American Zeppelins? The USS Shenandoah

Some of the most amazing American stories of Zeppelins come from the USS Shenandoah launched in 1923.  The Shenandoah was a copy of a German design captured from WWI.  It was built at Lakehurst which would remain the main airship hub until the Hindenburg disaster in 1937.

America was the only country in the world capable of producing enough helium to fill the needs of a Zeppelin style airship—some 2,000,000 cubic feet in 20 gas cells.  Thus the Shenandoah was the first helium filled rigid airship to take the skies. *Yay America* *grin*

A very brief physics lesson: Air pressure decreases as you rise in altitude.  You feel this in your ears when you climb a high mountain pass.  To a balloon this decrease in pressure allows the gas inside to expand—appearing to inflate the balloon further.  With too much expansion the balloon will pop.  This very basic mechanic is a major concern to airship which is essentially a very, very large balloon.  As it rises the gas expands and would rupture without some means to control the pressure inside the Zeppelin gas cells.

Hydrogen was dangerous but it was also very cheap so the German airships would just open valves to reduce the pressure and let the gas dissipate harmlessly.  But helium was like gaseous gold.  Even the rich American military couldn’t afford to vent helium willy-nilly.  Instead they would under-inflate their cells so that by the time they got to cruising altitude they would be at optimal expansion.  But this meant the ships had considerably less lift.  It also meant that the US airship commanders had a strong aversion to venting their helium if they could help it (ominous music).

Indeed this would be a factor in one of the most dramatic scenes of aeronautic history. Lieutenant Commander Zachary Lansdowne would in late 1924 order the removal of several automatic venting valves from the Shenandoah.  While not completely removed, the reduction seriously limited the rate at which helium could be vented.  Under normal conditions this would not have been an issue.  But in Sept 1925 the airship would be caught in a storm over Ohio.  Storms experience radical vertical winds and the Shenandoah would be caught in an updraft.  Rising at 1000 feet per minute the airship could not deflate its gas cells fast enough and basically began “falling” upward.  This ship shot up to over 6,000 feet.  The stress and expansion broke the ship in two.  The aft section would fall to the earth killing all including the captain.  But in a miracle of skill and survival, the bow section remained aloft!

Crippled with no steerage or automatic controls, the ship navigator, Charles Rosendahl assumed command of the 7 men still alive in the front half of the broken Shenandoah. Rosendahl would fight the storm and slowly vent his helium to make a safe landing.  All 7 men with him would survive.  The other 14 men perished.

While the reduced valve capacity probably did not help poor Commander Lansdowne, other experts concluded the design of the Shenandoah probably could not have survived the storm anyway.  The US had copied the design from a WWI “height climber”—an airship designed to make bombing runs from extremely high altitude.  Its frame was lighter and its general dimension (being very long and thin) were not suited to a Midwestern thunderstorm.  The fact that rigid airships were used at all in WWI is a story for another post *grin*.

Charles E. Rosendahl emerged a hero and would be a prominent figure in rigid airships the rest of his life.  He would fly on the first trans-Atlantic flight of the Graf Zeppelin and several trips on the Hindenburg.  His role in history is fixed in this event as he was the commander of Lakehurst the day the Hindenburg crashed.  But that brief moment is but an instant of this man’s long career.  For years he would advocate the use of lighter-than-air rigid airships in spite of the disaster’s he had seen.  Rosendahl knew then that the failures of the past were addressable in the future.  He even wrote a book on it, but I will be hard pressed to find a copy.

Again we see how bad weather encountering a ship not designed for it causes the destruction of a rigid airship.  Today our use of helium is more more affordable; valving off gas would be no issue.  Weather prediction could have steered the ship to safety or kept it out of the sky completely. 

The next post will be about the incredible history of Zeppelins in WWI.

Source Credits: I’m stealing all this info heavily from Dan Grossman’s site (http://www.airships.net) and the book “Dr. Eckner’s Dream Machine”, by Douglas Botting.