  The centuries-old idea of a lighter-than-air vacuum balloon has not
materialized yet as such structure needs to be both light enough to float in
the air and strong enough to withstand atmospheric pressure. We propose a
design of a rigid spherical sandwich shell and demonstrate that it can satisfy
these stringent conditions with commercially available materials, such as boron
carbide ceramic and aluminum alloy honeycomb. A finite element analysis was
employed to demonstrate that buckling can be prevented in the proposed
structure. Also discussed are other modes of failure and approach to
manufacturing.
