We used computers for some things, but there were no plans drawn. And it’s rare that you have a project that is so simple — one goal, and you can focus on that. People tend to formalize things more, and they do more drawings, and they make parts better than they need to be. We knew exactly what we were trying to do, and we compromised right to the very limit on every little part. So if a toy wheel worked, great.