Airships, invented as far back as 1900 were an advance on hot air balloons or blimps. They included an engine and rudders for propulsion. They also include a frame made of a light aluminum or composite material. The frame is enclosed with a polymer casing that is filled with helium gas. Helium, being lighter than air, causes the airship to rise. When the weight of the airship equals the buoyancy, it stops rising and floats in position. It is then propelled forward using the in-built engine and the rudders. Descent to ground is by bleeding the helium gas in a controlled manner. Airships are also called Zeppelins, after the German inventor.
The initial work on blimps and airships came from mankind’s fascination with flying in air. The first flights on hot air balloons were attempted as early as 1783. As soon as airships were invented in 1900, people attempted to fly in them. The 1937 disaster of the Hindenburg airship, which traveled successfully from Frankfurt in Germany across the Atlantic Ocean to New Jersey before crashing, killing the 36 people on-board led to rethinking on airships. The advent of airplanes for travel filled the role the early airships tried to play. Airship usage was then primarily limited to advertising, where they were an eye-catching novelty. For example, airship advertising would be done over a beach on holiday week-ends, or when ceremonial parades or carnivals take place. For fixed location advertising, such as over a sports stadium, the cheaper blimp was used. The Goodyear blimp became synonymous with such advertising.
There is a recent revival of interest in airships with NASA announcing a program for the development of a new family of airships that could lift and move very heavy cargo. NASA is working with several companies to build a prototype that could be tested as early as in 2012. Simultaneously a British company, Hybrid Air Vehicles, has announced a partnership with a Canadian company to manufacture airships that could transport weights up to 50 tones and at speeds up to 115 mph. One major technical breakthrough has led to these high load capability airships. When an airship loads or unloads cargo, its weight changes and consequently its buoyancy. To maintain constant buoyancy, ballast had to be carried. This limited the load carrying capacity of airships. A new approach to bleeding helium gas from containers into inflatable bladders is said to have overcome this problem.
The use of an airship for transport of heavy cargo is of special interest. At present, the heavy cargo has to be lifted with a crane, loaded on a truck-trailer, transported at slow speeds over roads and then unloaded, again using a crane. The operations of lifting by crane, securing the heavy cargo to the truck-trailer bed and unloading all have risks and costs associated with them. In addition, at many construction sites, the road access is inadequate and transport of heavy and large dimension cargo needs detailed studies on load-bearing capacity of the road and the culverts, turning radius for the truck-trailer at road turnings and the like. If the heavy cargo could be moved by an airship, it could result in major savings.
There are many locations where a fixed wing airplane or a helicopter becomes impractical. Fixed wing planes need an airstrip and even helicopters need a helipad for operation. An airship could get deployed at such locations. The deployment could be on hilly terrain or for disaster relief, as in an earthquake or flood affected area.
Military applications are always a spur to technology development. The applications being considered include movement of heavy armored vehicles like tanks or field guns into terrain where there are no roads or where road access has been destroyed. Airships and blimps are already being used for ground surveillance by the military and for policing and narcotics interdiction. All major aerospace companies including Boeing, Northrop Grumman and Raytheon are working on airship technologies for the military.
One of the major advantages of airships is that they can take off vertically from almost any surface including water.
The earlier airships had very low speeds compared even with road transport. The promise of higher speeds in the new designs would overcome that problem. However, the safety issues in transport of heavy cargo over long distances will remain a major concern. It is unlikely to be permitted over populated places until the technology has been proven to be safe. This could limit the application of airships to limited cargo movement applications.
The airship, by inherent design, does not have all the controls of a fixed wing airplane or a helicopter. It is, therefore, difficult to steer in heavy wind conditions and can also be affected by thermal currents. The envelope of the airship, made of polymer material is prone to puncture and that could happen when the airship in on the ground. Such punctures could cause loss of pressure once the airship is flying with the cargo.
There is no doubt that the evolution of airship technology, especially with the application of new materials to its construction, will open up another mode of transportation for mankind. New methods of control and guidance based on GPS and access to the internet could open up possibilities not imaginable even 10 years ago.
Besides cargo movement and surveillance uses, the rebirth of airships is causing innovators to think of new applications.
One of these, can actually be done with a blimp in place of an airship, is as a sky lantern to illuminate a large area such as a beach or a stretch of highway as an alternative to multiple electric poles and light fittings. The energy for the lamp could be derived from solar modules carried on the airship. At the height it flies, sunlight is available for more hours than on the ground.
Another entrepreneur is talking in terms of building a hotel-cum-casino that floats in air.
On a more serious note, Aeros the company that is partnering NASA is already talking of using airships to transport people, as an alternative to airplanes. They claim to be working on airships that can carry 150-180 people. They advocate this as a low carbon transportation solution. The fact that airships do not need an airport runway type of infrastructure would make it possible to use airships for point-to-point travel, theoretically between any two points.