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

As others have said it’s theoretically possible but no material exists that is strong enough, but also it isn’t really that much more effective than helium –

1l of air weighs 1.28g, 1l of vacuum of course weights 0g, but 1l of helium only weighs 0.178g

So vacuum actually only has 14% better lift than helium, with the massive problem of having material strong enough not to get crushed vs just a thin bag to contain helium in.