| Hot air balloons are one of the oldest | | | | It won't rise forever, though. The |
| flying machines ever invented, and they | | | | atmosphere thins as it goes up, and |
| work on a very simple principle: hot air | | | | eventually the air within the envelope |
| rises. | | | | is too thin to support the weight of the |
| For practical purposes, hot air balloons | | | | balloon. The more air within the |
| really can't compete with airplanes and | | | | balloon, the greater the buoyancy-so |
| helicopters. They're extremely difficult | | | | bigger balloons can go higher than |
| to steer, and they can only move as | | | | smaller ones. |
| quickly as the surrounding winds. But as | | | | A pilot can cause the balloon to rise by |
| a recreational activity, hot air | | | | turning on the propane burner and |
| ballooning can't be beat. You're | | | | heating the air within the envelope. To |
| outside, feeling the wind in your hair | | | | bring the balloon down, the pilot |
| and the sun on your face, drifting | | | | releases the parachute valve. That's a |
| serenely over the earth. If you've ever | | | | vent in the top of the envelope that |
| been in a hot air balloon, you know it's | | | | allows some of the hot air to escape, |
| an experience you won't soon forget. | | | | cooling the temperature of the remaining |
| Hot air is less dense, and lighter, than | | | | air within. This causes the balloon to |
| cold air. Because it's lighter, it tends | | | | sink gradually. |
| to rise. If you've ever taken a dive | | | | There are no horizontal controls in a |
| into a pool, you may have felt this | | | | balloon, but pilots can still control |
| effect in water: the surface water is | | | | the horizontal movement by raising and |
| warm, but as you move deeper, the water | | | | lowering the altitude of the craft. |
| gets cooler. That's because warm water | | | | Winds at different altitudes move in |
| is lighter than cool water and tends to | | | | different directions. If a pilot has a |
| rise to the top, like air. | | | | good working knowledge of the wind |
| The air within a hot air balloon is | | | | currents in the area, she can raise and |
| heated, and as it rises, it takes the | | | | lower the balloon to catch a current |
| balloon-and anything attached to it-with | | | | moving in the right direction. |
| it. A cubic foot of air within a balloon | | | | Still, piloting a balloon isn't an exact |
| can lift about seven grams of weight. | | | | science. It's impossible to target the |
| This isn't a lot of weight, which is why | | | | precise location where you'll land. |
| the balloon has to be so big. | | | | That's why it's usually necessary for |
| The balloon itself is called an | | | | someone on the ground to follow the |
| "envelope." It's usually made of nylon, | | | | balloon by car to meet the balloon where |
| which is the perfect fabric for hot air | | | | it lands and transport the equipment. |
| balloons: it's lightweight but sturdy, | | | | Launching and landing generally take |
| and it can withstand heat without | | | | more work than actually flying a |
| melting easily. | | | | balloon. The inflation process takes |
| Below the balloon, a burner is | | | | only about ten or fifteen minutes, and |
| positioned to send a jet of flame upward | | | | is done with a powerful fan. Once the |
| into the envelope. The burner uses | | | | balloon is full of air, it will still |
| propane as a fuel. The fuel is stored as | | | | lie on the ground until the burner is |
| a highly compressed liquid in canisters | | | | fired, heating the air in the envelope |
| attached to the burner with a fuel hose. | | | | and causing it to rise. |
| Because it's so highly compressed, the | | | | A balloon descends gradually, but can |
| liquid fuel flows quickly through the | | | | still land with a bit of a bump if the |
| hose to the burner when the pilot turns | | | | pilot isn't experienced enough to know |
| it on. There, it's ignited by a pilot | | | | how to bump the basket along the ground |
| light. The flame heats up the | | | | to lessen the impact. The wicker basket |
| surrounding metal of the burner, which | | | | helps absorb the force of the landing. |
| turns the fuel to gas before it gets | | | | Wicker is lightweight and flexible, and |
| lit. This makes the flame stronger and | | | | absorbs the energy of landing better |
| the fuel usage more efficient. | | | | than a solid, less flexible basket |
| If you look at a hot air balloon, you'll | | | | would. This way, riders aren't jarred |
| notice a big hole in the bottom where | | | | when the ride is over. |
| the burner is. So why doesn't the hot | | | | There's nothing like soaring over the |
| air escape through the hole at the lower | | | | earth in a balloon. Hot air balloons are |
| end? Simple: buoyancy. Hot air is | | | | exciting, fascinating, and pure fun. If |
| buoyant, which means it can only rise-it | | | | you've never taken a ride in one, you're |
| can't sink and drain out the bottom of | | | | definitely missing out on an experience |
| the balloon. As long as the air stays | | | | you'll never forget. |
| hot, it will continue to rise. | | | | |