HOT AIR BALLOON FLIGHT
One fine morning in June 2003, while we were with my son’s family in Ottawa, Canada, he took us to the office of Sky View. From there their cheerful hostess took us to the place from where the hot air balloons are launched.
We saw three huge balloons laid down on the ground. We were met by the operator who explained about the balloon and the flight.
The Balloon consists basically of the envelope (the balloon made of tough nylon), the skirt which is the bottom part of the envelope and which is made of fire resistant material, the burners and the wicker basket in which the passengers are carried. The basket, some times called the gondala also has a chamber in which cylinders of Propane gas are kept.
Most hot air balloons use a wicker basket for the passenger compartment. Wicker works very well because it is sturdy, flexible and relatively lightweight. The flexibility helps with balloon landings. In a basket made of more rigid material, passengers would feel the brunt of the impact force while landing. Wicker material flexes a little, absorbing some of the energy.
The balloon is about 70 ft high.
The propane is stored in compressed liquid form, in lightweight cylinders positioned in the balloon basket. The propane changes from a liquid to a gas as it comes out of cylinders, before it is ignited. This gas makes for a more powerful flame and more efficient fuel consumption. The lighter looks like a flame thrower. A huge fan throws air into the balloon and as it gets into the balloon it is heated by the flame, the balloon starts swelling majestically and becomes upright.
Generally since the basket is quite high, some passengers get into it in the lying down position and start standing as the balloon becomes upright. The crew hold on to the basket till the balloon is fully inflated.
We were lifted gently, watching the earth fall away below us. Soon, we were flying over the town, roads, railways and green plains at a height of about 2500 ft. We dipped down to kiss the waters of a limpid lake, then floated up again. Most of us had never seen the world from this perspective. There’s no rush, no urgency, no whirring of engines. It’s peaceful, serene and incredibly beautiful. There’s no feeling quite like it, nothing on earth that can match the magic of floating on air, the sense of being at one with the sky and looking down at a world that is looking up at you!
Piloting a balloon takes skill, but the controls are actually very simple. To lift the balloon, the pilot moves a control that opens up the propane valve. This lever works just like the knobs on a gas grill or stove: As you turn it, the flow of gas increases, so the flame grows in size. The pilot can increase the vertical speed by blasting a larger flame to heat the air more rapidly.
Before we realized it the one hour of flight was to come to an end and the pilot started looking for landing grounds. It is a remarkably serene, peaceful experience. Since the balloon moves with the wind, you don't feel any breeze at all. Without the rushing winds you normally associate with high altitudes, the experience of flying seems very safe and calming -- you simply lift off the ground and move with the air in the atmosphere.
When the pilot was ready to land, he discussed possible landing sites with the ground crew (via an onboard radio). They need to find a wide open space, where there are no power lines and plenty of room to lay out the balloon. As soon as the balloon is in the air, the pilot was constantly looking for suitable landing sites, in case there is an emergency.
We were warned that the balloon landing could be a little rough, but the pilot bumped along the ground to stop the balloon gradually, minimizing the impact. The basket remained vertical. The ground crew had made it to the landing site and held the basket down once it landed. The second balloon behind us had a rough landing. The crew had to pull it along the ground to a better spot and in the process the basket fell on its side giving a series of jolts to the passengers.
The hostess was there to receive us with a bottle of champagne and a Certificate of Hot air Balloon flying.
All in all we had a soaring experience.
FOR THOSE INTERESTED IN TECHNICAL POINTS:
Hot air balloons are based on a very basic scientific principle: warmer air rises in cooler air. Essentially, hot air is lighter than cool air, because it has less mass per unit of volume. A cubic foot of air weighs roughly 28 grams (about an ounce). If you heat that air by 100 degrees F, it weighs about 7 grams less. Therefore, each cubic foot of air contained in a hot air balloon can lift about 7 grams. That's not much, and this is why hot air balloons are so huge -- to lift 1,000 pounds, you need about 65,000 cubic feet of hot air.
Essentially, these are the only controls -- heat to make the balloon rise and venting to make it sink. This raises an interesting question: If pilots can only move hot air balloons up and down, how do they get the balloon from place to place? As it turns out, pilots can maneuver horizontally by changing their vertical position, because wind blows in different directions at different altitudes. To move in a particular direction, a pilot ascends or descends to the appropriate level, and rides with the wind. Since wind speed generally increases as you get higher in the atmosphere, pilots can also control horizontal speed by changing altitude.
The hot air won't escape from the skirt at the bottom of the envelope because buoyancy keeps it moving up. If the pilot continually fires the fuel jets, the balloon will continue to rise. There is an upper altitude limit, however, since eventually the air becomes so thin that the buoyant force is too weak to lift the balloon. The buoyant force is equal to the weight of air displaced by the balloon, so a larger balloon envelope will generally have a higher upper altitude limit than a smaller balloon.
Hot air balloons also have a cord to open the parachute valve at the top of the envelope. When the pilot pulls the attached cord, some hot air can escape from the envelope, decreasing the inner air temperature. This causes the balloon to slow its ascent. If the pilot keeps the valve open long enough, the balloon will sink.
