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

Because it would get crushed by the pressure differential. A craft large enough to float would crumple like a tin can.