Airships rise again
When Britain and then Germany abandoned airship development after the R101 and Hindenburg disasters in the 1930s, most thought the age of airships had reached its end. Heavier-than-air flight developed much more quickly than had been envisaged, and airliners soon took on the long-haul passenger-transport role airships had been expected to fulfil.
Now, in a corner of the shed once used to house the R100 in Cardington, near Bedford, a British firm is preparing for the dawn of a new airship era.
Airship Technologies hopes to have the first of its latest design, the AT-04, flying in a year's time. It will be 82m long with an envelope of 14,200m3, and will be capable of carrying 50 passengers plus 4 crew or a 6-tonne payload. Its top speed will be more than 130km/h.
In June, the company won a £230,000 cash injection under the DTI's Civil Aircraft Research and Technology Demonstration programme.
The airship's prospects have been transformed by technological developments, beginning with the availability of inert helium to replace the inflammable hydrogen gas formerly used to provide lift, and culminating in innovations to make airships easier to land, take off and moor (see panel).
The revival can be traced back to the 1970s, when Shell started looking at airships as a way of transporting natural gas. This project did not come to fruition, but it saw the establishment of Airship Industries, the forerunner of Airship Technologies, with Roger Munk leading the design team. Airship Industries built a total of 25 Skyship 500s and 600s.
Police used a Skyship 500 for surveillance at the 1984 Los Angeles Olympic Games, and the model has been used at every Olympics since.
Meanwhile, in the early 1990s, the American Blimp Corporation began building smaller airships for advertising purposes. ABC claims to have built half of the 38 airships estimated to be flying in the world today.
Sir John Walker, Airship Technologies' chairman, believes there could be a large military market for patrol and surveillance airships. He points out that unlike helicopters, airships can stay aloft for long periods. Their life-cycle costs can be a sixth and operating costs as low as 1/36th of a helicopter's.
Walker, who had a distinguished RAF career, foresees the following four main roles for airships:
Patrol and surveillance: Unlike a maritime aircraft, an airship can stop, drop a boat for a rescue or customs inspection, and pick it up again, says Walker. When hovering, it produces no downdraught and uses minimum power; a helicopter needs close to maximum power.
Early warning: a radar aerial for detecting cruise missiles operates at such a frequency that it needs a large vertical dimension. Fitting it inside an airship's gas envelope is the only practical way to get one airborne.
Mine counter-measures: mine- sweepers cost more per tonne than any other type of ship because their pressure, acoustic and magnetic signatures have to be low. An airship solves the problem much more cheaply. Some think airships could also be used in clearing landmines.
Anti submarine: airships played a successful role in guarding convoys from submarines in World War I. Modern submarines are quieter and difficult to detect by sonar. Active low-frequency sonar beacons, which are lowered under water, are becoming too big for helicopters to handle, and the sonar picks up the beat of helicopter blades on the water.
Surprisingly, says Walker, airships are not easy to shoot down. They have no infra-red signature and are virtually transparent to radar. If holed, they lose gas only slowly.
Meanwhile, German firm CargoLifter has plans for a huge ship to crack the heavy freight market.
Airships would be suited to tasks such as delivering a large power- station turbine from Europe or the US to a site in the developing world. Today, the lack of suitable roads at each end of the journey is a problem; in between, the turbine travels by sea, which is slow. An airship could pick up a turbine and fly straight to any destination in the world.
CargoLifter's proposed CL160 will be the largest airship ever built, at 242m as long as three Boeing 747s and will be capable of carrying 160 tonnes at over 75km/h. A one-eighth scale prototype with a fully operable crane system has been built and flight tests are scheduled for later this year. Test flights for the full-sized CL160 are planned to start in 2000.