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I have a character that achieves an ability similar to scattering and reforming or elemental swarming by controlling millimetre sized surveillance drones to morph into different shapes or disperse back into a swarm.

The drones will use a flapping winged method to fly similar to insects.

Is there any way I can make them silent or quieter? As I would prefer the swarm to seem more like magic or a super power rather than having a loud buzz when they are together.

The Square-Cube Law
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    The better you optimize your swarm to be silent, the lighter each drone will be. This means each drone will have as little functionality as possible, which begs the question: What exactly will the swarm do, besides looking cool? – justthisonequestion Jan 29 '20 at 07:32
  • @justthisonequestion their main function will be for surveillance, so they will be equipped with sensors, cameras and communication. one aspect will be to look cool as you say and others I haven't designed yet will interlock to form functioning structures like tools and weapons. –  Jan 29 '20 at 10:52
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    'interlock to form tools and weapons' sounds like a pretty ugly business. I don't think there's a good way to describe such a technology in detail. If you want hard sci-fi, rather search the beauty of your drones in simplicity. Have one task, like stealthy surveillance of a small area, and design a drone that absolutely nails it. If there's a new task, design a new drone. - I'm sure there will be a solution that suits you. Good luck. – justthisonequestion Jan 29 '20 at 11:28
  • @justthisonequestion Thanks, that's a good idea, ill think more about task specific drones. –  Jan 29 '20 at 12:28
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    Tiny flies only make tiny vibrations and tiny noises. As long as they're flapping out of sync with each other, your noise considerations are minor. – Separatrix Jan 29 '20 at 14:14

3 Answers3

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Your little drones are 2 rotors, spinning in opposite directions.

The net spin of the two rotors cancels out. The rotors are not flush against each other and can tilt slightly allowing directional control.

Lift is controlled by the angle of the blades within each rotor.

The spin is very fast, very quiet and constant. They never stop spinning.

image added

Willk
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    Drones like that already exist, and they tend to not be somewhat loud. – cowlinator Jan 29 '20 at 02:57
  • @cowlinator Really? And here I thought I had invented them. Link image? – Willk Jan 29 '20 at 03:22
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    Your sarcasm doesn't help. The point is that bicopter drones aren't quiet. – cowlinator Jan 29 '20 at 03:27
  • @cowlinator. No sarcasm intended, at all. I really thought it was a new idea! I would love to see one. Please, a link? Googling bicopter drones just shows me the tandem rotor type drones I have seen before. – Willk Jan 29 '20 at 13:40
  • Coaxial rotors, it's one of the helicopter options with the advantage of not needing a tail rotor, but no quieter. – Separatrix Jan 29 '20 at 14:12
  • Thanks @Separatrix! Coaxial rotors is what I was thinking of, but all rotor: it would look like a quarter stacked on a dime stacked on a quarter. – Willk Jan 29 '20 at 14:29
  • Like the T180-5 coaxial uav? Though I didn't check its size, the T180-120 seems quite large. – Separatrix Jan 29 '20 at 15:00
  • @Separatrix - yes more like the T180-5. But instead of bare rotors I envisioned a circular frame that would stabilize the 2 rotors relative to one another. Maybe that would just be wasted weight, though. Image added. It can be called the Ezekiel. – Willk Jan 29 '20 at 15:36
  • It's wasted weight, and you get into the complications of ducted fans where the lift falls off massively outside ground effect, open rotors are by far the better option. – Separatrix Jan 29 '20 at 15:40
  • I apologize, I misunderstood. Thanks for adding the diagram. – cowlinator Jan 29 '20 at 23:01
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Electrostatic propulsion drone.

https://www.theguardian.com/science/2018/nov/21/first-ever-plane-with-no-moving-parts-takes-flight

The first ever “solid state” plane, with no moving parts in its propulsion system, has successfully flown for a distance of 60 metres, proving that heavier-than-air flight is possible without jets or propellers. The flight represents a breakthrough in “ionic wind” technology, which uses a powerful electric field to generate charged nitrogen ions, which are then expelled from the back of the aircraft, generating thrust.

Like the described planes, these tiny drones generate charge across their bodies, producing thrust by the whisper silent ionic wind. If one is near you, and you are quiet, you might just barely hear the whisper. It is whispering "cowlinator…. An upvote if you please...."

Willk
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The frequency of sound from flapping wings depends on their size. Think of the flapping of a pigeon versus the buzz of a bee and the even higher whine of the mosquito.

Make your drones small enough, and the sound will be too high-pitched for human ears.

Or, if you want a wild-science twist, arrange them so the sound waves from each drone are cancelled out by the sound from its neighbor, in a mobile version of noise-canceling headphones.

Here are other ways of reducing drone noise but those should do :)

David Hambling
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