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So I came across these devices called lifters.

  1. Jul 8, 2007 #1
    So I came across these devices called lifters. Basically, when a huge voltage is applied between an uninsulated wire and a a cathode (tin foil, in these lifters), thrust is generated and the device flies.

    The idea is that the air becomes ionised at the anode and these ions accelerate towards the cathode. They push the anode away from them, which results in an upwards force.

    The net upwards force is greater than the downward force because the ions smash into neutral air molecules while moving to the cathode, so their total momentum after colliding is less (the neutral air molecules have some of this momentum, and do not collide with cathode), and so less of a force is applied downwards. Thus, a net upwards force results, and lift occurs.


    This device, therefore, should not fly in a vacuum. However, I have heard conflicting reports.

    I have heard that some experiments have shown a that they do work in vacuums, while others have not. I will post sources when I find them again.

    Has any body any ideas on this? (If this is in the wrong forum, move it lease, I do not mind!)
     
  2. jcsd
  3. Jul 8, 2007 #2

    NoTime

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    The cathode attracts the ionized air molecules.
    You need a mesh (screen) not a sheet of foil, otherwise the impact will cancel any acceleration.

    They will not work in a good vacuum, but may work in a poor vacuum.
    It's hard to get a good vacuum.

    Also, no one has yet built one that can carry the weight of the required power supply.
     
  4. Jul 8, 2007 #3

    wolram

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    Last edited by a moderator: Sep 25, 2014
  5. Jul 8, 2007 #4
    I've done a different experiment to it in that I sealed the lifter inside a plastic bag. It allows ionized air to circulate but to measure thrust, I have to put the lifter and the bag as one in a weighing scale. No weigh reduction is observed which means that lifter produce thrust by moving air molecules down.

    I could say, that in a perfect vacuum, void of anything including subatomic particles, there's more likelihood, it will not produce thrust.

    Its' also nearly impossible to have lifters lift itself off the ground with a conventional (heavy) HV power supply.

    Since lifters could only operate with the presence of fluidic medium, it's a lot more convenient and practical to just use propellers for propulsion even if energy source is electricity. Also, the production of ozone makes lifters not a clean form of propulsion.

    With a different design, I finally was able to produce reactionless thrust. But it strictly won't be discussed here.
     
    Last edited: Jul 8, 2007
  6. Jul 9, 2007 #5
    So the bottom line is, the thrust is derived from an inbalance in upward and downward vector forces?
    So I guess all the hearsay about them being able to work in a complete vacuum because of some other unknown mechanism is rubbish!
     
  7. Jul 11, 2007 #6
    Thrust is derived by pushing air down by ionization, classic Newton's third law of motion. So yes, at least in a classic lifter design, anything you hear that it works in vacuum, it's an antigravity, etc. is rubbish.

    Lifters are no antigravity, it's simply an atmospheric ion/jet propulsion engine, nothing more. It's good to note though that the volumetric efficiency in terms of thrust produced improves with speed like some sort of ramjet engine, but you'll need to have the electrode gap adjustable to take advantage of the effect.
     
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