17 December 2004

The Hindenburg disaster: Another look

Forrest M. Mims III

This issue of The Citizen Scientist features an interesting report by William H. Appleby about his study of the explosion of the German airship Hindenburg in 1937.

The Hindenburg was nearly the size of the Titanic. The huge lighter-than-air airship carried passengers in luxury across the Atlantic in exchange for tickets that cost $450, about the same as a new car in those days. The burning of the airship happened so quickly that it was amazing that any of the 97 passengers and crew escaped with their lives. While 37 people died, 62 survived, including a teenaged cabin boy who was soaked by water from a bursting tank as the huge air ship collapsed to the ground.

The fastest news reports in 1937 were carried by radio, and radio reporter Herbert Morrison was present when the Hindenburg arrived at Lakehurst Naval Air Station on 6 May 1937. His account of the disaster became one of the most memorable news reports ever broadcast:

"It burst into flames! ... It's fire and it's crashing! It's crashing terrible! Oh, my! Get out of the way, please! It's burning, bursting into flames and is falling on the mooring mast, and all the folks agree that this is terrible. This is the worst of the worst catastrophes in the world! ...There's smoke, and there's flames, now, and the frame is crashing to the ground, not quite to the mooring mast...Oh, the humanity, and all the passengers screaming around here!

Plane crashes have killed far more people than the Hindenburg. Yet the Hindenburg fascinates the public, because its destruction ended the brief era of passenger-carrying dirigible airships that carried their passengers in luxury around 1,600 kilometers (1,000 miles) a day.

Much has been written about the investigation of the Hindenburg crash and the various theories that were explored. Sabotage was considered and rejected. Because the ship was attempting to land during rainy conditions, a lightning bolt or electrostatic discharge might have ignited the fire. A google search on Hindenburg will take you to many articles about the possibilities.

This brings me back to William Appleby's article. The rapid destruction of the Hindenburg was for years attributed to the highly flammable hydrogen gas cells inside the ships outer covering. In recent years an alternate theory has arisen that the rapid destruction of the ship was caused by the dope used to coat its outer skin. This theory, which Appleby's article discusses, has risen to prominence, especially because of claims that the ingredients in the dope resemble a solid propellant rocket fuel.

Appleby has experimentally tested this theory by painstakingly fabricating simulated swatches of Hindenburg fabric. He ignited these swatches and measured the speed of the flame front. Appleby found that the simulated Hindenburg fabric burned much too slowly to account for the extremely rapid destruction of the airship, which took less than 40 seconds.

While Appleby's tests nicely simulated the fabric, they did not account for the presence of hydrogen. The ultimate question, then, is how will Appleby's simulated Hindenburg fabric respond to a fire accelerated by the presence of abundant hydrogen. Will the hydrogen simply whoosh away in a flash of flame? Or, if confined by the treated fabric, will it dramatically enhance the combustion of the fabric?

While Appleby's finding is not the bottom line, he has shed new light on the nature of Hindenburg disaster. Hydrogen burns without smoke and with a nearly invisible flame, but the Hindenburg fire illuminated the landscape and produced prodigious black smoke. Clearly the fabric gas bags inside the ship and the ships outer coating were responsible for much of the visible flames and smoke. The fuel for the engines, the baggage and the passenger and crews quarters also played a role. The question remains whether the dope that coated the airship was primarily responsible for such rapid destruction. This is the claim of some groups that advocate hydrogen-fueled vehicles, whose best interest is to minimize the potential dangers of hydrogen.

The Hindenburg disaster illustrates how easy it is to swing from one hypothesis to another while ignoring possibilities in between, especially when agendas will benefit from one claim or another. William Appleby's findings alone do not answer the Hindenburg question. But they provide an important starting point for reconsidering the Hindenburg matter and arriving at an objective solution.