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As a non Aeronautics expert I ask if non-fueled (electric?) vehicles which are minimally-noisy only science fiction or a real theoretical scientific concept aimed for close or very far future development?

I ask if there is any theoretical science that tries to describe how such a thing would be possible in the future...

Characteristics of such a vehicle:

  • Some non-fueled thrusting; if electrical, than an enough powerful battery or enough powerful solar energy exploitation mechanism
  • Fireless
  • Bladlessness: No jet, no propellers/rotors or turbines
  • Wingless
  • Silent or almost silent: Not the regular noise. Something very very quiet - at least 75% of the noise will be air molecules rotating solely from the whole objects' motion, but not from the engine itself.

This flying object may or may not be able to fly both in earth's atmosphere and out of it.
Bob Lazar's flying saucers maybe?

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    $\begingroup$ The engines (motors) themselves are extremely quiet, it is all the thrust-producing parts you put on them that make the noise. I'm not sure I see a question in there though? Are you asking if they exist? Can exist? Possible in the future? $\endgroup$ – Ron Beyer Nov 8 '16 at 15:43
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    $\begingroup$ We already built super quiet observation aircraft, and using electrical power would actually remove the noisiest part of the plane. Seems plausible to me. $\endgroup$ – fooot Nov 8 '16 at 15:58
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    $\begingroup$ @TomMcW that's because it is far from being bladeless, the blades are simply hidden $\endgroup$ – Federico Nov 8 '16 at 17:10
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    $\begingroup$ You might want to ask this on Worldbuilding.SE as "How could noise be eliminated a futuristic propeller airplane?" $\endgroup$ – SMS von der Tann Nov 8 '16 at 17:19
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    $\begingroup$ @Federico That's why I put "bladeless" in quotes. Plus, what the heck is a "digital motor?" Motors can't be digital $\endgroup$ – TomMcW Nov 8 '16 at 17:43
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Electric propulsion using ion thrusters is already in use for space applications. Today's ion thrusters deliver very high specific impulse at low power (typically in the order of 10 to 1000 W). Lower or higher outputs are possible and subject of current research and development. Ion thrusters work great in the vacuum/free fall environment where low thrust over long durations is useful, and electric energy can be generated on the spot with solar panels.

The usage of ion thrusters in the atmosphere is possible, but there are major challenges:

  • planes require a lot of thrust during take-off
  • the propellant does not contain the energy to drive the thruster
  • the atmospheric pressure changes all the working paramters. Existing ion thrusters for space are not useful in the atmosphere.

Today, ion thrusters are not ready for aviation and it might never happen, but there is some research going in this direction. Personally I do not believe that ion thrusters are useful for low altitude, but I can well imagine a scramjet engine for high altitude using ion thrust technology. In any case, even an ion thruster without any moving parts cannot be silent when working in the atmosphere. The particles expelled at very high speed will create a lot of noise, similar to a welding torch.

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  • $\begingroup$ Thank you dearly, and so much, for this answer! As I am not a physicist, I ask myself if such a technology is not dangerous? I am really sorry if it sounds funny, but I know that the whole concept of Atom bombs is based on manipulating atoms... Making them so unstable that they would brake, so that an Blast wave would spread out... Is it dangerous in that sense? And can you please also comment or expand if any other bladeless technology besides Ion thrusters is considered possible today, or all other bladeless technologies are considered science fiction? Thanks again! $\endgroup$ – JohnDoea Nov 8 '16 at 21:01
  • $\begingroup$ Bladeless && electric... $\endgroup$ – JohnDoea Nov 8 '16 at 22:41
  • $\begingroup$ Any idea how much thrust could be expected? As you said, they are much better suited to space where they are pretty much the only force acting on a body. Fighting against gravity and aerodynamic forces on earth would be rough. Maybe they could work on some type of blimp? $\endgroup$ – fooot Nov 8 '16 at 22:42
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    $\begingroup$ I doubt that ion thrusters are going to be silent, or even particularly quiet. They're working in atmosphere, and ejecting mass out the back. That's going to create turbulence, which will create noise just as a jet (or rocket) engine does. In addition, you're ejecting charged particles, so you might have a continuous spark discharge along your exhaust plume. $\endgroup$ – jamesqf Nov 9 '16 at 5:35
  • $\begingroup$ @Benia Ion thrusters are not dangerous unless you come too close. They are not so different from a welding torch. $\endgroup$ – bogl Nov 9 '16 at 8:09
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The engine/motor/battery/power-supply is not your problem (as Ron mentions in the comments) its generally your propellers that are making all the noise. A well made brush-less DC motor makes nothing more than a quiet whine even at high RPM's. Generally any motor noise you hear in cheap consumer stuff is the result of less precise mass production tolerances and cheap materials etc. Any propeller is moving a lot of fluid (be it air or water or what ever your medium is) will see that fluid eventually come into contact with things and the energy can either be dissipated thermally to heat or mechanically to sound/vibration (often both). This is a simple matter of physics, while maybe we will solve it in the future there are a practical limit to this.

You may want to take a look here as well as the study here.

If you don't want to make any noise while you fly, fly a glider.

Now Jets are a bit of a different ball game (when compared to props). First off an all electric ducted fan may show some benefits over its un-ducted counterpart and even Airbus is working on project to explore it. Traditional turbo and high bypass jets have come way down in noise, but a great deal of that is our increased understanding of exhaust flow, how to shape the back of an engine and general manufacturing capabilities and understanding. However in the end of the day, a jet works by moving air which will simply make noise based on the very physics of how it works the only way to keep a jet perfectly quite is to turn it off...

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    $\begingroup$ Gliders are not all that silent either. They are quietest you can get, but not quiet. $\endgroup$ – Jan Hudec Nov 8 '16 at 19:39
  • $\begingroup$ Why won't they be "silent" if there is no fuel-driven engine (or even an electric engine)? Thank you. $\endgroup$ – JohnDoea Nov 12 '16 at 15:29
  • $\begingroup$ @JohnDoea, the rush of air over the hull makes a surprising amount of noise. Surprising to me, at least. - Skip Miller $\endgroup$ – Skip Miller Jun 17 at 15:27
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MIT has produces a small-scale RC plane that's powered by ionic thrusters. These are not the same as ion thrusters in space; instead the ions here are created from the surrounding air. The benefit is that the plane doesn't need to carry its propellant.

Since there are no fast-moving mechanical parts, this is very silent. I could even see this being used to silence gliders even further - strategically placed thrusters on the hull might keep the boundary layer stable and laminar.

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  • $\begingroup$ Hi, what's a "hull"? I ran a Google search and got pictures of old European cities... $\endgroup$ – JohnDoea Jun 18 at 5:42
  • $\begingroup$ @JohnDoea: Other word for fuselage. $\endgroup$ – MSalters Jun 18 at 6:59
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If we only need a cargo drone, we already have them - a postal pigeon would match all your requirements. Does not require a pilot, but the payload is rather limited.

If you need a pilot for your story, no existing bird could carry a typical human. However we can envision this happening, by joining the two extremes: a largest flying dinosaur (weighted about 250 kg) and some lightest humans (below 30 kg). Bald eagle can lift about the same weight as the own mass (here) but the large animal may not be able to do the same.

We already can grow synthetic hamburgers that are made from muscle cells. Maybe in some far future would be possible to add lightweight bones, feathers and stitch everything into the aircraft.

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