A new generation of environmentally friendly 'hybrid airships' could be just about to take off

Germany is producing zeppelins again. More than 70 years after the infamous Hindenburg disaster, its latest airship was gently guided out of the hangar doors last month to make its maiden test flight.

The Zeppelin NT, built from endowment money left behind by German airship pioneer Count Ferdinand von Zeppelin, will make further test flights around Friedrichshafen over the coming months, before flying to London - where a former contestant from The Apprentice, Rory Laing, plans to offer tourist joyrides over the capital for £150 a throw.

What is it about airships that continues to capture the imagination? By rights, the lumbering airborne relics of a century past should be no more than museum curiosities, consigned like gas lamps to the sentimental roll-call of redundant technology. But like sacked television contestants, it's hard to keep an idea as audacious as the airship down. With the cost of oil at record highs, and airline chiefs warning of the end of cheap flights, the idea of the airship is being seriously floated once more.

The appeal is of the airship is easy to grasp. Environmentalists like George Monbiot cite their frugal use of fuel when compared to other forms of flight. They are also quiet and fly at low altitude, at around 4,000ft compared with 35,000ft, further lessening their environmental impact. Although they are relatively slow, typically travelling at 125 mph - as quick as a high-speed train, but still needing about 43 hours to cross the Atlantic - most need no runway and could be deployed without need for further airport expansion.

One British company, SkyCat, is even floating the idea that airships could take off from the reservoirs bordering Heathrow airport. Airships appeal, moreover, to romantic travellers who see something glamorous in their more stately form of travel.

Once it's flown around London for a while, the new Zeppelin will cross the Atlantic itself en route to San Francisco where it will conduct more tourist flights (a sister ship is already operating in Japan). In engineering terms, the Zeppelin NT represents a remarkable revival in the fortunes of the airship.

On the right vector

It's more nimble than the old airships. The NT uses "vectored thrust", which is in principle the same ability to direct its thrust in much the same way as a Harrier jump jet. This is important, because one thing holding the airship back is it vulnerability to wind, especially gusts. Most traditional airships need a dozen people to tie it to a mast; the NT, just three.

The renaissance has been a long time coming. The development of the airship in the latter part of the 20th century saw the once stately transport reduced to the role of tethered balloon: a static camera platform and floating advertising hording like America's Goodyear blimp. But since the millennium, ideas for a new generation of airships have abounded.

Lockheed Martin, the world's largest defence manufacturer, has been secretly testing the crewed hybrid P-791 that marries the buoyancy of an airship with the aerodynamics of an aeroplane. Deep in development in California is the Aeroscraft, another hybrid that touts itself as a sky yacht and looks a lot like Thunderbird 2 from the old TV show.

Then there is the Stratocruiser, a beautiful re-imagining of the zeppelin by Tino Schaedler, a London-based German set designer and thinker. It's a wonderful flight of fancy designed to incorporate a gourmet restaurant, swimming pool and nightclub with resident DJs.

"Over the last year or so we've seen a real renaissance in the airship ventures, both in manned tourism-based airships and in surveillance," explains Andreas Grünewald, a zeppelin enthusiast who blogs at Airshipworld . "It's something very present and growing, especially over the last year or so. There's a lot going on".

The trouble though with the buzz of a zeppelin revival is a simple one: carrying capacity. The Zeppelin NT has a passenger capacity of just 12, plus two crew. The Aeroscraft, more ambitious offering, could be adapted to manage anything up to 180. (A 747 carries about 460 people.)

Airships may be enjoying their most exciting phase since the 1930s. But don't sell your shares in the airlines just yet. Though people think the 1937 Hindenburg disaster killed off airships, they never took off for mass transit. The Hindenburg was from a fleet of just two, and fixed-wing passenger aircraft had already overtaken the zeppelin for passenger carriage.

"They were for a very limited number of wealthy passengers and mainly as an alternative to luxury passenger shipping services to a very few destinations," says Douglas Botting, author of Dr Eckener's Dream Machine, a biography of the zeppelin. "If the Hindenburg disaster had not stopped the zeppelin service dead in its tracks, world war two would have done." The airship's passenger days seemed behind it. But around a decade ago, a British designer, Roger Monk, working inside the shed in Cardington where Britain's own airship programme was conducted in the 1930s, began to revive the idea with his SkyCat. The SkyCat was the first serious "hybrid airship" combining the aerodynamics of a fixed-wing aircraft with the lighter-than-air properties of a balloon.

The SkyCat also employs a "hover-skirt" which allows it to land not just without a runway, but without a mast to tie it to, giving it a drawing-board advantage over the zeppelin. "In our case we don't need any ground crew whatsoever," says Michael Stewart of SkyCat. "We can land our ship anywhere: on water or snow or marsh and even rubble."

The latter point you keep hearing about airships; that they could be used for disaster rescue. An airship can fly over broken bridges and land without a runway, taking aid to precisely the point it is needed.

What's new, SkyCat?

The SkyCat is a beautifully conceived vehicle, but one that has so far failed to receive proper funding. The team have built a 25m-long model, dubbed the "Sky Kitten", but that's it. The problem is money. Airships are expensive and don't carry many people. SkyCat has been floating around for a decade and yet it has failed to raise the hundreds of millions needed to get it off the ground. But even if hybrid airships can find commercial backers, they still face a steep climb.

The next thing holding airships back is the cost of the gas. To fill the SkyCat with helium, for example,would cost between £1m to £3m. However, the helium doesn't need to be refilled each time the airship lands, and "you only lose about 1% a year", says Stewart.

But a further disadvantage is speed. SkyCat will fly with a top speed of 100mph, far less when flying into a prevailing wind. London to Manchester would be far slower than the train.

Another problem is their vulnerability to wind. Although, "as they increase in size they become less so", says Grünewald. "With increasing technology that problem will be reduced to the same level of vulnerability faced by aeroplane."

The sight of zeppelins over London is sure to rekindle interest in the airship. The rising price of oil may one day make them affordable. For a short-haul journeys, they could easily compete with the likes of ferries and trains, but the return to long-haul remains something of a dream. And yet who would have thought, a decade ago, that passenger airships would ever fly at all?