Boy oh Buoyant

By Jeffrey Kluger|Friday, December 01, 1995
I hadn’t anticipated spending part of a recent weekend suspended from a moving gasbag 800 feet above Times Square. As a rule, I never anticipate spending part of a weekend suspended from a moving gasbag 800 feet above Times Square, so imagine my surprise when I found myself doing just that.

In popular parlance, of course, moving gasbags suspended over cities are known as blimps, and New York certainly has its share. On any given weekend, the skies over the five boroughs are crisscrossed by a veritable exhalation of airships, including the Goodyear blimp, the Fuji blimp, the Sea World blimp, and the MetLife blimp. To be sure, in an era of Lockheed wide-bodies and Air France Concordes, any aircraft that can fit comfortably behind Bullwinkle in a Thanksgiving Day parade is not going to cut an especially dramatic figure, and few people would choose the plump and poky ship when other means of travel are available. But could the blimp be getting a bad rap? Is there more to these stately sky whales than meets the eye?

The history of lighter-than-air flying ships began in 1783 when the Montgolfier brothers--Manny, Moe, and Jacques--launched the first working hot-air balloon, in Annonay, France. At the time there was not actually much demand for hot-air balloons, but the Montgolfier brothers had apparently shown up late for Career Day, and after the Wright brothers and the Smith brothers got dibs on airplanes and cough drops, they had to settle for what they could get. Despite this, the Montgolfiers’ achievement was impressive: they built a balloon of fabric backed by paper that was 75 feet tall and 49 feet wide and contained 77,000 cubic feet of hot air, which was heated by burning straw and wool.

Hot-air balloons definitely had drawbacks, not the least being keeping the air hot. An alternative was to fill the bladder of the craft not with air but with hydrogen. Hydrogen is the lightest of all elements and thus the most buoyant. The problem is that hydrogen is also one of the most temperamental elements, given to exploding in the presence of a flame, a spark, or even an ill-considered remark:

Bystander: Hey, has that hydrogen put on a little weight or something?

Hydrogen: BOOM!

Nevertheless, in the same year that the Montgolfiers flew their balloon, French physicist J.-A.-C. Charles invented a lighter-than-air craft of his own, featuring a rubber-coated silk bladder capable of holding 22,000 cubic feet of hydrogen. So successful was Charles’s design that hydrogen craft quickly replaced hot-air models, and by the middle of the next century the ships were in wide use, principally by the military. During both the American Civil War and the Franco-Prussian War, balloons were put to work as aerial observation posts, helping both to determine the course of military history and to fill the newspapers of the era with countless memorable battlefield quotes (Yup, there’s Prussians down there).

Eventually the balloons were given a simple, onomatopoeic name-- blimp--thought to evoke the noise the giant gas bladder made when thumped by a thumb. But despite the clever moniker, the ships had problems, and one of the thorniest was their size. As lighter-than-air ships became more and more popular, builders sought to lift bigger and bigger loads of people and cargo. The bigger the load, however, the more hydrogen you needed to do the lifting, and this required enormous bladders, which were difficult to manufacture with the relatively low-quality fabrics available in the nineteenth century.

The answer was a whole new type of airship--the rigid airship, made with a skeleton of lightweight ribbing covered by a fabric balloon that would remain structurally sound no matter how big it got. The first rigid ship was launched in 1900 by Count Ferdinand von Zeppelin of Germany, who, as luck would have it, was already named after an airship. When World War I rolled around, Germany built dozens of the ships, equipped them with propellers, and flew them across the English Channel, where they were used to bomb Great Britain. By law, of course, when German engineers invent so much as an especially tasty strudel, they’re required to at least try to bomb Great Britain with it, and even today, whole British cities are occasionally felled by aerial bombardments of Leica cameras and Mercedes sedans.

For a while it looked as though German zeppelins were going to become the industry standard. In the thirties, however, all that changed when Germany built the largest rigid airship ever constructed, the 804-foot Hindenburg. Launched just three years before the outbreak of World War II, the ship was built in part to show the world the industrial prowess of the German nation. Unfortunately, as the Hindenburg was completing a transatlantic crossing in 1937, it was apparently struck by lightning, and before the ship even reached its mooring mast in Lakehurst, New Jersey, it was Deutschland, Deutschland all über the place.

From that moment on, things went downhill for hydrogen airships, with designers quickly switching to nonflammable helium. But the damage to the lighter-than-air reputation was done. Today only about ten helium ships are licensed in the United States, most of which are used for advertising or broadcasting. Such near extinction notwithstanding, the modern lighter- than-air ship is an elegantly engineered machine, one that owes a lot to its awkward ancestors.

The principal characteristic that all the modern-day members of America’s blimp flock have in common is that they are blimps, as opposed to zeppelins. The rigidity of rigid airships was always a disadvantage, says Jim Thiele, president of the American Blimp Corporation, an airship manufacturer in Hillsboro, Oregon. When you’re working with rigid structures, you have to be aware that if you bend them enough they break. This means that you have to make them extremely strong. With a soft structure, you can bend ’em and bend ’em and nothing ever happens.

In order to build such flexible ships, contemporary manufacturers like Thiele rely on materials not available to their nineteenth-century forebears. The main body of the blimps his company makes is composed of two parts: an inner layer (the bladder) and an outer layer, called an envelope. The bladder, which actually holds the helium, is made of leak-resistant polyurethane that’s welded together from strips. A 130-foot-long bladder capable of holding 68,000 cubic feet of helium weighs only 250 pounds and leaks away little more than 1 percent of its helium per week. While resistant to leaks, though, the bladder is not resistant to punctures, so it is protected by a comparatively heavy 450-pound envelope made of a polyester ripstop fabric. Although the envelope is the outer structure, it’s actually a few inches smaller in volume than the polyurethane balloon it surrounds. This deliberately poor fit helps prevent ruptures by guaranteeing that when the blimp is fully inflated, it is the sturdier envelope rather than the thinner bladder that takes the load.

But simply stuffing a bladder from the Big & Tall Men’s Shop into an envelope from Misses & Juniors is not enough to keep a helium-filled blimp flying. Helium is an inert element--that is, it does not react easily with other elements--and it is this nonreactiveness that allows it to be used so safely not just in blimps but at carnivals and birthday parties and in incandescent lamps. Indeed, so benign is the element that the National Helium Association recently considered launching a sweeping new marketing campaign (Helium: Its Atomic Number Is Spelled F-U-N!) and petitioning to have the gas’s periodic table abbreviation changed from He to Hee-Hee. But just because helium doesn’t explode does not mean it doesn’t expand; it can change dramatically in response to the temperature and pressure of the surrounding air.

If you took a blimp and filled it with helium and floated it higher and higher, Thiele says, the pressure inside would steadily climb as the atmospheric pressure dropped. Ultimately, the blimp would burst.

To prevent this from happening, all of Thiele’s blimps are also equipped with an additional, igloo-shaped balloon within the bladder, called a ballonet. Filled with ordinary air as opposed to helium, the ballonet represents about 20 percent of the total gas volume of the blimp when it leaves the ground. As the airship climbs higher and the atmosphere grows thinner, air is vented from the ballonet to keep the pressure within the bladder from growing too great. When the blimp descends into thicker atmosphere, air is pumped back into the ballonet to prevent the pressure from dropping too low.

Thiele filled me in on more critical blimp data, including the maximum weight of his average airship (4,400 pounds--including personnel), the top speed (55 miles an hour), the size and manufacturer of the pair of propeller-driving internal combustion engines attached to the passenger gondola (two 68-horsepower Limbach aircraft engines--similar to the type used in the old Volkswagen Beetles), and the natural source of helium used to fill most of his ships (an enormous subterranean deposit near Amarillo, Texas--a deposit that had long eluded detection until sharp-eyed Texans noticed that herds of livestock in the vicinity were hovering 1,500 feet above the ground).

No amount of talking about blimps, however, was going to take the place of riding in one, so I contacted one of American Blimp’s customers-- the MetLife insurance company--to request a couple of hours aloft. To my alarm, MetLife graciously agreed.

The mooring site where I was to find the MetLife blimp was at the Linden Airport in Linden, New Jersey, and as twentieth-century terminals go, it’s not exactly Dulles. The main waiting area is less a departure lounge than a suburban den, with rec-room paneling, furniture upholstered in rec-room plaid, and framed pictures that were flat-out rec-room bad. Near as I could tell, there were no air traffic controllers playing Twister on the linoleum floor, and I took that as a plus, but on the whole, the place did not inspire confidence.

Fortunately, my stay in the waiting-cum-rumpus room was brief; only minutes after my arrival, the van that would carry me to the blimp mooring area pulled up outside. Behind the wheel that afternoon was Charlie Graham, the man who would also be behind the blimp controls during my two hours aloft. As Charlie made the short drive from terminal to blimp field, he explained a bit about the airship biz, and what I heard gave me confidence that I was indeed in the hands of a true professional.

Piloting a blimp is like piloting no other aircraft, he said. Most of us are licensed to fly planes or helicopters as well, but you still need a separate FAA license to command a lighter-than-air ship. At the moment, there are only about 30 active blimp pilots in the entire world, which makes us rarer than space shuttle pilots.

When we arrived at the meadow where the MetLife blimp ought to have been, there was no blimp, no hangar, not so much as a single tarmac attendant waving those extraterrestrial flashlights with cones on the ends. All I saw was a 30-foot pole rising from the ground and half a dozen guys standing around in matching polo shirts. This is our ground crew, Charlie said, indicating the men. And this, he added, pointing to the pole, is our garage. Overnight, we moor the nose of the blimp to this mast and just let it float there.

After a few expectant minutes spent scanning the sky, I saw somebody point roughly northeast and spotted an unmistakable blue dot approaching from over the horizon. If it’s true that the two activities no one should ever witness are sausages and laws being made, it’s probably also true that blimp landings can be added to the list. Here’s how it works:

a) Blimp guys in matching shirts stand around doing nothing as blimp gets bigger and bigger and finally gets so big you can see if the pilot missed a spot flossing this morning.

b) Blimp gets so low that long ropes dangling from its nose begin to drag on the ground.

c) Blimp guys notice this and begin running really, really fast, trying to grab the cables and hold the blimp down.

d) Blimp catches an updraft and floats back up into the sky before the running guys can grab it.

e) Lather, rinse, repeat.

Wind is a big variable in landing a blimp, Charlie told me. The ideal situation is to hit a head wind just as you’re making your final descent. This slows you down and lowers your altitude and ground speed. It also helps to have a cloud cover since bright sun heats the helium and increases its buoyancy.

After another two or three approaches, exactly the right conditions suddenly prevailed, and the pilot was able to bring his blimp low enough for the ground crew to get hold of its cables and wrestle it into place. It took only a few moments after that for the other pilot to hop out and Charlie and me to climb aboard and cast ourselves off.

Leaving the ground in a lighter-than-air ship is a surprisingly busy business. I don’t know exactly what I imagined--an absolutely silent, wind-assisted ascent broken only by the voice of the IMAX narrator saying something like Since the first human observed the first bird flapping over the savanna, man has always dreamed of flying free, I suppose. But it was nothing at all like that. Outside the open window of the gondola, the twin Limbach engines whined and churned. In front of me, the nose of the blimp dipped, rose, and swung lurchingly from side to side while the ropes dangling from it swayed lazily back and forth. To my left, Charlie operated his throttles, rudder pedals, and ballonet cords in an absurd choreography that was equal parts Chuck Yeager, Wilbur Wright, and Willy Wonka. Soon, however, the ride stabilized, and as we glided about 600 feet above the New Jersey coast, Charlie began our tour.

We’ll be approaching Manhattan from the southwest, he shouted over the engines, so the first landmark you’ll see will be a pretty obvious one.

To the southwest of Manhattan, of course, is the Statue of Liberty, and as I looked beyond the nose of the ship, it indeed appeared to be dead ahead and getting deader. From ground to torch, the Statue of Liberty measures 302 feet. According to Charlie’s altimeter, we were less than 500 feet above the harbor, and within a few moments were thus close enough to the top of the monument that if Liberty hadn’t been wearing the hat, I could easily have determined whether the green hair had black roots.

We made a lazy circle around the statue--close enough to elicit visible waves from the people around the pedestal, far enough to get away safely if Liberty decided to drop the torch and pick up a rolled-up newspaper--before peeling off and heading for Manhattan proper. The most conspicuous feature of the part of the main island that we were now approaching was the World Trade Center towers looming just a few hundred feet ahead. Once again glancing at the altimeter, I saw that we were about 800 feet high; the towers, I knew, rise above 1,300. Now, I don’t pretend to be a Mr. Navigational Smarty-pants, but you didn’t have to be Ponce de León either to know that left, right, or up would have been good choices right about then. Happily, Charlie chose left, and we skirted the northwest tower and began to glide over the thicket of Manhattan itself.

From street level, the city of New York can be something of a challenge. From the perspective afforded by a 130-foot-long bag of helium it became--despite my best efforts at urban cynicism--almost idyllic. There was the landscaped expanse of Union Square just north of Fourteenth Street, reduced to a terra-cotta pampa shot through with green. There was the Twenty-third Street clock tower, close enough for the time to be easily readable on its huge westward face, far enough below for that face to be something closer to a Lady Timex. There was Times Square, nominally the Crossroads of the World, today barely looking like the Crossroads of the Block. There was the George Washington Bridge toward the northern end of the island, appearing barely big enough to be worthy of Martin Van Buren. There was, finally, the long flight back down the Hudson and into New Jersey.

When at last we reached the airport, Charlie, impressively, brought the blimp to a landing on just his first approach. More impressively, he didn’t point it out. Working his controls while the ground crew grappled with the cables, he nodded a good-bye, and I jumped out. The blimp then flew unceremoniously back into the blue, and Charlie drifted back off for another couple hours of atmospheric ad work trooping the MetLife colors. As trips aloft went, my two lighter-than-airborne hours had lacked a lot--no purpose, no destination, definitely no in-flight snack service. But even if I live in New York another 50 years, it’s almost certainly the only time I’ll travel so far uptown and know for certain I’m going to make all the lights.
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