Yeah it's nifty idea -- no need for explosive hydrogen or scarce helium. If the polymer sheet is strong enough, I wonder if one could use it to wrap a sort of s

Yeah it's nifty idea -- no need for explosive hydrogen or scarce helium. If the polymer sheet is strong enough, I wonder if one could use it to wrap a sort of scaffolding (a shape like https://en.wikipedia.org/wiki/Fullerene https://en.wikipedia.org/wiki/Fullerene but perhaps with struts through the interior for more strength), then evacuate the air from the interior in order to form a lighter-than-air "box". Submarines can withstand a few dozen atmospheres of pressure, this would have to withstand .. one, I suppose, so intuitively it seems plausible.