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Tony Sandy

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Is there an advantage of spin over percussion, when it comes to moving objects through space?

I've noticed that frisbees*, drills, javelins, propellers (planes, submarines, helicopters), arrows, rifling in gun barrels all cause spin or spin naturally. Is this because forward momentum creates displacement (pressure at the front/ vacuum at the back or in the case of deliberate propulsion as in jet engines, vacuum at the front, forward momentum from the back as the sucked in air expands at the back, pushing the craft forward)?
Also does percussion as in hammer drills and the rocket that was supposed to be propelled by minor nuclear explosions (staccato versus smooth flow), have any advantage over spin (think also of nail versus screw or saw versus axe)?

*discs show lack of resistance all round, by transferring what part of the edge is facing forward as pointed objects keep the narrowest part of themselves in the forward position - likewise spheres spin in the same way as discs, being rotated by friction, I believe.

Topics: Movement UFOs discs mechanics of space flight physics propulsion rockets
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  • Tony Sandy

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    Feb 29 2012: Actually I don't quite.

    What I was trying to get at, was that there's a common principle at work, to do with displacement (That 'Eureka!' moment). Apart from the objects mentioned, I also see it in windmills and swimming - where forward motion is obtained by scooping what is in front of you, behind. In fact I now realize it's the law of motion, about movement in one direction causing equal movement in the opposite direction.

  • Tony Sandy

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    Feb 21 2012: Good point. I give up!

  • Douglas Bell

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    Feb 20 2012: Hi Tony,

    Remember that space is an extremely good vacuum and aerodynamic resistance as we know it just doesn't exist. There's no reason to shape a spacecraft one way or another. As an example, look at the lunar landers. They traveled at 25,000 mph and had no more streamlining than an oak tree.

    Best wishes,
    Doug

  • Tony Sandy

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    Feb 20 2012: Doug,

    Do you think there is any connection between spin as I was originally discussing it and planetary / galaxy spin as with water going down a drain? (Viktor Schauberger and Michael Longo of The University of Michigan, seem to have seen some connection).

    I was also thinking of Alice Through the Looking Glass and the idea of running on the spot, to maintain position in the space /time.

    Also do you think galaxies and even the Earth, have a calm centre as with hurricanes? What I'm thinking of here is the observation I made once, when carrying a cup of coffee and suddenly turning. The cup moved along with me but the liquid stayed in the same position, relative to its former placement. Is this something to do with being a liquid and reduced drag / friction?

  • Tony Sandy

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    Feb 19 2012: Maybe this is why UFOs spin - to stay stably in the same place? Coupled with some form of anti-gravity to rise and lower the craft, might explain some of their manouvres?

  • Douglas Bell

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    Feb 18 2012: Hi Tony,

    Lots of spacecraft use spin to stay in a stable attitude. Unfortunately, it confers no useful means of propulsion. The propulsion examples you mention all depend on the craft's spin interacting with the atmosphere to provide forward thrust. They can't help move a spacecraft.

    Best wishes,
    Doug

    • Tony Sandy

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      Feb 20 2012: What I was thinking of Doug, was does the spin negate resistance on the leading edge or point ( if something like a javelin) and that is why they spin as a natural consequence of this. To use an analogy to clarify - would a box meet more resistance to movement than a ball or a flat square of rigid material, unless forced to stay upright, than allowed to go on edge (shield in windy conditions as opposed to flying kite?
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