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The Great
Airships
The two main technical problems
faced by dirigibles were the high
in flammability of hydrogen (the
gas most commonly
used to provide buoyancy) and the structural delicacy
of a dirigible. The craft had to
be light enough to float in the
air, tight enough to retain the gas within its
bags, and tough enough to
endure winds and storms. The size
of a dirigible made the drag caused by even
a moderate wind
significant; dirigibles crossing the Atlantic east
west, against the prevailing
winds, typically took twice as
long to cross as they did going the other way. Yet compared
to the challenges presented
in creating passenger planes,
these problems didn’t seem all that
formidable.
The structural problems were deemed to be a matter
of engineering, and the steady progress in
design and alloy metallurgy
offered promise that these problems
would ultimately be solved. The
hydrogen problem was
another matter. The only apparent alternative to hydrogen
was helium, which is just about
eight percent heavier than
hydrogen and completely inert—on the face of it, a
perfect substitute.
The problem was that helium was
not nearly as abundant as
hydrogen, and mining and refining
it was a costly process. In the 1920s the principal
source for helium in the
world were a handful of locations in the
United States—in Texas, Utah, and Colorado—and the
cost of helium at that time was ten cents a cubic
foot. The typical commercial
dirigible required two to three
million cubic feet of the gas, which sets the cost of
helium at upward of $300,000
per craft. By 1925, after considerable government
effort and support, the price of helium
went down to a penny a
cubic foot, but that was still a
thousand times more expensive than hydrogen.
From 1919 to 1937, most problems experienced by
dirigibles were caused by structural
breakdowns caused by
weather or wind stresses. The Hindenburg explosion
was the most gruesomely
public and spectacular disaster
involving a dirigible, but it was not typical, which was
why there was so much question about how the
explosion happened and why theories that the
ship had been sabotaged
were taken seriously. Actually, the
explosion was caused by a new paint used on the airship that
was highly inflammable.
At the end of the war, the Zeppelin Company was
headed by Dr. Hugo Eckener, protégé of Count
Zeppelin, who had died of
old age in 1917. The French had captured a single Zeppelin,
the L49, intact during the war
and permitted British and American airmen to inspect
it. At war’s end, only
six Zeppelins were commandeered by
the Allies before they could be destroyed by their
German crews; one, the L72, the
largest built to that time, was
designed for the express purpose of
bombing New York City.
The
Germans could only gnash their teeth as they
watched the Allied nations
using their blueprints to build
record-setting airships, and when the leading German airship
pilot, Ernst Lehmann, warned that simply copying
the plans without establishing a landing base experienced in
the handling of these ships would lead to disaster, experts
scoffed at what they regarded as a lame attempt to slow down
foreign dirigible development.
The parade of airships that were built in
the post-war period, only to be lost or destroyed, is
remarkable. The ZR-2, built by England for the U.S. Navy,
was to be housed at Lakehurst, New Jersey, in new hangars
built especially for it and a companion dirigible, the ZR-1,
to be built by the United States.
Both were based on the blueprints for the
German L72, the dirigible the Germans wanted to sail the
Atlantic in, before being forbidden to do so by the British,
who made the historic crossing in their R-34, a virtual
carbon copy. During the final tests over Hull, England, the
ZR-2 broke up and was destroyed, leaving the huge hangar in
Lakehurst embarrassingly empty.
In Washington, a pattern
began that would be repeated many times in years to come:
Admiral William A. Moffet, chief of the navy’s Bureau of
Aeronautics, staunchly defended the dirigible programme
and vowed to
learn from the “lessons” of the ZR-2, so
that the lives lost would not be in vain. (The
illogic of this approach was one
of the factors that eventually
drove Billy Mitchell to criticize the navy.
Because the
airships often seemed to meet disaster in the
midst of calm flying (as the Roma, did
during a carefully controlled
test flight at Langley Field), the
pilots were frequently
unfairly
blamed for the mishaps.
Richard Byrd had just missed being
a passenger on the ill-fated
flight, and one wonders if Moffet
would have been so accepting
of the loss and in such a learning mood
had the celebrated explorer
been among the fatalities.)
A similar fate was met by the Roma,
a semi-rigid dirigible
built in Italy by Umberto Nobile—it
was destroyed during test flights
at Langley Field, Virginia, in
February 1921, when it
crashed into high voltage lines after
being forced down by a sudden
down-draft. The U.S. Army’s biggest dirigible,
the C-2, exploded as soon as it left its
hangar in October 1922. The
L-72, renamed the Dixmude by the
French, was on a flight to Africa
in the winter
of 1923 when it disappeared over the
Mediterranean. The wreckage discovered a week
later indicated that the
ship had broken up in rough weather.
Louis H. Mayfield, commander of
the ZR-2 when it broke up and crashed into
the Humber River, near Hull.
Thinking that there may have been
something to Lehmann’s warning, the
Zeppelin factories and
hangars at Lake Constance and
Friedrichshafen, slated to be
destroyed, were spared (though
Eckener had to convert them so they
manufactured kitchen utensils
to keen them afloat!
In 1923 a new company, the Goodyear-Zeppelin
Corporation, was created to produce dirigibles,
combining the newly developed alloy duralumin with
German expertise and experience
(much as German rocket scientists
were pressed into service in the American missile and
space programs after World
War II). The two flagship U.S.
dirigibles, the ZR-1 and the ZR-3,
named the Shenandoah and the Los
Angeles, were completed (in the
factories in Akron, Ohio, and
Friedrichshafen, respectively) and put into service in 1924.
The C-2 explosion had made the
navy reluctant to use hydrogen,
and there was simply not enough
helium for both ships, so it was
decided that the two dirigibles would share the same
helium and alternate flights.
The Shenandoah, which was built to military specification,
toured the western states testing
moorings and airfields. Then it returned to Lakehurst to
transfer its helium to the Los
Angeles for a more public tour
promoting commercial dirigible flight. Technical problems
with the Los Angeles forced it
back to Lakehurst, and the navy decided
to have the Shenandoah
fulfil its sister ship’s
engagements.
The airship’s commander, Zachary Lansdowne, complained to
his superiors that the ship was
not prepared for the line squalls
and thunderstorms that were common in
the Midwest. The ship was
sent anyway, and on September 3,
1925, the Shenandoah met a storm and broke up over
the Ohio countryside. Lansdowne and thirteen of the
crew were killed when the control
car tore loose and fell.
Several
crew members sent into the hull earlier to secure one
of the bags of gas,
including Lieutenant Charles E. Rosendahl,
clung to the bag while the rest of the craft peeled
away, and landed safely
twelve miles away. It was the
crash of the Shenandoah that prompted
Brigadier General Billy Mitchell’s intemperate
remarks about the way the navy was
handling its aircraft program.
The poignant photos of eastern Ohio farm
folk sadly viewing the twisted wreckage
of the Shenandoah stayed with many Americans and weakened
popular support
for dirigible flight a
dozen years before the Hindenburg disaster.
A Naval Court of Inquiry conducted a lengthy
investigation,
which included Lansdowne’s widow
testifying about her husband’s misgivings, and Lieutenant
Rosendahl, buttressed by Admiral
Moffett, defending the
navy’s decision. The court blamed Lansdowne for the
accident and made a great
many self-serving pronouncements about how the loss of the
Shenandoah was the price to
be paid for the lessons learned. After much
debate, Congress caved in and approved the navy
plan to build three
replacements for the Shenandoah, two of
them nearly twice its size and the
other a smaller all-metal
dirigible, the ZMC-2, the only dirigible that was
still in active service
during World War II.
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