Raju was thrilled to learn that one could go up in the air using a hot air balloon. But he was curious to know how far up one could go. Also, what it would look like from the balloon. He had many questions: “We will be able to get some very nice pictures of the ground below. I wonder what these balloons are used for? Can we go beyond the clouds? Will the balloon keep going upwards? How far up can we go in these balloons? Will we have to fire the burner more as we ascend and as the air becomes colder at higher altitudes? What will happen if the balloon gets punctured? What if it starts raining as the balloon is going up? How heavy is the basket? How is the balloon steered in the required direction or does it just drift with the air currents? How is the bucket connected to the balloon? Can a balloon collide with an airplane?” He asked all his questions in one go.
Raju’s father smiled at his curiosity. He liked that Raju always asked questions. “Stop Raju, I will answer all your questions – but one at a time. You have blasted me with so many questions that I think I must have forgotten half of them,” he laughed.
He continued, “Modern hot air balloons are made out of nylon fabric and the throat of the balloon close to the gas burner is lined with fire resistant material. Today, there are hot air balloons of a variety of shapes available, as they are also used for commercial purposes. However, the traditional shape is most common. Like umbrellas, they are also made from sectors stitched with a double fold along with the vertical load tapes. These load tapes are stitched in the form of loops to connect the bucket to the balloon. The inner wall of the balloon is coated to make the fabric impermeable to the air.”
He added, “One of the main purposes of hot air balloons is to get an experience of floating in the air and a bird’s-eye view of the things below. Some offer this ride commercially to passengers, students, photographers, etc. They are also used for advertising displays at very low heights. Sometimes during a match they release a hot air balloon above the stadium and a camera is mounted on it. The aerial shots from this camera are shown sometimes. The balloon will mostly display the name of the main sponsors of the event. Before satellites, hot air balloons were used for spying. They can also be used in research in meteorology ie the study of weather parameters. Weather research balloons are usually unmanned as it is very severely cold at the high altitudes that they dwell. These are operated remotely. As far as steering of the balloons is concerned, there is no specific mechanism – it depends on the drift of the wind. The pilot can only ascend or descend by either heating the air by the burners or venting out the hot air from the balloon.”
(Writer is a mechanical engineer and runs a hands-on science activity centre at Margao)