Then came the Kremer Prize. For nearly two decades, scientists had been struggling to win a 50,000 prize, offered by the British industrialist Henry Kremer, for the first sustained human-powered flight. One day in 1976, MacCready realized the pound was trading for two U.S. dollars. And he'd co-signed a $100,000 loan for a relative's business that had unexpectedly come due when the business failed. "A team in Britain had been working on very sophisticated plans, and I tried to find some ingenious way," MacCready says, "but all I came up with were the same ideas they had." He gave up until he undertook a half-game, half-research project with his sons while driving cross-country one summer. By estimating the bank angle of the wings of soaring birds and counting the seconds it took them to complete a circle, he discovered you could calculate their lift. "That gave me a different avenue—I realized if you tripled the wingspan and cord [wing width] of a hang glider without increasing its weight, you could reduce the horsepower by a factor of three. All you'd need was 0.4 horsepower, which a good cyclist could deliver." Bingo, the puzzle was all but solved. Over weekends with friends and his sons, MacCready perfected the Gossamer Condor, an ungainly and fragile vehicle with a 90-foot wingspan covered in Mylar
sixteen-thousandths of an inch thick. It weighed just 70 pounds and flew at the speed of a walk.
After expenses, however, the $100,000 MacCready won wasn't enough. But then Kremer doubled the amount for the first human-
powered crossing of the English Channel. "He thought it would take another 18 years," says MacCready, who merely cleaned up the Condor's aerodynamics. In 1979, cyclist Bryan Allen flew the Gossamer Albatross across the channel in 2 hours 49 minutes. The debt was paid.
More important, MacCready now knew more than anyone about slow, efficient flight. Solving the problem of human-powered flight made solar-powered flight seem possible, and in 1981 the Solar Challenger, smaller than the Condor but similar-looking, flew 163 miles from Paris to England at 11,000 feet on nothing but sunshine.
The next year MacCready won a Lindbergh Award, which recognizes individuals who balance technological achievement and environmental preservation. Preparing his acceptance speech, he thought more deeply about what he'd been doing and why. "In the last years of his life Lindbergh was a devoted environmentalist," MacCready says. "In Kenya he was watching a hawk soar, and he asked himself which he'd rather live in—a world with airplanes and no birds or with birds and no airplanes. He was an aviator but he picked the birds." Lindbergh's epiphany has guided the company ever since. "I'm more interested in a world that works than what sells. We make strange devices that do more with less."
Not that such a focus has hurt sales. Partnering with General Motors, AeroVironment designed a solar-powered car for a 1,867-mile race across Australia in 1987. The Sunraycer beat every other car by two days. Impressed, GM asked MacCready to create an electric car, which eventually became the revolutionary EV-1. For an IMAX film, AeroVironment built an 18-foot mechanized pterodactyl. Making the unstable bird fly from the thrust of flapping wings forced the company to develop a sophisticated autopilot system; the concept would eventually become the heart of its mini UAVs. "The electronics were a complex job and came at a time when we didn't have a lot of electronics wizards," says MacCready. "Doing it built up our muscles in that area."
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.