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Weighted Balloon String

For neutrally bouyant balloons
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I want to have thin cord that, while appearing outwardly to be normal string, has a core made of heavy wire. This wire is heavy enough that, after tying the string onto a helium balloon, the string can be cut to the exact length for it to exactly counterbalance the balloon's lift. Thus, the entire setup is neutrally buoyant, floating in space without rising or sinking.

Why? Well, this way, as I prance around town carrying my helium balloon, I can grip the string somewhat towards the middle of its length. Thus, I'm carrying the weight of the string's bottom half, and the balloon floats upwards without being encumbered by the string's full mass. However, if I let go of the string, the balloon won't float upwards as it would normally be expected to; it'll just float in place with the string hanging under it. To anyone else, it'll seem like the balloon is held down by magic. To me, it's just a neat trick.

DrWorm, May 19 2011

Anti-Gravity Boulder http://amasci.com/amateur/gravrok.html
[Wrongfellow, May 20 2011]

[link]






       You'd have to carry a pair of wire cutters, and, as helium leaked out of the balloon, be continually trimming bits of wire of the end. Oh, and if you let go of the balloon, a slight breeze might blow it out of reach. But a lovely concept. [+]
mouseposture, May 20 2011
  

       (+) In a restraurant I once worked in we would tie match packs to the string and remove matches, adding back part matches, until they were neutrally bouyant.
Customers seemed to like batting them around the place.
  

       <in high squeaky voice> I like helium. Bun [+]
Grogster, May 20 2011
  

       I used to ballast balloons and let them float around in the house. Fish shapes were lovely.   

       Ballasting to a hover only works well with full Mylar balloons, in my experience, and only indoors. Latex balloons and half-empty Mylar change volume and do not hover. Tight Mylar balloons are really resting on thermal-density gradients, which usually only happen inside.   

       Cute idea, but reality says [ ].
baconbrain, May 20 2011
  

       If the string were weighted with a material which degrades over time at a suitable rate, boyancy could be maintained.   

       Perhaps a series of very small versions of the (little paper bundles of crystals which explode when thrown at the ground - what the hell were they called?). When the srting drags on the ground, a little at a time is blown away.
Twizz, May 20 2011
  

       // what the hell were they called //   

       "Great fun ..."   

       The string could be dipped in a liquid which slowly evaporates; but matching the diffusion rate (which is dependent on environmental factors) would be extremely difficult.
8th of 7, May 20 2011
  

       You can get a balloon to hover by tying it to a long piece of string, long enough that it pulls the balloon downwards, and then letting it float with some of the string on the floor.   

       It's self-correcting - if the balloon moves too far upwards, more of the string is lifted off the floor, and pulls the balloon back down; if it moves too far down, more string rests on the floor, and the weight is taken off the balloon.
Wrongfellow, May 20 2011
  

       I've done that with a hydrogen-filled balloon. Tie a long strip of paper to the balloon so it drags on the ground. Light the paper. As it burns, weight is lost, and the whole thing rises, ending in a mid-air explosion.
spidermother, May 20 2011
  

       Again with the hydrogen...
Alterother, May 20 2011
  

       That is a great link, Wrongfellow. I really want to make one of those now!   

       And yes, as many of you have pointed out, helium does escape from balloons - but that's the advantage of this idea. When the balloon starts to fall, all you have to do is trim the wire a bit.
DrWorm, May 21 2011
  
      
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