Aeronautics and astronautics – Aircraft – lighter-than-air – Airships
Reexamination Certificate
1997-12-19
2001-05-01
Eldred, J. Woodrow (Department: 3644)
Aeronautics and astronautics
Aircraft, lighter-than-air
Airships
C244S126000, C244S058000, C244S059000, C136S245000, C136S291000, C136S256000
Reexamination Certificate
active
06224016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to a novel stratospheric vehicle, novel airship gore and energy producing covering for high altitude platforms and method of producing the novel flexible energy producing covering. More particularly the invention pertains to a three-dimensional flexible covering which incorporates flexible solar cells as part of the outer layer of a bonded flexible envelope for high altitude airships, dirigibles and other such stratospheric, near space and space vehicles. The novel flexible energy producing bonded covering is a lightweight thin film material, typically 300 to 400 microns thick and weighs about 300 to 600 grams per square meter.
The novel lightweight flexible energy producing material is particularly suited for aircraft, spacecraft and lighter-than-air vehicles such as dirigibles, blimps and balloons constructed to operate in the stratosphere, at the threshold of space and in space. The energy producing skin is capable of converting sunlight into electricity and operate at low and high voltages of 40 to 6,000 and preferably 100 to 600 volts while having a total skin thickness of a few hundred microns. The invention achieves its advantages by combining thin plastic film flexible solar cells with thin film and fabric airship materials to produce a lightweight, durable, energy producing flexible covering particularly suited for airship technology.
The construction and design of high altitude platforms and airships involve a series of considerations all of which require a consideration of weight. The greater the weight, the greater the volume of lift gas required which increase the amount of covering necessary to contain the lift gas which results in a further increase in weight. These increases in weight and volume also impose additional power requirements to maneuver the airship or to place a vehicle in space or at the threshold of space. As a result a lightweight high energy producing material breaks the volume weight power cycle and allows a stratospheric vehicle to operate at a higher altitude and in space and to more efficiently gather and utilize energy.
As used herein the term vehicle and high altitude platform includes airships and other vehicles that operate in the stratosphere, threshold of space and in space which require a lightweight, energy producing material to maintain a given altitude or orbit or require lightweight materials for launching into space.
The flexible solar cell energy producing cover is bonded to the substrate of the flexible airship envelope while electrical contacts are being made to a conductive conduit carried between layers which also becomes part of the structural strength of the novel flexible energy producing covering. In one embodiment of the invention a special electrically conductive fabric layer is employed allowing the fabric substrate to electrically conduct electrical current along the length of the airship through the warp of the fabric while adding structural strength to the novel energy producing material. In another embodiment of the invention the electrical conduit provided by the fabric warp is combined with a conductive conduit in the form of a metallic ribbon or electrically conductive fibers sandwiched and electrically insulated by a flexible non-conductive polymer bonding adhesive.
The airship substrate may also be gas impervious or slightly gas pervious depending upon the particular method of the invention selected for producing the novel flexible energy producing covering. In the preferred application of the invention the airship substrate is substantially gas impervious and the method of the invention provides for the joining of the flexible solar cell layer with a non-conductive adhesive under heat, pressure and a vacuum to prevent the presence of small air bubbles from being trapped in the adhesive layer and rupturing or interfering with the integrity of the system in stratospheric applications.
In applications where the airship substrate is slightly gas pervious the flexible solar cell layer can be joined with the airship substrate with a flexible polymer adhesive under heat and pressure without a vacuum since small air bubbles upon expansion in the stratosphere can migrate into and through the gas pervious airship substrate. In the preferred embodiment the laminating process is performed under heat, pressure and a vacuum to remove air and provide a novel flexible and resilient energy producing covering particularly suited to high altitude and space vehicles.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. 1.97 and 37 C.F.R. 1.98
The sun is an ideal power source for long duration (one year or longer) stratospheric airships because of the lack of moisture and thin air in the stratosphere. At approximately 20-50 kilometers (12-31 miles), sunlight is a very strong, predictable source of energy. The major reasons solar power has not been utilized on airships are traditional, rigid solar cells are heavy and difficult to incorporate onto an airship envelope and the added weight of the solar cell added to the weight of the covering limits the absolute altitude at which the airship can operate with a given amount of lift gas and engine power.
Rigid solar cells are heavy because they are made with a glass substrate which is one of the heavier materials available and are usually mounted on stiff panels to prevent them from being twisted and cracked since they are rarely more than a few microns (thousandth of an inch) thick. Rigid solar cell arrays have been calculated to produce only about half the power for the same mass than lighter flexible solar cell arrays produce. This is because flexible solar cell arrays are made from thin layers of amorphous silicon deposited onto plastic film. Not only are these materials lighter than crystalline silicon bonded to glass, but they are inherently flexible and do not require stiff panels to protect them from twisting and cracking. This invention does not pertain to mounting rigid solar cells to an airship but instead to mounting flexible solar cells to an airship. However the problems encountered in mounting rigid or flexible solar cells to an airship are similar.
One common problem to mounting solar cells to airships is weight and particularly the added weight of the special mounting devices and other items that are required to mount rigid solar cell arrays onto the thin, curved flexible skin of an airship. While flexible solar cells are lighter there remains the common problem of expandability which is comparable to attaching small mirrors or strips of plastic to a balloon and then adding wiring and electrical connector and hardware between the mirrors or strips of plastic. These resulting rigid panels have to be attached with special mounting devices and electrical connectors to compensate for the flexing and this increases the weight without increasing power output.
A further problem in addition to weight is that large panels of rigid solar cells or flexible solar cells mounted on the surface of the airship are much like adding flat windowpanes or adding a covering to a covering that increases the size, drag and power required of the propulsion system. Such flat windowpane panels or added covering increases drag and impairs maneuverability and requires more power to propel the airship. Reducing the size of the panels and mounting more of them on the airship surface like mosaic tile is impractical as it adds additional weight by virtue of the additional wiring and electrical connectors required to connect the panels to the airship skin. Examples of prior art applications of rigid solar cells in panels and arrays with supporting frames for carrying the rigid cells is illustrated by Stark U.S. Pat. No. 4,364,532 and the attachment of solar cells to the flexible envelope of an airship is illustrated in Nakada U.S. Pat. No. 5,348,254.
Nakada U.S. Pat. No. 5,348,254 provides a specially fabricated single semi-circular solar cell that appears to be attached to the flexible envelope of t
Chen Sam M.-S.
Connell Valentine R.
Lee Yee-Chun
Lin Yu-Lun
Mason Brandon G.
Breneman & Georges
Eldred J. Woodrow
Sky Station International, Inc.
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