USS Shenandoah (ZR-1) - Design and Construction

Design and Construction

Shenandoah was originally designated FA-1, for 'Fleet Airship Number One' but this was changed to ZR-1. The airship was 680 ft (207.26 m) long and weighed 36 short tons (33 t). It had a range of 5,000 mi (4,300 nmi; 8,000 km), and could reach speeds of 70 mph (61 kn; 110 km/h). Shenandoah was assembled at Lakehurst Naval Air Station in 1922–1923, in Hangar No. 1, the only one large enough to accommodate the ship; her parts were fabricated at the Naval Aircraft Factory in Philadelphia. Lakehurst had served as a base for Navy blimps for some time, but Shenandoah was the first rigid airship to join the fleet.

The design was based on Zeppelin bomber L-49 (LZ-96), built in 1917. L-49 was a lightened "height climber", designed for altitude at the expense of other qualities. The design was found insufficient and a number of the features of newer Zeppelins were used, as well as some structural improvements. The structure was built from a new alloy of aluminum and copper known as duralumin. Girders were fabricated at the Naval Aircraft Factory. Whether the changes introduced into the original design of L-49 played a part in Shenandoah later breaking up is a matter of debate. An outer cover of high-quality cotton cloth was sewn, laced or taped to the duralumin frame and painted with aluminum dope.

The gas cells were made of goldbeater's skins, one of the most gas-impervious materials known at the time. Named for their use in beating and separating gold leaf, goldbeater's skins were made from the outer membrane of the large intestines of cattle. The membranes were washed and scraped to remove fat and dirt, and then kept in a solution of water and glycerine in preparation for application to the rubberized cotton fabric providing the strength of the gas cells. The membranes were wrung out by hand to remove the water-glycerine storage solution and then rubber-cemented to the cotton fabric and finally given a light coat of varnish. The 20 gas cells within the airframe were filled to about 85% of capacity at normal barometric pressure. Each gas cell had a spring-loaded relief valve and manual valves operated from the control car.

As the first rigid airship to use helium rather than hydrogen, Shenandoah had a significant edge in safety over previous airships. Helium was relatively scarce at the time, and the Shenandoah used much of the world's reserves just to fill its 2.1 million-cubic-foot volume. Los Angeles—the next rigid airship to enter Navy service—was at first filled with the helium from Shenandoah until more could be procured.

Shenandoah was powered by 300 hp (220 kW), eight-cylinder Packard gasoline engines. The first frame of Shenandoah was erected by 24 June 1922; on 20 August 1923, the completed airship was floated free of the ground. Helium cost $55 per thousand cubic feet at the time, and was considered too expensive to simply vent to the atmosphere to compensate for the weight of fuel consumed by the gasoline engines. Neutral buoyancy was preserved by installing condensers to capture the water vapor in the engine exhaust.

It was christened on 10 October 1923 by Mrs. Edwin Denby, wife of the Secretary of the Navy, and commissioned on the same day with Commander Frank R. McCrary in command. Mrs Denby named the airship after her home in the Shenandoah Valley of Virginia, and the word shenandoah was then believed to be a native American word meaning "daughter of stars".