Warbird Information Exchange

1 cubic foot of any substanceat standard temp and pressure, uncompressed, is 7.5 gallons.

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lets see 2700 / 26 = 103.8 cuft per gallon
Your missing the point helium is very very cold when it is a liquid.

We filled fuel tanks with wiffle balls to stop sloshing of fuel while racing (before fuel cell foam) and it worked great! unitl the fuel filter became clogged with wiffle ball shavings....

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No you couldn't! That is so wrong!

In answer to Airlift48's question, that is correct. As it is compressed, its lifting capability is decreased. It is so basic; as it is compressed, it becomes more dense. Static (lighter than air) lift is a matter of relative densities and displacement, not absolute weights - the same way that a 95,000 ton aircraft carrier is able to float in water. The 95,000 tons of steel aircraft carrier takes up more space than the equivalent 95,000 tons of water it is displacing, therefore it is less dense and consequently it floats on the water.

A cubic foot of uncompressed helium is lighter than a cubic foot of regular air, but a cubic foot of compressed helium in a pressurized vessel like an aluminum tank is NOT lighter than the same volume of air. You have to expand or decompress the helium for it to "float" a payload and the differential must be great enough to account for the weight of that payload, too.

Helium has a density (@ 0 degrees C, 101.325 kPa) of 0.1786 grams/liter. Nitrogen, which everyone knows makes up approximately 78% of the Earth's atmosphere, has a density (under the same temperature and pressure conditions) of 1.251 grams/liter. That means that Nitrogen is about 7 times heavier than Helium.

If you compress helium to 2000 psi (roughly 133 times atmospheric pressure), you're putting 133 x 0.1786 grams into each liter of volume = 23.81 grams per liter - which is way more than the same volume of uncompressed dry air (78% Nitrogen and 21% Oxygen, which is about 1.2759 grams per liter).

The result is that even without the pressure cylinder, the "compressed" helium would no longer "float" because it is 18.66 times heavier than the same volume of air.

you're all full of hot air.

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