Since the hindsight is still 20/20, and now thankfully we have the hindsight of 2020, it’s time to celebrate. In particular, to celebrate a commercially irrelevant but wonderful technology that could allow humans to fly through the air on our own, like birds. It is the stuff of dreams.
One of the rare virtues of the movie “Wonder Woman 1984” that I saw recently is that it shows a woman flying through the air like a bird or a plane, just like 50 years ago we saw Superman fly. in the air. Last month I saw dozens of real human beings flying many stories through the air, lifted off their surfboards by wind-powered kites. Incredible to see and, I imagine, incredible to experience. But the centuries-old dream of human flight is simpler: Can people fly in still air, using their own power?
Like a bird
The fact that birds are flying shows that we could too. We’re just heavier, so it’s harder, which is actually a very general rule. Insects can fly with wings even smaller than their tiny bodies, but large birds like albatrosses and condors need wings that are much larger than their bodies. Fortunately, this relationship is such a simple and universal concept – weight per unit area – that with a little physics we can calculate how much more difficult it can be for people to fly than condors. So maybe with smart materials and design we could bridge the gap. We could remake the story of Icarus, using carbon fiber instead of wax and feathers.
Let’s say a condor weighs around 15 kilograms and a human weighs 60, which is a good round ratio of 1: 4 by weight. The heavier is harder principle, called wing loading, is based on body surface area. He says it will be twice as difficult (square root of four) for us to fly, everything else being equal.
So, before we get into new things, let’s see what might actually stay the same. Condors and humans are both warm-blooded vertebrates, so it’s likely that human muscles can generate as much average power per weight as condor muscles. And given the aerodynamic elegance that nature has turned into the wings and feathers of soaring birds, it’s unlikely that we humans can do much better than they do at lift or propulsion. So the shape of the next Icarus will have aerodynamic efficiency at best as good as that of the birds. What could be improved by a factor of two?
Birds are made of meat, bones and feathers. Not Kevlar (stronger than sinew), carbon fiber (stiffer than bone) or plastic like Mylar (smoother and lighter than feathers). And they can’t inflate like a balloon the size of an airplane. So let’s imagine using our most sophisticated modern materials to build an ultralight mechanical “bird”. The size of an airplane, smooth and well inflated, containing an ultralight mesh woven entirely and seamlessly from carbon fiber. The rigidity of this wing would come mainly from the inflation of the plastic.
This would leave the carbon fiber mesh to accomplish four other purposes: to buckle in response to the wind, to prevent the kite from wrinkling when folded; stiffen the thin parts of the wing that pressurization cannot stiffen; “Flapping” and “tilting” the wings using human power; and carrying micro-vibrations from the wing surfaces into the pilot’s fingers and toes, which would then “feel” the airflow from the wings much like birds do, using nerves in skin and bones.
Designing and building such a complex and delicate airfoil would be costly and uneconomical. Obviously, he would only hold his form on calm days. But it could be built – and it would work. And when that mystical structure exists and is connected with just one strong person pulling and pushing, it will fly like a bird, not an airplane. This person will swim in the air.
We know something like this can work because a simpler, clunkier version was made decades ago, at a lower cost. In 1979, professional cyclist Bryan Allen pilot The most fragile and best-designed plane of all time, the Gossamer Albatross across the Channel, won the famous Kremer Prize, barely, on the first try.
He was sitting indoors on a bicycle frame, his legs pedaling on the propeller. The whole plane weighed half the weight of the pilot. It had been designed by aerodynamic genius Dr Paul MacCready and a dozen crack engineers, one of whom (Stanford professor and venture capitalist Dr Morton Grosser) wrote the book ” Gossamer Odyssey ”on the project. This plane was built like an ordinary plane, stretching the skin over fragile compressible struts. A little breeze could break it in half.
This single historical episode from four decades ago gives us a crucial data point. He gives an example of a structure that humans can barely fly for a while on their own. Presumably, every improvement to this structure would result in less pilot effort. Twice as effective would mean half the power of the pilot, which would mean normal strength athletes could pilot it. Below, I offer four technical innovations that together could provide this improvement in efficiency, so that humans can fly.
First, jump the propeller. The propellers rotate, which is convenient for engines and driveshafts. But spinning wastes energy because it moves a little air quickly, rather than a lot of air slowly, much like the throb does.
Then match the powertrain to the human. The drivetrain on a bicycle, from foot to shoe, pedal, chain and wheel, is a wonderful way to turn the wheels. But it’s not designed to extract the most consistent and stable power from a human body, evenly distributed across all muscles. Rowers do this best using the back and arms, but even they still don’t benefit from the original vertebrate power stroke – the spinal twist. Worse, when rowing, the rower has to clench his fists full time to grab the oars. Optimal whole-body strength would open and close the hands in concert with spinal extension and breathing.
Let the human feel the air flow. Birds can take advantage of updrafts as they can feel the wind whispering on their feathers. If there was a sensitive vibratory conduit from the skin of the wings to the human skin (or fingernail), like fine carbon fibers, our nervous systems could learn to fly by touch.
Finally, gain tension through pressure, not compression. The Condor Gossamer, MacCready’s first attempt at a human-powered airplane which won him his first Kramer Prize in 1977, was built like an old-fashioned airplane, with a thin film (plastic) stretched over the spars and ribs, which could break. The more the tension of the film can be supported by pressurized gas rather than compressed shafts, the lighter the structure and the less breakable.
I am a physicist, not a fundraiser. I can’t do the project, but I know there are many innovators who could. And I know I could barely be able to fly in my lifetime if I stayed strong and healthy. But someone else will have to take the lead. Any takers?
The opinions expressed in this article are those of the author and do not necessarily reflect the editorial policy of Fair Observer.