If you have seen one of the many hot air balloons in the sky, you may have asked yourself the question: How does a hot air balloon fly?
In one word: buoyancy
Understanding the question, “How does a hot air balloon fly?” is a matter of understanding buoyancy. Similar to a boat in the water, in that the boat must be not as dense as the water itself, the air in a hot air balloon must be less dense than the air around it.
This is where the burner on a balloon comes into play; it fills the balloon with hot air. As most people know, hot air rises. Hence, the balloon rises.
Aside from just knowing about buoyancy and hot air rising, understanding the three main parts of a balloon – the envelope, burner, and basket – are important to understanding how does a hot air balloon fly.
The balloon itself, which is often colorful is the envelope. Most the time hot air balloons that people ride in are made from synthetic fabric – this is light, durable, and strong. The material is sewn tightly together to prevent leaks. Different vertical sections are called gores. The top of the balloon is called the crown (and it normally has a little hole called the parachute vent that is controllable by a pull cord). At the bottom, you have the throat where the balloon opens up.
Propane cylinders normally supply the envelope with hot air. While a balloon can run off of one burner, many are equipped with at least a second one.
This has two purposes:
- Two burners provide more hot air and give the balloon more lift.
- The second burner is for safety in case the first one fails.
This is the part that carries the passengers. Generally, a wicker basket is used because it is light and durable. Not to mention, the basket is absorbent, which is good for taking in some of the impact in case the balloon lands quicker than the pilot intends.
Launching a Hot Air Balloon
Now that we talked about the three parts of a hot air balloon let us take a look at the initial question at hand: How does a hot air balloon fly?
To fly, or “launch,” a hot air balloon you:
- Unwrap the envelope and lay it out on the ground.
- Tie the burners and basket to the envelope.
- Use a large fan (or fans) to fill the balloon with cold air first.
- Remove the fan and start the burners.
- Once the balloon is hot enough, it will rise.
Controlling the Flight
A hot air balloon – while peaceful and transcending – does not offer as much control of the flight as a plane or helicopter would. You cannot control the direction you fly in as much. Basically, hot air balloon pilots control the rising and falling of the balloon.
The pilot makes the balloon descend by opening up the envelope, decreasing the amount of hot air. The pilot makes the balloon rise by turning on the burners, adding more hot air to the balloon.
How does a hot air balloon fly other than going up and down? Experienced pilots will tell you that moving sideways is possible by catching air currents. Wind gusts blow differently depending on how high in the air you are. This does not give the hot air balloon pilot very many options. Because of the varied nature of a balloon’s course, a ground crew normally follows the balloon.
But even the most seasoned hot air balloon pilots do not have as much control over the wind; the flight journey is often wind dependent, but in a way this makes flying in a hot air balloon that much more of an adventure.
More information can be found here.