The AeroVelo team, consisting largely of graduate students, built Atlas, a helicopter 154 feet across with four rotors, each blade about 33 feet in radius. Constructed of carbon fiber tubes, Mylar, polystyrene foam, balsa wood and synthetic cord, Atlas weighed roughly 122 pounds.
Power came from the legs of Todd Reichert, an elite cyclist and speed skater, engineer and Robertson’s AeroVelo partner. Pedaling his modified upright racing bicycle suspended from wires, Reichert generated an average of 550 watts of power.
The AeroVelo team studied previous attempts and incorporated some of the lessons learned through its first human-powered project, the Snowbird, an ornithopter or flapping-wing aircraft. Snowbird was an enormous craft with a wingspan of 105 feet and weight of just 94 pounds. In August 2010, with Reichert again supplying pedaling power, the ornithopter achieved flight — albeit brief, about 19 seconds.
From Snowbird, the team understood the importance of compensating for twist or structural deformation of the craft while under aerodynamic loading. All airplanes flex when flying, but those made of such light, flexible materials especially do. The group spent nearly a third of its development efforts building and testing canards — small lifting wings used for better stability and control — at the end of each rotor blade. The canards were to compensate for the flex and provide the control needed to keep the helicopter from drifting outside the prescribed box.
“It was a convoluted mess whenever we tried to use these controls, often causing a rotor to tip into the ground,” Robertson says. “The canards proved unworkable, and we finally just took them off.”
Instead, the team steered the helicopter through thrust vectoring, a method that changed the power between the rotors. Reichert accomplished this simply by leaning the bike.
AeroVelo won the Sikorsky Prize on June 13, 2013, while flying in an indoor soccer stadium. It used the money to provide internships for the graduate students — most were volunteers — and to pay for materials for upcoming projects. The team expects to take to the air again in 2016 when they go after the 50,000-pound (sterling) Kremer International Marathon Competition sponsored by the Royal Aeronautical Society in the United Kingdom. To win, an aircraft must start from rest, complete two circuits, including a figure eight, and complete the distance of 42 kilometers — the length of marathon — within one hour.
The students are at work on a novel “clean sheet” design of a human-powered, propeller-driven aircraft. It will have to be highly maneuverable and likely will require more than one human to supply the needed power and speed, says Robertson.
“No matter what we do, we want to blow the public’s mind and show that as a society, we can do more with less through great engineering and innovative ways of thinking,” he says. “We don’t expect human-powered flight to ever become practical, but we’re looking for efficiencies everywhere, and the lessons learned here can be applied elsewhere.”
Although the public generally understands skydiving, some people see little romance in leaping from an airplane, plunging until achieving terminal velocity and then arresting the drop to Earth by pulling a parachute.
But stepping off into an abyss, unfurling the wings of a specially designed suit and swooping forward in a controlled descent — well, that evokes Peter Pan, Superman or Buzz Lightyear “falling with style.” A man in a wingsuit gliding down the contours of a mountain like a great bird of prey strikes most people as sheer madness, but there is something magical about this extreme sport.