What was the greatest dirigible tragedy in history? I bet just about everyone thought of the Hindenburg which crashed and burned in a spectacular fashion when coming in for a landing at Lakehurst, New Jersey in 1937. The giant dirigible had made 10 routine roundtrips between Germany and the US before the terrible explosion. What actually happened still isn't clear but the description of the event by radio reporter Herb Morrison is mind numbing.
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"It's crashing. It's crashing terrible. Oh, my get out of the way, please. It's bursting into flames. And it's falling on the mooring mast. All the folks agree this is terrible, one of the worst catastrophies on the world. Oh, the flames, four or five hundred feet in the sky, it's a teriffic crash ladies and gentlemen. The smoke and the flames now and the frame is crashing to the ground, not quite to the mooring mast. Oh, the humanity and all the passengers."
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The report has a couple of interesting features. It was the first recorded news report to be broadcast nationally by NBC, but perhaps more interestingly it does not appear to describe a hydrogen explosion. The Hindenburg was a dirigible, not a blimp. This means that it wasn't just a giant bag of gas, like the airships we see hovering over football games. Rather it had a rigid framework, made of aluminum, over which a cotton skin was stretched. Inside were separate bags of hydrogen gas which held the ship aloft. And what a ship it was! The Hindenburg was the largest flying machine ever built, 804 feet long. It would have dwarfed a Jumbo 747 and was roughly the size of the Titanic. The crash that Morrison described killed 35 of the 97 people on board along with a crew member on the ground. Interestingly, the description and existing newsreel footage portray a rapid fire, not an explosion. Witnesses spoke of flames like a spectacular fireworks display; this is uncharacteristic of hydrogen which burns with a virtually colorless flame. This has led some researchers to conclude that the cause of the accident was not ignition of the hydrogen, but rather of the flammable cover.
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It was common practice to dope the cotton with iron oxide, cellulose acetate and aluminum powder, a highly combustible mixture. The theory is that an electrostatic charge built up on the stretched cotton during a storm and when mooring lines were dropped there was a discharge through the metal frame igniting the fabric. Surviving samples of the Hindenburg's skin have been tested and have been found to be extremely flammable. Indeed, even at the time the Zeppelin Company, builders of the Hindenburg, may have thought that hydrogen was not the cause of the disaster. They instantly took some measures to reduce the flammability of the fabric that was being readied for the construction of the Graf Zeppelin, the Hindenburg's sister ship. A fireproofing agent, calcium sulfamate was added to the skin and aluminum was replaced by bronze which is far less combustible. Measures were also taken to reduce the electrical potential between the skin and the internal structure by impregnating the ropes holding the fabric in place with graphite, a conductive material. The Graf Zeppelin, filled with hydrogen, went on to fly millions of miles safely. Publicly, the Zeppelin Company blamed hydrogen for the explosion. But there may have been a political card played here.
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At the time, the United States was the only country that had supplies of non-flammable helium gas but was unwilling to sell it to the Germans听fearing that it would be used to construct airships for military purposes. This was not an unjustified worry because the Germans had constructed over a hundred airships during the first World War to bombard London. America had plenty of helium and had in fact constructed helium filled dirigibles years before the Hindenburg accident. Although virtually everyone thinks the Hindenburg crash was the greatest dirigible accident in history, it was not. Four years before, the USS Akron, a military airship designed to carry small aircraft crashed in a storm off the coast of New Jersey killing 69 of 72 people aboard. Tragically, a blimp sent out to look for survivors also crashed killing its crew.
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Accidents like the Akron and the Hindenburg and of course the advent of the airplane spelled the demise of the great airships. But the Zeppelin Company is making a comeback. The Company which has had other interests since the 1930s is going back into the airship business. This time with helium. The Zeppelin NT as the new semi-rigid dirigible will be called is almost as long as a football field and will have swiveling propellers, one on each side and two at the rear. It will be almost as maneuverable as a helicopter and will have a top speed of 90 miles per hour. The cabin will only carry 12 passengers but they will have a spectacular view. The idea is to use the airship for tourist trips along the Rhine Valley. It will probably not be a cheap thrill since the Zeppelin NT has a $7 million price tag. But even those who cannot shell out the money for a trip on the new Zeppelin may benefit from airship technology. The Japanese are designing blimps which would float at an altitude of 65,00- feet and would be used for the reflection of waves used in cellular phone communication. The blimp's skin is to be made of PVC coated with polyethylene and the ship will be kept aloft for years. So we may yet see a revival of the great airships, of course with various added safety features.
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But contrary to popular opinion, these great ships of the sky were very safe in their day. Zeppelins were flown for 40 years before the Hindenburg accident and carried close to half a million passengers safely. There were no civilian casualties before the Hindenburg and in fact the chance of death on a Zeppelin was about half that on a modern airplane. And no Zeppelin was ever hijacked.
