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In lugnet.off-topic.geek, Jon Palmer writes:
> Imagine a winch pulling a rope or cable through a series of pulleys
> (horizontal) that are staked to the ground. The pulleys are arranged so that
> the rope makes a zig zag pattern on the ground. There is an object at one
> end of the cable, being reeled in by the winch at the other end (ignore for
> now that the object would collide with the pulleys)
>
> The pulleys and winch stay in place because they are anchored to the ground.
>
> Now imagine this setup on a much larger scale in space. The pulleys and
> Winch, no longer tethered to anything, would not be able to stay in the same
> spot.
>
> But what if the winch and pulleys had thrusters on them to maintain their
> position? Is that possible?
I'll say "sure" but with this question as a follow-up.
Pulleys are usually used on Earth to gain a mechanical advantage. In space,
since the object is weightless (but still has mass!) there isn't the need
for the pulleys... at least as far as I can see. So my question is, "are
the pulleys a decorative part of this scenario? Or do they serve yet
another function which hasn't been discussed?"
> Start with the winch. It's reeling in the object at the other end of the
> cable. In my mind the winch would also reel it's self in, so that it and
> the object would meet in the middle. If it had thrusters, in this case
> aimed towards the object, could it maintain it's position if it supplied
> thrust which was equal in energy to the pulling of the cable? Disregard
> fuel use etc.. Imagine that the thrusters could maintain a constant rate
> throughout the reeling process.
>
> So now think about the smaller pulleys that are spaced out along the cable.
> In order for them to maintain the precise zig zag pattern (this is crucial)
This was what triggered my question above. What is the significance of the
zig zag pattern?
> they would need thrusters too. I imagine if they didn't have them the winch
> and object would eventually pull the length of the cable straight.
Agreed.
> Imagine for a moment that this is possible. The small pulleys would
> disengage and shoot away (or explode perhaps)
I always liked the idea of explosive bolts etc. :)
> from the cable just before the
> object hit them. This would correct the course of the object. ex: It was
> going left, now it's going up and to the right, on its way to the next
> pulley.
>
> Thoughts?
Yup... still wondering what's with all the zigging and the zagging.
All the best,
Allan B.
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Message is in Reply To:
 | | A space physics question
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| Imagine a winch pulling a rope or cable through a series of pulleys (horizontal) that are staked to the ground. The pulleys are arranged so that the rope makes a zig zag pattern on the ground. There is an object at one end of the cable, being reeled (...) (22 years ago, 28-Dec-02, to lugnet.off-topic.geek, lugnet.space)
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