Brook Sat Mar 30, 2013 8:39 am
Notes from a guy at NASA on these who puts it in his "gray box"
L a NASA expert thinks they may be UAV drones, but he is not sure. It's in his "gray box".
First of all, the objects appear to be flying aerodynamically--by which I mean they appear to have wings and they appear to be moving in such a manner as to keep air flowing over the wings in such a way as to generate lift. This is unlike what I would call "trufos" which usually don't have wings or any other obvious aerodynamic surface, do not necessarily move at a uniform speed, and in fact may hover. So, from that perspective, these objects do not necessarily display any unconventional physics.
Each object appears to be self-directed and capable of maneuvering--with precision-- relative to its neighbors. If the objects were birds, they seem to have a wing loading (weight divided by wing surface area) about like that of a Canadian goose. Geese can't really soar very well because their wing loading is too high. Also, geese don't normally fly around in circles, just for the fun of it. The metabolic cost of flight is actually pretty high, especially for high wing-loading; that's why geese are almost always seen either flying to escape a potential predator, flying to a feeding site, or migrating long distance. They only fly for essential purposes. When they fly in close formation, they invariably do so in echelon formation so that the trailing bird(s) experience much reduced aerodynamic drag.
These objects don't display any apparent means of propulsion. There are only one or two frames in which one object may have been seen flapping its wings. (I say may, because it is not clear whether the wings were actually flapping or whether I was seeing a recording artifact).
In the frame where the wings were 'flapping" (around 1 min, 23 sec) the object did not appear to accelerate relative to its neighbors, which certainly should have happened if it were truly flapping.
If these are conventional aerodynes, the objects must have some means propulsion that is not readily visible (like a ducted fan). As unlikely as it sounds, they look to me like Unpiloted Air Vehicles (drones) demonstrating swarm-like behavior. Why would someone be flying UAVs like this over Mexico City? Who would it be? I don't know what altitude they were flying at, but if they were in controlled airspace, it would probably be illegal to fly UAVs like this. They would have to have been launched from and recovered to somewhere nearby.
First, some definitions for the non-specialists. There is a difference between 'gliding' and 'soaring'. Any bird or airplane with functioning wings and tail feathers can glide. If you take it up to some altitude and release it, it falls, starts converting its altitude into speed, and eventually reaches a balance between forward speed and its rate of descent.
For common airplanes like the Cessna 172 that I used to fly, the pilot's handbook shows that it would fly horizontally about 1000 ft for every 100 ft that it drops. In other words it has about a 10 to 1 glide ratio.
Soaring occurs when the bird or airplane utilizes naturally occuring winds and/or updrafts to achieve lift at a rate faster than it would be dropping due to its glide ratio. Gliding means starting at a high altitude and moving to a lower one, soaring means starting at a low altitude and moving higher (or staying at the same altitude while flying horizontally).
As a practical matter, in order to be able to soar reliably (i.e., as though your life depended on it--which it does for soaring birds) you have to have a relatively high glide ratio. Modern high performance competition gliders have glide ratios greater than 40 or so.
The glide ratio is directly related to wing aspect ratio (ratio of length to width); the higher the aspect ratio, the higher the glide ratio.
For reference, the Cessna 172 has a wing aspect ratio around 8. The White Pelican has an apparent wing aspect ratio of about 10. high performance competition gliders have wing aspect ratios of about 30.
It's kind of hard to tell from the grainy video, but it looks to me like the 'UFOs' have wing aspect ratios of ≈ 10. (i.e., to me they look not too different from Cessna wings). If so, I would expect them to be able to glide but not to soar.
Another point: at the very beginning of the video, it appears that some of the objects perform a formation aerobatic maneuver (i.e., a 'wingover' or, what would be an aileron roll, for an airplane). This is the kind of thing you see the Blue Angels doing. I can't decide if that interpretation is real, or if I'm seeing some kind of trick of perspective. If it is real, then that eliminates birds as a possibility."
