The Rise and Fall of the Metal Airship
From New Scientist: ” METAL airships are one of the oldest notions in aeronautics. As early as 1670, Italian mathematician Francesco Lana published his Demonstration of the Feasibility of Constructing a Ship With Rudder and Sails, Which Will Sail Through the Air. Lana proposed evacuating the air from a set of copper spheres, which he reasoned would weigh less than the surrounding air and would ascend until the weight of the sphere reached equilibrium with the surrounding atmosphere. He calculated that four vacuum spheres, each with a diameter of 7.5 metres, could lift a boat carrying six passengers.
Lana, alas, could not procure the copper spheres himself because of his obligations as a Jesuit. “I would have willingly [built it] before publishing these my inventions,” he explained, “had not my vows of poverty prevented my expending 100 ducats.”
Lana’s notion was not entirely fanciful. Recent experiments had demonstrated that air had weight, and in 1650 the German inventor and scientist Otto von Guericke had drawn together small copper hemispheres with such a strong vacuum that teams of horses could not pull them apart. Still, there was a difference between creating a sturdy 50-centimetre sphere and fashioning 7.5-metre globes that could rise into the clouds. As Lana’s compatriot Giovanni Borelli pointed out, for Lana’s spheres to be light enough to fly, the copper would have to be so thin that on evacuation they would be crushed by atmospheric pressure.” The Rise and Fall of the Metal Airship
