Originally aired during the week of July 28, 2008
It's up, up, and away this week on the Montshire Minute as we consider the science and history of balloon travel. Let's begin our journey with some words by William Pène du Bois who says in his book
The Twenty-One Balloons, "The best way of travel...if you aren't in any hurry at all, if you don't care where you are going, if you don't like to use your legs, if you don't want to be annoyed at all by any choice of directions, is in a balloon. In a balloon, you can decide only when to start, and usually when to stop. The rest is left entirely to nature." Indeed, nature provides much of the beauty and incentive to travel by hot air balloon. Those who want to get from point A to point B would find this form of travel fairly impractical. You have only indirect control over direction and speed. But if you simply wish to experience the joy of flying, there's nothing quite like it.
What do a sheep, a duck, and a rooster have to do with hot air ballooning? They were its first passengers! In 1783, the Montgolfier brothers sent these animals on an eight-minute flight over France. Two months later, Marquis François d'Arlandes and Jean François Pilâtre de Rozier became the first human beings to fly in an untethered balloon. These pioneers flew in a Montgolfier balloon and covered approximately five-and-a-half miles over Paris in about 25 minutes.
Around the same time that Joseph and Etienne Montgolfier were developing the hot air balloon, Jacques Charles was working on a competing technology—the gas balloon—which did not require a heat source, but instead used a buoyant gas. In December 1783, a mere ten days after the first manned hot air balloon flight, Jacques Charles and Ainé Roberts ascended in the hydrogen-powered "La Charlière". This flight lasted for over an hour and a half and covered more than 27 miles. As it turned out, gas balloons became the predominant technology for more than 150 years. Today, hot air balloons are more common.
Hot air balloons are breathtaking to behold, floating so serenely up in the sky. But how do they get up there? The science is relatively straightforward: hot air is less dense, and therefore lighter, than cold air, causing it to rise. Essentially, as air is heated in a balloon, the molecules move more quickly and spread out; hence it takes fewer molecules of hot air to fill the same space. This results in lower density inside the balloon than outside. Voila! You have lift off!
A gas balloon does not require heat. It stays aloft by being filled with a gas less dense than air, such as helium or hydrogen. A blimp is a good example of a gas balloon.
The Montshire's visiting exhibition From Here to There features a miniature hot air balloon. Witness science at work as the balloon takes flight!
The burner is roaring under the envelope, heating the air in the hot air balloon and causing it to rise higher and higher. Just how high could it go? That depends on many factors, including the size of the balloon and the amount of oxygen in the air. Flights in hot air balloons have been recorded at over 50,000 feet. However, balloonists typically find flying most enjoyable at 1,200 to 3,000 feet above the ground.
How does a balloon get back down? Well, we know that when the air inside the balloon is heated, the balloon rises. Conversely, when the air inside the balloon cools or if hot air is vented out at the top, the balloon will descend. So, the basic controls are heat to make the balloon rise and venting to make it descend.
To see a hot air balloon rise and sink, visit the Montshire by September 7 and explore the traveling exhibition From Here to There.
We're soaring through the air, pushed along by the wind, but all is peaceful. We can't feel any breeze at all since our hot air balloon moves at the same speed as the wind. As aviation pioneer Alberto Santos-Dumont described, "The balloon seems to stand still in the air while the earth flies past underneath."
But which direction should we make the earth move? The balloon has no steering wheel, no rudder... We must rely on the caprices of the wind to move horizontally. Fortunately, the wind blows in different directions at different altitudes; hence, we can ascend or descend to catch the preferred wind. As you can see, hot air ballooning is largely improvised. Lucky for us, some members of the balloon crew are following our course by car and will pick us up when we land.
The Montshire's hot air balloon is easy to track. It is on the second floor of the Museum through September 7 as part of the traveling exhibition From Here to There.
