Systems and methods for use of randomized sparse arrays in a space environment

Abstract

Disclosed methods and apparatuses embody techniques for advantageous packing and deployment of an inflatable net for use as a randomized sparse array offering gain and beam-count equivalent with a conventional phased-array of the same number of antenna elements and near-equivalent spatial discrimination (beam definition) as compared with a conventional phased array of the same effective diameter. Operation of the deployed net as a randomized sparse array greatly relaxes the mechanical tolerances associated with deployment, such that array performance does not depend on achieving precise or predetermined spatial relationships among or between elements in the array. Additionally, the voids inherent in the net structure offer greatly reduced overall mass and volume, making practical the stowage and launch of inflatable nets that deploy into very large arrays.

Description

SYSTEMS AND METHODS FOR USE OF RANDOMIZED SPARSE ARRAYS IN A SPACE ENVIRONMENTTECHNICAL FIELD

[0001] Disclosed methods and apparatuses relate to antenna systems of space vehicles, and particularly relate to foldable antenna structures deployable as randomized sparse arrays in the space environment.BACKGROUND

[0002] Satellite communications form an integral part of modem telecommunications infrastructure, enabling global connectivity for a wide range of applications. As demand for satellite-based services grows, there is an increasing need for larger satellite antenna systems offering greater spatial resolution for a given antenna gain, to enable high user density applications. Larger antenna systems must be foldable or otherwise stowable within the dimensional limitations of the space vehicles with which they are associated, for vehicle launch into the intended orbital paths.

[0003] However, deployable satellite antennas raise significant engineering challenges. The deployment mechanisms must be reliable. In the context of existing designs for deployable phased array antennas, conventional deployed structures must provide precise shape and alignment, yielding mechanical tolerances of less than *4 wavelength across the deployed array to ensure nominal radiofrequency (RF) performance. Additionally, all deployed antenna structures must be robust enough to maintain their shape within required tolerances and withstand the harsh space environment, specifically including the forces of station-keeping accelerations, thermal cycling, radiation pressure, aerodynamic drag in the case of low earth orbits, and minor perturbations from gravitational anomalies in orbit.SUMMARY

[0004] Disclosed methods and apparatuses embody techniques for advantageous packing and deployment of an inflatable net for use as a randomized sparse array offering gain and beamcount equivalent with a conventional phased-array of the same number of antenna elements and near-equivalent spatial discrimination (beam definition) as compared with a conventional phased array of the same effective diameter. Operation of the deployed net as a randomized sparse array greatly relaxes the mechanical tolerances associated with deployment, such that array performance does not depend on achieving precise or predetermined spatial relationships among or between elements in the array. Additionally, the voids inherent in the net structure offergreatly reduced overall mass and volume, making practical the stowage and reliable launch of inflatable nets that deploy in the space environment into very large arrays.

[0005] An example embodiment comprises an antenna system of a space vehicle, where the antenna system includes a net formed of inflatable lines. At least some vertices of the net each are populated with one or more inflatable antenna elements attached in fluid communication such that inflation of the inflatable lines inflates the inflatable antenna elements. Further included are a deployment mechanism and an inflation mechanism. The deployment mechanism is configured to deploy the net from the space vehicle via progressive unfurling of the net from a furled configuration used for stowage of the net onboard the space vehicle. Correspondingly, the inflation mechanism is configured to inflate the inflatable lines in association with deployment of the net, thereby urging the net into an expanded, quasi-planar arrangement in which the populated vertices are spaced apart for cooperative operation as a randomized sparse array. As a further feature of the antenna system, the inflatable lines and the inflatable antenna elements each include a reactive layer that hardens in space, thereby maintaining the quasi-planar arrangement in the absence of inflation pressure.

[0006] Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a diagram of an inflatable net in a rolled configuration, according to one embodiment.

[0008] Figure 2 is a diagram of an inflatable net in a Z-folded configuration, according to one embodiment.

[0009] Figure 3 is a diagram of an inflatable net in an expanded, quasi-planar arrangement for use as a randomized sparse array, according to one embodiment.

[0010] Figure 4 is a diagram of an inflatable antenna element, according to one embodiment.

[0011] Figure 5 is a diagram of a subarray of inflatable antenna elements, according to one embodiment.

[0012] Figure 6 is a diagram of example dimensional details for an inflatable antenna element, according to one embodiment.

[0013] Figure 7 is another diagram of an inflatable net in an expanded, quasi-planar arrangement for use as a randomized sparse array, according to one embodiment.

[0014] Figure 8 is a diagram of stiffening arms for an inflatable net, according to one embodiment.

[0015] Figure 9 is another diagram of an inflatable net in an expanded, quasi-planar arrangement for use as a randomized sparse array, according to one embodiment.

[0016] Figure 10 is a block diagram of a space vehicle (SV) configured to deploy an inflatable net in space for use as a randomized sparse array, according to one embodiment.

[0017] Figures 11 and 12 are diagrams of example deployment mechanisms and deployment arrangements for an inflatable net, according to respective embodiments.

[0018] Figure 13 is another diagram of an inflatable net in an expanded, quasi-planar arrangement for use as a randomized sparse array, according to one embodiment.

[0019] Figures 14 and 15 are block diagrams of signal processing and power components included in the inflatable net for antenna-array operation, according to one embodiment.

[0020] Figures 16 and 17 are diagrams of example layer-based structures for implementation of the inflatable lines used to form the net structure of an inflatable net, according to respective embodiments.

[0021] Figures 18 and 19 are logic flow diagrams of methods of operations associated with stowing, deploying, and using an inflatable net as a randomized array, according to respective embodiments.DETAILED DESCRIPTION

[0022] A point recognized herein is that randomized sparse arrays offer promising solutions for addressing high user density applications, with orders of magnitude improvements in spatial resolution over conventional phased array systems, while also allowing satellites to launch with compact antenna configurations that can then unfold to much larger sizes once in orbit. For a given antenna gain, these large deployed sizes improve spatial resolution (the spatial discrimination in gain between simultaneous locations) according to the ratio of the effective antenna system diameter and the antenna system frequency. In addition to the performance gains attaining from the potentially large deployed sizes and the stowage advantages, the randomized sparse nature of the structure relieves the relatively stringent spatial requirements applicable to conventional phased-array structures.

[0023] Here, a conventional phased array has antenna element placement positions — array grid positions — that are on a two-dimensional periodic grid with grid position pitch for a given array notionally varying from 0.5 to 1 wavelength. Placement locations are highly planar, with typical planarity requirements of <1 / 4 wavelength deviation across the structure. Orientation is defined as the normal vector to the plane containing the placement positions and, in the context of satellite communications (SATCOM), the normal vector is typically pointed to the nadir. Common examples of conventional grids include hexagon tiling grids and rectangular grids,where the antenna elements are positioned uniformly and typically close to 0.5 wavelengths in diameter.

[0024] Whereas a conventional phased array includes one antenna element per array grid position, a randomized sparse array may use single antenna elements at individual grid positions or may use subarrays of multiple antenna elements at individual grid positions. Particularly, because of the very large deployed grid sizes that are practically achievable with randomized sparse arrays, the grid positions of a randomized sparse array can be populated with conventional phased arrays. That is, randomized sparse array in one or more embodiment herein, is a grid of smaller conventional phased arrays, where the dimensional positions of the centroids of the individual conventional phased arrays are randomized at least to some extent with the larger quasi-planar shape of the randomized sparse array.

[0025] Further, the requirements for planarity and periodicity of a conventional phased array with respect to the deployed positions of the antenna elements / array grid complicate reliable launch packing and subsequent deployment in the space environment. Contrastingly, randomized sparse arrays are antenna arrays where the array grid positions are randomized in x, y, z positions relative to each other. Specifically, while dispersion of the grid points may broadly uniform within any of the dimensional axes in use, there is no strict planarity or uniformity requirement. The placement positions may be fully random or may be derived from any three-dimensional function, including periodic or spiral grid points, with the function randomized using random displacement vectors for the respective grid points. However the randomization is achieved, the resulting deployed structure ensures that no particular wavelength or wavelength fraction appears periodically across the RSA.

[0026] For example, consider a mesh net that is based on a simple square grid. If the sides of each grid are 10 wavelengths and if the mesh net comprises a ten by ten grid, the interim structure would look like a 100 by 100 wavelength grid. The grid locations — mesh vertices — could be based on an underlying uniform grid but each location could be offset from its nominal uniform position by random offset(s), such that deployment of the mesh structure into a generally planar arrangement yields a structure having array grid positions that randomly vary in the x, y, and z dimensions, not only as a consequence of the mesh design, but also as a consequence of the variable affecting deployment in the space environment.

[0027] Calibration after deployment of a randomized sparse array accounts for the actual realized locations of the grid points in the array, where an array grid point is a “populated” vertex in the deployed net structure — i.e., a vertex carrying one or more antenna elements. If the deployed array structure is very rigid, such location calibration may be required only once.However, in one or more embodiments herein, the calibration procedure repeats on a slow time scale, to account for possible changes in the locations, e.g., as function of forces acting on the randomized sparse array, temperature expansion / contraction, etc.

[0028] The number of array elements I positions and the overall array size may be determined by calculating the number of elements required to close the (communications) link with adequate margin and then determining the aperture diameter needed to achieve the spatial resolution required. The required spatial resolution may be dictated by the nature of the communication services to be provided. For example, some communication types require small, pencil beams — i.e., high spatial resolution — to achieve a desired user density and frequency reuse with respect to a satellite service area.

[0029] With the above details in mind, a particular point recognized herein is that inflatable structures, such as inflatable nets, provide numerous advantages for the realization of randomized sparse arrays in the space environment. Advantages include the ability to achieve very small “packed” configurations relative to the deployed array size, because of the voids inherent in the net structure, along with tangle and clumping resistance, because of the use of inflatable lines for deployment. Tangle and clumping resistance and, more broadly, the overall reliability of deployment is enhanced in one or more embodiments herein, by adding a kinetic element to the deployment process.

[0030] Figure 1 illustrates an example inflatable net 10 according to one embodiment, with the inflatable net 10 depicted in an example furled or stowed configuration for fitment within a space vehicle. The inflatable net 10 includes first inflatable lines 14 running in a first direction and second inflatable lines 16 running in a second direction, with intersections of the first and second lines 14 and 16 defining vertices 18. Note that the inflatable net 10 is designed and fabricated so as to introduce randomization in the x, y, and z locations of the vertices 18 when inflatable net 10 is in its unfurled or deployed configuration. Thus, while the first and second lines 14 and 16 in one or more embodiments may run normal to one another in a general sense, the individual vertices 18 are not necessarily formed by right angle crossing.

[0031] Also, other crisscrossing or interlacing arrangements are possible for the first and second lines 14 and 16. Further, while Figure 1 illustrates a rolled configuration for stowage, Figure 2 illustrates an alternative stacked or Z-folded configuration of the inflatable net 10 for stowage.

[0032] In an example embodiment, the inflatable net 10 is a deploy able as a randomized sparse antenna system — a randomized sparse array — that a) relaxes the mechanical tolerance requirements of conventional phased arrays from less than *4 wavelength to many wavelengthsacross the deployed structure, and b) for a given gain, beam count, and effective aperture diameter: reduces the volume and mass of the material required to be stowed prior to deployment by a factor greater than one hundred when compared to a conventional phased array.

[0033] Figure 3 illustrates the inflatable net 10 in an unfurled or expanded quasi-planar arrangement, for operation as a randomized sparse array (RS A). The diagram uses the reference number “12” to designate the deployed configuration of the inflatable net 10. That is, the inflatable net 10 becomes or is otherwise operated as a RS A 12 after being deployed.

[0034] To achieve the deployment, the inflatable net 10 includes, as mentioned, first inflatable lines 14 running in a first direction and second inflatable lines 16 running in a second direction. Here, “first” and “second” are labels for convenient distinction and it should be understood that this first and second directional relationship may exist only when the inflatable net 10 is expanded for operation as a RS A 12. In at least one embodiment, the second direction is perpendicular to the first direction, although randomization of the vertex locations in the x, y, and z dimensions means that the “perpendicular” label is only true in a generalized sense.

[0035] The crossing of the first inflatable lines 14 with the second inflatable lines 16 forms vertices 18. In at least one embodiment, the vertices 18 are formed by bonding or otherwise attaching the first inflatable lines 14 with the second inflatable lines 16 at the crossing points. In at least one embodiment, the first inflatable lines 14 are in fluid communication with the second inflatable lines 16 at some or all of the vertices 18. Also seen in Figure 3 are the net openings or voids 20 formed by the crisscrossing first and second inflatable lines 14 and 16, upon deployment of the inflatable net 10.

[0036] Figure 4 illustrates an inflatable antenna element 22 according to an example embodiment. One or more of the vertices 18 carries an inflatable antennal element 22, or an array thereof, and each inflatable antenna element 22 may be in fluid communication with one or both of the first and second inflatable lines 14 and 16 at the involved vertex 18. Further, each inflatable antenna element 22 is electrically coupled via one or more signal lines 24 and physically coupled or retained at the involved vertex 18 via one or more physical connections. For example, the inflatable antenna elements 22 may be integrally formed in the first inflatable lines 14 or the second inflatable lines 16, or may be formed in, bonded to, or otherwise connected with a vertex surface 28 existing at each vertex 18 that includes one or more inflatable antenna elements 22.

[0037] Figure 5 illustrates an example where the vertex surface 28 at each one among a plurality of the vertices 18 carries a subarray 30 of inflatable antenna elements 28. In one or more embodiments, each inflatable antenna element 22 is a 4 steradian tripole. A tripole is anantenna element that consists of three antenna sub-elements oriented such that the radiation pattern of each sub-element is orthogonal to the radiation patterns of the other two sub-elements. For example, a tripole can be formed using three dipoles with a shared centroid as illustrated in Figure 6. As a variation, each inflatable antenna element 22 is a 2K steradian half-tripole with a ground plane mirror. Further variations are possible and the disclosed inflatable net 10 I RSA 12 are not limited to the use of tripoles.

[0038] In at least one embodiment that is based on the use of subarrays 30 of inflatable antenna elements 22 at each vertex 18 among a plurality of vertices 18 of the RSA 12, the inflatable antenna elements 22 within each subarray 30 have random or quasi-random orientations. Figure 5, in particular, provides an example of quasi-random orientations for a subarray 30 of 4TT steradian tripoles.

[0039] Figure 6 illustrates example dimensionality of a 4K steradian tripole. In particular, the example tripole is sized at a half-wavelength for an assumed wavelength of 0.19672131 m. Assuming the tripole is formed using metallized inflatable tubes, 0.002 m is an example assumed tube diameter, with an overall tripole mass of 0.004273 kg, an overall tripole length of 1.8187 m, and an overall tripole surface area of 0.01143 mA2.

[0040] Figure 7 illustrates another example view of the RSA 12, shown in relation to a reference plane. Although the RSA 12 is substantially planar, it is not flat in practice or by design. Indeed, deviations from the ideal plane and deviations in the spatial relationships between respective vertices 18 or groups of vertices 18 are desired because they eliminate “periodicities” that would otherwise affect operation of the RSA 12. With these deviations being a feature of the design, the need for achieving rigorously exact dimensionality and geometry for the RSA 12 is eliminated.

[0041] One also sees in Figure 7 an exploded view of an example vertex 18, carrying a subarray 30 of inflatable antenna elements 22. Each vertex 18 that carries one or more inflatable antenna elements 22 may be considered as a “populated” vertex 18, and Figure 7 depicts the use of one or more signal and power lines 42 going from an involved space vehicle 40 (or a centralized antenna hub not shown in the diagram). The exploded- view portion of Figure 7 also illustrates the aforementioned signal lines 24 used within the subarray 30, for electrically connecting each inflatable antenna element 22. In one approach, the signal lines 24 within each subarray 30 carry analog antenna signals, while the signal lines 24 included in the signal / power lines 42 carry digital signals. With such approaches, each subarray 30 includes analog-to-digital converters (ADCs) and / or digital-to-analog converters (DACs), along with associated digital signal processing circuitry.

[0042] Figure 7 also illustrates the use of stiffening arms 44 in or more embodiments. These stiffening arms are, for example, part of the overall inflatable structure of the net 10, but the inflatable lines or tubes from which they are formed may have added wall thickness for greater bending resistance. Tn at least one embodiment, the inflation of the stiffening arms 44 during the overall inflation process facilitates the spreading of the inflatable net 10 into its generally planar, deployed configuration for operation as a RSA 12. Figure 8 illustrates an example arrangement of stiffening arms 44 in one embodiment.

[0043] Figure 9 illustrates a large RSA 12 in the context of example dimensions. With the compactness for stowage achievable with the inflatable net 10 and without the need for precise geometries or exacting symmetry, deploying large antenna arrays economically and reliably becomes feasible. For example, the RSA 12 may extend 200 m or more in the X and Y directions. And, again, RSAs are not designed for and do not require strict uniformity or planarity in the positions of the vertices 18, thereby removing onerous requirements for achieving precise structural shapes or alignment post deployment.

[0044] Figure 10 illustrates further example details for a space vehicle (SV) 40, such as a communications satellite for use in a satellite communications system. The SV 40 includes a communications payload 62 comprising bent-pipe (analog) or digital transmit / receive (TX / RX) transponders for relaying communications traffic to or from respective terrestrial terminals and / or other satellites, such as in constellation of satellites.

[0045] A SV bus 64 provides for telemetry and control of the SV 40 and includes a power module 66 for powering the inflatable net 10 for operation as a RSA 12, in its deployed configuration. Correspondingly, the SV 40 includes one or more solar arrays 68, which are used to generate operating power for the SV 40 at large, including for the RSA 12. SV 40 also includes a low duty-cycle, antenna element location calibration system. The low duty cycle calibration occurs at a rate much greater than the communications symbol time (>1000x). Such calibration accounts for changes in the deployed shape of the RSA 12, such as from thermal cycling or responsive to forces acting on the structure.

[0046] The inflatable net 10 includes a SV interface 70 that comprises digital and analog circuitry and associated physical connections for interfacing the inflatable net 10 to the SV 40, in terms of power and communication signals. Connections include communication signal connections 72 with the communications payload 62, power connections 74 with the SV bus 64, and inflation control signal connections 76 with an inflation mechanism 78 that comprises part of an overall antenna system 80. The SV interface 70 further includes or is associated with mechanical anchoring of the inflatable net 10, to provide stress relief and mechanical retention ofthe inflatable net 10 to the SV 40, when the inflatable net 10 is deployed for operation in the space environment as a RS A 12.

[0047] In one or more embodiments, the inflatable net 10 includes one or more pyrotechnic igniters 82 that are activated via inflation control signals applied via the inflation control signal connections 76. For example, the inflatable lines 14 and 16 that form the inflatable net 10 have a series of pyrotechnic ignitors 82 distributed throughout them — i.e., within their internal pneumatic pathways — such that sequential ignition of these distributed pyrotechnic igniters 82 during deployment of the inflatable net 10 urges the inflatable net 10 into its expanded, quasi- planar configuration for operation as a RS A 12. Pyrotechnic ignitor controls 84 within the inflation mechanism 78 provide the inflation control signals 76 and comprise, for example, digital control circuitry for controlling the timing and pattern of ignitor activation during deployment, along with interface circuitry for outputting the corresponding inflation control signals 76.

[0048] The overall antenna system 80 may be understood as further including the inflatable net 10, along with a deployment mechanism 86. Figure 11 illustrates one example of the deployment mechanism 86, wherein the inflatable net 10 is wrapped around a motorized roller 90. In this context, the deployment of the inflatable net 10 is progressive, with the rolled part 92 of the inflatable network 10 progressively paying out as a deployed portion 94 of the inflatable net 10. The aforementioned inflation mechanism 78 in at least one such embodiment times or stages activation of the respective pyrotechnic igniters 82 distributed within the pneumatic passageways or chambers of the inflatable net 10, such that the deployed portion of the inflatable net 10 inflates in correspondence with deployment.

[0049] Figure 12 illustrates another stowage and deployment arrangement for the inflatable net 10 in one more embodiments, based on a “Z-folded” arrangement. With such arrangements, progressive deployment of the inflatable net 10 involves progressive unfolding, with the deployment mechanism 86 configured with reciprocating arms or other mechanical arrangements adapted for deployment of the successive folded sections of the inflatable net 10.

[0050] Figure 13 illustrates further example details for the inflatable net 10 / RS A 12, including a central signal processing module (CSPM) 100 for operating the RS A 12 as an electronically scanned array (ESA). The illustrated embodiment assumes that each populated vertex 18 includes a subarray 30 of inflatable antenna elements 22, with each subarray 30 having its own remote signal processing module (RSPM) 102. Signal / power lines 42 couple each RSPM 102 to the CSPM 100, and the CSPM 100 may be understood as comprising at least part of theaforementioned SV interface 70. Here, the signal / power lines 42 are shown as each including one or more signal lines 104 and one or more power lines 106.

[0051] Here, these lines 104 and 106 may be electrical wires or filaments and, in one or more embodiments, they are integrated into the inflatable lines 14 and / or 16, while in other embodiments, they are not integrated and are free flying or only loosely attached to the inflatable lines 14 and / or 16. While Figure 13 and several of the earlier figures suggest the free-flying arrangement, it shall be understood that the lines are depicted in that manner for visibility — i.e., easy visual distinction from the inflatable structural elements of the net 10.

[0052] Figure 14 illustrates an example arrangement for the CSPM 100. Elements include one or more digital signal processors or other type(s) of computer processors 110, signal input / output circuitry 112 for interfacing with the RSPMs 102 via the signal lines 104 and power lines 106. Additionally, the CSPM 100 includes one or more types of computer readable media, shown as “storage” 114. The storage 1 14 comprises, for example any one or more or any mix of EEPROM memory, FLASH memory, RAM, etc.

[0053] The storage 114 in at least one embodiment holds computer program instructions (CPI) 116 for execution by the processor(s) 110, where such execution causes the processor(s) 110 to carry out the signal CSPM-related processing operations associated with operating the RSA 12. One or more data items 118, such as provisioned or dynamically determined configuration data for use by the processor(s) 110 may also be held in the storage 114.

[0054] The CSPM 100 further includes power circuitry 120. For example, the power circuitry 120 comprises one or more voltage regulators configured to provide regulated supply voltages to the various circuits comprised within the CSPM 100, based on receiving power from the SV 40.

[0055] Figure 15 illustrates an example arrangement for a RSPM 102 used with a respective subarray 30. Elements include one or more digital signal processors or other type(s) of computer processors 130, and signal input / output circuitry 132 for interfacing with the CSPMs 100 via the signal lines 104 and power lines 106. Additionally, the RSPM 102 includes one or more types of computer readable media, shown as “storage” 134. The storage 134 comprises, for example any one or more or any mix of EEPROM memory, FLASH memory, RAM, etc.

[0056] The storage 134 in at least one embodiment holds CPI 136 for execution by the processor(s) 130, where such execution causes the processor(s) 130 to carry out the RSPM- related signal processing operations associated with operating the RSA 12. One or more data items 138, such as provisioned or dynamically determined configuration data for use by the processor(s) 130 may also be held in the storage 134.

[0057] The RSPM 102 further includes power circuitry 140. For example, the power circuitry 140 comprises one or more voltage regulators configured to provide regulated supply voltages to the various circuits comprised within the RSPM 102, based on receiving power directly from the SV 40 or via distribution from the CSPM 100.

[0058] Further example elements of the RSPM 102 include antenna interface circuitry 142, which includes one or more analog front ends (AFEs) 144, and analog-to-digital (AD) and digital-to-analog (DA) converter circuitry 146. The antenna interface circuitry 142 provides for the conversion or interface between the analog-domain RF signal transmitted and / or received via the inflatable antenna elements 22, and the digital-domain signaling going between the RSPM 102 and the CSPM 100.

[0059] Figure 16 illustrates an example two-layer configuration for implementation of the inflatable lines 14 and 16. Each such inflatable line 14 or 16 comprises an inner layer 150 of laminate structure forming an inflatable tube or capillary, with these tubes or capillaries compartmented in some embodiments, e.g., with respective compartments being associated with respective pyrotechnic ignitors 82 for staged inflation of the inflatable net 10 during progressive deployment. As a further feature, each inflatable line 14 or 16 in the example embodiment includes a reactive layer 152 of laminate structure — also referred to as a curable layer.

[0060] Figure 17 differs from Figure 16 in that the example construction of the inflatable lines 14 and 16 includes an additional outer layer 154, in a three-layer lamination arrangement. In both configurations, one or more of the layers may be made of polyester (PE) film. The MYLAR brand of polyester film is one example. Other materials may be used, such as polyethylene (PE) or polyurethane (PU).

[0061] Figure 18 illustrates a method 1800 according to one or more embodiments, wherein the method 1800 includes stowing (Block 1802) an inflatable net 10 in a SV 40, e.g., packing the inflatable net 10 in a rolled or folded arrangement, and deploying (Block 1804) the inflatable net 10 in space, in a quasi-planar arrangement, via unfurling and inflation. Further, the method 1800 includes operating (Block 1806) the deployed inflatable net 10 as a RSA 12.

[0062] Figure 19 illustrates another method 1900 of operation according to one or more embodiments, with the method 1900 focusing on the deployment operations. The method 1900 includes initiating (Block 1902) deployment of an inflatable net 10 from a SV 40, e.g., in response to reception of a ground command at the SV 40.

[0063] The method 1900 further includes activating (Block 1904) a deployment mechanism responsive to the initiation — see, e.g., Figures 10-12 for deployment- mechanism examples. Still further, the method 1900 includes monitoring (Block 1906) progressive deployment of theinflatable net 10, e.g., based on timing, optical indexing, mechanical rotation or reciprocation, camera-based image processing, and corresponding sequential or timed (Block 1908) firing of the i-th pyrotechnic ignitors 82 distributed within the inflatable net 10. That is, as the inflatable net 10 pays out from the SV 40, the ignitors 82 in the paid-out portion of the inflatable net 10 are triggered.

[0064] Assuming that deployment is not yet complete — YES from Block 1910 — the method 1900 includes logically incrementing (Block 1912) the index(es) of the pyrotechnic ignitors 82 to be fired next, and operations return to the monitoring / firing steps of Blocks 1906 and 1908. Once deployment is complete — NO from Block 1910 — the method 1900 continues with activating (Block 1914) the fully deployed inflatable net 10 for operation as a RSA 12. Note that in embodiments which include one or more reactive layers 142 in the inflatable lines 14 and 16, for cure-based stiffening, the SV 40 or the controlling ground network of the satellite communications system may impose a delay to allow for completion of curing before beginning antenna-array usage, and the SV 40 and / or the ground network may perform initial validation and / or calibration operations of the RSA 12 before use with “live” communications traffic.

[0065] While Figure 19 suggests a closed-loop monitoring -based deployment process, one or more embodiments use an open- loop process, such as one based solely on timed unfurling — e.g., a defined payout rate — and corresponding timed control of inflation. Further, while deployment examples considered thus far do not actively exploit kinematics, at least one embodiment of the antenna system 80 includes a configuration of the deployment mechanism 86 that utilizes a spinning force or a spring force to aid in deployment of the inflatable net 10. As for inflation details, one or more embodiments involve an inflatable net 10 with distinct inflation compartments, allowing for staged or piecemeal inflation of the inflatable net 10 as it pays out from the SV 40.

[0066] In one or more embodiments, the SV 40 is configured to perform low duty-cycle digital calibration of the “final” or deployed locations of the populated vertices 18 or, more particularly, the deployed locations of the inflatable antenna elements 22 / subarrays 30. Such calibration compensates for mechanical tolerances greater than one wavelength. In more detail, the inflatable net structure and deployment technique(s) yield a “no-clumping” deployment that spreads net structure relatively well, with the calibration learning the deployed locations of the elements. Repeating the calibration process accounts for changes in the event that some elements “move” during thermal cycling or other forces.

[0067] In one or more other embodiments, the inflatable net 10 comprises a continuous, interconnected inflation chamber or multiple interconnected inflation chambers. In at least onesuch embodiment, the pyrotechnic ignitors 82 are carried onboard the SV 40 rather than integrated into the inflatable net 10, and pneumatic connections between the inflation mechanism 78 and the inflatable net 10, such as may be terminated in the SV interface 70, communicate expansion gases into the inflatable net 10. Note that one or more embodiments substitute one or more thermal heating units in place of the pyrotechnic ignitors 82. At least one such embodiment uses ice sublimation to create the expansion gases used for inflation of the inflatable net 10.

[0068] Also, as noted, one or more embodiments of the inflatable net 10 include one or more reactive layers 142 — e.g., distinct layers or layer-like coatings — which harden in association with deployment. The reactive layer(s) 142 comprise, for example, an epoxy that hardens responsive to irradiation by ultraviolet (UV) light. Temperature-reactive layers may also be used. As yet another option, binary-chemical curing may be exploited, such as where the deployment mechanism 86 sprays or otherwise wets the inflatable net 10 as it deploys, initiating a chemical reaction that causes an exposed reactive layer 142 in the inflatable lines 14 and 16 to harden, thereby stiffening the inflatable lines 14 and 16.

[0069] As for the inflatable antenna elements 22, they may be formed as metalized film balloons or as compressed wire dipole or tripole structures that spring into shape during deployment. In a hybrid approach, the inflatable antenna elements 22 are metalized film balloons but they are assisted in assuming the proper shape with spring forces from a compressed wire structure. Also, as noted before, the signal lines or wires include in the inflatable net 10 may be separate from the inflatable lines 14 and 16 or integrated therein, e.g., based on the inflatable lines 14 and 16 having one or more layers of metallized film, or based on having thin- film conductor wire bonded to one of the layers forming the inflatable lines 14 and 16.

[0070] Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is / are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMSWhat is claimed is:

1. An antenna system of a space vehicle, the antenna system comprising: a net formed of inflatable lines, where at least some vertices of the net each are populated with one or more inflatable antenna elements attached in fluid communication such that inflation of the inflatable lines inflates the inflatable antenna elements; a deployment mechanism configured to deploy the net from the space vehicle via progressive unfurling of the net from a furled configuration used for stowage of the net onboard the space vehicle; and an inflation mechanism configured to inflate the inflatable lines in association with deployment of the net, thereby urging the net into an expanded, quasi-planar arrangement in which the populated vertices are spaced apart for cooperative operation as a randomized sparse array; and wherein the inflatable lines and the inflatable antenna elements each include a reactive layer that hardens in space, thereby maintaining the quasi-planar arrangement in the absence of inflation pressure.

2. The antenna system according to claim 1, wherein each inflatable line comprises a laminated tube having multiple laminar layers, including the reactive layer.

3. The antenna system according to claim 1 or 2, wherein the reactive layer comprises a temperature-reactive layer.

4. The antenna system according to claim 1 or 2, wherein the reactive layer comprises a photoreactive layer.5 The antenna system according to claim 1 or 2, wherein the reactive layer comprises a chemically reactive layer, where the chemical reaction is stimulated by a chemical supplied during deployment such as inflation gas.

6. The antenna system according to any one of claims 1-5, wherein the net is flexible in a pre-cured state that exists before reaction of the reactive layers, and semi-rigid in a cured state that exists after reaction of the reactive layers.

7. The antenna system according to any one of claims 1-6, wherein the reactive layer comprises an outer coating.

8. The antenna system according to any one of claims 1-7, wherein the inflatable antenna elements each comprise a metallized film balloon.

9. The antenna system according to any one of claims 1-8, wherein, the inflatable antenna elements in a tripole shape may take on non-uniform orientations upon inflation.

10. The antenna system according to claim 9, wherein each inflatable antenna element has a tripole shape when inflated.

11. The antenna system according to any one of claims 1-10, wherein at least one populated vertex is populated with a subarray of inflatable antenna elements.

12. The antenna system according to any one of claims 1-11, wherein the populated vertices are each populated with a subarray of inflatable antenna elements, and wherein individual inflatable antenna elements in a tripole shape in each subarray may have non-uniform orientations upon inflation.

13. The antenna system according to any one of claims 1-12, wherein the inflation mechanism comprises one or more pyrotechnic inflators operative to produce inflation gas, and further comprises one or more pneumatic connections to respective inflation connections of the net.

14. The antenna system according to any one of claims 1-13, further comprising one or more stiffening arms, each spanning over a respective portion of the expanded, quasi-planar arrangement.

15. The antenna system according to claim 14, wherein the one or more stiffening arms comprise a set of arms, each arm extending from a centroid region of the expanded, quasi-planer arrangement towards a perimeter edge.

16. The antenna system according to any one of claims 1-15, further comprising a first digital processing module centralized with respect to each of the one or more inflatable antenna elements and a corresponding digital / analog processing module for each vertex that carries a respective one or more inflatable antenna elements, and further comprising interconnecting signal lines extending from the first digital processing module to the corresponding digital / analog processing modules.

17. A method of deploying an inflatable net from a space vehicle, for operation as a randomized sparse array, the method comprising: operating a deployment mechanism configured to deploy the inflatable net from the space vehicle via progressive unfurling of the inflatable net from a furled configuration used for stowage of the inflatable net onboard the space vehicle; and initiating inflation of the inflatable net in conjunction with deployment of the inflatable net via the deployment mechanism.

18. The method according to claim 17, wherein initiating the inflation comprises initiating a staged inflation process in which different pyrotechnic inflators are triggered at different times, the different pyrotechnic inflators distributed within the inflatable net.

19. The method according to claim 18, wherein initiating the staged inflation process comprises initiating respective ones or respective subsets of the different pyrotechnic inflators on a timed basis, referenced to activation of the deployment mechanism.

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