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Comment by leobg | Hacker News Reader

My immediate thought was: We could use those to power wings and fly!

You see, I spent the last weeks reading up on Otto Lilienthal. And while we might think that we have already "cracked" flying, we actually haven't. Humans still cannot fly. We can only board. What we do not have achieved is the sense of "flying like a bird", which Lilienthal was after. The idea that you control your movements through the air directly, not mediated through knobs and buttons, but by using your own body.

Motors that provide rotational power are not suited for wings. The are suited only to propellers. So that's where artificial muscles perhaps would be able to shine.

Also, I imagine that a bird needs to have fine-grained sense perception in its wings, to be able to compensate for subtle differences in air speed and pressure. And it seems that this is something these researchers are doing as well, with those sensors embedded in the fabric.

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There have been massive struggles taken on by individuals and small teams to create ornithopters that can carry people. A solely human powered ornithopter was able to stay airborne for 19 seconds - using a mediatory lever to transfer push/pull leg power into wing motions.

https://www.youtube.com/watch?v=DM9GJ3JOJv0

Then there is, of course, the story of the skycycle, which is rotational.

https://www.nytimes.com/1979/06/13/archives/american-pilot-p...

Both of these machines should be comparable, I think, to rowing versus the ideal of Lillienthal, which is like swimming.

Cool video. I wish they would have used an electric car for the camera man. As it is, the car's engine noise tremendously distracts from the grace of the ornithopter.

To fly like a bird, you probably need more motion control over the wings than just "up and down". I believe birds can angle their wings, they can curve them, and they can sense differences in air speed and air pressure across the wing's surface. That's why it seems to me that any form of artificial muscle would be a huge step.

The video was taken about 10 years ago, I doubt an electric vehicle would have been a viable option. As it is today, one that can go that fast is pretty expensive right? It's a massive weakness to the 'thopter that it can't do an independent take off and landing.

Yes, I think you're right. The pilot for the skycycle was blown like a kilometer off course by a strong gust of wind and almost wanted to give up. If he'd had the level of control you talk about, he'd probably have been able to keep going the direction he wanted to in spite of the wind.

I’m sorry, I hadn’t seen that the video was 10 years old. Totally valid point. As of today, renting a Tesla for a day or two is easy and doesn’t cost that much either. The bigger problem is that you’ll want to own one afterwards, and feel silly in any other car.

The problem of “flying” in the sense you describe is fundamentally limited by the square cube law. Even birds, whose anatomies are literally evolved for flight, will have a tough time staying in the air if they are scaled up to have a similar mass to us humans.

Wikipedia says a Pteranodon[0] might have weighed up to 200kg. I wonder if the different mix of gases in the atmosphere during the Cretaceous period made any difference to how much weight could be supported while flying.

0: https://en.m.wikipedia.org/wiki/Pteranodon

In the sense that more oxygen was available to muscles, maybe. In any buoyancy or aerodynamics sense, the effect would be miniscule at best.

Annoyingly, the wikipedia article was wrong, and mistakenly gave the figures for Quetzalcoatlus in that paragraph. Pteranodon weighed more like 20-30kg (I've edited it).

The constraint on the size of flying animals is launch, not flight. Pterosaurs could get bigger than birds because they used quadrupedal launch, meaning they could use their flight muscles during the initial leap.

I never cease to be amazed how damn _big_ dinosaurs were. The size comparison on the page for Quetzalcoatlus is seriously mind boggling - the thing was almost the size of a small plane!

There were pterosaurs much larger than humans.

While there were pterosaurs as large as a giraffe (having similar proportions when on ground), they were very light for their size, probably no more than 2 to 4 times heavier than a human.

Lilienthal himself didn't, as far as I know, address your precise argument (the water strider bug scaling issue). But your comment reminded me of this snippet from his 1889 book:

  The bodies of flying creatures are not so materially lighter than those of other animals, as to justify us in considering this difference in weight an essential condition of flight. It is often asserted that the hollow bones of birds facilitate their flight, especially since the hollows are filled with heated air, but it does not require much thought to come to the conclusion that this diminution of weight is barely worth mentioning. Also, we have not been able as yet to prove that the muscle and bone substance, as well as other parts of the bird's body, are specifically light. [...] After a bird is plucked, no one will assert that it is propor tionally lighter than other animals, and our housewives are certainly not under the impression that a pound of bird's flesh, even with the hollow bone included, is more bulky than an equal weight of flesh from another animal. [0]

[0] Otto Lilienthal, Birdflight As the Basis of Aviation, pages 2-3, https://s3-eu-west-1.amazonaws.com/bga-sg-archive/Books/BIRD...

Some birds and several pterosaurs got to human masses and more. Staying in the air is not much of a problem, but launching is. Pterosaurs have a massive advantage here in that they launched with all four limbs, meaning they could use their flight muscles to launch. Birds can't do this and have to rely on their legs (which are useless in the air).

The obvious step would be not try to fly, would be improving hang gliders to be safer, catch better the wind currents or avoid obstacles proactively and have more autonomy. If the device suddenly fails, you still are in a hand glider.

Also engineering a motor that would flap like a colibri for hours without failing will be really hard and uncomfortable by the generated heat burning your back, but a motor that would flap here and there like a vulture for one or two minutes and then rest again would be much more easy to design and maintain. Would need also less weight of combustible.

Flapping like a colibri would, I suppose, also be rather loud and create noise. What fascinated Lilienthal was the way large birds like storks fly: They do flap their wings to take off, and also when there are no thermals. But most of the time, they glide or use thermals to gain altitude.

I do have to say, whenever I see a stork above, or even just a red kite or pelican, I feel envious. Our drones and planes just seem crude in comparison.

To be clear: I'm not talking about flight as a means to get from A to B as quickly as possible. That's the domain of the jet engine, and no bird can match it. I'm talking about flying as a thing you do for the enjoyment of it, as a thing of beauty and wonder. In short, that which inspired humans to dream about flying machines in the first place.

Hang gliders are probably too fast to ever be safe (70kmh average), require big turns, take forever to fold and unfold, are big and heavy, but paragliders are fantastic in this regard (more like 40kmh for non-speed flying). Position is different (comfy chair with feet up vs laying on stomach), but once you fly you don't think about it.

Basically the only thing missing is the functionality for paraglide to become rigid structure on demand and they will be bombproof. There is some initial progress in this regard but its a long way from reality. Endgame would be probably some electrically-induced rigidity via some easy-to-manage remote. Or some smart behavior in between based on whats happening, that would allow easily things not considered possible currently.

Although technically it is gliding, but to me wingsuits look close enough to flying that adding the mechanism for flapping doesn't really increase the experience of flying by much. (Spoken from a point of view of a spectator and not someone who has done some form of flight besides in airliners.)

We can't fly by flapping wings like birds but we can certainly glide like raptor birds by para- or hand-gliding

Very true. But imagine you could strap on such the wings of a glider along with artificial muscles that map to, say, your arms and hands. You could take off and fly and land like a bird. No need for a cliff or runway or anything. You'd also be as silent as an eagle circling above the tree tops.

would be nice indeed !

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