The $ 250,000 Sikorsky Prize for human-powered flight has finally been won. A Canadian team, AeroVelo, built a helicopter that was pedaled to an indoor altitude of a little over 3 meters and remained aloft for 65 seconds. While it is an incredible sight to see a human suspended in mid-air by the power of sheer ingenuity and grunt, hopefully this feat will draw to a close this fantastic, but unfortunately dead-end avenue of human-powered flight.
That is not to say we don’t have a future in human-powered flight (HPF). Regrettably though, if HPF can hardly be controlled when inside, we are either going to need to start building bigger buildings, or get a new design strategy. Early this year we laid out, from an engineering perspective, why turning props, and even more distastefully, turning pedals might not be the best way for a human to power an aircraft. There are more creative and effective ways to extract power from the human frame on the input side, and couple it to the craft and ultimately the air on the output side.
I welcome criticism here but want to first point out that improvements to the AeroVelo design will not readily permit open-ended performance increases, nor will they even asymptotically approach some theoretical limit to flight time. In fact, this particular design appears to be able to fly no longer than the time it takes to unwind the spools that couple the pedal power to the props.
That’s not to say potential work-arounds to this don’t exist, but with such a large footprint, most other easily conceivable options are probably off limits. A chain, for example, would be obviously prohibitive, but even belts would add frame stress, contribute significant amounts of friction, fail without sufficient tension, and need additional geometric consideration.
Basically, this rather crafty lawnmower pullstart coupling used by AeroVelo, is highly effective at getting you $ 250,000 cash, but not for sustained flight.
The AeroVelo Atlas – a popular name these days – uses a four-rotor system, with each blade spanning 67 feet. The carbon tube frame weighs just 115 pounds. Those are some pretty impressive specs. Discussions from engineering enthusiasts on the internet are still trying to nail down the horsepower issue here, and they appear to be coming to some kind consensus if only by sheer number of stochastic guesses. The take away is that the pilot/rider probably put out 1-2 horsepower for a few seconds in the beginning (while rising to altitude), then he likely sustained about one horsepower for the next minute. More important for such a light craft, is probably the horsepower-to-pilot weight ratio. Ground effect probably is not a significant player here.
It is relevant to mention here, that competing designs — like the University of Maryland’s Gamera — attempt to couple in power from the arms. Unfortunately, the incremental power input here is just not worth the extra overhead needed to access it with pedal-based power. Their design basically doubles the weight of the extraction apparatus and only gets marginal return.
The success of the Atlas is surely a milestone for mankind, although if you merely called it a triumph of the quadriceps, you may be forgiven. We might hope that the next Sikorsky prize is offered instead by Boeing or Lear.
Now read: The future of perpetual flight