About Hot Air Ballooning
How do balloons fly?
Hot air balloons fly because hot air rises. When the pilot heats the air inside the envelope, it becomes lighter and the balloon floats up into the sky. A hot air balloon is inflated partially with cold air from a gas-powered fan, before the propane burners are used for final inflation.
The pilot can control the balloon’s height by adjusting the temperature of the air inside the balloon. To make the balloon come down, the air inside the balloon is allowed to cool. To climb, more heat is added, increasing lift.
How do you steer a balloon?
The short answer is that you don’t!
However, it isn’t as uncontrolled as that might seem.
The pilot gets full aviation weather reports from various sources, which may include government or private services. Prior to flight, the pilot releases small helium balloons to see the wind direction and speed. Often there are layers of wind that are going in different directions or moving at different speeds.
After analyzing the weather reports and the actual conditions observed, the pilot will make a decision to fly or not, as well as selecting a launch site appropriate for that flight. since the balloon floats with the wind, the pliot knows which direction the balloon will travel so the launch site is selected which will allow the balloon to fly into an area with appropriate landing sites.
Once airborne, the pilot can move the balloon up and down to utilize the varying directions of wind to change course. Some days the change in direction is quite significant, while at other times there may be little or no change in direction at any altitude. All these factors are taken into account when the pilot determines if the flight will take place or not.
There are even days when there may not be enough wind movement above the earth to fly at all. If there is little or no wind, or if the wind direction is constantly changing, the pilot may decide it isn’t safe to fly. If the balloon just sits overhead with little movement, it may be very difficult for the pilot to find a suitable landing spot.
How many people fit in a balloon?
Balloons come in all different sizes, from small one person balloons to very large balloons that can carry 15 or more passengers. Balloon ride companies operate a wide range of balloons so check with the company you want to fly with to see how many people will be aboard during your flight. Those booking a balloon flight at this event will be booked by weight according to the capacity of each balloon.
What are balloons made of?
The large fabric part, or envelope, is usually made of rip-stop nylon or dacron polyester. The lower portions around the opening are usually made from a fire-resistant material like Nomex, similar to what race car drivers and firemen wear.
Baskets are usually woven out of wicker since it is strong, lightweight and flexible. It is also very easy to maintain and holds up well under the stress of repeated landings.
Why do balloons use wicker baskets to fly in?
While many materials have been used for balloon baskets, wicker is by far the most popular for several reasons:
- It is lightweight and flexible
- It is strong and can withstand the stress of landing
- It is flexible
As a bonus, it also looks nice and fits the traditional image of ballooning as an old-world activity!
What fuel do hot air balloons use, and where is it carried?
Propane is the most common fuel, but butane is sometimes used in remote areas when propane is not available. The fuel is carried in aluminum or stainless steel tanks that range from 10 to 25 gallons in size. Average fuel consumption is about 15 gallons an hour for an average sport size balloon.
A hot air balloon is a lighter than air aircraft consisting of a bag, called an envelope, which contains heated air. Suspended beneath is a gondola or wicker basket, which carries passengers and (usually) a source of heat, in most cases an open flame. The heated air inside the envelope makes it buoyant since it has a lower density than the colder air outside the envelope. As with all aircraft, hot air balloons cannot fly beyond the atmosphere. Unlike gas balloons, the envelope does not have to be sealed at the bottom, since the air near the bottom of the envelope is at the same pressure as the surrounding air. In modern sport balloons the envelope is generally made from nylon fabric and the inlet of the balloon (closest to the burner flame) is made from a fire-resistant material such as Nomex.
A hot air balloon for manned flight uses a single-layered, fabric gas bag (lifting “envelope”), with an opening at the bottom called the mouth or throat. Attached to the envelope is a basket, or gondola, for carrying the passengers. Mounted above the basket and centered in the mouth is the “burner”, which injects a flame into the envelope, heating the air within. The heater or burner is fueled by propane, a liquefied gas stored in pressure vessels, similar to high pressure forklift cylinders.
During the manufacturing process, the material is cut into panels and sewn together, along with structural load tapes that carry the weight of the gondola or basket. The individual sections, which extend from the throat to the crown (top) of the envelope, are known as gores or gore sections. Envelopes can have as few as 4 gores or as many as 24 or more.
Envelopes often have a crown ring at their very top. This is a hoop of smooth metal, usually aluminum, and approximately 1 ft (0.30 m) in diameter. Vertical load tapes from the envelope are attached to the crown ring.
At the bottom of the envelope the vertical load tapes are sewn into loops that are connected to cables (one cable per load tape). These cables, often referred to as flying wires, are connected to the basket by carabiners.
The most common technique for sewing panels together is called the French felled, French fell, or double lap seam. The two pieces of fabric are folded over on each other at their common edge, possibly with a load tape as well, and sewn together with two rows of parallel stitching. Other methods include a flat lap seam, in which the two pieces of fabric are held together simply with two rows of parallel stitching, and a zigzag, where parallel zigzag stitching holds a double lap of fabric.
The top of the balloon usually has a vent of some sort, enabling the pilot to release hot air to slow an ascent, start a descent, or increase the rate of descent, usually for landing. Some hot air balloons have turning vents, which are side vents that, when opened, cause the balloon to rotate. Such vents are particularly useful for balloons with rectangular baskets, to facilitate aligning the wider side of the basket for landing.
Baskets are commonly made of woven wicker or rattan. These materials have proven to be sufficiently light, strong, and durable for balloon flight. Such baskets are usually rectangular or triangular in shape. They vary in size from just big enough for two people to large enough to carry thirty. Larger baskets often have internal partitions for structural bracing and to compartmentalize the passengers. Small holes may be woven into the side of the basket to act as foot holds for passengers climbing in or out.
A burner directing a flame into the envelope gasifies liquid propane, mixes it with air, ignites the mixture, and directs the flame and exhaust into the mouth of the envelope. Burners vary in power output; each will generally produce 2 to 3 MW of heat (7 to 10 million BTUs per hour), with double, triple, or quadruple burner configurations installed where more power is needed. The pilot actuates a burner by opening a propane valve, known as a blast valve. The valve may be spring-loaded so that it closes automatically, or it may stay open until closed by the pilot. The burner has a pilot light to ignite the propane and air mixture. The pilot light may be lit by the pilot with an external device, such as a flint striker or a lighter, or with a built-in piezo electric spark.
Propane fuel tanks are usually cylindrical pressure vessels made from aluminum, stainless steel, or titanium with a valve at one end to feed the burner and to refuel. They may have a fuel gauge and a pressure gauge. They may be intended for upright or horizontal use, and may be mounted inside or outside the basket.
Stainless steel fuel tanks, wrapped in red insulating covers, mounted vertically, and with fuel gauges, during refueling.
The pressure necessary to force the fuel through the line to the burner may be supplied by the vapor pressure of the propane itself, if warm enough, or by the introduction of an inert gas such as nitrogen. Tanks may be preheated with electrical heat tapes to produce sufficient vapor pressure for cold weather flying. Warmed tanks will usually also be wrapped in an insulating blanket to preserve heat during the setup and flight.
On the ground crew
The ground crew helps control the envelope with ropes during inflation. The ground crew then “chases” the balloon during the flight to assist in dismantling, folding, and packing the balloon in the chase vehicle. The ground crew should wear gloves whenever there is a possibility of handling ropes or lines. The mass and exposed surface to air movement of a medium-sized balloon is sufficient to cause rope friction burns to the hands of anyone trying to stop or prevent movement. The ground crew should also wear sturdy shoes and at least long pants in case of the need to access a landing or landed balloon in rough or overgrown terrain. Those interested in joining a ground crew may contact the event balloonmeister for more information.
Depending on the size of the balloon, location, and intended use, hot air balloons and their pilots need to comply with a variety of regulations. All balloonist participating in this event are commercial licensed pilots.