why would a rigid airship body with helium or hydrogen would float but not one with a vacuum inside?

Question

My thinking here is that if my rigid airship body is, say, 24g, with vacuum, why would it float with helium or hydrogen inside, when they have mass and thus weight? Makes very little sense, unless it has something to do with the density?

I haven’t actually done this yet, and I’m working out ideas for one. Everyone I know tells me I’m wrong for thinking a vacuum (assuming a full one, although they are elusive) would float over helium or hydrogen.

In: 11

Answer 1

A balloon filled with vacuum would indeed float, and be more buoyant than the same volume filled with a gas. However, it’s much harder to maintain a vacuum than it is to fill the space with gas. A gas filled balloon has roughly equal pressure with the atmosphere, and as such has less force on its body. It also takes up the most space, since a balloon filled with vacuum would pull in everywhere it can.