How Does the Balloon Work?

How Does a Balloon Work?

In order to understand competition ballooning, some base knowledge of how hot air balloons work and their anatomy is required, because I'll be using a lot of jargon in this section and throughout this website.

A hot air balloon is composed of 3 main components: the basket, the burners, and the balloon.

The Basket

The basket houses any on board passengers and the pilot, as well as the following items:

Propane tanks
Aircraft documentation
Fire extinguisher
"Drop Line" (used during landings)
Strikers (redundancy)
2-way radios

This is by no means an exhaustive list, but rather a reference. In competition, the basket can also contain navigation tools, laptops, competition markers, and more.

The basket typically uses wicker as the support structure, although in recent years the collapsible basket has seen a rise in popularity. In that case, it is composed of fabric sides with material inserts for protection and ratchet straps tensioning the entire assembly to provide stability.

The Burner

The burner is the key to the entire assembly. Without the burner, there is no heating implement to create the temperature difference that causes lift.

In a modern burner, propane enters the assembly through hoses. In the image above, it enters on either side of the operators hands. There, it encounters three valves: the pilot light, blast valve, and liquid (whisper) valve.

The pilot light is functionally the same as the pilot light on a gas grill. It maintains a small sparking flame which lights the fuel from either of the other valves that remains constantly lit.

The blast valve is the primary flight valve. When opened, it guides the propane through a series of coils. This takes it from a saturated liquid state (at very high pressure and room temperature) to a superheated vapor state while maintaining high pressure. It then shoots through a series of jet nozzles, producing a muted but very powerful flame.

Finally, the whisper valve. The whisper valve bypasses the superheating process, opting instead to send the propane directly to the jet. This maintains a liquid state and produces a lower pressure but brighter flame. If you have ever had the privilege of witnessing a hot air balloon glow, you have most likely seen this flame.

The Balloon

The final component of this assembly is the balloon. The balloon is surprisingly complex for what may seem to be a simple concept.

The balloon is constructed a skeleton of "load tapes". Load tapes are composed of very high strength fabric that holds the weight of everything the balloon carries. In the image above, the load tapes are the grid-like structure seen around the balloon panels. Additionally, should a tear in the envelope occur, the load tapes act as a stopper to prevent that tear from spreading.

In between the load tapes is the fabric of the balloon. There are several types of fabric which offer their own advantages and disadvantages. All of the fabric have some sort of a coating which prevents air inside from escaping.

Inside of the balloon are several ropes and pullies to manipulate the motion of the aircraft. The most important of these is the "red-line". The red line pulls down on the parachute at the top (seen as the discontinuity in the shape of the envelope at the very top). This allows hot air to escape the balloon, reducing the lifting capacity and most commonly causing a descent or reduction in vertical motion.

At the bottom of the balloon, just before the connection with the burners, is a specialized fabric called Nomex. Nomex is the same fabric used in firefighting suits and feels much more "canvas-y" than the rest of the balloon. Nomex is used because it does not burn but scorches instead, making it ideal for proximity to the balloon.

How Does It Fly?

Hot air balloons take advantage of density-based bouyancy. For most fluids (liquids and gasses), as their temperature increases their density decreases. Functionally, this means that if I have 2 containers of the same size but one is at 0 Fahrenheit and one is at 100 Fahrenheit, the hotter one will have less atoms in it than the colder one.

The difference in atom quantity leads to a difference in weight than the surrounding environment. This forces the lower weight volume to seek a similar air density, causing lift.

So How Do You Steer?

Balloons don't steer in the traditional sense. They have no on-board propulsion implement capable of changing direction or momentum instantaneously.

What they do have, however, is the burner and the red line. The burner heats the envelope, and the red line functionally cools the envelope. This means that the only true control a pilot has is up and down, but it hasn't answered the left-right issue yet.

For that, we have to thank the Earth. This is because the key in balloon steering is wind. At different altitudes, the wind is blowing in different directions. This means that purely through ascent and descent, pilots can decide what direction they want to go.

Pibals

A common question after the steering conversation is "How do you know what way the wind is going". There are several answers to this question. The most common and oldest method is surprisingly simple. Pilots will inflate a large black balloon with helium, release it, and watch with a sighting compass. Helium has a set rate of ascent, so this allows the pilots to have a rough idea of what the wind is doing.

In recent years, this question has become much more technically involved. Now, there are several winds aloft models and tools that can be used, which break down wind speed, direction, and altitude by time. Additionally, pilots can attach sensors to the bottom of the balloons which track change in position and altitude to provide more accurate information.

Photo Credit: Jackson Hot Air Jubilee

Inflation

Before flying, the balloon must be "stood up". This starts with the balloon being laid out on the ground and assembled. This involves building the basket and laying it on its side. Then, the envelope (in the bag) is placed in front of the basket. This makes it easier to connect the balloon to the basket. This is done by attaching 4 carabiners (one at each corner of the burner frame) to the basket. After it is connected, the rest of the balloon is pulled out of the bag.

Now that the balloon is assembled, it has to be filled with air. This is done using small engine gas-powered fans. Once the mouth is large enough to put heat into the balloon without burning it, the pilot crouches and uses the burner to apply heat until the balloon stands up.

Landings

So once your done flying, how do you land? The answer is surprisingly simple: drop until you hit the ground. In reality, there is much more nuance to this question. When the pilot determines that they are ready to land, the next goal is to look for (preferably) an open, grassy field to land in. Then, they perform a controlled descent until the basket makes contact with the ground. Sometimes, if it is breezier, this involves some dragging.

The #1 goal throughout this process is safety and respect for the land we are on. Rarely are pilots able to land on property they own. Obtaining landowner permission is always a priority, especially if the retrieval involves driving on the field or yard.

Retrieval and Packup

The final step in the process is to pack everything back up. The balloon packs down surprisingly small. The envelope bag itself is roughly 4 feet in diameter or smaller for racing balloons, and can pack down into approximately a sphere shape. This involves the help of the ground crew, the unsung heroes of ballooning.

The packup is why balloon pilots often drive pickup trucks, vans, or trailers. These vehicles are critical to the storage of the balloon. If a pickup truck or van is involved, pilots may use a liftgate to help with the heavy lifting.

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