Flying Theory of Hot Air Balloon
Composition of hot air balloons
A hot air balloon is made up of the envelope, burner, and basket.
The EnvelopeThe envelope is coated with a special material. It is made of heat resistant, high strength polyester or nylon. It is light, strong and tear resistant. According to FAI’s envelope size classes, Taiwan’s balloons fall into 3 classes: AX8, AX9, and AX10. The sizes range from 2200 cubic meters to 6000 cubic meters and can carry 4~10 people.
Heating system - Burner, fuel tankThe burner is what provides lift in a hot air balloon. It is made of metal and the fuel is pressurized propane stored in the fuel tanks. After fully vaporizing the liquid propane in the tank through the coil and mixing the vapor with air at the exit, the fuel reacts with the pilot light to create flames. Through the pilot’s intermittent control of the main valve, the air in the envelope can be heated. When the air is heated, its volume expands and its density decreases, thereby creating lift.
The BasketThe basket is weaved from rattan. Because of the material’s light weight and elasticity, it can reduce the impact between the basket and the ground. Also, rattan is an abundant material, and therefore it is widely used in the production of balloons. The basket is mainly used to carry the pilot, passengers, fuel tanks and equipment. The basket’s size is dependent on the size of the envelope. Normally, it is rectangular in shape. The smallest baskets can carry one person while the largest can carry over 20. Currently, Taiwan balloons are all AX class balloons, including: class size 8, 2400 to 3000 cubic meters; class size 9, 3000 to 4000 cubic meters; class size 10, 4000 to 6000 cubic meters. All the baskets are rectangular and can carry 4 to 6 people.
Principles of hot air balloon flight
Through intermittent control of the burner by the pilot, the air in the envelope is heated. As the air is heated, its volume expands and its density decreases, thereby creating lift.
A hot air balloon is not truly “piloted”. It simply flies where the wind blows. Normally, in the Northern Hemisphere, winds will generally deflect from the ground to high altitudes in a clockwise direction (under the interaction of the pressure gradient force, the Coriolis force, and the friction force). Therefore, balloon pilots must collect wind data before each flight to understand wind conditions at different altitudes on the day. Furthermore, through burner control and heating the air in the envelope, the pilot can change the balloon’s vertical height and reach the desired destination.