The rise and fall of the metal airship

In 1844, Parisians with an extra franc in their pocket could wander to the outskirts of the city and buy entry to a mysterious building on Impasse du Maine, a narrow dead-end street just behind the new railway station at Montparnasse. Inside a cavernous hangar, proprietor Edmond Marey-Monge and his team of workmen laboured away, soldering together long sheets of metal to make a giant sphere. Just what this contraption was for only became clear after examining the blueprints: valves for introducing hydrogen and attachments for a passenger gondola hinted at a new mode of transport. The gleaming sphere, Marey-Monge announced, was a "ballon de cuivre" - a brass balloon.

METAL airships are one of the oldest notions in aeronautics. As early as 1670, Italian mathematician Francesco Lana published his Demonstration of the Feasibility of Constructing a Ship With Rudder and Sails, Which Will Sail Through the Air. Lana proposed evacuating the air from a set of copper spheres, which he reasoned would weigh less than the surrounding air and would ascend until the weight of the sphere reached equilibrium with the surrounding atmosphere. He calculated that four vacuum spheres, each with a diameter of 7.5 metres, could lift a boat carrying six passengers.

Lana, alas, could not procure the copper spheres himself because of his obligations as a Jesuit. "I would have willingly [built it] before publishing these my inventions," he explained, "had not my vows of poverty prevented my expending 100 ducats."

Lana's notion was not entirely fanciful. Recent experiments had demonstrated that air had weight, and in 1650 the German inventor and scientist Otto von Guericke had drawn together small copper hemispheres with such a strong vacuum that teams of horses could not pull them apart. Still, there was a difference between creating a sturdy 50-centimetre sphere and fashioning 7.5-metre globes that could rise into the clouds. As Lana's compatriot Giovanni Borelli pointed out, for Lana's spheres to be light enough to fly, the copper would have to be so thin that on evacuation they would be crushed by atmospheric pressure.

Nonetheless, Lana's idea transfixed Europe for the next century. By 1672, translations and engravings depicting his balloon had appeared in Germany, and in London Robert Hooke penned an English translation. A century later, Lana's copper balloons were still celebrated in poems. They appear in a German interplanetary travelogue of 1744 envisaging trips to Mars, and in 1768 an epic poem in Latin predicted their use in airlifts to rescue those "shaken by repeated earthquakes". But with the first successful flight of a hot-air balloon in Paris in 1783, Lana's concept of a rigid vacuum airship fell by the wayside.

Except, that is, in Paris itself. In 1844, inventor Edmond Marey-Monge suggested in the journal Comptes Rendus that for "aerial navigation to be able to render the same services as the navy", balloons must be in "a position to resist, like our ships, the bad weather of ten or fifteen years of service". Unlike fragile balloons made of fabric, metal airships could stay aloft indefinitely while performing their commercial or military duties.

After three years working in a custom-built hangar at number 10 Impasse du Maine, on what was then the southern edge of Paris, Marey-Monge was ready to fulfil Lana's vision. Rather than extract the air from a set of spheres, he planned to fill a single giant sphere with hydrogen. His balloon would be 10 metres across and made from 0.1-millimetre-thick brass sheets banded and soldered together. "I prefer the spherical form," Marey-Monge explained, "because under the smallest surface it contains the greatest capacity", and so, kilo for kilo of brass, gets the greatest lift from the gas it contains.

And lift was just what Marey-Monge needed, because despite the thinness of the metal, his balloon weighed 400 kilograms. His choice of material had several other drawbacks: not only were the curved brass plates difficult to solder together, but French foundries were unable to create the long, thin panels he needed. Marey-Monge had to import brass sheets, each 5 metres long and 50 centimetres wide, from a Prussian foundry. Then he had to construct a temporary wooden frame for workers to build the sphere around. To cap it all, the sheets were so thin, they developed countless tiny holes, and to prevent leaks he was forced to line the interior with thin layers of tissue, glue and varnish, adding another 16 kilograms to its weight.

While Parisians bought their tickets to watch the giant orb take shape, the project also captured imaginations abroad. The merits of metal balloons were debated at length by armchair aeronauts in Britain, including one who wrote to Mechanics Magazine to suggest an "iron balloon" 400 foot (120 metres) wide as "not contrary to the spirit of the times" - though, he allowed, it might "gambol about the Earth's surface with great danger to life and limb of the human race, as well as terror to animal creation generally".

Marey-Monge planned to launch his balloon on 2 June 1844. Extracting the wooden supports from inside the globe proved a delicate operation, as the balloon's skin was thin and easily damaged. But at last the vast globe seemed ready to fly. And so, with a turn of the valve, Marey-Monge filled his contraption with the 523 cubic metres of hydrogen it would need to break free of the Earth. And then... nothing. It wasn't budging.

Marey-Monge thrust his head through the hole at the base of the balloon and into the dark chamber. The air at the bottom of the sphere was still perfectly breathable, so much so that he could stand there for a full 15 minutes contemplating the cruelties of gravity. Pumping in the precious remainder of his hydrogen supply did not help: when he thrust his head inside again he could hear the hiss of lost money as the gas escaped through leaks in the brass skin.

The balloon never did fly, and Marey-Monge wound up selling the brass for scrap. It was little consolation for a project that had taken three years and cost him a fortune. Despite its ignominious end, the brass balloon had fired the Victorian imagination. Patents for metal airships appeared with some regularity, including a proposal in 1887 for a steel blimp 126 metres long. Yet even Marey-Monge eventually concluded that metal airships would remain unworkably fragile and leaky until a metal light enough to allow overlapping layers could be procured.

By 1897 a candidate had presented itself. Amid Germany's pioneering work in Zeppelin construction, designer David Schwarz conceived of a daring approach: why not an aluminium dirigible? After building two prototypes, with the help of the Prussian Airship Battalion he launched a 38-metre airship from Tempelhof Field in Berlin. Built in the familiar "blimp" shape, it contained bags of hydrogen within a skin of riveted aluminium plates 0.2 millimetres thick.

Incredibly, it worked. On 3 November 1897, Schwarz's airship lumbered aloft, and sailed 6 kilometres into the German countryside. But mechanical mishaps and its rigid design meant that instead of gently nudging to a stop, the metal colossus crumpled into a field like so much expensive foil.

Despite this, rigidity is one of the great attractions of metal-clads. Because their skin is less prone to deformation at higher speeds, a sleek metal-clad should be able to fly much faster than a textile-covered blimp. Goodyear's original airship designer, Ralph Upson, certainly thought so. In 1929, he formed the Metalclad Airship Corporation to build an aluminium-clad helium airship, the ZMC-2, for the US navy. Although notoriously difficult to handle, the "Tin Bubble", as it was dubbed, could reach a speed of 100 kilometres an hour, and it put in 2200 flight hours before it was decommissioned in 1941.

No more metal-clads have taken to the skies since: they were too expensive to build and too difficult to handle. But the dream never quite died. Upson's engineer Vladimir Pavlecka continued to patent innovations in the hope of a relaunch right until his death in 1980. Other designs have included one patented in 1964 that promised "jet-propelled dirigible airships". Such notions are still floated wistfully by airship designers at conferences.

Curiously, one man who remained ultimately unconvinced was none other than Francesco Lana himself, who feared what his metal airship might be capable of. "Fortresses and cities could thus be destroyed," he wrote, "as iron weights, fireballs and bombs could be hurled from a great height." So while airships were conceivable, the priest decided in 1670 that the havoc they would wreak meant that humans would never leave the ground. God, he concluded, "would surely never allow such a machine to be successful."