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On May 6, 1937 at 19:25, the German zeppelin LZ 129 Hindenburg caught fire, exploded and was utterly destroyed within a minute while attempting to dock with its mooring mast at Lakehurst Naval Air Station in New Jersey. Of the 97 people on board, 13 passengers and 22 crew-members were killed. One member of the ground crew also died, bringing the death toll to 36.
The LZ-129 Hindenburg and her sister-ship LZ-130 Graf Zeppelin II were the two largest aircraft ever built. The Hindenburg was named after the President of Germany, Paul von Hindenburg. It was a brand-new, all-aluminium design: 245 m long (804 feet), 41 m in diameter (135 ft), containing 200,000 m³ (7,060,000 ft³) of gas in 16 bags or cells, with a useful lift of 112.1 metric tons force (1.099 MN), powered by four 1200 horsepower (890 kW) Mercedes Benz engines giving it a maximum speed of 135 km/h (84 mph). It could carry 72 passengers (50 transatlantic) and had a crew of 61. For aerodynamic reasons, the passenger quarters were contained within the body rather than in gondolas. It was skinned in cotton, doped with iron oxide and cellulose acetate butyrate impregnated with aluminium powder. Constructed by Luftschiffbau Zeppelin in 1935 at a cost of £500,000, it made its first flight in March 1936 and completed a record Atlantic double-crossing in five days, 19 hours, 51 minutes in July of that year.
The Hindenburg was originally intended to be filled with helium but a United States military embargo on helium forced the Germans to modify the design of the ship to use highly flammable hydrogen as the lift gas. Because hydrogen is half as dense as helium, giving about 10% greater lift capability in air, additional passenger compartments were also added during construction. The Germans had prior experience with hydrogen in airships, so this switch from helium did not cause great alarm. Knowing the risks of hydrogen gas, the engineers used various safety measures to keep the hydrogen from causing any fire when it leaked, and they also treated the airship's coating to prevent electric sparks that could cause fires. Such was their confidence in their ability to handle hydrogen, a smoking room was even present on the Hindenburg.
Historic newsreel coverage
The disaster is remembered partly because of extraordinary newsreel coverage, photographs, and Herbert Morrison's recorded radio eyewitness report from the landing field. The crush of journalists was in response to a heavy publicity push about the first trans-Atlantic Zeppelin flight of the year. The crossing was the first of eighteen planned for 1937 by the Zeppelin company.
Morrison's words were not broadcast until the next day. Parts of his report were later dubbed onto the newsreel footage (giving an incorrect impression to some modern eyes accustomed to live television that the words and film had always been together). Morrison's broadcast remains one of the most famous in history – his plaintive words "Oh, the humanity!" resonate with the memory of the disaster.
Herbert Morrison's famous words should be understood in the context of the broadcast, in which he had repeatedly referred to the large team of people on the field, engaged in landing the airship, as a "mass of humanity." He used the phrase when it became clear that the burning wreckage was going to settle onto the ground, and that the people underneath would probably not have time to escape it. It is not clear from the recording whether his actual words were "Oh, the humanity" or "all the humanity."
There had been a series of other airship accidents (none of them Zeppelins) prior to the Hindenburg fire, most due to bad weather. However, Zeppelins had accumulated an impressive safety record. For instance, the Graf Zeppelin had flown safely for more than 1.6 million km (1 million miles) including making the first complete circumnavigation of the globe. The Zeppelin company was very proud of the fact that no passenger had ever been injured on one of their airships.
The Hindenburg accident changed this. Public faith in airships was completely shattered by the spectacular movie footage and impassioned live voice recording from the scene. Because of this vivid publicity, Zeppelin transport came to an end. It marked the end of the giant, passenger-carrying rigid airships.
Questions and controversy surround the accident to this day. As with many historic events, interpretations of the causes are often colored by politics and polemics.
On the one hand, some speculate that the German government of that era placed the blame on flammable hydrogen in order to cast the U.S. helium embargo in a bad light. Others suggest that present-day proponents of hydrogen as a transportation fuel have forwarded a revisionist "flammable fabric" analysis of the fire in order to deflect public concern about the safety of hydrogen.
Nonetheless, there remain three major points of contention: 1) How the fire started, 2) Which material (fabric or gas) started to burn first and 3) Which material (fabric or gas) caused the rapid spread of the fire.
Cause of ignition
At the time, sabotage was commonly put forward as the cause of the fire, in particular by Hugo Eckener, former head of the Zeppelin company and the "old man" of the German airships. The Zeppelin airships were widely seen as symbols of German and Nazi power. As such, they would have made tempting targets for opponents of the Nazis. However, no firm evidence supporting this theory was produced at the formal hearings on the matter.
Although the evidence is by no means conclusive, a reasonably strong case can be made for an alternative theory that the fire was started by a spark caused by static buildup. Proponents of the "static spark" theory point to the following:
The airship's skin was not constructed in a way that allowed its charge to be evenly distributed, and the skin was separated from the aluminium frame by nonconductive ramie cords. A potential difference between the wet zeppelin and the ground was thus created. The ship passed through a weather front where the humidity was high. This made the mooring lines wet and therefore conductive. As the ship moved through the air, its skin became charged. When the wet mooring lines connected to the aluminium frame touched the ground they grounded the aluminium frame. The grounding of the frame caused an electrical discharge to jump from the skin to the grounded frame. Witnesses reported seeing a glow consistent with St. Elmo's fire.
Another popular theory put forward referred to the film footage taken during the disaster, in which the Hindenburg can be seen taking a rather sharp turn prior to bursting into flames. Some experts speculate that one of the many wire frames supporting the blimp may have snapped and punctured the skin of the dirigible. This would have allowed hydrogen out of the Hindenburg, which could have been ignited by the static discharge mentioned previously. This, however, remains theory, because no concrete evidence has shown that the Hindenburg was punctured, and no eyewitness accounts back up this theory.
Initial fuel for combustion
Most current analysis of the accident assumes that the static spark theory is correct. There is still a debate, however, as to whether the fabric itself or the hydrogen used for buoyancy was the fuel for the initial fire.
Proponents of the "flammable fabric" theory, first posited by Addison Bain in 1997, point out that the coatings on the fabric contained both iron oxide and aluminium-impregnated cellulose acetate butyrate dope. Cellulose acetate butyrate dope is known to be flammable and iron oxide is well-known to react with aluminium powder. In fact, iron oxide and aluminium are sometimes used as components of solid rocket fuel or thermite. (However, the oft-cited claim that the ship was "coated in rocket fuel" is a significant overstatement.) While the coating components were potentially reactive, they were separated by a layer of material that should have prevented the reaction from starting.
Opponents of the flammable fabric theory point out that the makeup of the coatings do not constitute the proper proportions for rocket fuel. Furthermore the recent technical papers  point out that even if the ship had been coated with typical rocket fuel, it would have taken many hours to burn - not the 34 seconds that it actually took.
After the disaster, the Zeppelin company's engineers determined this skin material, used only on the Hindenburg, was more flammable than the skin used on previous craft and changed the composition for future designs. Nonetheless, the Hindenburg had flown for over a year (and through several lightning storms) with no reports of adverse chemical reactions, much less fires on the fabric.
The proponents of the "flammable fabric" theory also point to fact that the naturally odorless hydrogen gas in the Hindenburg was "odorised" with garlic so that any leaks could be detected, and that there were no reports of garlic odors during the flight or prior to the fire. Again the proponents of the flammable fabric theory invoke that observation while elsewhere claiming that hydrogen and its resulting fire escapes and burns upwards.
Rate of flame propagation
The proponents of the "Flammable Fabric" theory also contend that the fabric coatings were responsible for the rapid spread of the flames. They point out that hydrogen burns invisibly (emitting light in the UV range) so the visible flames (see photo) of the fire could not have been caused by the hydrogen gas. Also, motion picture films show downward burning.
Opponents of the "flammable fabric" theory point out that once the fire started, all of the components of the ship (fabric, gas, metal, etc) burned. So, while it may be that the combustion of the metal and fabric changed the color of the flame, the presence of color does not imply that hydrogen did not also burn. Further, while all fires generally tend to burn upward, including hydrogen fires, the enormous radiant heat from the burning of all of the materials of the ship would have quickly led to ignition over the entire surface of the ship, thus explaining the downward propagation of the flames.
Also, a set of modern  experiments that recreates the fabric and coating materials contradicts the "flammable fabric" theory. These experiments conclude that it would have taken about 40 hours for the Hindenburg to have burned if the fire had been driven by a fabric fire. The actual burn time was 34 seconds. These experiments, as well as other industrial tests of the coating materials, conclude that the covering materials was combustible but nonflammable. Two additional scientific papers  also strongly reject the "flammable fabric theory".
- Hindenburg Disaster Newsreel Footage
- The Hindenburg (1975 Movie)
- The rock group Led Zeppelin's eponymous first album features a photo of the Hindenburg disaster on the cover.
- Page at Great Zeppelins website, with various pictures
- Complete passenger and crew listing
- Footage from Castle and Pathé coverage of the Hindenburg disaster
- An Article Supporting the Flammable Fabric Theory
- Two Articles Rejecting the Flammable Fabric Theory
- Experiments Reject the Flammable Fabric Theory
- Duggan, John (2002). LZ 129 "Hindenburg" – The Complete Story. Ickenham, UK: Zeppelin Study Group. ISBN 0-9514114-8-9.
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