A technician wheels an experimental one-person helicopter called firebird out of a large gray hangar at London Southend Airport in England. It has a bare-bones look, as if cobbled together in someone's garage. A red tubular-steel frame encloses a single exposed seat and a pair of fuel tanks, hung beneath a two-bladed rotor. That's it. No fuselage, no complicated controls, not even an engine.
Soon a test pilot wearing a crash helmet and overalls climbs in and works a hand pump that forces hydrogen peroxide up to the rotor, where the liquid flows along pipes embedded in the blades. At the tip of each blade is a tiny, one-pound rocket motor. When the fuel enters the motors, it hits layers of silver and stainless steel mesh, causing the hydrogen peroxide (H2O2) to decompose explosively into steam (H2O) and oxygen (O2). The process unleashes about 100 horsepower from each unit— a far superior power-to-weight ratio than in any internal combustion engine— but it creates no flame or pollution. With a loud hiss, the helicopter takes off, leaving behind a spiral plume of steam and a crowd of onlookers wondering if they have just witnessed a new wave in aviation.
Intora, a defense consultancy business in Southend-on-Sea, England, claims that Firebird can be ultracheap to build and maintain because it contains so few moving parts. Once the pilot primes the motors, they can suck fuel from the tank continuously. The main rotor drives itself. And because all the thrust occurs at the tips of the blades, Firebird is incredibly maneuverable and easy to fly. Brian Nalborough, Intora's CEO, says the copter can be controlled by novices after just a few hours of training. Firebird could whisk commuters to work or lift firefighters into danger zones; an unmanned, radio- controlled variant could conduct agile military surveillance while keeping the pilot safely on the ground. The craft's small size and extreme mobility would make it hard to shoot down, while its low price would make it expendable.
This potential for unmanned surveillance convinced Nalborough to tackle the challenge of manufacturing the unusual bird as a potentially lucrative departure from his usual business brokering international trade deals. "We supply equipment to— various governments. If I named them, they might get a little bit upset," he says, grinning cheerfully. Intora thinks it can interest some of those clients in a Firebird priced at about $80,000. "We built this hangar here at Southend to manufacture up to eight helicopters a day," Nalborough says. The company hopes to begin production within a year.
If so, that will be quite a turnaround for a promising but beleaguered technology. Past attempts at tip-driven rotors on helicopters, such as the British Fairey Rotodyne, failed to arouse much commercial interest, in part because they were too loud for shuttling passengers around urban settings. Previous one-man flying machines have been stymied by expense, safety, and reliability problems. Intora claims it has circumvented both sets of difficulties by refining the hardware and focusing on military customers.
As with the Rotodyne, the concept for Intora's machine dates back to the 1950s, when an eccentric American inventor named Gilbert Magill sketched out his plans for a portable "minicopter." It's been rough flying since then. Magill ran out of money in the mid-1980s, and a bank seized his assets, including the helicopter design. Eike Mueller, a former engineer at NASA, raised $200,000 to pay off the bank, improved the design, and flew a prototype before Magill's death. Still, Mueller could not raise extra development capital, because the machine was so unconventional. He and Magill sold the patents to Liteco, a Swiss company.
After Liteco folded, Intora picked up the patents and hired Mueller as project director at Southend. Two years later he left in a flurry of mutual recrimination and lawsuits.
Through all the changes, the Firebird concept has remained much the same— including its unusual propellant. Hydrogen peroxide is so unstable that a slight coax from a silver catalyst breaks it down catastrophically into oxygen and steam. Concentrated solutions of hydrogen peroxide— more than 30 percent, mixed with water— have acquired a risky reputation because they can start runaway reactions if exposed to impurities in the wrong kind of container. "It's not something you want people playing with in their backyards," says Michael Wallis, president of the Experimental Rocket Propulsion Society of northern California. One of his members had a minor blowup when he stored H2O2 improperly during the society's ambitious program to build a single-stage-to-orbit rocket.
But other rocket fuels such as liquid oxygen are far more hazardous, which may explain why Mueller's take on peroxide is so sanguine. "I used to deal with it at NASA, and we never had an accident. If you see someone smoking a cigarette at a gas station, that is much more dangerous," he says. Mueller retains faith in Firebird, even though he lost his connection with the project. He believes that the helicopter could be sold in the United States as a $30,000 kit, because the Federal Aviation Administration allows experimental licenses for home-built aircraft. Then farmers could use it to search for cattle, gas companies could use it to inspect pipelines, and anyone could fly it as a high-tech, extra-maneuverable ultralight aircraft.
That prospect makes Nalborough nervous. Fearing liability issues if inexperienced users cause accidents, he has been more interested in selling assembled units to aviation professionals. But he would need certification from the British Civil Aviation Authority to do so in England. When Intora filed an application, Nalborough claims the CAA promised limited permission within a matter of weeks and complete approval within six months. "We did everything they told us to do, and then— silence. After more than a year, they sent a letter saying it would cost 150,000 pounds [about $225,000] to get certification and 18 to 36 months for approval," he says. He suspects British aviation bureaucrats didn't relish the prospect of writing an entirely new set of regulations for a powered-flight aircraft without an engine. For now, it's back to the military markets.
In a videotaped demonstration, the helicopter took off from a trailer behind a pickup truck, flew under a low bridge, then landed back on the trailer with a precision that no conventional helicopter could match. The government of Dubai was impressed by a 1999 test flight and expressed interest in ordering a fleet of the helicopters as soon as the design is perfected.
For the rest of us, the big question is whether Firebird could become the personal flying machine predicted in countless 1950s popular-science magazines. One reason for optimism is that some of the key patents are about to run out. When that happens, the design will be up for grabs, and someone less cautious than Nalborough might develop a version for private use. It's a long shot, but one of these days you may yet see a skeletal flying machine cavorting around the rural skies, leaving a trail of steam drifting in the clean country air.
Intora's Web site (www.intora-firebird.com) contains lots of photos and information about the hydrogen peroxide helicopter. For a discussion of the use of hydrogen peroxide as a fuel, visit the Hydrogen Peroxide Workshop (www.ee.surrey.ac.uk/SSC/H2O2CONF).