Lighter than air

Empty, it weighs three tons, but just add helium and it's ...

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I feel as though I'm stuck to the bottom of a huge orange beach ball, floating through the sky. The wind pushes us up and down, side to side. Were it not for the loud and steady rumble of two giant fanlike engines, I might think I was on a runaway birthday balloon.

Fortunately, this 165-foot-long craft is in the able hands of veteran pilot Steve Adams. He's been flying lighter-than-air ships for 20 years.

"The only thing usual about airships is that there is nothing usual about them," Mr. Adams says as he pulls levers, pushes foot pedals, and spins huge wheels mounted on either side of his seat to control the craft. Watching him work, I wonder: Did Willy Wonka invent this machine? (See Roald Dahl's "Charlie and the Chocolate Factory.")

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From 1,300 feet above Boston, sailboats floating in the Charles River look like toys in my nephew's bathtub. A high school football practice reminds me of a Foosball table. Riding a blimp gives you a dramatic new view of the world. Big windows, low altitude, and slow speed let you soak in the view. It's fairly quiet, too - but that's because everyone on board must wear sound-deadening earmuffs to cut down the very loud roar of the engines.

The first lighter-than-air craft was the Montgolfier brothers' hot-air balloon, which carried two passengers on a 25-minute flight over Paris in 1783. Balloons lifted by hydrogen gas soon followed. In the 1800s came the dirigible and German zeppelins. Zeppelins were huge, steel-framed, lighter-than-air ships. Some even carried airplanes! Dirigibles had semirigid frames. Blimps - the only lighter-than-air ships aloft today - have no internal framing and are lifted by helium gas. Helium doesn't have as much lifting power as hydrogen, but it's much safer.

Helium and hydrogen are lighter than the oxygen, nitrogen, and other gases that make up our atmosphere. And just as a bubble of air rises through a column of water, a "bubble" of helium trapped in a blimp rises through the air - and pulls the passengers with it.

Blimps are simple flying machines. They have three basic parts: The biggest part is the "envelope," the "blimpy" part of the blimp. The envelope is a huge bag made of polyester that holds helium. Inside the envelope is a "ballonet" of regular (heavy) air. The air acts as ballast. By adding or releasing air from the ballonet, the blimp rises or falls. This is how the pilot adjusts the blimp's lifting power.

The second piece is the gondola, where passengers and the pilot sit. Today's blimps carry about eight to 10 people. But some airships in the 1930s had 100 people on board. They had passenger cabins, dining rooms, lounges, and promenades.

From the cockpit in the gondola, the pilot controls the third part of a blimp - the engines. In the old days, airships were steam-powered. Today's blimps use gasoline engines. The engines turn propellers that push the blimp where the pilot wants it to go.

Moving a blimp through windy skies is tough. "It's like moving a beach ball upwind on a beach with sticks," Adams says. The blimp's normal cruising speed is 60 miles per hour.

Blimps use the same steering methods today that they used 100 years ago. The airship is steered left or right using foot pedals attached to wires that move vertical rudders mounted on the tail of the envelope. The wheels on either side of the pilot's seat control horizontal elevators in the tail to guide the airship up or down.

Blimps have been used for many purposes since they were first created in 1856. Early on, they were used mostly by the military, to spy on enemy positions. Blimps can stay aloft for long periods of time at little cost. (During World War II, blimps off the West Coast of the United States guarded against enemy attack.)

In time, airships became passenger carriers. The German zeppelins were the most famous passenger airships. But after the Hindenburg - the largest aircraft ever made - exploded into flames while landing in 1937, no one wanted to fly in them anymore. People thought they were too dangerous. (See story at right.)

Today, blimps are popular for use in publicity and advertising. (The Trumpasaurus, the blimp on which I rode, is owned by the Monster.com Internet company.) Huge decals can be heat-sealed to the envelope and gondola to turn a blimp into a massive billboard in the sky. The technology used for this is much like that used to turn city buses into giant ads.

The Trumpasaurus flies all year, from one event to the next. It may hover over Mardi Gras in New Orleans one week, and float over Florida's Daytona 500 the next. A 15-person support team accompanies the airship in a small convoy of trucks as it flies from city to city.

One of the most famous blimps is the Goodyear blimp, owned by the Goodyear Tire Company. But did you know there is more than one? Three Goodyear blimps fly over football games (sometimes a television camera is mounted below the gondola to broadcast pictures) and other events. In addition, there are two Goodyear blimps in Europe, one in Australia, and another in Brazil.

It's not easy to become a blimp pilot. For one thing, there are only 34 blimps in the world. For another, you need to qualify for a special license to fly them, like an airplane pilot's license.

Flying above Boston on a clear fall day, looking out across the city to the Atlantic Ocean, it's easy to understand the job's appeal. Adams loves his job. "It's a labor of love," he says, "but there is nothing I'd rather do."

(c) Copyright 2000. The Christian Science Publishing Society

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