New airship carries commercial hopes

CargoLifter: Old idea, hi-tech design

A new breed of hi-tech giant airships planned by a German company could be the heavy lift aircraft of the future.

The CargoLifter is intended to carry payloads of up to 160 tonnes - about the weight of 27 full-grown African elephants - at a speed of 100 km/h (62 mph) and a maximum height of 2,000 metres (6,500-feet) non-stop over several thousand kilometres.

Filled with 500,000 cubic metres (17.6 million cubic feet) of non-flammable helium, the airship will be 260 metres (850-feet) long and is designed to carry large loads to remote locations.

According to the German company behind the airship the CargoLifter will not need a landing strip and will have more endurance than a conventional aircraft.

Strong keel

To enable the craft to carry heavy weights the manufacturers have come up with a new design.

The large Zeppelins built early in the last century could carry big loads but they were themselves heavy. To keep them rigid they had a strong metal frame.

It would have taken three Zeppelins the size of the CargoLifter to carry the same payload.

The much smaller 'blimps' currently in operation consist of a lighter aerodynamically shaped envelope that, like a balloon, is kept rigid by the pressure of the gas. The pilot, passengers, and engines are carried in a gondola mounted underneath.

The CargoLifter is of a modified semi-rigid design. Like a blimp it has no frame, but to allow it to carry heavy weights the airship has a fixed keel which also houses the cargo bay, the flight deck, crew's quarters and engines.

Early promise

Lighter-than-air transport considerably predates the aeroplane. The first balloons flew in the 18th century and by 1900 the Germans were producing rigid airships capable of carrying considerable loads over long distances.

Early Zeppelin - weight penalty

Built by Luftschiffsbau-Zeppelin, they consisted of a cigar-shaped, trussed and covered frame supported by internal gas cells containing hydrogen.

Beneath the 128 metre (420-foot) craft, a keel-like structure connected two external cars, each of which contained a 16-horsepower engine geared to two propellers. The first craft attained speeds approaching 32 km/h (20 mph).

By the mid-1930s, the Zeppelins had doubled in size. The largest airship ever built, the Hindenburg, was 245 metres (804-feet) long, and powered by four 1,100-horsepower diesel engines, giving it a maximum speed of 135 km/h (84 mph).

In 1936 this airship carried a total of 1,002 passengers on 10 scheduled round trips between Germany and the United States.

On May 6, 1937, while landing at Lakehurst, New Jersey, the Hindenburg was completely destroyed when it crashed and burst into flames, with a loss of 36 lives.

End of an era

Hindeburg disaster destroyed industry

The cause of the fire has always been assumed to be an electrostatic discharge setting light to a hydrogen leak.

Recent research by a retired Nasa engineer has shown that the airship's lifting gas was not a direct cause of the fire.

An expert on hydrogen, Addison Bain studied photographic evidence of the disaster together with remnants of the airship and came up with an alternative theory.

He found that the airship's fabric had been coated with a mixture of cellulose nitrate 'dope' and aluminium powder, which is potentially flammable in its own right.

As the Hindenburg came into land it passed between two thunderstorms and built up a large static charge.

As it touched down most of this electricity passed harmlessly to earth, but parts of the covering remained charged. A spark between two panels set fire to the dope/aluminium mixture in the fabric.

The fire quickly spread and in turn set off the hydrogen in the Zeppelin's gas cells.

Bain's research has since been confirmed by contemporary German records which were suppressed at the time because of the impact they would have had on the image of German industry just as Nazi power was reaching its zenith.

The Zeppelin airship works were destroyed by Allied bombing during World War II and building of the huge rigid airships was never resumed.

This was partly because transport aircraft offered a much faster and safer alternative, but also because of the psychological impact of the Hindenburg disaster. Graphic images of the crash burnt their way into the public consciousness.

Small scale trials

Even though harmless helium has been used in all airships built since, their construction has been limited to small blimps, used mostly for advertising purposes and on a limited scale by the US Navy for coastal patrols.

'Joey' - ready for the future

Now, over 60 years since the last giant commercial airship was built, Germany is once again at the forefront of the lighter-than-air aviation industry.

A full size prototype of the CargoLifter is still several years away but a 1:8 scale version - called Joey - is already in existence.

This experimental airship is 32 metres (104-feet) long. Like the CargoLifter, it has a keel made of carbon-fibre structural elements and a hull, so that the experience gained can flow straight into the development and production of the fullscale airship.

Despite Joey's relatively small volume of 1,000 cubic metres (35,000 cubic feet) the aircraft is fully functional and will be able to carry out test flights to provide a practical check on the concept and computer calculations.

Later it will be possible to use Joey for training CargoLifter pilots.

CargoLifter is in competition with Zeppelin which has a smaller proof-of-concept aircraft flying.