Aeronautics and astronautics – Aircraft structure – Airship hull construction
Reexamination Certificate
2002-08-05
2004-09-21
Carone, Michael J. (Department: 3641)
Aeronautics and astronautics
Aircraft structure
Airship hull construction
C244S126000, C244S128000
Reexamination Certificate
active
06793180
ABSTRACT:
TECHNICAL FIELD
The present invention relates to aircraft, and more particularly, relates to a lighter than air foldable airship hull.
BACKGROUND INFORMATION
There are two basic forms of lighter-than-air-craft: the balloon and the airship. Both are able to ascend into the sky and stay there because they contain a substance that is less dense than the air that surrounds them. The fundamental difference between the airship and the balloon is that an airship is powered and horizontally controllable while the balloon is neither. The altitude of a free-floating balloon can be regulated to a considerable degree by dropping ballast and venting gas or by allowing hot air to cool or to be heated, but lateral movement is determined solely by which way the wind blows.
At first, hot air was used to lift balloons. However, flight time was limited because of the heated air eventually cooled. Sustained hot-air ballooning did not become feasible until after World War II with the innovation of the propane burner, which permits reheating while the craft is aloft.
For more than a century the principal and preferred lifting substance for both balloons and airships was hydrogen, the lightest of the elements, despite it being highly dangerous because of its extreme flammability. It was not succeeded by helium (which although somewhat inferior to hydrogen in lifting strength will not burn) until a crash American research program beginning in 1917 developed means of extracting it cheaply in large quantities.
By the start of the First World War the airship had been developed into two main types—rigid and non-rigid (technically, the latter is more accurately described as pressure-rigid). Cylindrical in cross-section, both were given buoyancy by gas and motion by engine-driven propellers and were controlled by vertical rudders and horizontal elevators.
In the rigid type, a framework supports an external covering of fabric called the envelope, or skin. Within the framework are contained bags of gas. In the non-rigid airship, the shape of the envelope is maintained by the pressure of the gas that fills it; there is no framework. The rigid airship's control car and engines are suspended from the framework; in the non-rigid they are attached directly to or suspended directly from the envelope. (In some later rigid airships the engines were mounted internally, driving the propellers by transmission belts.)
The earliest airships were powered by steam engine, by human muscle and by electric motors. The airship, however, like the airplane, did not become a truly viable proposition until the advent of the internal combustion engine.
Rigid airships, also called dirigibles (and sometimes, although incorrectly, “zeppelins”) can be used to transport freight. They can be relatively fast—significantly faster than a tractor and trailer combination—and have potentially high load carrying capacity They are economical: fuel consumption is negligible as compared to that of conventional aircraft. They can be landed in a variety of locations requiring no preexisting infrastructure (they could allow cargo to be loaded and unloaded in undeveloped areas that are served by nothing more than the equivalent of a pack-trail or logging road).
The use of dirigibles to transport cargo or passengers is not new, nor a concept just off the drawing board, still in need of extensive field-testing. However, early airships acquired a poor reputation for safety, perhaps undeservedly. Nevertheless, from about 1919 until 1937, when the 804 foot, 6.7 million cubic foot dirigible, the Hindenburg was destroyed by fire at the New Jersey landing field, dirigibles amassed an impressive number of successful flights, carrying both passengers and cargo.
After the Hindenburg disaster, the production of commercial airships was virtually discontinued. In recent years, about the only airships likely to be seen are small non-rigid advertising “blimps.” However, since the days of the Hindenburg, substantial technological improvements have been made in the materials that can be used for airship construction. There are a number of light-weight high-strength, corrosion-resistant alloys and composites for hull structures. For the outer covering or skin, there now exist a variety of tough, durable fabrics. For the gas cell linings, there are a variety of impermeable synthetic films. The problem of the highly flammable hydrogen as the buoyancy gas has been overcome through the use of helium gas and hot air and the modern propane burner.
An inherent advantage of the airship over conventional aircraft is that they obtain their lift through the use of buoyancy: aerostatic lift. Conventional heavier-than-air aircraft use a powered aerodynamic lift (air flow over the wings). With lighter-than-air aircraft using helium or a combination of helium and hot air, the fuel cost of getting and keeping the airship aloft are negligible. Due to their ability to operate at lower speeds, the energy requirement to propel the buoyant airship is dramatically less than for conventional aircraft. In fact, the first mechanically driven airship (circa, 1852) was a 143-foot craft that was propelled at a speed of about 6 miles per hour by a 3-horsepower steam engine.
The advantages of fuel conservation are somewhat offset by the lower operating speed of the airship, which attains a maximum cruising speed up to about sixty miles per hour. In theory, higher speeds are obtainable, but fuel consumption increases disproportionately as speed is increased. However, considering the fact that dirigibles can be designed to carry a payload of as much as 500 tons, a speed of sixty miles per hour and the ability to be able to land most anywhere more than compensates for the slower speed compared to heavier than air aircraft, and a speed advantage over ocean cargo ships.
Since an airship can rise or descend vertically, no runway space is needed for takeoffs and landings. Once airborne, whether taking off or landing, it needs a clear approach; but on the ground all that is needed is level terrain—such as any ordinary field would provide—about twice the length of the craft, to permit movement around a mooring mast.
Hot air airships offer a compromise between the ease of use common to hot air balloons and the maneuverability of rigid airships. Basically, they are elongated hot air balloons with a propulsion engine and added tail fins and rudders. Most hot air airships flying today are pressurized models. The internal pressure makes the envelope more rigid and prevents “denting” of the nose at higher speeds.
Airships can be used to carry bulky loads, of the kind that conventional carriers find economically unfeasible, over any kind of terrain—ice fields, large expanses of water and into continental interiors, as well as into regions that are undeveloped for surface vehicles. Through the use of winches for loading and unloading, crews of men and equipment could be lowered into logging operations, where logging is done in environmentally fragile areas. Logs could be “yarded” out without resorting to the construction and use of erosion-causing logging roads. Areas could be worked that might be accessible only at extremely high cost.
Since smaller power plants are required for airship propulsion than for that of power-lifted craft, pollution and noise are considerably decreased.
Another advantage of the airship is that, with vibration greatly decreased, it would find a use as a flying laboratory. Other suggested uses for the spacious, quiet craft are the transporting of persons for sightseeing or research.
Large-scale use of airships present some problems. The size of a hangar required to hangar conventional rigid airships is considerable. Another problem is the space and facilities needed for ground-handling the airship. The foremost problem of storage is the amount of space required to handle just a few airships. Although paved areas and runways are not needed, more land area is necessary to handle a few conventional rigid airships than would be needed for several airports.
Still another problem arises wi
Fabel John A.
Nachbar Daniel
Carone Michael J.
Coolidge Daniel S.
Matz David
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