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Geek Culture / A way to make a small object neutrally buoyant in air

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Dark Java Dude 64
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Posted: 20th Dec 2011 04:06
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I realized a while back that as helium filled balloons leak, they go through a stage where they have just enough helium to be neutrally buoyant in air, and you can put them anywhere in the air and they will stay there unless something moves them. I thought that you could take something light and strong like a small (1 inch wide or so) and hollow carbon fiber ball and either put a vacuum in it or fill it with extremely low pressure hydrogen, then if done right, the ball would be neutrally buoyant. Would this work? I think it would be really neat to have something that would do that. Balloons of course are no fun when it comes to this because they only are in that stage for an hour or so, and it's hard to be with the balloon when it does that. Ultimately, it would have to be just as heavy as the air it displaces.

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Benjamin
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Posted: 20th Dec 2011 04:14
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Quote: " hollow carbon fiber ball and either put a vacuum"


As far as I'm aware there's no material that will withstand the external pressure while being light enough, though it'd be cool if there were.



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Posted: 20th Dec 2011 04:40 Edited at: 20th Dec 2011 04:40
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yeah atmosphere pressure is pretty strong. i can't appreciate its strength until i find myself trying to pry a plunger off of a laminated floor.

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Dark Java Dude 64
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Posted: 20th Dec 2011 05:52 Edited at: 20th Dec 2011 05:53
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That's one thing that would keep this from working... As far as i know, atmospheric pressure is somewhere around either 14.7 or 14.2 psi, im not sure which, but if the sphere was small enough, maybe even down to just one centimeter, the surface area would be low enough and the structural strength of the ball would be enough to handle that pressure. However, the the surface area to internal volume ratio would be too low. Then though there is the possibility of low pressure hydrogen, that would make the ball's structural requirements lower. Carbon fiber materials are very light and string and could possibly provide the ball with the required low weight. Or maybe, some sort of very thin material on a carbon fiber frame, if that would be any lighter. I do indeed think it's possible, it's just a matter of finding a way to do it!



Quote: "i can't appreciate its strength until i find myself trying to pry a plunger off of a laminated floor."
Haha that made lol! Dem' plungers is powerful stuff when combined with the atmosphere man!

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Neuro Fuzzy
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Posted: 20th Dec 2011 06:08
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Quote: "Carbon fiber materials are very light and string and could possibly provide the ball with the required low weight. Or maybe, some sort of very thin material on a carbon fiber frame, if that would be any lighter. I do indeed think it's possible, it's just a matter of finding a way to do it!"

I did some calculations with the density of carbon fiber (1.7g/cm^3), the density of air (0.0013g/cm^3) and a 1mm thick layer of carbon fiber. Unless my calculations are off (and they might be), you'd have to have a 4.4 meter sphere before it became neutrally buoyant.

I don't think it's implausible structurally. I mean lightbulbs have a pretty good vacuum and they're fine.

Maybe my math is wrong. I haven't double checked it, but I got mathematica for christmas (early I know ) and I was itching to solve some equations with it.

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Dark Java Dude 64
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Posted: 20th Dec 2011 06:46
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Haha that is very large! I dont know how strong 1mm thick of carbon fiber is, and i know that the circle shape helps with strength, but 4.4 meters wide is an enormous area! That would exert about 1,385,814.5 pounds of force on the entire sphere... But a combination of a strong yet thing and light weight fabric stretched over a carbon fiber frame may be able to hold the enormous inwards pressures.

I looked that program up, its pretty awesome!

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Benjamin
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Posted: 20th Dec 2011 19:45
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Quote: "I mean lightbulbs have a pretty good vacuum and they're fine."


True, but due to the materials they are somewhat heavier than the volume of air they displace.



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Dark Java Dude 64
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Posted: 20th Dec 2011 22:07
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Quote: "True, but due to the materials they are somewhat heavier than the volume of air they displace."
Well said!

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Teh Stone
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Posted: 21st Dec 2011 02:51
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The discovery channels "mythbusters" made a helium balloon mad out of lead once. It was a nightmare for them, had loads of problems with the material ripping

And I don't think anyone would want t fill that volume of hydrogen, anymore
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Dark Java Dude 64
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Posted: 21st Dec 2011 03:00
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Yeah that episode was awesome! But remember, we are not filling anything with hydrogen, we are sucking air out if anything. However, a large metal balloon filled with hydrogen may actually be neutrally buoyant, without any leakage issues or the need for an internally strong structure...

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Oster200
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Posted: 21st Dec 2011 22:48
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Quote: "i can't appreciate its strength until i find myself trying to pry a plunger off of a laminated floor."


ahh i remember doing that once. It got stuck at a store and i was trying to take it off the tile and it ripped the tille of the ground so i just left the plunger stuck to a tile in the middle of a isle!

Always end the name of your child with a vowel, so that when you yell the name will carry. - Bill Cosby
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Dark Java Dude 64
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Posted: 21st Dec 2011 22:54
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Haha that's funny!

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