How Hot Air Balloons Work
Understanding how hot air balloons work is nearly as simple as understanding one basic scientific principle: hot air rises.
Hot air balloons have three main parts - a basket, which carries the pilot and passengers; an envelope, the colorful enclosure that holds air; and a burner, which heats the air inside the envelope.
The balloon is spread out on a flat surface and then inflated by use of a large fan. Then the air inside is heated with the help of a propane burner. A ground crew helps inflate the balloon and keep it tethered while the pilot and passengers get inside. The ground crew releases the balloon when the pilot is ready to fly.
To make a hot air balloon rise, the pilot simply heats the air in the envelope with a propane burner. The warm air lifts the balloon into the sky, and the pilot can then gain or maintain altitude by repeatedly heating the air in the envelope. To move horizontally, the pilot relies on the wind. By taking advantage of the fact that wind blows in different directions at different altitudes, he or she can also move in different directions by moving higher or lower.
Pilots can slow their ascent, or can descend, by pulling a cord to open a valve at the top of the envelope, called the parachute valve. Opening the valve allows hot air to escape and the air inside the envelope to cool. In this way, the pilot can cause the balloon to descend.
Unlike other aircraft, hot air balloons do not have the ability to make precise landings on scheduled runways, so the ground crew follows the balloon on its flight in the "chase vehicle." The chase crew keeps in touch with the pilot via a radio and helps him or her find a place to land. Once the balloon is on the ground, the ground crew helps tether the craft and deflate it.
The hot air balloon is then packed up and ready for the next flight!
For more information:
howstuffworks - How Hot Air Balloons Work
eballoon.org - How the Balloon Works
Wikipedia - Hot Air Balloon