How does a hot air balloon maneuver?

Answer 1

Piloting a balloon takes skill, but the controls are actually very simple. To lift the balloon, the pilot moves a control that opens up the propane valve. This lever works just like the knobs on a gas grill or stove: As you turn it, the flow of gas increases, so the flame grows in size. The pilot can increase the vertical speed by blasting a larger flame to heat the air more rapidly.

Additionally, many hot air balloons have a control that opens a second propane valve. This valve sends propane through a hose that bypasses the heating coils. This lets the pilot burn liquid propane, instead of propane in gas form. Burning liquid propane produces a less efficient, weaker flame, but is much quieter than burning gas. Pilots often use this second valve over livestock farms, to keep from scaring the animals.

Hot air balloons also have a cord to open the parachute valve at the top of the envelope. When the pilot pulls the attached cord, some hot air can escape from the envelope, decreasing the inner air temperature. This causes the balloon to slow its ascent. If the pilot keeps the valve open long enough, the balloon will sink. Essentially, these are the only controls -- heat to make the balloon rise and venting to make it sink. This raises an interesting question: If pilots can only move hot air balloons up and down, how do they get the balloon from place to place? As it turns out, pilots can maneuver horizontally by changing their vertical position, because wind blows in different directions at different altitudes. To move in a particular direction, a pilot ascends and descends to the appropriate level, and rides with the wind. Since wind speed generally increases as you get higher in the atmosphere, pilots can also control horizontal speed by changing altitude.