> I don't know if we have the technology to build a compressive structure that can withstand atmospheric pressure and yet be lighter than the air it displaces.

> I don't know if we have the technology to build a compressive structure that can withstand atmospheric pressure and yet be lighter than the air it displaces. That sounds like an interesting problem to work on. I imagine getting it to work out would be easier the larger the structure is, within reason. It doesn´t exist so far. There are very strong forces involved. I`d say it´s more likely there would be connected small enclosures that could make that work. Perhaps some sort of solid foam blocks with vacuum inside - but it may provide much less lift than a true vacuum.