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lowhugchain

macrumors newbie
Original poster
Jun 17, 2008
1
0
This is so cool...

http://www.youtube.com/watch?v=1l_v1K3GwUc

I need to get some helium!

2016z6.jpg
 
Some helium - and a healthy dose of reality.

That much helium isn't nearly enough to lift a man.
 
Serious question, forgetting about helium - how much hydrogen would it take to lift the average man? And what kind of area would that hydrogen occupy?
 
Serious question, forgetting about helium - how much hydrogen would it take to lift the average man? And what kind of area would that hydrogen occupy?

Balloons work by displacing a volume of air that is equal in weight or greater than the load being lifted. So, if an average man weighs 175 lbs (79.4 kg) then the volume of air would have to weigh that much. At sea level dry air has a density of 1.3 kg/m^3, and hydrogen has a density of 0.09kg/m^3. So, to displace 79.4 kg of person we need 79.4/(1.3-.09) = 65.6 cubic meters of hydrogen. This would exactly balance you. Any more and you'll be lifted.


</nerdy scientist>
 
Balloons work by displacing a volume of air that is equal in weight or greater than the load being lifted. So, if an average man weighs 175 lbs (79.4 kg) then the volume of air would have to weigh that much. At sea level dry air has a density of 1.3 kg/m^3, and hydrogen has a density of 0.09kg/m^3. So, to displace 79.4 kg of person we need 79.4/(1.3-.09) = 65.6 cubic meters of hydrogen. This would exactly balance you. Any more and you'll be lifted.


</nerdy scientist>

Amazing post, thanks :)

Pity about the space requirement, especially considering there was only the one Hindenburg.
 
Balloons work by displacing a volume of air that is equal in weight or greater than the load being lifted. So, if an average man weighs 175 lbs (79.4 kg) then the volume of air would have to weigh that much. At sea level dry air has a density of 1.3 kg/m^3, and hydrogen has a density of 0.09kg/m^3. So, to displace 79.4 kg of person we need 79.4/(1.3-.09) = 65.6 cubic meters of hydrogen. This would exactly balance you. Any more and you'll be lifted.
I worked it out differently (and far more slowly! :))

From this Mythbusters experiment we can get a bit more of an idea experimentally. It takes approx 3500 ballons to lift a 4 year old off the ground (lets assume a 4 yo girl is about 15kg). Therefore an average man of 75kg would need 5 times that amount, 17 500 balloons worth of helium. Each balloon is 10L so ugh. It would take you a lot off hydrogen balloons, assuming you could find some that would hold hydrogen!

From this site helium apparently has 93% the lifting capacity of hydrogen, so you'd only need ~16 250 balloons (keeping calculations simple!).
 
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