One of history’s most enchanting airship designs also happens to be one of its earliest. In 1670, Francesco Lana Terzi, an Italian physics and mathematics professor, published Prodromo. His design literally resembles a flying ship, complete with mast and sail. (There’s a reason the passenger-containment portion of a hot air balloon is still called a gondola.) The vessel was even designed to be steered with a rudder. Note, for example, the person steering with a paddle at the stern in an engraving from Johann Sturm’s Collegium Experimentale sive Curiosum. What made this particular design airworthy were the four spheres made of very thin copper foil tethered to the craft.
Lana Terzi’s clever design was inspired by Otto von Guericke’s work on vacuums. If Lana Terzi could pump the air out of these spheres to the point of creating a vacuum, the spheres would be lighter than the surrounding air and would thus lift the ship from the ground. Lana Terzi never tested his idea, nor has anyone since. Today, scientists and engineers agree that the design wouldn’t work, since the pressure of the surrounding air would crush the spheres.
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