Hi /n/. Out of intellectual boredom, I've decided to mess around with ideas on making sustainable passive flight systems - blimps, balloons and so forth. Clearly the choice of gas is He, since H is flammable etc. but I can't for the life of me find any method for extracting it from the air itself.

At sea level (15C), Air contains 0.000524% Helium, but at higher altitudes, I can only assume that this percentage would be higher as helium concentrations would be greater at higher altitudes (although this isn't anything more than conjecture - it would only be nice if I were correct).

Power isn't such a great issue thanks to solar energy and passive wind farming (which are both getting significantly more efficient, especially solar).

The necessity for other elements or compounds for extraction is obviously not ideal, due to the requirement that the vehicle not touch down for supplies.

tl'dr; How do you get grade A (or at least 80% pure) Helium gas from ambient air?

PS: /g/ told me to come here. If you want me to go back because I'm obviously not asking a transport question, feel free to suggest a message for /g/ from /n/.