Many were sceptical when the Zeppelin was relaunched in the 1990s, but the modern airship has found a 21st century market
It may not have the grandeur or sheer scale of its pre-war predecessors that ferried affluent Americans and Europeans across the Atlantic, but at 75m (246ft) - longer than an Airbus A380 - the fourth of a new generation of Zeppelins inspires awe nonetheless.
In the final stages of assembly in Zeppelin Luftschifftechnik's (ZLT) hangar outside the Lake Constance resort of Friedrichshafen, where Count Ferdinand von Zeppelin flew his prototype in 1900, the Zeppelin NT 07 is still an innovative piece of engineering, even if the dirigibles that bore its name last flew almost 70 years ago.
With its 8,425m3 (297,000ft3) helium-filled hull held in place by a rigid inner aluminium and carbonfibre frame to which the 12-seat gondola, rudders and three vectoring 200hp (147kW) Lycoming IO-360 engines are attached, the 8t aircraft can fly for around 900km (485nm): not quite the legs to traverse the ocean, but enough for the sightseeing, aerial advertising and surveillance flights that are its markets today.
Zeppelin NT (for "new technology") number four is in fact destined for the USA, but unlike the Graf Zeppelin and the Hindenburg, the modern-day airship will journey there by sea. Earlier this month, ZLT finalised a deal with Californian start-up Airship Ventures, which plans to operate tourist flights over San Francisco bay later this year. In a piece of joined-up history, Airship Ventures is based at the former naval station at Moffett Field, which housed US airships before the Second World War.
ZLT is continuing the Zeppelin tradition at Friedrichshafen
Three other Zeppelin NTs have been built since a group of investors put a plan together to relaunch the famous airship name in the mid-1990s. The first went into service in 2001 and is based next to the Friedrichshafen factory, where ZLT's sister company Deutsche Zeppelin Reederei (DZR) takes sightseers on 30min to 2h flights over Lake Constance.
Operating up to 10h a day, seven days a week for most of the year, the aircraft has accumulated over 12,000 flight hours and carried around 80,000 passengers. A second was sold to Japan in 2004 with Nippon Airship in Tokyo launching services three years later. The third, the prototype, was not used for tourist flights but for prospecting diamond mining sites in Botswana for De Beers, where its low speed and stability at low altitudes made it a perfect platform for carrying aerial surveillance equipment.
After accumulating almost 1,500h, the prototype was damaged beyond repair in September last year while it was moored during a cyclone.
Although Friedrichshafen is synonymous with Zeppelin, there were many sceptics when a small team of enthusiasts - backed by Friedrichshafen-based automotive components group ZF (a successor to the count's original business) and the Zeppelin Foundation - unveiled a plan to launch a 21st century version of the airship.
They intended, says ZLT chief executive Thomas Brandt, to exploit the "cognitive memory of the people in the town and the huge amount of heritage", but to come up with an entirely new airship design that "challenged the fundamental weaknesses" of the original airships as well as modern blimps.
For a start, it was essential that the aircraft could be controlled at all times and for this a strong propulsion system was needed - hence the three engines. Secondly, the engines should be able to swivel to provide vertical and forward propulsion. Thirdly, the engines should be attached to the triangular inner structure itself, so that even when the empennage is torn, the aircraft is able to land under its own power.
The first Zeppelin NT made its maiden flight in 1997 and was certificated in 2001. DZR operates its aircraft with one captain and a cabin attendant - even though passengers are carried, the European Aviation Safety Agency does not require a second pilot because the Zeppelin operates at low speed and altitude. DZR tends to recruit and train former helicopter pilots because of the similarities in handling characteristics.
Aside from a marquee that serves as a passenger check-in at Friedrichshafen, the only ground infrastructure is a mast truck to position the airship while moored, and a 300m2 (3,230ft2) area for landing. Passenger steps unfold from the door.
For those on board, panoramic windows in the 10.7m-long gondola offer spectacular views from the normal cruising altitude of 900ft, with passengers able to unbuckle and move about the cabin just a few minutes after take-off.
A glimpse inside the giant ballonet, made from three layers of laminated material, reveals two large chambers: when taking off, the larger one is filled with helium. As the helium contracts at higher altitudes, a lower sack fills with air, with the flight management system controlling the process automatically. The two propellers on the side can rotate 120e_SDgr, the rear one by 90e_SDgr, allowing the Zeppelin to take off and land vertically as well as hover and turn on the spot.
The Zeppelin can stand up to adverse weather, although the nature of the flights means DZR does not fly about one day in five. "It's much more reliable than a balloon," says Brandt. "But in heavy rain or when there are gusts over 30kt [55km/h], people don't want to go up." Flights are also cancelled if visibility is less than 5km or the cloud base descends below 1,310ft.
The new airship has confounded spectics
It may be vital to Friedrichshafen's tourist industry - 12,000 people a year come to town to fly on the Zeppelin and many more visit the factory and Zeppelin museum - but ZLT is not a major industrial employer.
The company employs just 15 technicians, with around 65 others working mainly for DZR as pilots and call centre staff, some of them part-time or seasonal. Brandt is realistic about prospects for the Zeppelin NT and because of its relatively low payload and range does not believe the design has any practical use beyond its existing markets - for example cargo.
"It's a very special niche, and the idea of 50 or 60 of these being produced is just not feasible," he says. "The whole market is maybe 30, so it would be very difficult for a competitor to come up against us."
Big waterfront cities with a vibrant tourism sector - Sydney, New York, Hong Kong and perhaps London, Paris or Venice - and an entrepreneurial operator able to see the opportunity are where new customers may emerge, he says. And although ZLT's giant hangar has space for up to three Zeppelins, Brandt insists: "I will be happy to build one a year."