Analysis of the Human Bird Wings | Hacker News Reader

Analysis of the Human Bird Wings

wired.com

27 pointsmhb27 comments

I had to follow back to the submitted article's author's earlier blog posts, a couple of degrees of linking back, to figure out where the "log-plot of the wingspan vs. mass for different birds along with the human with wings" came from. It came from the author himself, without a validation study, and "anyone can edit" Wikipedia. People who know their history of physics well will remember that Galileo showed that in general, as an animal's size scales up, its mass increases with the cube (third power) of the scale factor while its surface area increases only with the square (second power) of the scale factor.

http://dinosaurtheory.com/scaling.html

http://galileo.phys.virginia.edu/classes/609.ral5q.fall04/Le...

To scale up flight by arm motion to the mass of a human adult would have to result in a very different wing loading from that of any bird. There is a lot of hand-waving about electric motor power (at what weight?) for the wings in the video being discussed here on HN, but no verifiable figures about what energy is input into the wings versus what weight the total assemblage has.

As astute comments pointed out in the earlier main thread about the video, it would be easy enough to verify this extraordinary claim just by letting some professional journalists take a look at the rig and weigh it and photograph it up close and do their own videography of a set of flights of the rig and its operator. There is no reason to take an amateur, self-produced video with unverified claims seriously about an issue that is so contrary to well studied principles of aeronautics. Until there is better quality evidence, there is no warrant for believing this extraordinary claim.

The electric motors--if using the heavy-duty outrunners mentioned in the last thread--are on the order of 2-4 kg each, for a total of about 10 lbs. The weight of the fabric/kite is on the order of 1kg (http://www.humanbirdwings.net/about/working-on-the-wings/).

The batteries appear to be lightweight li-poly packs, so really powerful for very light weight.

Ignoring impossible feats of physics, the video is fake. There is a comment on the first Wired article which points out incontrovertible evidence of poorly done compositing around the 20 second mark with the guy on the left running "through" the wingtip without bumping it.

Uncut, raw video from the side of complete take-off and landing (since there is supposedly someone taking video from the side) would be enough to prove its real. Too bad this isn't real.

That 20 second mark is pretty damning - the shadow cast on the wing by the guy on the left is visible before his body is in front of the wing.

Thanks for crushing my dreams.

There's a few frames around 20 second mark that look strange - here's one where the guy seems ready to run through the left tip, his left thigh is behind the wing, and his left foot seems to be in front: http://imgur.com/riyjn

Next frame he appears in front of the wing entirely. I don't know - does post processing software do weird things that cause visual artifacts?

My pleasure. I worked on the visual effects team for a movie with a _lot_ of compositing. This is cut-rate stuff. Can you imagine what sort of things we will believe if someone were doing this sort of fakery with a real budget?

Exactly - I read the Wired article yesterday and didn't even think to second-guess it even though in general I'm something of a skeptic. I just marveled at how clever and technologically advanced humans have become.

Ironically, this is a demonstration of how clever and technologically advanced we are, but not in the way I originally thought!

There is nothing strange going on around the 20 second mark. The sun is very low and the wing is almost aligned to the position of the sun. You can also see the left tip is bended upwards, so the guy is clearly running around that tip. But because the lens is zoomed in it's a little hard to see the actual depth.

His "shadow" (CG, no doubt) is on the front of the wing, while he is still "behind" the wing.

http://imgur.com/NqgTL

His take off speed and the angle of attack for his wings looks suspect. As much as I want this to be real it looks like he is in a stall the moment his feet lift off the ground. I am looking at this from a traditional fixed wing aircraft view though so my views could be flawed.

"Either this part of the video was made with a real hand held camera, or they have found better ways to 'fake shake' the video."

Good fake camera shake isn't too hard. After you take your tripod shots to add CGI to, also take some actual shaky footage of the same scene, or of anything else about the same distance away. Then motion-track the shake from your shaky footage and apply the same motion to your CGI shot. High-fives all around.

In conclusion: unrealistic camera shake would tell you something, but realistic camera shake doesn't tell you anything. It's like, "yep, these look like real people rather than cartoon characters, so this definitely wasn't faked using old Simpsons episodes ..."

All of this discussion is a complete waste of time. The burdon is on the publishers of this video to demonstrate these wings in front of a live audience of reputable journalists and engineers. Until then, can we move on?

Wouldn't you FIRST test the ability to glide back down before you add motor and power to get in the air?

The lack of any video gliding down from a building etc. immediately made this extremely suspect for me.

Then the fact I use an electric bicycle with a 48volt 1kwh battery for long distances. It's lithium but it's still big and EXTREMELY heavy. So is the motor. And those wings would need even more battery and more powerful motors.

What's up with all the people trying to discuss the physics involved? The video is blatantly fake, for other reasons entirely: the obvious viral factor, shady YouTube channel, bad acting, fake camera movement, etc. This thing is probably a Red Bull viral, inspired by that other "walking on water" viral.

A lot of people don't realize that there are motors on his backpack that power the wings. The movement of the arms guides the brushless motors using components seen in the Wii controller and only marginally assist the power sent to the wings.

That, and the perspective as he runs on the "takeoff" is completely out of whack.

Previous night's discussion with something more than just "I can tell from some of the pixels."

http://news.ycombinator.com/item?id=3732385

It may be fake, but it isn't impossible.

Absolutely fake. If this is not obvious to you, learn more physics.

you can tell by the pixels right? if its so obvious you would be able to explain your problems with the video in a succinct manner

Flapping wings do not simply vibrate vertically. Wings are hinged so they can greatly reduce the amount of air they push back up on the up stroke and to generate significant amounts of lift it takes a really dramatic motion. You can see how bad the motion is by compare flapping motion 35 seconds in vs an actual bird.

Also, trying to generate the type of energy required for flight with your arms is significantly harder than your legs.

It looks as if the author -did- look at the event with a fairly in-depth analysis, and the results were plausible yet inconclusive.

His results seem to suggest that the video wasn't CGI'ed, correct?

Well, no. They suggest that the camera shake wasn't added in after the fact with postprocessing of an existing image -- or at least that the image was fairly high-res and blur was also added after the fact. He doesn't rule out that the whole video wasn't computer-generated, nor that the dude was running into a greenscreen, nor for that matter a green cable that was digitally altered out, or anything like that. Some of these would venture into "faked" as opposed to CGI -- a cable which did not need to be shopped out might be an example, although whether you could have a nice construction crane nearby to operate it would be a worthwhile question, since the video doesn't give it much place to hide and the larger it is the more dangerous it would be to hang someone off of it and then move it from point A to point B.

There is a very real possibility that the wing was pulled by a cable. The kite adapted is actually one of those ones you usually pull behind a boat and which glides you up into the air.

That's also something I haven't considered. Whether or not this was really done, if you wanted to create the same effect by faking it, you could do it at least in part by doing two different "takes" -- one where you pull the guy from the front and view with a camera behind him, and another where you pull the guy up from behind and view with the camera on his head. There is a blurry whitish splotch when he first gets air which could be a tree in the distance, but if you wanted to fake it, that could be a way to disguise the cable.

This would give a plausible way to fake the first and the last scenes, where you see the man from behind, as well as the "in the air" scenes where you just see from his perspective: you could in principle put him in a boom lift vehicle -- perhaps suspended from it or perhaps even just sitting in it -- and the image would look very similar.

The side-view shot would be much more difficult to fake.

Why don't you bless us with your obviously superior grasp of the laws of nature?

If it's so obvious, the math justifying your position should comfortably fit in an HN post.

Why are there no birds even close to the weight of adult human males? Why do birds have a huge keel-like breastbone on which equally huge and powerful flight muscles attach? If energy required to take of scales geometrically with weight, how much force would an adult human need to generate to take flight and which muscles, attached where on the human skeleton, would be used for this?

Reply on news.ycombinator.com