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Of course, my inclination says that density should increase then, having an opposite effect but at the same time, i am inclined to believe that by fitting more helium in a "ballon" would allow more lift power.

How am I wrong? And how can once increase "buoyancy" / lift power given "light" materials?

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Helium and hydrogen have no power to lift anything.

A lighter-than-air craft is able to fly because it is lighter than air (i.e., it weighs less than the volume of air that it displaces.) Helium or hydrogen are used because they fill the space, and they are lighter than air.

If you compress the lifting gas, that means you are putting more of it into the envelope. More weight. That's the opposite of what you want. You want the least weight possible. The ideal would be to "fill" the envelope with vacuum. Having no gas in the envelope would mean having no weight at all.

Unfortunately, any "container" for vacuum must be strong enough to withstand the external atmospheric pressure without being crushed. The lightest possible "container" for a given volume of vacuum ends up weighing far more than a balloon with the same volume, filled with helium---far more than the weight of the air that it displaces.

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  • $\begingroup$ How about a large large large globe tank of nothing. Would it mean that the larger the boundaries got, the more likely to "fly" ? I am guessing sucking out everything so it goes close to vacuum, wether it is small or gigantic will exort same total amount of pressure, or will a larger globe require more reinforcement as it grows, yet keep the same inside pressure as a smaller one? $\endgroup$
    – mjs
    Commented Aug 7, 2019 at 18:46
  • $\begingroup$ @momo: the larger the vacuum globe, the more square inches of external air pressure, so the heavier and stronger the construct would have to be $\endgroup$
    – Adrian Howard
    Commented Aug 8, 2019 at 1:59

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