Satellites require facilities to send and receive radio communications to provide critical command and control signals to and from the spacecraft while in orbit. Additional radio communications receivers and transmitters support the satellite's mission to provide a communications link to or from the ground stations, to and from other spacecraft, and to and from space-based and ground-based sensors. Many of the antennas needed for these applications are large structures comprising one or multiple elements.
Many of the satellites being developed today are small, but require large antennas to support their mission. These antennas are too large for implementing as fixed structures on the satellite at launch, and therefore must be stowed for launch and then later deployed while in orbit.
The present invention can be more easily understood and the advantages and uses thereof more readily apparent when the detailed description of the present invention is read in conjunction with the figures wherein:
In accordance with common practice, the various described features are not drawn to scale, but are drawn to emphasize specific features relevant to the invention. Like reference characters denote like elements throughout the figures and text.
Ideally, to meet the launch and in orbit constraints, the stowed antenna must be stowable in a compact configuration and subsequently expandable in orbit by activating a deployment process. Additionally, the deployed antenna must be self-supporting and sufficiently rigid to support the properly-spaced antenna elements and/or sensor elements.
The present invention utilizes a uniquely inventive deployable boom to deploy multiple antenna elements and supporting components from a stowed condition upon reaching orbit. Core boards affixed to the boom support antenna elements, sensors, and associated electronic or electrical components for space applications. Using the design methodology and resulting embodiments described herein, antennas of many types and sizes, including very large antennas, can be assembled on the ground, stowed for launch, and deployed in orbit.
Spacer boards 18 (also referred to as separator boards) are disposed between consecutive core boards 12, each spacer board defining a central aperture through which the boom passes. The spacer boards maintain proper spacing between the core boards (and thus between the antenna elements) and provide stability during deployment and operation. Note that the distance between consecutive core boards may not be equal along the length of the boom. And in fact, the spacing is likely not equal as that distance is determined by the operational requirements of the antennas affixed to the core boards.
The close-up view of
A material of the boom 14 comprises carbon fiber, fiberglass or a composite structure of carbon fiber and fiberglass formed in layers.
The stowing arrangement, the deployment system and the support structure can support various antenna types for space-based communications. Exemplary antennas, some of which are illustrated in the accompanying figures include, but are not limited to: element antennas (e.g., a dipole antenna), antenna arrays (e.g. a Yagi antenna array, a log periodic array that extends across several core boards) and traveling wave antennas (e.g. a helical antenna). Certain antenna types are referred to herein, but these are not intended to limit the scope of the invention as set forth in the claims.
The antenna element(s) disposed on a single core board can operate as a single antenna, independent from the other antenna elements disposed on other core boards and supported by the support structure. Use of the term ‘array’ may be misleading, as the term “array” herein refers to multiple antenna elements extending across a plurality of core boards and cooperatively operating as a single antenna (i.e., a single multielement antenna), thus requiring only a single signal feed (e.g., a coaxial cable).
The antenna support structure comprises the one or more core boards 12, the one or more spacer boards 18, the boom 14, the top core board 21, and the alignment and tension cords 24 or 25.
The distance between each element of the antenna array (as attached to its respective core board) is fixed along the antenna boom to ensure required antenna performance is obtained. This fixed distance is maintained by the distance (spacing) between the core boards, which is in turn determined by lengths of the tension cords between the core boards when the boom is fully deployed and the cords are tensioned.
The spacing of the elements in a Yagi antenna, for example, is critical for the antenna to provide sufficient gain and satisfy other antenna performance objectives. The core boards are spaced to meet these operational requirements for a given frequency of operation and antenna element type and maintained at that spacing during operation by the tension cords.
In addition to physically supporting the antenna elements and providing the coaxial or wire feeders interconnects for these elements, the core boards carry stand-alone or integrated sensors, active and passive electronic components, and printed circuit board circuit pads, tracks, and interconnects for these components that operate in conjunction with the antenna elements and provide the required antenna and sensor functionality to ensure the mission objectives are satisfied.
For example, hybrid couplers and balun matching transformers, can be mounted on a core board with electrical tracks and pads formed thereon to interconnect and support other components on the core board and the antenna elements connected to that core board. Interconnects with components on other core boards in the array can also be provided by conductive wires or coaxial cables between core boards.
In a preferred embodiment, each core board 12 comprises a G10, FR4, Teflon® (a registered trademark of Chemours Company of Wilmington, DE) or another copper-clad printed circuit board material on which electrical interconnects can be formed by machining or etching the copper cladding. After etching or machining, the remaining copper cladding functions as conductive metal traces or tracks that form circuit interconnects. Multi-layer core boards with buried patterned conductive traces can also be used.
As known by those skilled in the art, the core boards may comprise a layer of another conductive metal in lieu of copper. This conductive material can also be etched or machined to form the interconnects.
Conductors extending between core boards pass through the other openings 35 and slots 37 depicted in the core board 12. Four openings 38 receive stow pins when the antenna support structure is in a stowed configuration, as further described below.
The core board 12 of
Each core board is sized (e.g., diameter) and shaped (circular, square, or another configuration) according to the application.
Each core board, except the top-most core board 21, defines the central aperture 30 (see
The tension cords are affixed to regions 39 with an epoxy or another space rated adhesive. These regions are illustrated as conductive openings, but that configuration is not necessarily required. Also, more or fewer than the six illustrated regions 39 may be employed in any embodiment.
A round dowel of Teflon© (a registered trademark of Chemours Company of Wilmington, DE), fiberglass or Delrin® (a registered trademark of E. I. du Pont de Nemours and Company of Wilmington, DE or one of its affiliates), or other space rated material, is inserted into the top end of the boom. The boom is ‘C’ shaped in cross section and thus the dowel can be inserted into the boom through the open ‘C’. Screws (or another fastening element) are inserted into holes in a side of the boom. These holes align with tapped holes in a side surface of the dowel. Thus, the screws secure the dowel into the boom. Mounting holes are also tapped into the top surface of the dowel, and these holes are aligned with holes 44A in the top core board 21. Screws (or another fastening element) are inserted into the holes in the top core board down into the holes in the top surface of the dowel to secure the top core board to the boom.
As further described, the boom is stored in a flat configuration and forms into the ‘C’ shape immediately as deployed. A ‘C’ shaped structure, such as the boom, has greater shear strength than a simple flat structure or a closed structure, such as one having a round or oval cross section.
Alternatively, a pair of the antennas 16 in
In an embodiment that requires the antenna to rotate about the boom during deployment, such as with the helical antenna 47 of
In an embodiment where any twist in the boom needs to be removed to ensure the deployed boom is straight along its length and the attached antennas are aligned and correctly positioned, the bearing described immediately above is rotated so that the core boards and the top core board are rotated relative to the boom. The rotational force is provided by tensioning the cords along the length of the boom. As the cords are tensioned, by application of a force on the bottom core board, the core boards rotate around the boom and are pulled into alignment by the tension cords running parallel to the boom. The initial tension force on the tension cords is measured prior to applying additional tension forces.
The longitudinal boom-like structure, comprising the core boards, spacer boards and the boom (see
The stow tube is mounted on a deployer mechanism 52. See
The separator boards also serve as tension cord guides during deployment; they prevent the tension cords (that are attached to the core boards and terminated at the bottom core board) from snagging and tangling with other tension cords and with the deployment mechanism.
The spacer boards are constructed from the same material as the core boards or from another inert material (such as FR4 or Kydex) that is transparent to radio frequency energy. The core boards, constructed from FR4 or a similar material, are also transparent at radio frequencies.
The core boards and the separator boards are mounted in a longitudinal array, as depicted in
The tension cords are attached to both the spacer boards and the core boards with an epoxy or another adhesive while held in a jig to maintain the required spacing between consecutive boards. The attachment points are indicated by reference character 39 in
When stowed, the core boards and spacer boards are stacked within the stow tube 50, with the top core board holding the stack in place within the stow tube. See
While stowed, the antenna elements 16 (see
The flexible or spring-like metallic material of the antenna elements 16 permit the elements to be positioned within the stow tube 50 such that they will return to the proper antenna configuration (e.g., straight) after deployment and release from the stow tube.
Preferably the antenna elements comprise Nitnol, a super-elastic metal alloy that is also used for heart stents. As a medical material, it is not necessary to qualify the Nitnol for spaceflight as it is inert, does not out-gas in a vacuum, and is not affected by proton radiation or atomic oxygen (random oxygen molecules in the vacuum of space that tend to erode satellite surfaces).
Stow pins 54 are shown in
Stowed tension cords 24 or 25 are placed proximate the separator boards, that is, near the boom and stow pins 54. At this location, the tension cords are located away from the antenna elements to minimize snagging with antenna elements during deployment. The separator boards also help to prevent snagging of the cords during deployment as the support structure and antenna components emerge from the stow tube 50.
The separator boards are dimensioned to accommodate only a small gap between the circumference of the separator board and the inside surface of the stow tube 50. Thus, when stowed, the elements from one core board cannot interfere or tangle with the elements on the neighboring core boards. The separator boards serve as a barrier between the antenna elements on each core board and maintain the tension cords in an orderly fashion and at a distance away from the antenna elements and other components mounted on the core boards.
The core boards are also dimensioned with a tight tolerance to the inside surface of the stow tube. Thus, there is no space for elements to migrate out of their place above or below their core board location. See
The tube sleeve also provides some damping of element motion during antenna deployment. Preferably, this damping is advantageous to slow and possibly avoid side-to-side element motion, which would be induced by the sudden release of the element from the stow tube as the elements spring out from their stowed position upon exiting the stow tube. Quick damping is especially required in the vacuum of space. The damping action also settles the antenna elements into their fixed position immediately after deployment and prevents them from interfering with elements that are subsequently deployed.
The damping tube sleeve is held in place over the antenna element with a small bead of epoxy 64 (see
A deployer mechanism 52 (see
As the boom unrolls, the top core board 21 moves out from the stow tube first. Any antenna elements attached to the first core board then deploy outward from their stowed configuration.
As the boom continues to extend from the stow tube, the remaining core boards and spacer boards exit the tube 50, one board at a time.
The tension cords 24 are attached to each core and spacer board and also to the base of the stow tube. The tension cords pull each successive board out from the stow tube during deployment until all of the boards have been extracted.
When the structure has been fully deployed, a tension force is applied to the tension cords to ensure that each of the core boards and each of the antenna elements is correctly spaced to meet the antenna performance requirements.
The present invention claims priority under 35 U.S.C. 119(e) to the provisional patent application filed on Sep. 7, 2022 and assigned application No. 63/374,765. This provisional patent application is incorporated in its entirety herein.
Number | Date | Country | |
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63374765 | Sep 2022 | US |