15
Early Flying Structures
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Early Flying Structures
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The Montgolfier Brothers’ Hot Air Balloon
A hot air balloon is a balloon aircraft which is lifted by hot air. The first manned and untethered hot air balloon manufactured by the Montgolfier brothers lifted off the ground near Paris on 21 November 1783, a flight which took 25 minutes and covered about 7.5 km. The two brave passengers, a scientist and a marquis became the
pioneers of flight, as this event marked an important milestone in the history of conquering the air.
Dome
The Montgolfier balloon was constructed of sackcloth lined with paper. Today’s hot air balloons are made of non-elastic materials, therefore they do not change their size when heated.
Flight with hot air
There was an iron grill under the open bottom of the balloon, with burning straw and wood on it. The hot air and smoke lifted the balloon off the ground. Modern hot-air balloons heat the air in the envelope by burning propane gas in the burners. The heat generated in this way causes the balloon to rise.
Basket
Also called gondola, it is usually made of woven wicker or rattan as these materials are lightweight but strong and durable.
Forces
If the buoyant force is greater than the weight, the hot-air balloon rises.
If the buoyant force is equal to the weight, the hot-air balloon floats at the same height.
If the buoyant force is smaller than the weight, the hot-air balloon descends.
Buoyant force: It is generated by the heat produced by the burning of propane gas in the burners.
This is the force of gravity acting on the total mass of the hot air balloon. It points towards the Earth’s centre of mass. The buoyant force must be greater than the weight of the aircraft to lift it.
Modern hot air balloon
After the Second World War, scientific and technological
progress made hot
air balloons safer,
more durable
and more
manoeuvrable.
Operation of hot air balloons
Hot air balloons cannot be steered directly, they are carried by the wind. The wind blows in different directions at different heights. So, the only way
to change direction is by climbing or descending.
