Today, we ask, "Why did the Hindenburg burn?" The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
What child of the 1930s
doesn't remember the Hindenburg! That great silver
whale, the length of three football fields, its
tail emblazoned with swastikas, black on red, that
hydrogen conflagration waiting to happen. Since
1936, it'd carried passengers across the Atlantic.
Then, 60 years ago this May 6, 1997, it caught
fire and was consumed within 32 seconds. The
radio announcer wept, "Oh, the humanity," as it
went down. Yet, miraculously, two out of every
three passengers survived.
It seemed so obvious in retrospect. Hydrogen is
unstable in air's oxygen. All you need is a spark.
Conspiracy theories followed the disaster, but they
fared poorly against so much hydrogen.
There was a catch, but with all that hydrogen who
would notice it? It is that materials don't burn in
hydrogen. It's only hydrogen itself that burns,
once it's mixed with oxygen. Then it creates a
near-colorless blue flame -- nothing like the great
fireball we remember each May 6th. Hydrogen-filled
airships have been brought down by anti-aircraft
guns without catching fire.
The first woman balloonist, Madam Blanchard, died
in 1817 when she ignited the hydrogen in her
balloon with a fireworks display. But the balloon
didn't burn. Rather, the hydrogen burned off and
the balloon dropped to a rooftop. She died only
when the wind caught the unburned deflated gas bag
and dragged her over the edge.
Now Malcolm Browne summarizes recent experiments
being done to see why the Hindenburg burned the way
it did. The result is
something I should be poignantly aware of from my
own model airplane building. I covered those models
with damp tissue paper that dried taut as a drum.
Then I drenched the paper in acetone-based airplane
lacquer -- what everyone used to call dope. If you
put a match to a model airplane, it went up just
like the Hindenburg.
The Hindenburg's frame was likewise covered with
canvas that'd been soaked in that same acetone
lacquer. Worse than that, the lacquer had particles
of aluminum mixed in with it to give the ship its
silvery shine. At high temperatures, aluminum adds
to the flammability. So the real fire hazard wasn't
the hydrogen inside, it was the dirigible's skin.
Reports from Lakehurst, New Jersey, that stormy
spring evening told of St. Elmo's fire dancing on
the Hindenburg's upper surface. Whatever started
the fire, the stuff that burned with such explosive
speed was that terribly incendiary fabric. When
that happened both the fabric, and the hydrogen
being released, competed for the surrounding air's
oxygen.
So we left off making great airships and we quit
filling even our little blimps with inexpensive
hydrogen. A whole era ended in a flash. It ended so
quickly, that we're only now finding out what
really happened -- on that terrible day so long
ago.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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