Once upon a time, there were two brothers who were so fascinated with flying that they invented the world’s first flying device. I am not talking about the Wright brothers, and the flying device in question is not an airplane. Not many of us know that the actual pioneers of flying were Montgolfier brothers, who invented hot air balloon in the year 1783.
While airplanes provide the comfort of flying, and skydiving can give you the adrenaline rush of flying, but the leisurely experience of flying can be enjoyed only on a hot air balloon. These rides are known for their breathtaking view of the horizon and are quite popular among people of all ages. But have you ever wondered how does a hot air balloon manage to float in the air? Today we will be discussing the principle behind the flight of hot air balloon.
Thermal Expansion of air
The hot air balloon functions on the simple concept of thermal expansion of air. Consider this: the name 'hot air balloon' itself gives away its working principle based on hot air.
We all know the fact that hot air rises above the ground and moves up because it is less dense when compared to cold air. But what makes hot air lighter than cold air? According to the principle of thermal expansion, when the air is heated, the air molecules acquire kinetic energy and start moving rapidly. These rapid moving air molecules collide with each other and move further away, thus increasing the space between the molecules. And that is why hot air is less dense with respect to cold air.
Construction of Hot Air Balloon
To make a hot air balloon, you need three things: an envelope, a basket, and a burner. The envelope is made of strong, durable, synthetic material like nylon with a small hole on top and bottom. The hole on top of the envelope is called parachute vent and it is generally shut tight with a cork. The parachute vent can be opened to release hot air for a quicker descent. The hole at the bottom of the envelope provides the opening for the burner to heat the air inside the envelope. The burner generally consists of two propane cylinders that generate fire for heating the air. Last, but not least, is the basket that is meant to carry passengers.
Working of Hot Air Balloon
Once the envelope is filled with tons of air, the burner ignites a fire that is used to heat the air inside the envelope. Since the hot air in the balloon is lighter than the cold air of the surroundings, the hot air balloon starts to ascend. The balloon keeps moving higher till the air inside it is comparatively cooler than the air above it. In order to bring the balloon back to the ground, one needs to stop blasting the burners. Once the burner stops heating the air inside the balloon, the hot air starts to cool down, ensuring that the air in the balloon is denser than the air below it. The cooler the air inside the balloon becomes, the lower will be the flying altitude of the balloon. Alternatively, one can open the parachute vent to release the hot air and speed up the process of descent.
