I first heard/thought about vacuum balloons when reading Diamond Age (which I can recommend as an interesting book!) and ran off and did a bunch of math and fig

I first heard/thought about vacuum balloons when reading Diamond Age (which I can recommend as an interesting book!) and ran off and did a bunch of math and figured out how difficult they would be to build and use. However, on planets with a much denser atmosphere, they would be pretty handy. Having a platform hanging under, or sitting upon, vacuum balloons on Venus for example would make for a science platform that moved around the planet and could exist where temperatures were more amenable to current electronics. For those wondering about "the math", the simple version is to find the nominal density of atmosphere at the altitude you want to sit, take your material of choice and it's density. And then use (material_volume x material_density) < (atmosphere_volume x atmosphere_density), the amount of vacuum you need is then (atmosphere_volume - material_volume). You can plot it out, for every gram of material you need x cubic centimeters of vacuum. If you can find a solution where the material properties allow it to withstand the pressure differential, then you can, in theory, demonstrate a vacuum balloon if you can build it. Note that it will almost always be a spherical balloon as pressure on a sphere becomes compression strength of the material you're using.