Hot Air Balloon Book: Build and Launch Kongming Lanterns, Solar Tetroons, and More
Lana's airboat In 1663 Lana designed a lighter than air ship the details of which he later published in 1670 in his book Prodomo This design used four large floating copper spheres from which a boat is suspended The boat had a sail and hull as Lana intended it to be propelled by the wind and steered much as a boat on the sea Lana never tried to build his airboat and of course there would have been practical problems if he had To make the airboat fly I estimate that the copper skin of the big spheres would have to be less than 0 004 inches 0 1 mm thick This is about the thickness of a human hair and only about four times the thickness of household aluminum foil At this thickness the sphere would collapse under its own
weight even before you tried to pump out any air Portugal and Brazil Bartholomeu Lourenco de Gusmao was born in Sao Paolo Brazil in 1685 At that time Brazil was a part of the Portuguese empire so when it became clear that Gusmão was a brilliant student and had quickly outgrown the opportunities for study in Brazil it was natural that he should travel all the way to Portugal to study at the University of Coimbra At Coimbra he studied mathematics physics chemistry astronomy and philology the language of literature It must have been during these studies that Gusmão discov ered the work of Francesco Lana and Gusmao began to develop Lana's ideas for flying machines Gusmão knew that Lana's copper spheres would not be practical but his early attempts at designing a flying machine used equally strange devices to lift the boat such as powerful magnets U Gusmão's magnetic airboat Passarola
Some say that Gusmão observed a soap bubble rising in the hot air above a candle flame and realized that hot air was the source of lift he was looking for Whatever the source of his inspiration in 1709 he asked if he could demonstrate a model of a flying machine to King John V of Portugal Over the course of three days he made three separate demonstrations in front of the royal court where he propelled a ball up to the roof by combustion We don’t know how Gusmao's model worked but some writers believe that it was a paper hot air bal loon maybe even with a small burner fixed to the opening at the bottom If this is true then Gusmão produced a working model hot air balloon 73 years before the Montgolfier brothers Unfortunately he did not write down exactly how either his demon stration or his new design for an airboat worked Sadly Gusmão did not live to complete his air boat The Inquisition started to investigate him in 1724 and rather than face any charges he fled to Toledo in Spain He died of a fever only weeks after he arrived Scotland The 18th century was a time of rapid development in chemistry and physics Earlier researchers such as Robert Boyle and Robert Hooke had investigated the physical properties of air But scientists like the Scotsman Joseph Black the Englishmen Henry
Cavendish and Joseph Priestley and the Frenchman Antoine Lavoisier were now interested in the chemi CC cal properties of individual gases rather than the mix ture that makes up air Joseph Black was Professor of Medicine at Glas gow University but lectured in chemistry as well In 1766 Black read a paper written by Henry Cavendish that described new gases that Cavendish had isolat ed One gas was particularly odd Cavendish called it inflammable air because you could actually burn the gas in air Almost as strange was its very low den sity 13 liters of the new gas weighed the same as only 1 liter of ordinary air We know this gas today as hydrogen Black knew the low density meant that a light bag filled with the new gas might just be able to float in the air This would be a superb demonstration for his students it would really show off the properties of the new gas But what to use for the bag Paper was no good because the gas passed right through it For hundreds of years pig bladders had been used to make balloons and lightweight balls for games so Black went to the local butcher's shop Rather than a pig bladder which would have been a bit small Black chose an allantois from a butchered cow An allantois is a long sausage shaped membrane that is both strong and gas tight Back at his home Black filled the allantois with Cavendish's new gas and tied off the opening While Curious visitors to Black's house watched the allan
