Wednesday, September 22, 2010

Human powered flight and energy harvesting kites

A strange confluence of events and circumstances has given me some ideas about human powered flight. I watched a snail slithering...just kidding. While vacationing in Florida I watched a guy parasurfing. That night I went home and went to sleep. The next morning was a Sunday so Comedy Central was playing a rerun of the Colbert Report's Friday night show. I had watched some of the show Friday but had not seen the interview with Saul Griffith. Saul Griffith is a genius who is working on wind power generation using high altitude kites to capture the high winds available above 2000 feet. When we got home from Florida I looked up Saul and found a website where he was explaining how the kites work with the aid of a large screen audio-visual presentation.

Last night I woke up thinking about human powered flight which is not uncommon for me but I realized that the actual terminology "human powered" is a limitation that need not exist. The small sail that was used by the parasurfer to skim over the waves at high speed and the piano sized kites used by Saul's power generation facility both had far more pulling power than was being used. Then I began thinking that a tandem device, one part prosthesis, one part kite, could give human beings the power to fly. Rather it could allow us to harness the wind long enough to elevate the flyer to the height necessary to then glide (predominantly) to his destination.

I attempted to use a sheet as a sail on my ripstick once and ran into all the problems of wind power at ground level: insufficient strength, sensitivity to direction of wind, etc. Parasurfing improves upon windsurfing by removing the power source to the sky above the surfer giving him much more maneuverability relative to the wind. The next logical step, in my mind, is to allow the parasail to drag a winged human, instead of a surfing human.

I had been trying to conceptualize a bicycle paired with a retractable set of wings as a means to allow the wings to reach the necessary speed for lift before opening them and taking off. In this concept the bicycle would simply fall away as the flyer opened a hang glider like set of folding wings and began to gain altitude. The problem with this approach is twofold. The first issue is that the speed necessary to generate sufficient lift of a human is too high to be achieved under normal bicycling conditions. Secondly once the rider/flyer leaves the bicycle the power source evaporates and thus the lift disappears. A kitesail on the other hand continues to provide power after the flyer takes off. The power is translated by the wings into lift and the flyer (or his software) may simply determine the altitude needed.

The next question then is how to disempower?unempower? the kitesail without simply cutting it loose. I had this same question watching the parasurfer, wondering how he would stop when he was done. What I had not anticipated was that he could change directions, having assumed that he must simply follow the direction of the wind and then let go. I watched as he approached the pier and then performed a tacking like maneuver and reversed direction back toward the area of the shore from which he came.

In flight the ideal scenario would be retrieval of the parachute once gliding began so that it could be redeployed to gain more altitude or used in an emergency as a parachute. High strength, lightweight cabling with a retractor could be used to reel the kitesail and the flyer toward one another but the only way I can conceptualize the kitesail collapsing is by releasing one side of it and then rolling up the fabric. This may prove a cumbersome load for a human/wind powered flyer to carry and then redeploy.

An alternative method could be to release one side of the kite sail and retract it and then lower it toward the ground so that it could be dropped for later recovery. An airborne-deployable parachute/kitesail could be worn on the body for use in an emergency.

The first step to researching these possibilities is to go parasurfing.

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