“It is far better to face the bullets than to be killed at home by a bomb,” proclaimed a British Army recruitment poster publicized during World War 1. The poster was alluding to air attacks that Britain was being subjected to.
At the start of World War One, Britain found itself totally ill-prepared to deal with the threat from enemy airships called Zeppelins, which are practically large bags filled with hydrogen gas. Floating at thousands of feet, Zeppelins could turn off their engines, and drift silently among the clouds carrying out surprise attacks. For the very first time, civilians were under threat.
The German Zeppelin LZ 18 at Berlin-Johannistal, 1913.
Zeppelins were first flown commercially as passenger airliners in 1910. By the time the First World War broke out, Zeppelins had flown over ten thousand fare-paying passengers on over 1,500 flights.
The principal feature of the Zeppelin's design was a fabric-covered rigid metal framework made up of transverse rings and longitudinal girders containing a number of individual gasbags. The framework of most Zeppelins was made of duralumin which is a combination of aluminium and copper as well as two or three other metals—its exact content was kept a secret for years. Early Zeppelins used rubberized cotton for the gasbags, but hydrogen molecules are so tiny that they escaped through the sheets. Then the Germans discovered goldbeater's skin, made from the intestines of cattle. The name comes from the product’s original use—they were traditionally used to sandwich sheets of gold in order to beat them down to gold leaf, just 1 micron thin. The sheets are tough enough to withstand the goldbeaters’ hammers, and they could be joined together and folded into impermeable layers.
Mark Steadman from the Post & Tele Museum explains how goldbeaters skin is manufactured:
Goldbeaters skin is made from part of a cows intestine, the outer layer of the caecum to be precise, which is also called blind gut or even the appendix. The outer layers of the blind-gut are carefully stripped off into sheets of around 60 cm in length by 25 cm in width. They are then cleaned of fat by dipping the gut in a mild alkaline solution and scraped with a blunt knife. The cleaned gut is then stretched over a frame. One quite remarkably quality of this material is that separate sheets can be joined or welded when wet by carefully rubbing the overlap of the two sheets. Several layers can be made this way as well, for example, airship gasbags usually consisted of up to seven layers of skin.
The living tissues in the sheets grew together making a seamless and Hydrogen proof join. As well as being impermeable to Hydrogen it was also light and very strong, making it the perfect gasbag material.
An engraving showing the goldbeating process.
An incredible amount of cow intestines were needed to make these gasbags. A report prepared by Captain L. Chollet for the U.S. National Advisory Committee for Aeronautics in 1992 mentions that one cow furnishes only one such skin and 15 of them were required to prepare one square meter of the fabric. Each Zeppelin operated by the Germans had a balloon surface area of 20,000 to 30,000 square meters, requiring more than 250,000 cows to produce the bags that held the hydrogen gas in each Zeppelin. This wartime requirement put such a stress on the meat industry that Germans had to forgo their beloved sausages so that the army could have enough airships to rain down bombs upon British cities.
“The collection of the goldbeater's skins was very systematic in Germany during the war,” wrote Captain L. Chollet. “Each butcher was required to deliver the ones from the animals he killed. Agents exercised strict control in Austria, Poland and northern France, where it was forbidden to make sausages.”
Despite the ban on sausage making, the supply of goldbeaters skin ran out during the First World War, forcing the Zeppelin Company to recycle the material from older airships as well as use an inferior artificial substitute for the construction of the gasbags. The poor quality of these wartime gasbags were considered responsible for the loss of many war-time airships and their crew.
Women workers preparing the gasbag skins. Photo: airshipsonline.com
Gasbags under construction and testing. Photo: airshipsonline.com
The German military made extensive use of Zeppelins as bombers and as scouts during the war, resulting in over 500 deaths in bombing raids in Britain. The defenders found them surprisingly difficult to shoot down, despite being essentially floating balloons full of inflammable gas. Standard bullets and shrapnel made small holes causing inconsequential gas leaks. The British eventually developed new bullets, the Brock containing oxidant potassium chlorate, and the Buckingham filled with phosphorus, which reacted with the chlorate to catch fire and hence ignite the Zeppelin's hydrogen.
To counter the increasingly effective British defenses, the German army introduced new Zeppelins which were capable of flying higher, up to 21,000 feet, to escape enemy bullets. But increased altitude brought extreme cold and decreased oxygen which in turn led to altitude sickness. Besides, the wind was high and unpredictable at increased altitudes that made maneuvering the craft difficult. Many Zeppelins got caught in strong winds during air raids and failed to reach their targets.
Workers inspecting the gasbags. Photo: airshipsonline.com
The German defeat in the Great War marked the end of dirigibles in warfare, as the victorious Allies demanded a complete abolition of German air forces and surrender of the remaining airships as reparations. A week before the Treaty of Versailles was signed, many Zeppelin crews destroyed their airships in order to prevent delivery. The remaining dirigibles were transferred to France, Italy, Britain, and Belgium in 1920.
During the war, a total of 84 Zeppelins were built, of which 60 were lost. Half of this was lost to accidents. In the 51 raids made against England, more than 5,800 bombs were dropped resulting in over 550 deaths and over 1,300 injuries. It has been argued the raids were effective far beyond material damage in diverting and hampering wartime production: one estimate is that the due to the 1915–16 raids “one sixth of the total normal output of munitions was entirely lost.”
References:
# L Chollet, “Balloon fabrics made of Goldbeater's skins”, NASA
# Mark Steadman, “The Goldbeater, the Cow and the Airship”, Post & Tele Museum
# “Zeppelin”, Wikipedia
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