> I don't understand anything in aerodynamics Same here. > Why then a quadcopter is the default shape for smaller drones? Large fixed-wing planes are expensi

> I don't understand anything in aerodynamics Same here. > Why then a quadcopter is the default shape for smaller drones? Large fixed-wing planes are expensive. Piloting them requires jumping through many high-hanging and heavily regulated hoops. The most dangerous parts of the flight near the airports happen in well-known space, according to pre-defined paths known to all parties. In many places of the airspace, pilots are guided by data from the ground. Optical from visual approach slope indicator (these weird light arrays around airports which are visible as 0-4 red circles depending on whether you’re too high or too low). Radio from beacons. Most importantly humans, the job title is “air traffic controller”. For the scale of a conventional airplanes, accurate map data is available. GPS data+SRTM height map is accurate enough for most cases. Also, real-time weather data is pretty accurate at that scale. None of the above applies to small drones. They’re cheap, most are piloted by amateurs and no licensing is required. They can take off and land whenever. No ground control is available. At their scale, no offline map data is available, and ground-induced wind turbulence is borderline unpredictable. This might change in a few years. We might get chips smart enough to reliably do right things based on the limited input data despite the unpredictable factors. We might get sensors sensitive enough to generate much better data for these chips. E.g. if you have spatial data for 1x1x1km space around the drone, with 1mm spatial precision, and 20ms refresh rate consistent over the whole volume, today’s mobile chips will do mostly OK in good weather. We might get good enough sensors to cover all airspace with them, and make robotic equivalent of air traffic controllers, a software that detects future collisions and tells the drones to do something about it. Or broadcast current wind conditions at 1m^3 resolution. Least likely but still, we might get good enough actuators & power sources to combine these two. Birds do OK, many of them can hover, glide, and arbitrarily combine hovering with gliding. When you can stop flying and hover, or land almost everywhere, collision avoidance becomes way simpler. That’s one reason how birds and modern-day small drones are functional.