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Google's Wing Drone

The question What operational aspects of Alphabet's Wing drone delivery service will be the same as that of an airline? includes a cropped photo of a google drone from FAA Certifies Google's Wing Drone Delivery Company To Operate As An Airline.

It is a winged aircraft with two long rows of vertical electric motors and propellors, and two more forward pointing motors for thrust, one on each wing.

The nose of the spacecraft is large and hemispherical and appears to be covered in small hemispherical dimples.

Question: Why the dimples?

Images below have been cropped, zoomed and substantially sharpened to enhance the visibility of the dimples.

Google's Wing Drone

Customers who took part in Wing's drone delivery test program in Virginia approach their package after it was dropped on their lawn. Credit: Wing Source

Google's Wing Drone

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  • $\begingroup$ I've included the commercial-aviation tag because the craft is for commerce and this answer explains that though the company is not an airline, it is still considered a "air carrier". $\endgroup$ – uhoh Mar 7 '20 at 3:21
  • $\begingroup$ The easiest way to reduce speed especially for these which take photographs.. reducing the RPM might not help in all situations but drag does. $\endgroup$ – user46196 Mar 7 '20 at 8:59
  • $\begingroup$ Like a giant golf ball ? $\endgroup$ – blacksmith37 Mar 7 '20 at 16:17
  • $\begingroup$ @blacksmith37 it's hard to be sure from this photo, but it looks to me that these are probably "outies" rather than the "innies" found on golf balls, but I'm not sure how much of a difference that makes. $\endgroup$ – uhoh Mar 7 '20 at 21:00
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These are not actually dimples but shallow bulges. I found a higher-res image online and checked it out. You have to expand the image to full-size and look closely; the angle of sunlight and shadow gives them away: enter image description here Similarly, this side view shows that the bumps continue down the side: Side view

The drone is not very large, less than 2 m (6 ft) long. They are not large enough to have significant aerodynamic effect at the speeds the drone flies. Lots of much faster planes have rows of rivet heads which stand out more than these do. They are about the size, shape and spacing one might expect from internal fixings holding a light supporting framework together, maybe there are pop-rivets under there. Another possibility is anchor points for internal equipment or wiring.

To be honest I am disappointed. Dimples are used on golf balls to stabilise flight and have in the past been studied as a way to reduce drag on aircraft. I had hoped at first that work might have been brought back to life. Then again, some cetaceans (whales etc) do have knobbles on their fins, we think to control the boundary layer and reduce drag, but these are just too small and shallow and not organised in the expected way for that.

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  • $\begingroup$ I can't convince you that they are aerodynamic anti-dimples? :-) This certainly sounds like it's got a good chance of being the right answer, thanks! $\endgroup$ – uhoh Mar 8 '20 at 16:29
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    $\begingroup$ They are just too small and shallow for the scale of the aircraft. Some cetaceans (whales etc) do have knobbles (or "anti-dimples" as you call them), we think to control the boundary layer and reduce drag, but these are just too small and shallow. Moreover, lots of planes have rows of rivet heads which stand out more than these do. I just updated my answer accordingly. $\endgroup$ – Guy Inchbald Mar 8 '20 at 16:42
  • $\begingroup$ Excellent! I'm waiting for a picture of a real whale here in Aviation SE, so far I've only seen artificial ones (okay those aren't even artificial whales) $\endgroup$ – uhoh Mar 8 '20 at 17:00
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    $\begingroup$ The humpback whale is one. See for example commons.wikimedia.org/wiki/… I should note there are other theories as to what the knobbles are for. $\endgroup$ – Guy Inchbald Mar 8 '20 at 18:39
  • $\begingroup$ Since you found a higher-res image, would you be so kind as to edit your post to embed the image (if allowed by the hosts copyright terms) and include source info or at least include the link so others may see it. $\endgroup$ – FreeMan Mar 9 '20 at 15:27

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