Human-Powered Helicopters: A 600-Year-Old Dream in Sight
A team of engineers just broke a world record. But they're only getting started.
Colin Gore, a PhD student in materials science at the University of Maryland, carefully hooks his bike shoes into the cranks of a motor-less helicopter. He sits in the spider-like machine's central hub, surrounded by four delicately engineered carbon fiber arms, each of which supports a super-light rotor. The machine spans the length of a basketball court, yet it weighs only 75 pounds. With Gore's slim frame in place, it now weighs 210 pounds. And it's ready for flight.
In a reclined position, Gore grips the helicopter's hand cranks and begins to move his hands and feet like the pistons of a four-stroke engine. Slowly, as the motion of his arms and legs reels in a line attached to each of the four rotors, pairs of the helicopter's blades begin to spin in opposite directions. Moments later, Gore is doing what has been dreamed about for centuries: He is flying a human-powered helicopter.
More than that, though, he is breaking a world record. The man-and-machine combination hovers a foot or two above the ground -- as if dangling on a string -- for 40 seconds, the longest amount of time such a feat has been accomplished.
"It's already one of the highlights of my life," Gore told me -- and that was even before his flight. But 40 seconds, world record notwithstanding, isn't what Gore and his team are seeking. Gore, along with 35 fellow engineering students at U of M, are chasing after the Sikorsky prize: a 30-year-old contest that promises $250,000 to the first team that can build a human-powered helicopter to fly for 60 seconds -- at three meters off the ground.
The challenge is a daunting one. Human-powered airplanes have been built before, certainly, and to amazing success. The first one, a seven-winged bicycle-powered craft, was flown in 1923, just two decades after the first heavier-than-air flight. In 1988, a machine built by MIT set a record flying for seven hours across 70 miles. But man-powered helicopters, although first sketched by Leonardo DaVinci in the 15th century, have been a persistent engineering challenge. The previous record in the race for the Sikorsky prize was set in 1994, when a Japanese team hovered for 19 seconds. Only three teams have achieved any flight at all.
"Human-powered airplanes have been flying for some decades and a lot of people wonder, 'Well, what's so much harder about a helicopter?'" says William Staruk, a graduate student and the team's project manager. "The problem is that a helicopter has to lift itself vertically into the air directly against gravity." An airplane, on the other hand, has to generate only enough forward motion to overcome the force of drag. "So we end up requiring on the order of three times more power than a human-powered airplane does."
The helicopter Gore is powering is called the Gamera II, which is an updated design of a craft that flew for 11.4 seconds last year. It borrows its name from a flying giant turtle monster from Japanese horror movies. (It's also a reference to the school's mascot, the Terrapin.) With promising preliminary testing, it seems possible that this design will break through the minute barrier.
The Gamera II is 30 pounds lighter and several times more powerful than its original design. The improved efficiency is owed mainly to a redesigned truss system. In fabricating the Gamera I, the team utilized standard carbon fiber tubing for structural support. Now, they use a proprietary "micro truss" system in which spindles of carbon fiber are wrapped around a truss of three small carbon-fiber rods. Each three-foot section of truss is half the weight of the traditional tubes and, yet, 50 percent stronger. Two 200-pound men could stand on one end of the tube without it breaking (that is, if those men could balance on a one-inch-wide triangle). Staruk won't tell me how the trusses are made, other than that they're produced on a machine that's like of loom for the space age. The team hopes to patent the design.
For all of the high-tech materials involved, a lot of the craft's structures are handmade. Carbon fiber composites can literally be sewn into place, which makes it very useful in intricate structural work, but introduces an element of human error. "If one little thing goes wrong, the whole thing can fail," Staruk says.
And it does. When I arrived to meet with the team at the flight test on Monday, they were in repair mode. During an earlier flight, one of the arms supporting a wing had failed, sending one half of the wing into the ground and the other half into the body of the machine. Science, of course is not always exactly a science. So the team has spare parts (which they replace amid unending loops of dubstep music).
While the team's chances of capturing at least the time portion of the Sikorsky challenge are good, they'll face some competition this summer. AeroVelo, a team out of Toronto, Canada, is currently fundraising on Kickstarter to fund a human-powered helicopter design. In 2010, the team successfully built a human-powered flapping-wing plane, an ornithopter, which was the first of its kind. They've already exceeded their goal of $30,000, and say they're aiming to have a craft manufactured by August.
But Staruk isn't afraid of the competition. "We're excited to see what they can do," he says.
You also have to wonder, though: Why? What use is an enormous human-powered helicopter whose whole point is to hover off the ground for (in the best case scenario) just a minute? Not much, especially seeing how's there's no way to steer the device. "No one's ever going to use our helicopter for a practical use," Staruk says. "The value of the project is mostly in the education aspect."
When you pick the machine apart into its components, you find advances in engineering. In addition to the micro trusses, Staruk and his team have also gained novel insights into the ground effect -- the phenomenon that gives propellers an extra boost in power when they're close to the ground. They found that they can amplify this effect if they use blades that point flat or upward at the tips. (Most helicopters have blades that twist downwards.) "It's not common that students get to work on a project where they get to design and build something to fly that's never been done before," Staruk says.
Besides all that, though, there's the fact that impossible-sounding challenges can often push science forward on their own. One little discovery in one area might lead to a big one in another. If the dream of a human-powered helicopter is realized this summer, by the Gamera team or another one, the field of aviation could benefit in a tangible way. And even if it doesn't, the project's success could still inspire a new generation of engineers -- the ones who will go on to invent the next big thing.
As Gore puts it: "Things do not have to be practical to be exciting."