轻于空气的飞行课件.pptxVIP

The title of Millbrooke’s chapter “The Invention of Aviation” is incorrect in asserting that aviation began in France in 1783. The Chinese invented aviation (heavier-than-air) with kites. The French invented lighter-than-air flight. They could do so because of modern science.;LTA飞行之一 气球;The beginnings of LTA flight were based on technological applications of scientific principles. * Science = Know-what * Technology = Know-how;Evangelista Torricelli – a protégé of Galileo, discovered air pressure in earth’s atmosphere – the higher you go the lower it gets;By trapping air, a gaseous compound, in a J-shaped tube and compressing it with a quantity of mercury Boyle discovered that the volume of a gas varies inversely with the pressure applied to it. This is know as Boyle’s Law and is the basis of studying the density of a gas.;Henry Cavendish discovered hydrogen, the lightest element in existence and learned how to produce it by pouring sulfuric acid硫磺酸 over iron filings铁屑.;Joseph Priestley and Antoine Lavoisier share the credit for discovering oxygen, one of the two main constituents of air, the other being nitrogen氮. Air is a compound of roughly 78% nitrogen and 22% oxygen, with trace elements mixed in.;Fundamental Principles: Air gets lighter as it is heated. Enclosing hot air in a relatively light container creates an  imbalance in the density of air within the container  lighter) and the air outside the container (heavier) giving  the container lift and thereby causing it to ascend上升. Hydrogen is lighter than hot air; therefore a container  filled with hydrogen does not have to be as big as one  filled with hot air to provide equal lifting power.;Joseph and Etienne Montgolfier, scientifically informed见多识广 paper makers at Annonay, France realized that a paper bag filled with hot air will ascend providing them with the concept of the hot air balloon. Etienne was the first human being to achieve tethered LTA flight.;The first balloon flight – the ascent