IELTS TASK 1 - diagram

The diagrams show the designs and mechanics of a common hot balloon. Overall, the balloon consists of several mechanisms cooperating to produce the weight difference between internal and external air.
The biggest part of the balloon is the envelope, which is made from many gores and panels sewed together. It expands at the top and tapers at the bottom as it gets closer to the basket. At the top, there is a flap called the valve to control the rate of escaped air. The envelope is attached to the basket using several ropes and the burner hangs above the basket. In the basket, there are some propane cylinders providing fuel for the engine to work.
The burner will ignite the mixture of propane and air to propel the hot air into the envelope. The hot air will then be trapped inside and the escape rate will be regulated by the self – sealing valve at the top, which makes it possible to control the difference in weight between the internal and external environment. As the hot air inside the balloon is lighter, it will drive the balloon up while the cool air outside goes down.