Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and fluid sustained
Reexamination Certificate
2000-12-01
2003-09-09
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and fluid sustained
C244S02300R
Reexamination Certificate
active
06616094
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates initially, and thus generally, to lifting platforms. More specifically, the present invention relates to apparatus for improved performance of ground effect devices, e.g., hovercrafts, attractor devices and vertical take-off and landing (VTOL) devices. Furthermore, a lifting platform is provided that may also function as an attractor.
The present approach to a lifting platform differs in concept to the conventional hovercraft in that the elements of both hovercraft and helicopter are integrated into a single system. The characteristics of both are combined to provide, at one end of the range, a hovercraft that has the ability to rise over obstacles, and at the other extreme a free flying platform. In all cases the power requirements are optimized. When operating as a conventional hovercraft the power requirement is the same as that for an optimized hovercraft. When operating at a low altitude the power requirement is greater than that for a hovercraft operating close to the ground, but much less than that for a helicopter. When operating at altitude the power requirement is somewhat less than that for a helicopter.
The lifting platform design in accordance with the present invention represents a series of platforms specifically designed for operational altitude by incorporating various proportions of what may be termed “Helicopter” lift with “Hovercraft” lift.
BACKGROUND OF THE INVENTION
It is contemplated that the present invention could relate to many possible fields. Initially, it is thought that the invention could apply to fields including, but in no way limited to, hovercrafts and other ground effect vehicles, vertical take-off and landing (VTOL) vehicles, turbine engines and vortex attractors.
Ground Effect Vehicles
In the most conventional sense, the means for any type of levitation has been dominated by a single lift mechanism: the wing. The wing yielded a mode of travel that was a substantial improvement in many ways over other ground-based modes of travel. However, in some applications, wings have some important shortcomings.
Some important shortcomings will be enumerated below:
a) The velocity asymmetries around the surfaces of wings are the basis for the lift they generate. When wings move through the air, they produce substantial drops in pressure at their upper and lower surfaces. The forces generated on the upper and the lower surfaces of the wing, however, point in opposite directions so that they almost completely cancel out.
b) Because wings have low lift factors they have to be large in order to generate a practical amount of lift. The large size of the wings causes them to create a lot of drag when they move through the air.
c) Winged aircraft have a fairly narrow range of speed that they work well in. In order to get off the ground they must have a much larger wing than they need after they have gained speed. The large wing needed to take off creates a lot of drag at high velocity. That makes if very hard to fly at supersonic or hypersonic speeds. Importantly, in regard to the present invention, it makes them very difficult to generate lift at low speeds.
d) Wings have to be moved at fairly high velocity in order to produce practical amounts of lift. That means that they have a lot of room to operate and that winged aircraft are dangerous to bystanders. That is true even for rotary winged craft (helicopters).
e) Wings waste a lot of energy because they shed powerful vortices into the passing air as they generate lift. The energy that goes into those vortices contributes nothing to the generation of lift by the wing.
f) Wings can suddenly stop producing lift. If a winged aircraft flies too slowly the wings stall and can cause a crash.
g) Wings can't produce lift when they are standing still. To make a craft that can hover while it is standing still, means that the wings must be incorporated into a mechanism that swings them through the air. That mechanism and the wing together is called a rotary wing mechanism. It is very complicated and requires a lot of maintenance to operate reliably.
h) Rotary wing mechanism is inefficient.
i) Rotary wing craft are complicated and thus require a lot of maintenance.
j) The rotary wing mechanisms operate asymmetrically when a helicopter moves forward through the air. Without a corrective mechanism the helicopter produces greater lift on one side than the other side. The forward sweeping wings would experience a much higher air velocity than an aft sweeping wing. An elaborate hinge system is able to correct some of those air flow asymmetries at low speed. However, there is no corrective mechanism that allows a helicopter to operate at speeds faster than 250 m.p.h.
Thus, to address certain of these concerns, e.g., the ability to efficiently and cost-effectively hover and traverse at speeds safe to surrounding persons, various types or designs of ground effect or air cushion devices have been developed over the years. Ground effect crafts, or “hovercrafts”, are any of the machines characterized by movement in which a significant portion of the weight is supported by forces arising from air pressures developed around the craft, as a result of which they hover in close proximity to the Earth's surface. It is this proximity to the surface that chiefly distinguishes such craft from aircraft, which derive their lift from aerodynamic forces created by movement through the air.
Two main classes of air-cushion vehicles exist: those that generate their own pressure differential irrespective of forward speed; and those, more closely related to true aircraft, that require forward speed before the pressure differential can be generated. The former are classed as aerostatic craft (ACVs); the latter are called aerodynamic ground-effect machines (GEMs). Perhaps the first man to research the air-cushion vehicle concept was Sir John Thornycroft, a British engineer who, in the 1870s, began to build test models to check his theory that drag on a ship's hull could be reduced if the vessel were given a concave bottom in which air could be contained between hull and water. His patent of 1877 emphasized that “provided the air cushion could be carried along under the vehicle” the only power that the cushion would require would be that necessary to replace lost air. Neither Thornycroft nor other inventors in following decades succeeded in solving the cushion-containment problem. In the meantime, aviation developed and pilots early discovered that when they were flying very close to land or water surface their aircraft developed greater lift than in free air. Through research, it was soon determined that the greater lift was available because wing and ground together created a “funnel” effect, increasing the air pressure. The amount of additional pressure was found to be dependent on the design of the wing and its height above ground. The effect was strongest when the height was between one-half and one-third of the average wing chord.
Practical use was made of the ground effect in 1929 by the German Dornier Do X flying boat, which achieved a considerable gain in performance during an Atlantic crossing wherein it flew close to the sea surface. World War II maritime reconnaissance aircraft also made use of the phenomenon to extend their range.
In the 1960s, American aerodynamicists developed an experimental craft, making use of a wing in connection with ground effect. Several other proposals of this type were proffered, and a further variation combined the airfoil characteristics of a ground-effect machine with an air-cushion lift system that allowed the craft to develop its own hovering power while stationary, then build up forward speed, gradually transferring the lift component to its airfoil. Although none of these craft got beyond the experimental stage, they were important portents of the future because they suggested means of using the hovering advantage of the air-cushion vehicle and overcoming its theoretical speed limitation of around 200 miles per hour (320 kilo
Barefoot Galen L.
Vortex Holding Company
Ward & Olivo
LandOfFree
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