Have you ever seen a Flying Purple Eater? If you go to the National Balloon Classic in Indianola, Iowa, in August, you just might. The Flying Purple Eater is an insect-like hot-air balloon -- one of more than 100 -- that takes part in this three-day event.Held each year, this hot-air balloon competition and race began in 1970 as the first U.S. National Championship in ballooning. Do you know how hot-air balloons work? Balloons are aerostats, which means that they are lighter than air when inflated. Once a balloon is in the air, it moves with an air mass or wind, which carries it along at the same speed and in the same direction as the air.
Do you remember how the Wizard landed in Oz? He was in a hot-air balloon. The pilot of the balloon has control of the altitude (how high or low the balloon flies) and can alter its course by finding an air mass going in a slightly different direction. Hot air balloons use ordinary air as the lifting gas. By heating the air inside the balloon, the pilot makes that air lighter than the outside air, and the balloon rises. As the internal air cools, the balloon becomes heavier and descends unless the pilot adds more heat.
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