How does the pilot control the balloon?
The pilot controls the vertical access by heating or cooling the balloon (envelope). If the pilot adds heat to the envelope the balloon goes up and if he lets the envelope cool, the balloon will go down. If the pilot wants to stay buoyant in equilibrium, he will keep the envelope at the same temperature. The balloons fly by the wind. If there are winds of different direction in different heights the pilot can go up or down and steer the balloon according to the direction of the wind.
