Vacuum airship
![Francesco Lana de Terzi's flying boat concept c.1670](/Images/godic/202502/19/Flying_boat2600.png")
A vacuum airship, also known as a vacuum balloon, is a hypothetical airship that is evacuated rather than filled with a lighter-than-air gas such as hydrogen or helium. First proposed by Italian jesuit priest Francesco Lana de Terzi in 1670, the vacuum balloon would be the ultimate expression of displacement lift power.