Simplified spacecraft antenna reflector for stowage in confined envelopes

Abstract: A method for stowing a unitary flexible antenna reflector 10 in a confining envelope and deploying the reflector from the envelope. In a most general sense, the invention includes the steps of: a) applying a deforming force to diametrically opposed positions 16 and 18 near an edge of the reflector 10 to place the reflector in a deformed state; b) maintaining the reflector 10 in the deformed state until deployment; and c) releasing the reflector 10 from the deformed state. In a specific embodiment, the step of maintaining the reflector 10 in a deformed state includes the step of attaching a restraining element between the diametrically opposed positions on the edge of the reflector which is released on deployment.

Description: This invention relates to spacecraft antenna reflectors and also to a method for stowing an antenna reflector according to claims 1 and 5. In particular, the present invention relates to a simplified design for spacecraft antenna reflectors to facilitate stowage and deployment from protective, confined launch envelopes. While the present invention is described herein with reference to a particular embodiment, it is understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional embodiments within the scope thereof. Prior art document US-A-4926181 discloses an antenna reflector as indicated by the features of the preamble portion of claim 1. Such a reflector is composed of a flexible reflector membrane, which is formed in a single piece technique, an underlying support structure and a registration assembly in order to restore the original shape of the reflector membrane when it is deployed from a rolled or stowed configuration. Spacecraft antenna reflectors are typically constructed as concave disks. Electrical specifications for the reflector dictate disk dimensions, specifically diameter and cross-sectional curvature. Spacecraft payload weight limits often constrain the reflector thickness to a level that renders the reflector vulnerable to dynamic forces associated spacecraft launch. Atmospheric drag and launch booster vibration may be particularly damaging to the reflector if the reflector is mounted in a typical operational configuration (i.e., on support towers on the external surface of the spacecraft) during launch. It is therefore desirable to stow the reflectors in a confining envelope designed to protect the reflectors from launch stress. The shape of the confining envelope requires that the intrinsic antenna reflector shape be temporarily modified to fit inside the envelope during launch. After launch, the reflector is released from the envelope and returned to the original shape thereof on deployment. In accordance with conventional teachings, the antenna reflectors are designed with additional components to facilitate reflector shape modification for stowage. One often used approach is to use a segmented reflector with a cantilevered rib frame which unfolds on deployment as an umbrella unfolds. These designs, however, are costly, complicate reflector manufacture, and require complex systems for folding and unfolding the reflectors for proper stowage and deployment. Therefore, while certain techniques may be known in the art for stowage and deployment of spacecraft antenna reflectors, a need remains in the art for further advancements. A simplified and improved antenna reflector and method for stowing such an antenna reflector is achieved by the features of claims 1 and 5. SUMMARY OF THE INVENTION The need in the art is addressed by the present invention which provides a method for stowing a unitary flexible antenna reflector in a confining envelope and deploying the reflector from the envelope. In a most general sense, the invention includes the steps of: a) applying a deforming force to diametrically opposed positions near an edge of the reflector to place the reflector in a deformed state; b) maintaining the reflector in the deformed state until deployment; and c) releasing the reflector from the deformed state. In a specific embodiment, the step of maintaining the reflector in a deformed state includes the step of attaching a restraining element between the diametrically opposed positions on the edge of the reflector which is released on deployment. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1(a) is a simplified perspective view of an illustrative embodiment of the inventive antenna reflector in a manufactured configuration. Fig. 1(b) is a top view of the illustrative embodiment of the inventive antenna reflector in a manufactured configuration. Fig. 1(c) is a side view of the illustrative embodiment of the inventive antenna reflector in a manufactured configuration. Fig. 2(a) is a top view of the illustrative embodiment of the inventive antenna reflector in a stowed configuration. Fig. 2(b) is a side view of the illustrative embodiment of the inventive antenna reflector in a stowed configuration. Fig. 3(a) is a top view of the illustrative embodiment of the inventive antenna reflector in a deployed configuration. Fig. 3(b) is a side view of the illustrative embodiment of the inventive antenna reflector in a deployed configuration. DETAILED DESCRIPTION OF THE INVENTION In accordance with the present teachings, an antenna reflector is provided with elastic characteristics which allow the shape of the reflector to be redefined for stowage and returned to an original shape on deployment. Fig. 1(a) is a simplified perspective diagram of an illustrative embodiment of the flexible thin-shell antenna reflector 10 of the present invention in a manufactured configuration. Fig. 1(b) is a top view of the illustrative embodiment of the inventive antenna reflector 10 in a manufactured configuration. Fig. 1(c) is a side view of the illustrative embodiment of the inventive antenna reflector in a manufactured configuration. As shown in Figs. 1(a) - (c), in the illustrative embodiment, the reflector 10 is a parabolic shell having a coupling fixture 12 attached to the center thereof to which a support mast 14 is coupled. The reflector 10 is constructed of a single thin, concave homogeneous sheet of a flexible, semi-rigid material such as graphite-fiber reinforced plastic. The reflector 10 may be fabricated in a conventional manner, i.e., multi-layer lamination over a precision form of the correct shape. The dimensions of the reflector 10 may be determined in a conventional manner. The reflector may be made of conductive material or nonconductive material which is coated with conductive material. In accordance with the present teachings, a design consideration of significant import is that the reflector 10 be sufficiently flexible to be deformed into a stowage shape and deployed to a fully nondeformed state on deployment. This requires a construction in which the deformation strain on the reflector is below the creep strain limit, that is, the force level at which the reflector will not return to the original shape. Fig. 2(a) is a top view of the illustrative embodiment of the inventive antenna reflector 10 in a stowed (deformed) configuration. Fig. 2(b) is a side view of the illustrative embodiment of the inventive antenna reflector 10 in the stowed configuration. Fig. 3(a) is a top view of the illustrative embodiment of the inventive antenna reflector in a deployed configuration and Fig. 3(b) is a side view of the illustrative embodiment of the inventive antenna reflector in the deployed configuration. As illustrated in Fig. 2(a), the reflector 10 is deformed by the application of a uniform force at diametrically opposed points 16 and 18 at the periphery of the reflector 10. The reflector 10 may be maintained in the stowed configuration by a string 20 as shown in Fig. 2(a) or by a container (not shown) in which the reflector 10 is stowed, e.g., the side rails of a space shuttle. If a string is used, it may be cut by a pyrotechnic device 22. In the alternative, a material may be chosen for the reflector 10 which allows the reflector to be deformed at one temperature and maintained in the deformed state until deployed at another temperature. In short, the invention is not limited to the manner in which the reflector is maintained in a deformed state and deployed. Thus, the teachings of the current invention obviate the disadvantages of the segmented design by providing a single-piece homogeneous reflector can be fabricated using existing manufacturing processes, which can be deformed to fit into a protective launch envelope and returned to the desired shape upon deployment. No excess weight from cantilevers and motors is necessary, no motor control systems are required to perform stowage deformation or redeployment, and the lack of segmentation virtually eliminates possible catenation effects. The present invention allows for the elimination of the manufacturing steps required for segmenting conventional reflectors, including costly cantilevers, ribs, and motor and control systems, and therefore allows for significant cost savings. While the present invention has been described herein with reference to a particular embodiment for a particular application, those having ordinary skill in the art and access to the present teachings will recognize additional modifications applications and embodiments within the scope thereof. It is therefore intended by the appended claims to cover any and all such applications, modifications and embodiments within the scope of the present invention.

Claims: An antenna reflector (10) stowable in and deployable from a confining envelope, comprising: a reflector (10) made of a flexible semi-rigid material having a manufactured configuration; and means for applying a deforming force to generally opposed portions (16,18) of said reflector sufficient to place said reflector (10) in a deformed state for stowage within said confining envelope, but not so great as to exert a deformation strain on said reflector material; means for releasing said reflector from said deformed state to facilitate deployment of said reflector from said confining envelope so that said reflector returns to said manufactured configuration by releasing the deforming force; characterized in that the reflector (10) is of a one piece construction; and the flexible semi-rigid material has a predetermined creep strain limit and is sufficiently rigid to return to its original shape when it is deployed and the deformation strain is less than said creep strain limit of said reflector material. The antenna reflector as set forth in claim 1, wherein said reflector (10) is of parabolic shape. The antenna reflector as set forth in claim 1, wherein said semi-rigid material is a graphite-fiber reinforced material. The antenna reflector as set forth in claim 1, wherein said generally opposed portions of said reflector comprise diametrically opposed circumferential, marginal edge portions of said reflector. A method for stowing an antenna reflector (10), having the features of any of claims 1 to 4, comprising the steps of: applying a deforming force to generally opposed portions (16,18) of said reflector adjacent an edge of said reflector, to thereby place said reflector (10) in a deformed state within said confining envelope, wherein said deforming force is established to exert a deformation strain on said reflector (10) which is less than said creep strain limit of said reflector material; maintaining said reflector (10) in said deformed state until deployment; and releasing said reflector from said deformed state by releasing the deforming force and deploying said reflector from said envelope. The method as set forth in claim 5, wherein said maintaining step includes the step of attaching a restraining element (22,20) between said generally opposed portions (16,18) of said reflector (10).

Inventors: ROBINSON STEPHEN A, ROBINSON, STEPHEN A.
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1992
Main classification: H01Q15
IPC codes: H01Q1, H01Q15, B64G1