H2

[i]

No, not that H2.

This H2.

Given a volume of hydrogen gas at STP here on Earth, does anyone know of a formula that will calculate the largest mass it will be capable of lifting? Alternatively, a formula for calculating what volume of hydrogen gas at STP is required to lift a certain mass would work equally well.

Also, does anyone know if the composition of the environment the hydrogen is placed makes a difference? As an extreme example, would a volume of H2 rise more slowly, at the same rate, or faster in an N2 environment than an equal volume of H2 within a UF6 environment?

 

[ddrueding]

Wouldn't this be a simple function of the molecular density inside vs. outside? ANd be dependant on, well, just about everything? (temp, atmospheric pressure, density of the gasses, etc.)

 

[ddrueding]

Oh, and a tiny bit of fluid dynamics, based on the shape of the H2 cloud, the density of what it is passing through and the speed at which it is moving.

 

[i]

Wouldn't this be a simple function of the molecular density inside vs. outside? ANd be dependant on, well, just about everything? (temp, atmospheric pressure, density of the gasses, etc.)

Yes, temperature and pressure could impact this situation to a great degree.

Which is why I indicated STP (~273K, ~101.3 kPa). That leaves only the relative density of the "host" gas to worry about, which would presumably be accommodated for in the equation.

Air resistance, etc. would be negligible. If it still bothers you, assume the hydrogen is contained within a perfect sphere composed of an infinitely thin, frictionless material. :wink:

 

[jtr1962]

This should get you started. By assuming the mass per mole of hydrogen gas (i.e. 2 atoms per molecule) is 2.01594 grams, I end up with a lifting power of 506.39 grams (1.1164 lbs) per cubic meter at STP. Naturally, you need to subtract the weight of the balloon holding the hydrogen to get the net lifting power.

Note: Second calculation on that page relating to helium is partially wrong. 1000 L of He is 40.87 mole but they multiply the mass per mole of He by 32.70 rather than the 40.87 that it should have been multiplied by. However, the 32.70 is apparently a typo because the mass per cubic meter of He is indeed correct at 163.6 grams.

 

[i]

Thanks jtr! That's perfect!

 

[e_dawg]

Did we learn nothing from the Hindenburg?


(of course, those H2 devotees among us will point out that H2 was not to blame)

 

[ddrueding]

Did we learn nothing from the Hindenburg?


(of course, those H2 devotees among us will point out that H2 was not to blame)

Nope, it was all that damn oxygen that happened to be around at the time.