Just a thought here...
One of the comments above send my mind down a rabbithole. How feasible would it be, with metal 3D printing, to set the device up in a vacuum, and print (say) a sphere with internal bracing against collapse? Then, could you flood the chamber with air and keep a balloon full of vacuum which would float?
And then what use would it be? I guess you could add buoyancy to all sorts of things, but would *lots* of buoyancy be better than just using a lightweight gas?
Biting the hand that feeds IT
