In 1922, America started its own Zeppelin construction program. Given the number ZR1 and christened the "Shenandoah", this was to be America's first rigid airship to be built by the U.S. and more importantly, the first major airship to be filled with a nonflammable gas, helium. During the winter of 1922, the U.S. had witnessed the fiery destruction of the Roma, an Italian built, semi-rigid that belonged to the U.S. Army. The ship had collided with high-tension wires, igniting the volatile hydrogen. Only 11 men out its crew of 45 survived the inferno. Following this disaster, the U.S. Government decided that future American airships would not use hydrogen as its lifting gas but helium in its place.
Helium had many short-falls in airship use. For starters, helium was many times more expensive than hydrogen. Hydrogen cost about $2.50 per 1000 cubic feet where as helium at the time cost up to $120.00 per 1000 cubic feet. This meant that to fill the Shenandoah with helium it would cost an extra $235,000! The second drawback was that helium is less buoyant than hydrogen. Helium has only 93% the lifting force of hydrogen, thus making it necessary to build larger airships to lift the standard weights of airship cargoes. The last drawback effected the rest of the world but not the U.S. in that there were only two ways to get helium. One method was to extract it form the air by using huge machines that were extremely expensive and very inefficient. The other was to mine it as a natural gas. The only problem with this second option was that it had only been found in the United States. At this time, there were no other sources of underground helium deposits known. This gave the U.S. a global monopoly on helium, a fact that was not lost on other airship-producing countries.
The Shenandoah was patterned after a German WWI height climber but built larger and with more structural bracing. Unfortunately, The design turned out to be too fragile. The Shenandoah, America's first home-built airship, was ripped in two by heavy winds over Caldwell, Ohio in December of 1924, only two years after her launching. Of her 43 crew members, 29 actually survived the crash. One of these men was an officer named Charles Rosendahl. He, along with Rear-Admiral William Moffett, would become the driving force behind America's airships.
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