Physics of Hot Air Balloons

Jaimie Barnes
Physics 212x

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STEERING

To move the balloon upwards the pilot increases the amount of propane to the burner, which which increases the flame and the buoyant force on the balloon.

To move the balloon downwards the pilot either decreases the amount of propane to the burner, deceasing the flame and the buoyant force on the balloon, so that its altitude decreases. The other way is for the pilot to open the parachute vent at the top of the envelope to release some of the hot air in the envelope, again decreasing buoyant force and the height of the balloon.

To maintain a relatively constant altitude, the pilot alternates in firing and not firing the propane to the burner, increasing and decreasing the buoyant force, so the balloon maintains a relatively stable altitude.

The wind is relied upon to move the balloon horizontally, the pilot's only control is to move the balloon up and down into different altitudes where the wind is blowing in a different direction. However the wind only leaves limited options, so an exact course of a balloon's flight cannot be predicted.




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