|Vol. 17, No. 4||Sept. 25, 1997|
A typical hot air balloon is 63 feet in height (almost seven stories high) and 55 feet in diameter. The weight is 214 pounds for the envelope (the proper term for the colorful balloon part) and 450 pounds for the entire system including fuel and passengers. Most envelopes have a volume of 65,000 to 105,000 cubic feet.
They fly simply by getting hot. As the air inside the balloon becomes hotter than the air outside, it gets lighter. When the weight of the air inside the balloon, plus the weight of the balloon and its passengers, is less than the weight of the same volume of air outside, the balloon will begin to float.
The balloon (envelope) is made of reinforced nylon, although certain balloons are made of dacron. Despite their very light weights, these materials are very resistant. The cloth's interior is leak-proofed. Baskets are made of wicker or rattan and entirely hand-woven.
Propane is kept in pressurized tanks attached to the basket floor. A single hot air balloon carries 30-40 gallons of liquid propane. Flames may shoot up to 15 to 20 feet and make a loud, characteristic sound when the burner ignites.
Balloons fly as fast or as slow as the wind that carries them. Since a hot air balloon has no propulsion system, speed is completely dependent on wind velocity.
On board there is an altimeter, a rate-of-climb meter, an inside-envelope temperature thermometer and a two-way radio.
Inflating a hot air balloon requires a team effort, since a balloon is very cumbersome on the ground. If the wind flares up, it may take a four-person team to inflate a hot air balloon. The first step is to spread the envelope out on the ground and then attach it to the basket, which is laid down on its side.
Each hot air balloon has a torch pointed right up into the center of the balloon. The torch, called a burner, burns propane to heat the air inside the balloon like a home furnace would heat the air inside your home-although the heat a balloon furnace produces is about five times as strong as that of a home furnace. Using a small fan, the hot air is blown into the envelope. The 200-300 degree Fahrenheit heated air rises and brings the balloon to its vertical position.
Balloons are not steered. Winds are generally layered in different directions at different altitudes. The pilot ascends until he or she finds a wind going in the right direction. The pilot has close control over altitude and the rate of ascent or descent by manipulating the burner and vents. Most balloons have a parachute valve at the top to release hot air, which can be opened by pulling a valve line. Once air is released, the balloon will descend.
Yes, a balloon pilot's license is issued by the Federal Aviation Administration. Requirements include passing a written examination, logging 35 hours, flying six training flights with a certified instructor, training in ascent and rapid descent and passing a flight test.
Balloons generally fly between 1,000 to 3,000 feet above the ground. They also can choose to skim the treetops or fly much higher, to about 20,000 feet.
A hot air balloon is recovered by a chase crew traveling aboard a small truck or van. The crew follows the balloon (roads permitting) and must reach the landing site before the balloon touches down. For each balloon launch, a radio-equipped ground crew of three to four people is needed to ensure a successful flight.