David Learmount/LONDON
Transporting outsized, heavy machinery or plant to a remote site on a different continent is a logistics nightmare which might involve three or more modes of transport. The unit, perhaps a hydro-electric generator, often has to be designed not only for its mechanical efficiency, but to enable modular transport and reassembly under conditions that are far from ideal.
A perfect logistics system would lift the unit, fully assembled, direct from its point of manufacture and lower it on to the foundations where it will operate. It sounds unreal - the creation of a logistical magician - but the first cargo lifts by a new system which promises factory-to-site single mode heavylift transport have already been reserved, even though the system is still on the drawing board.
THE TASK
In 1993, a group of German heavy machinery and plant manufacturers met to solve their mutual logistics problem. The industrialists started with a blank sheet of paper and a commonly held conviction that existing choices for air and surface transport were unnecessarily inefficient. Lighter-than-air technology was on the agenda, but no-one present thought it would provide the answer; it has won the contest, however, according to CargoLifter, the Wiesbaden, Germany-based company formed to turn the concept into reality.
CargoLifter president Dr Carl von Gablenz and his team shun the word "airship", because it is laden with old concepts and old limitations which the new company says are irrelevant to this project. Von Gablenz is an engineer, banker and lawyer, but he is also a respecter of aviation tradition, being the grandson of Lufthansa's co-founder. He says that lessons learned from earlier successful airship programmes are being used, but CargoLifter's aims, modes of operation, and even the available design, construction and control technology are different from those applicable, for example, to the Zeppelin.
Early airships were conceived as a means of transport, and once the means had been defined, the tasks which they could best perform were determined. In the case of the CargoLifter, the tasks were defined, and then the best means of performing them was sought. The company's name, for example, embodies the task, not the means, and its favoured terminology is not "airship", but "total logistics system" or "skycrane".
The first CargoLifters are to be designated CL160s, to reflect the fact that they will carry a 160t payload. The market will determine later whether larger craft will be built to carry even heavier loads - 400-450t is on the cards. If the lifting capacity goes as high as 500t, says marketing chief Hinrich Schliephack, the Cargo-Lifter's "skycrane" abilities could revolutionise engineering projects like bridge building.
The advantage of a lighter-than-air craft is that, when the payload is increased, the linear dimensions do not have to be increased as much, because lifting capacity is proportional to the craft's volume rather than, as with a fixed-wing aircraft, to wing area and speed. Speed implies the need for runways, which the CargoLifter will not require.
CargoLifter's speed sounds pedestrian at 45-60kt (80-110km/h). Heavy freight using multi-modal surface transport, however, tend to travel at an average speed of 4-5kt. Compared to this, the company is offering to move heavy loads 10 times faster and about 20% cheaper.
Surface transport of heavy equipment to remote construction sites may also require road and bridge strengthening and/or widening, for example, and that would add to the effective transport time and to its cost. While there could be weather constraints on CargoLifter's operations, that is almost certainly true of all the other transport modes. If the delivery is to a construction site, for example, work almost always is constrained by seasonal conditions.
The size of the CL160 is impressive. At 242m (786ft) long, and 61m in girth, it is three times the length of a Boeing 747. Construction materials are modern plastics, including polyester and Kevlar. The envelope volume will be 450,000m3 (15.8 million ft3), in a series of cells filled with non-flammable helium gas. Each cubic metre of gas supports 1kg of weight. As no aerodynamic lift is required to carry this weight, there is no induced drag. The only energy expended in transporting the load is that necessary to accelerate the CargoLifter to cruising speed and then to overcome its profile drag.
Motive power will be provided by four diesel engines driving vectoring propellers, with manoeuvring thrusters at the bow and stern. Total cruising fuel consumption at 55kt is 4.5 litres/km (1.18USgal/km). Ballast to compensate for the use of fuel will be created by recovering water from the exhaust.
THE RANGE
The still-air range is 10,070km (5,400nm) but, unlike in the pioneering days of the Graf Zeppelin, modern weather reporting and forecasting means that advantageous tailwinds can be used to reduce trip time. Nevertheless, the potential journey duration means crewing precepts have to draw more on maritime practices than aviation ones. CargoLifter says it is working with both aviation and maritime authorities to determine crewing regulations and the skills and qualifications required for licensing.
The cargo container is massive - 50 x 8 x 8m - and is designed to be able to be loaded and emptied from all sides. It can contain a single unit or 36 standard marine cargo containers. The container is carried below the envelope, attached to a loading frame with winches for raising and lowering the cargo on four sets of cables, and ballast tanks for uploading water when setting down the load, and the converse operation when picking the load up.
CargoLifter's most impressive characteristic, for either pick up or set down of cargo, is its ability to remain almost stationary overhead without using any energy except for the manoeuvring thrusters which keep it in position.
While being lowered, the load itself is stabilised laterally and positioned precisely using a four-point ground anchoring system, and the airship is stabilised vertically through the exchange of load for ballast and laterally by the manoeuvring thrusters. CargoLifter uses the crane comparison extensively, referring to the whole system as a "flying crane".
Any commodity which needs to be transported in bulk is a potential payload for CargoLifter. Apart from heavy machinery, grain or fluids are also natural cargoes for the airship. Industry may see the logistics potential, but so might agencies such as the United Nations, the company says, providing supplies and relief aid to disaster-hit regions, especially where the surface infrastructure has been destroyed by floods, wind or earthquakes.
MILITARY USES
The military also could find uses for the heavylift capability, although the airship is more of a strategic than a tactical logistics tool. Wherever a combination of sea and land transport has previously been used, CargoLifter might well compete. Underlining the potential of this market is the fact that Lockheed Martin SkunkWorks is studying the concept of a very large airship to replace cargo vessels now used to position military material. Countries which consist of an archipelago, such as Indonesia, have shown "amazing" levels of interest in the CargoLifter concept, reveals Schliephack, adding that China is showing interest also.
To serve a world market with a relatively slow machine, a worldwide network of dispersed operating bases is a clear need. The fact that a CargoLifter assembly site is planned for the USA, as well as Europe, is evidence of the company's appreciation of the need to be well positioned in its marketplace. In addition to the first assembly/operational base at Brand, Cargo-Lifter plans an eventual network of six operating bases in North America, two in South America, six in Europe, two in Africa and the Middle East, one in Russia, seven in Asia-Pacific and one in Australasia.
In 1816, air transport pioneer Sir George Cayley said: "The air is an endless ocean which touches the door of very house. This ocean needs a workable airship which is able to sail it." Airships have been workable for a long time, but their position in the market has been usurped by faster machines. Finally, perhaps, a combination of technology and the accurate identification of the airship's place in the transport market will make it less of a rarity.
Source: Flight International
