Vacuum balloon
Yes, my partner and I tried to build one.
It was a competition grade balsa and polyethylene construction measuring 4’ x 8’ containing 128 cubic feet of air. At sea level, that’s about 10 pounds of air and the construct weighed 1.25 pounds. We needed to pump 1.3 pounds of air out of the device for it to float.
It nearly floated after vacuuming air from it to lower the internal pressure and thus weight, prior to the frame collapsing.
What I really needed was a CAD and physics simulation program to design the thing and test it without spending days gluing balsa. It was fun anyway. It nearly flew for a historical first!
Cheers,
