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Preparing a 0g test for space drive that apparently conflicts with law conservation

  1. Dec 16, 2008 #1
    Preparing a 0g test for “space drive” that apparently conflicts with law conservation

    Plans of testing a working model in a 0g environment are being considered for the first semester of 2009 (Zero Gravity Flights) we hope to demonstrate we have a practical working idea.
    I would be grateful if members of this forum were to check out the idea at http://www.wjetech.50webs.com/ we know it works (97% sure)
    Opinions will be welcome
     
  2. jcsd
  3. Dec 16, 2008 #2

    Doc Al

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    Not to worry--conservation of momentum is safe and sound.

    Try your "test" on a frictionless surface. Apparently you've never scooted your office chair across the floor without using your feet.
     
  4. Dec 16, 2008 #3
    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    This is a reincarnation of the "sealed truck gets lighter when pigeons take flight"-hypothesis. Which have been proven false I might add

    A crystal-clear violation of Newtons third law - not gonna happen :)
     
  5. Dec 16, 2008 #4

    LURCH

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    First of all, I wish to commend you on a fairly creative idea presented with great professionalism. It is quite refreshing to see a new concept presented clearly and precisely. However, I'm afraid Troels is correct.

    To elaborate:

    Although it is true that a turbulent fluid is less efficient at transferring momentum than a steel ball, this fact is true in both directions. So, compared to a steel ball, or a fan that generates a laminar flow, a fan generating a turbulent flow will have to push harder to accelerate the 100 g RAM-mass to the same velocity. In fact, the amount of extra energy expended by the fan will be exactly equal to the amount of energy lost to turbulence. In the end, net acceleration of the vehicle; 0.

    Still, I hope you'll keep working along these same kinds of ideas. Somebody has to come up with the new innovations, and you seem to have the kind of thinking that might produce something usefull.
     
    Last edited: Dec 17, 2008
  6. Dec 16, 2008 #5

    russ_watters

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    Just to bridge the gap there, posts 3 and 4 correctly point out that the claimed scenario #2 doesn't work. Post #2 correctly points out what is actually propelling the device in the Youtube link. It is, in fact, the very same friction, without which, you wouldn't be able to walk!

    Scenario 1 is just a basic misunderstanding of conservation of energy/momentum.
     
  7. Dec 16, 2008 #6
    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    1. You never know for sure until you try it. Go ahead and try it and let us know how it goes.

    2. Don't expect it to work. That air hockey table or aluminum tubes might seem "frictionless", but they still do give friction there. The reason the backward movement isn't noticed on the table setup is that the backwards force on the apparatus due to the push of the air is spread out over time. Using the impulse-momentum theorem:

    change in momentum = Force (time)

    Hence if you make the time longer the Force is made smaller...perhaps small enough not to overcome the static friction due to the aluminum tubes. In this case, no backwards motion on the apparatus due to the air would be observed while the fan is making its way towards the wall. On the other hand (using this same relationship) when the fan makes contact with the wall, the time is very small so the Force in this instance is very large. This force can overcome the static friction due to the aluminum tubes and the apparatus moves in that direction. Consider this...with no static friction at all, wouldn't the force from the wind on the apparatus cause it to move backwards (at least a little bit) before the fan made contact with the wall? Why don't you see this on the Youtube video?

    As another post mentioned, I applaud the attempt but at the end of the day the principles of Physics are an engineers friend. Violate them with caution.
     
  8. Dec 17, 2008 #7
    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    Your experiment with the fan-powered cart within the sealed atmosphere was misleading. The cart exerted it's force when hitting the wall ofer a short period of time. This force was great enough to break the static friction between the vestle and the table. Durring the time the Fan was accelerating, the net force of the air on the back of the vestle was exerted over a longer period of time and was a lesser force. This force was not above the maximum force for static friction, thus the box did not move.
     
  9. Dec 17, 2008 #8

    LURCH

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    More importantly; how are you going to test this in 0g? Are you actually gettigna ride on the Vomit Comet?! That would be so freakin' awesome!
     
  10. Dec 17, 2008 #9

    FredGarvin

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  11. Dec 17, 2008 #10

    Dale

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    If you are that confident then you should start taking bets. I wonder what odds Vegas would give you, but even if they gave you 10:1 against you would still be "sure" to come out ahead.
     
  12. Dec 17, 2008 #11

    D H

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    Re: Preparing a 0g test for “space drive” that apparently conflicts with law conserva

    NASA does sponsor student experiments; the company for which I work has hired students who participated in such experiments -- great experience. The competition is fierce. A proposal that violates the laws of physics will not fly (literally).
     
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