Hot air balloons are also an ingenious application of basic scientific principles. In this article, we'll see what makes these balloons rise up in the air, and we'll also find out how the balloon's design lets the pilot control altitude and vertical speed. You'll be amazed by the beautiful simplicity of these early flying machines.
 A four-passenger CargoLifter hot air balloon. See more hot air balloon pictures. |
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.
If you’re interested in getting a birds-eye-view of the world, then you should check out the paragliding article, video and images at Discovery’s Fearless Planet.
