Harold: I found this on the net by doing a google search on "helium lifting power" Hope it helps:

Helium Lift Power

name Paul

status other

age 30s

Question - I would like to know the lifting power of Helium

eg: How much helium to lift 1kg

Any information would we great.

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Revised May 2008

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That depends on the density of air and the density of the helium. For

simplicity's sake, let's say the air and the helium are at the same

temperature and pressure. In that case, four grams of helium will occupy

about the same volume as 28.5 gm/mole of air. To lift an object, you need for

the mass of the object + the mass of the helium to be less than the mass of

the air it displaces. Since any object you want to lift will probably have

a much greater density than air or helium, let's neglect its volume for

simplicity's sake (in other words, we'll neglect the mass of the air

displaced by the object, because it will probably be only a small part of

the mass of the air displaced by the helium and the object together). Then

we can say that you need the mass of the object + helium to be less than

the mass of the air displaced by the helium.

M + Mh < Ma,

where M is the mass of the object, Mh is the mass of the helium, and Ma is

the mass of the air displaced. Our shortcut of neglecting the volume of

the object just says that

Ma = (28.5/4)Mh,

that is, a given mass of of helium will displace (28.5/4) times its mass of air.

Knowing that 4 grams of helium occupies that same volume as 28.5 grams of

air, we can see that four grams of helium will lift almost 25 grams:

M + Mh < Ma

M + Mh < (28.5/4)Mh

M < (28.5/4)Mh - Mh

M < Mh [(28.5/4) - 1]

M < Mh (7.125 - 1)

M < Mh (6.125)

M < 4g (6.125)

M < 24.5 g.

An easier way to look at this is to note that since four grams of helium displaces 28.5 grams of air, the "payload" for the helium is 28.5 g - 4 g = 24.5 g.

On a per gram basis, this means that one gram of helium will lift a payload (including the mass of the balloon) of (24.5 g payload)/(4 g helium) = 6.125 g payload /g helium. You can also see this in the above derivation if you just figure the mass of helium to be 1 g instead of 4 g.

So, to lift 1000 grams (1 kg), you need about 163 grams (~0.16 kg) of helium:

M < Mh (6.125)

M/(6.125) < Mh

Mh > (1000g)/ (6.125)

Mh > 163.3 g.

How much volume of helium is this? It depends on the temperature and

pressure. Neglecting the volume of the object to be lifted becomes a more

serious error as it becomes a larger fraction of the total volume. Under

normal conditions (ambient temperature and pressure), this is a small error.

Mike