"Vacuum" Air Balloon I have bounced around various sites and forums but I wanted to get a feel from some of those that may actually know. I have a theory on how this could work but basically wanted to get some opinions. My theory is not new but has a few added components. A geodesic sphere could be made that is say 1000ft in diameter. At that size it could be lifted or severely weight reduced with warmer air for displacement. Rigid Zepphlins have been build to incredible sizes. That is with aluminum I feel that weight could be more adventageous with composite materials (Carbon, M5...). At this point if a rigid ship such as this pulled a tiny pressure differential towards a vacuum within the ship it would become bouyant. Due to the combination of temperature and pressure differential. This would seem to have a few applications one of which would be the interior of the sphere would be habitable. It would also allow a "vacuum" balloon to be built without the use of the notorious unobtainum. If someone could explain to me where I am mistaken, I would love to hear from them.