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.