Human-powered Gamera helicopter hovers its way into the record books
By Paul Ridden
August 19, 2011
A biology student has just hovered her way into the record books in a four-rotor, human-powered helicopter named after a giant flying turtle from Japanese kaiju movies. Gamera was built to try and claim the American Helicopter Society's Sikorsky Prize, that was set up in 1980 and has yet to be claimed. The team's first flights in May resulted in a 4.2-second U.S. national record, and now the record page has had to be rewritten again after the young pilot's frantic combination of hand and foot pedaling action kept Gamera in the air for nearly three times longer, during the recent summer flight sessions.
For the last two years, a team of 50 graduate and undergraduate students from the Alfred Gessow Rotorcraft Center at the University of Maryland's Department of Aerospace Engineering has been designing, building and tweaking a lightweight, four-rotor helicopter that's powered by the human pilot suspended at its center. The hope is to build a craft capable of walking away with the American Helicopter Society's Sikorsky Prize of US$250,000.
The rules of this challenge - named in honor of helicopter pioneer Igor Sikorsky - state that the craft should get all of its power from the human pilot and that it should thus be capable of hovering for 60 seconds within a 10-meter (32.8-foot) square area. During this time, the lowest part of the machine must reach an altitude of 3 meters (9.84 feet) above the ground - if only momentarily. As of August 2011, no-one has claimed the prize.
The closest so far was 1994's Yuri I (19.46 seconds at an altitude of 0.2 meters/0.65 feet) designed by the Nihon University Aero Student Group. Gamera sports a similar design - with a 42-foot (12.8-meter) rotor at the end of each of the four points of a cross, and the pilot sat in the middle. Each crossbar of the frame is 60 feet (18.2 meters) long.
"The similarities are more a result of convergent evolution than direct inspiration," the team's Joe Schmaus told Gizmag. "Helicopters are notoriously challenging to control and human powered flight has only ever been possible with the aid of ground effect. A quad rotor is the only configuration we have identified that is passively stable and allows the rotors to be as deep in ground effect as possible."
Gamera's main structure is made from carbon fiber using a specially-developed truss construction method, that allows highly optimized composite trusses to be created very quickly. The team also developed a novel method to minimize buckling, where airframe trusses at critical points have been reinforced with so-called baby trusses. Elsewhere, the craft is made of balsa, foam, mylar, and other lightweight materials to help keep its weight down - the entire weight is just 210 pounds (95.25 kg), including the weight of the pilot - while also offering structural strength.
The lightweight pilots used throughout the project have also been experienced cyclists, and were free to design their own training regimes based on their specialist knowledge. The team "became aware through our testing that a more focused training plan that optimized for muscular endurance rather than cardiovascular endurance, and one which trained the motion that is unique to Gamera, would produce even better results," said Schmaus. "Moving forward we are working with specialists in Biomechanics to develop a targeted training plan."
On the eve of the most recent record attempt inside the University's Reckord Armory, Gamera crashed during testing - forcing an emergency all-night repair. However, the next day a few bleary-eyed team members watched as pilot Judy Wexler powered aloft for 12.4 seconds in the presence of officials from the National Aeronautic Association (NAA). However, it's a time of 11.4 seconds from a subsequent flight that's just been confirmed as a new national record by the NAA and submitted to the Fédération Aéronautique International in Switzerland for consideration as a world record. The flights also represent the longest human-powered flight by a female U.S. pilot.
Even though the team members believe that Gamera is capable of longer duration flights, they are now faced with something of a dilemma.
"The Sikorsky Prize has the very ambitious target of 10 feet and 60 seconds that we do not think our current vehicle can achieve," said Schmaus. "Through the development of Gamera we have learned many things about extreme ground effect aerodynamic design and also about lightweight structural design. At this point we are combining these two knowledge bases to determine whether to go for another record setting, but not prize-winning, flight with Gamera or put all our energy into designing a vehicle capable of the Sikorsky Prize."
The next phase of the Gamera project will be decided shortly. Updates will appear on the project's website.
In the meantime, you can watch all 12.4 exhilarating seconds of human-powered flight in the following video: