How Do Blimps Fly?
Blimps are filled with helium, a gas that is lighter than air. You may have seen helium balloons at a parade or a party. What happens when you let go of the string of a helium balloon? It rises into the sky. Similarly, helium provides the lift in a blimp. Once in the air, small engines turn propellers that control the speed and direction of the blimp. How Do Hot-air Balloons Fly? Just like a blimp, a hot-air balloon uses a gas that is lighter than air to achieve lift. In this case, the lighter-than-air gas is simply hot air. The pilot of a hot-air balloon controls a flame located at the bottom opening of the balloon. By turning on the flame and heating the air inside the balloon, he can make it rise. By turning off the flame and letting the air inside cool, he can make it descend. Unfortunately, a pilot has little control over the direction his balloon moves across the sky, because there are no motors or propellers on a hot-air balloon. To move in a certain direction, the pilot has to
