Nanoscale propulsion system that works in vacuum - or not?

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Discussion Overview

The discussion revolves around the feasibility of a nanoscale propulsion system that utilizes electrons to produce thrust in a vacuum environment, particularly in microgravity. Participants explore the theoretical underpinnings, potential mechanisms, and practical challenges associated with such a system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes a design involving a metallic torus within a dielectric structure, suggesting that electrons could be expelled using energetic photons to create thrust.
  • Another participant questions the source of the direct current needed for the system and raises concerns about the engine becoming positively charged, which would attract ejected electrons back.
  • A participant clarifies that the DC current could come from solar panels and describes how electrons could be continuously supplied to replace those ejected, although this raises further questions about the feasibility of such a supply.
  • Some participants acknowledge that while the electron-momentum concept is theoretically sound, it is currently unfeasible due to the lack of a mechanism to introduce new electrons into the system.
  • One participant introduces the idea of pair production from photon energies, speculating about the potential for metamaterials to create positron-electron pairs for propulsion purposes.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of the proposed propulsion system, with some agreeing that the concept is theoretically interesting but practically unfeasible due to the challenges of maintaining a fresh supply of electrons. There is no consensus on the viability of the proposed mechanisms or the potential for alternative solutions.

Contextual Notes

Participants note limitations regarding the assumptions about electron supply and the implications of charge dynamics in the proposed system. The discussion also touches on advanced concepts in quantum electrodynamics (QED) without resolving the complexities involved.

cremor
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Moved this question from the quantum physics section to this section, since... Well it fits this section better since electrons apparently do obey conservation of momentum in the 'classical' sense.

Why not produce thrust in microgravity with electrons? Plenty of harnessable electricity in space.

While I'm on it, I bet you're exponentially better at solid-state physics than I am, so I have no pressure of making a fool out of myself. ;)

http://imgur.com/i9jWmFE

Imagine the crudely presented structure in 3D (a metallic torus confined within a dielectric sarcofage, with holes left in it for electric current input + the photon-electron input-output/nozzle/whatever you want to call it. A direct current is fed onto the torus (which is confined within an electrostatically-repellent dielectric structure), while electrons are expelled off the inner rim of the torus with energetic-enough photons, giving them momentum in the direction of the movement vector of the photons.

Could this kind of nanoscale device be effective (mass to thrust ratio wise) at producing thrust - or is this an obvious fluke somehow?
 
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cremor said:
Moved this question from the quantum physics section to this section, since... Well it fits this section better since electrons apparently do obey conservation of momentum in the 'classical' sense.

Why not produce thrust in microgravity with electrons? Plenty of harnessable electricity in space.

While I'm on it, I bet you're exponentially better at solid-state physics than I am, so I have no pressure of making a fool out of myself. ;)

http://imgur.com/i9jWmFE

Imagine the crudely presented structure in 3D (a metallic torus confined within a dielectric sarcofage, with holes left in it for electric current input + the photon-electron input-output/nozzle/whatever you want to call it. A direct current is fed onto the torus (which is confined within an electrostatically-repellent dielectric structure), while electrons are expelled off the inner rim of the torus with energetic-enough photons, giving them momentum in the direction of the movement vector of the photons.

Could this kind of nanoscale device be effective (mass to thrust ratio wise) at producing thrust - or is this an obvious fluke somehow?
So far your post is not making sense to me. Where does this DC current come from? When you eject electrons, your engine becomes positively charged, and attracts the ejected electrons back. And what is the photon/electron interaction you are alluding to? The photoelectric effect?
 
berkeman said:
So far your post is not making sense to me. Where does this DC current come from? When you eject electrons, your engine becomes positively charged, and attracts the ejected electrons back. And what is the photon/electron interaction you are alluding to? The photoelectric effect?

DC current comes from example solar panels, and is conveyed to the torus with electrical conductors coming in through the dielectric from the sides of the torus (the outer 'rim', if you will). This should be conceivable from the sketch behind the link, the blue lines on the sides (these are electrical conductors), one of which is marked 'unidirectional flow of electrons' (so 2 dc inputs in the 2d picture, 1 from each side). Naturally, the torus would become positively charged, if there was no source that could provide a fresh supply of new electrons to replace the ejected ones.

Yes, basically photoelectric effect, although I'm not sure if it is semantically correct to use that very term in this scenario. You expel electrons with photons interacting with the electron plasma (this interaction takes place on the inner lumen of the torus, or the inside edge of the 'doughnut', if you will), providing a gradient of momentary positive charge, which is constantly neutralized with a fresh supply of electrons jumping from the DC conductors in the immediate vicinity of the outer rim of the torus. A small gap between the conductors and the torus should be ok for electrons to move over of, since there is an electrical gradient present due to the photon-electron interaction expelling electrons from the torus.

So, as clarification, the blue arrow-like shapes on the side (one dubbed unidirectional flow of electrons) bring the fresh electrons to the torus, and the ejected ones go in the direction of the green arrow (energetic photons).
 
cremor said:
DC current comes from example solar panels, and is conveyed to the torus with electrical conductors coming in through the dielectric from the sides of the torus (the outer 'rim', if you will). This should be conceivable from the sketch behind the link, the blue lines on the sides (these are electrical conductors), one of which is marked 'unidirectional flow of electrons' (so 2 dc inputs in the 2d picture, 1 from each side). Naturally, the torus would become positively charged, if there was no source that could provide a fresh supply of new electrons to replace the ejected ones.

Yes, basically photoelectric effect, although I'm not sure if it is semantically correct to use that very term in this scenario. You expel electrons with photons interacting with the electron plasma (this interaction takes place on the inner lumen of the torus, or the inside edge of the 'doughnut', if you will), providing a gradient of momentary positive charge, which is constantly neutralized with a fresh supply of electrons jumping from the DC conductors in the immediate vicinity of the outer rim of the torus. A small gap between the conductors and the torus should be ok for electrons to move over of, since there is an electrical gradient present due to the photon-electron interaction expelling electrons from the torus.

So, as clarification, the blue arrow-like shapes on the side (one dubbed unidirectional flow of electrons) bring the fresh electrons to the torus, and the ejected ones go in the direction of the green arrow (energetic photons).
I'm not understanding where this "fresh supply" of electrons comes from. A solar panel is a closed system -- you don't get a fresh supply of electrons from them...
 
berkeman said:
I'm not understanding where this "fresh supply" of electrons comes from. A solar panel is a closed system -- you don't get a fresh supply of electrons from them...

Point. An obvious fluke it is then, I was under the impression, that in a photovoltaic material the energy transfer results in excitons coupling into some kind of quantum spawning of an electron... Cursed facts!
 
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So basically, nothing wrong with the electron-momentum idea, except that it is perfectly unfeasible at the moment because of the obvious lack of new mass in form of electrons introduced to the system. Still, it's embedded in QED theory, that energy transform can occur via photon energies shifted into particles with rest mass (I'm referring to pair production). A little bit crazy, but are there any theories of for example metamaterials that would posess the ability to make positron-electron pairs at high rate, even perhaps being able to divert them from the inevitable annihilation process for other uses (non-canonical QED theory I suppose)?

http://www.nature.com/nphoton/journal/v8/n6/full/nphoton.2014.95.html the only thing I found.
 
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cremor said:
So basically, nothing wrong with the electron-momentum idea, except that it is perfectly unfeasible at the moment because of the obvious lack of new mass in form of electrons introduced to the system. Still, it's embedded in QED theory, that energy transform can occur via photon energies shifted into particles with rest mass (I'm referring to pair production). A little bit crazy, but are there any theories of for example metamaterials that would posess the ability to make positron-electron pairs at high rate, even perhaps being able to divert them from the inevitable annihilation process for other uses (non-canonical QED theory I suppose)?

http://www.nature.com/nphoton/journal/v8/n6/full/nphoton.2014.95.html the only thing I found.
Have you read about how Ion Thrusters work? https://en.wikipedia.org/wiki/Ion_thruster

:smile:
 
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Yes. I would assume that their level of optimization is more advanced than my (mis)conception. Heheh. I didn't bring them up because the need to have the physical propellant on board is obvious right off the bat.

By the way, there are concepts of solar 'sails', or charged wires spread out into space that would catch drag off cosmic particle jets. Any ideas around of using them in combination with an ion thruster? As in capture high-energy particles flowing in interstellar space and store them to be used more efficiently with an ion thruster. Are there for example a lot of free electrons, or some heavier particles in greater amounts flowing through the interstellar medium by any chance? Or does the ball bounce off the post again? ;)
 
cremor said:
Yes. I would assume that their level of optimization is more advanced than my (mis)conception. Heheh. I didn't bring them up because the need to have the physical propellant on board is obvious right off the bat.

By the way, there are concepts of solar 'sails', or charged wires spread out into space that would catch drag off cosmic particle jets. Any ideas around of using them in combination with an ion thruster? As in capture high-energy particles flowing in interstellar space and store them to be used more efficiently with an ion thruster. Are there for example a lot of free electrons, or some heavier particles in greater amounts flowing through the interstellar medium by any chance? Or does the ball bounce off the post again? ;)
The nearest (hypothetical) thing I can think of is a Bussard ramjet.
 

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