One of the more, um, unusual designs to emerge in the ongoing pursuit of personal flying machines combines two awesome ideas we don’t see often enough: Rocket and helicopter.
As menacing as the combination might sound, the Dragonfly is rather tame. It’s super-simple to fly and uses two small but powerful hydrogen peroxide motors mounted at the tips of the rotor. The engines are small, just 8 inches long 1.5 pounds apiece. But don’t be fooled by their diminutive size. This baby will top out at 100 knots if you’re really pushing it.
“Each engine is equivalent to 102 horsepower,” says Ricardo Cavalcanti, the man marketing the latest iteration of an idea that’s been bouncing around since the 1950s. “So 204 horsepower to move a unit that is only 230 pounds.”
And the exhaust? Water vapor.
Using hydrogen peroxide and a catalyst has been around for decades and has propelled vehicles ranging from rocket-powered cars to what might be the most famous personal flying machine ever, James Bond’s Bell rocket belt.
The Dragonfly doesn’t use the same hydrogen peroxide you have in the medicine cabinet. It uses readily available commercial-grade liquid diluted to around 50 to 70 percent. Though there is “rocket grade” hydrogen peroxide that was used for things such as the rocket belt, the stuff fueling the Dragonfly falls somewhere between really volatile and what you dab on cuts and scrapes.
Cavalcanti says the Dragonfly uses the simple decomposition of hydrogen peroxide to power the rotor without any other chemicals. Like other aircraft using the fuel, the Dragonfly has a relatively high consumption of about 11 gallons per hour. The latest version can fly for about 90 minutes. At just under $4 a gallon, this personal flight machine is not cheap to fly.
Rotor head assembly on the Dragonfly
Because the rotors are powered at the tips, there is no need for a tail rotor to counter the torque generated by the traditional fuselage-mounted engine. The small rotor at the tail is there to help turn the vehicle during flight.
The flight controls are much simpler, too. Once the hydrogen peroxide motors spin the rotor up to approximately 750 RPM, the pilot simply pulls on a collective lever, similar to a normal helicopter, to climb to the desired altitude. Once there, the Dragonfly is very simple to fly.
“Everything can be done with one single hand,” Cavalcanti says.
"Cockpit" view showing main control lever (red grip) and collective/throttle (black grip on left side)
The clever design allows the pilot to move the control lever which tilts the main rotor to control the direction of flight. If the lever is moved left or right, the small rotor on the tail is engaged to help the Dragonfly turn. There are no pedals like those found on a traditional helicopter.
The Dragonfly has been in development for many years; Cavalcanti is the most recent to work on taking the design public. Cavalcanti says he has spent three years refining the aircraft after acquiring the design. Gilbert Magill started the idea in the 1950s under a military contract to develop a one-man helicopter that was easy to fly.
Magill’s design used similar hydrogen peroxide thrusters as the Dragonfly, but the size and range was not enough to maintain the military’s interest. The idea has since then bounced around until landing with Cavalcanti at Avimech, his Arizona-based aircraft maintenance company.
Cavalcanti says the Dragonfly has more than 300 hours of flight time on the airframe and his company has flown it several hours with the recent refinements to the propulsion system. He was taking orders at the big Airventure aviation show in Oshkosh, Wisconsin and says it takes about four months for delivery.
The simplicity of a hydrogen peroxide-powered helicopter doesn’t come cheap. The single-seater shown here goes for $120,000.
Photos: Jason Paur / Wired.com
Video of the Dragonfly in flight during earlier development in Switzerland.
