Patent ID: 12228114

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account that large, complex panels are often deployed in space due to the requirement for large surface area on an object like a solar array or antenna and the constraint of limited space in the launch vehicle. When deployments are relatively simple and require one or two movements to deploy, many options are available for the deployment mechanism.

The illustrative embodiments recognize and take into account that when deployments get more complex and involve multiple folds, there are two, traditional options that are employed. One option comprises complex tendons/pulleys that deploy and establish the tensile part of tension/compression load path that must be reeled in or out using motors. The other option comprises hinge/motor assemblies where each motor requires communications and power interfaces and where the motor is only part of the deployment and not part of the final load path.

The illustrative embodiments provide a deployable panel assembly that employs shape memory alloy (SMA) based hinges. An SMA (e.g., nitinol) is a memory alloy that returns to an original shape when heated. Subpanels comprising the deployable panel assembly fan are initially folded over each other in a compact configuration. In response to an applied energy source such as an electric current, the SMA in the hinges returns to an original extended position, thereby unfolding and deploying the subpanels. The illustrative embodiments use an SMA such as nitinol as both a local motor as well as a tensile component part of the final load path.

With reference now toFIG.1, an illustration of a block diagram of a deployable panel is depicted in accordance with an illustrative embodiment. Deployable panel100comprises a number of subpanels102that can be folded together and then unfolded into a planar array. The subpanels102are organized into a number respective subpanels pairs104. Some of the subpanels102might belong to more than one of the subpanel pairs, but functionally, the deployable panel100operates with respect to subpanel pairs104.

Deployable panel100is held together by a number of nitinol (or other SMA) hinges120. The subpanels comprising each of the subpanel pairs104are connected by a respective nitinol hinge122. Nitinol is a shape memory alloy made from nickel and titanium. Nitinol has the ability to move between different shapes due to reversible phase transition when heated above its transformation temperature (e.g., by an electric current). In the context of deployable panel100, a nitinol hinge122might comprise a bar with an initial extended (straight) state126and is then bent into a folded state124prior to deployment. Nitinol hinge122might also comprise a graphene pad140(or other heating element) bonded to one or more nitinol strips142. Graphene pad/heating element140facilitates heating the nitinol to the transformation temperature with a lower electric current. Upon application of electric currents138from an electric source, and resultant heating via the graphene pad/heating element140, the nitinol in the nitinol hinge122“remembers” the original shape it was trained to and returns to the extended state126(seeFIGS.3A-3C).

The shape memory capability of the nitinol hinges120allows the respective subpanel pairs102(and by extension, all of the subpanels102) to move between a folded position112to a coplanar position114in response to electric currents138(or external thermal source) applied to the nitinol hinges120.

Each of the subpanel pairs104includes nitinol (or other SMA) springs128attached to at least one subpanel within the pair connect to the other subpanel by tethers134. When each of the subpanel pairs104unfolds to the coplanar position114they are in an open position116in which the subpanels are not in direct contact with each other. In response to electric current, the nitinol springs128, similar to the nitinol hinges120, change shape by moving from a lengthened state130to a shortened state132and in so doing pull the subpanels on the subpanel pairs104together (via the tethers134) into a closed position118.

When the subpanels are pulled together, cone hole110extending from one of the subpanels in each pair fit into accommodating cone holes110the other subpanel to ensure alignment of the subpanels as they are being pulled together. Magnets106in adjacent ends of the subpanels hold the subpanels together end-to-end after they are pulled together by the nitinol springs128via the tethers134.

The memory quality of the nitinol and the use of magnets allows precision preloading (training) of kinematic mating between the subpanels102to achieve a seamless final surface to the deployable panel100when in the final deployed state without surface features on the front of the panel.

FIG.2depicts a pictorial diagram illustrating a deployable panel in accordance with an illustrative embodiment. Deployable panel200is an example implementation of deployable panel100inFIG.1.

In this example, the deployable panel200comprises an array of nine subpanels202-218arranged in three rows220,222,224of three subpanels each. The center subpanels204,210,216of each row are linked to the wing subpanels in each row by SMA hinges226, which allows the subpanels in each row to move between a first, folded position in which the outer wing subpanels (e.g.,202,206) are folded over the center subpanel (e.g.,204) (seeFIG.4B) and a second, extended position in which the subpanels are coplanar in response to a first electric current or external thermal source that changes the shape of the SMA hinges (seeFIG.4E). The SMA hinges226connecting the wing subpanels202,206,208,212,214,218to the center subpanels204,210,216might comprise a graphene heating pad or other heating element bonded to an SMA strip. Application of an energy source such as electric current or external thermal source to the graphene pad enables the nitinol to reach the transformation temperature with a lower current than would be required if the nitinol were used alone as a simple conductor.

The center subpanels204,210,216of each row are also connected to each other by a second group of SMA hinges228, which enable the top and middle rows220,222of subpanels to move between a folded position in which the center subpanels204,210of the top and middle rows are folded over the center subpanel216of the bottom row (seeFIG.4A), and an extended position in which the center subpanels204,210,216of the rows are coplanar (as shown inFIG.2) in response to a second electric current that changes the shape of the second group of SMA hinges228. The SMA hinges228that connect the center subpanels204,210,216might comprise a graphene heating pad sandwiched between two SMA strips.

Once in the subpanels202-218are coplanar, SMA springs230are shortened by application of electric current, which causes them to pull the subpanels together via tethers232. As the subpanels meet, cones234extending from one subpanel in each respective pair provide alignment by sliding into corresponding cone holes236in the other subpanel within the pair. As shown in the present example, the tethers might run through the cones234and cone holes236.

FIGS.3A through3Edepict a sequence of pictorial diagrams illustrating the deployment of a subpanel pair from a folded position to a coplanar, closed position in accordance with an illustrative embodiment. Such unfolding of two subpanels relative to each other forms the basic operational unit of more complex deployable arrays (seeFIGS.4A-4E).

FIG.3Adepicts a pictorial diagram of two subpanels302,304comprising a subpanel pair300in a folded position. As shown, the subpanels302,304are connected by a SMA hinge306that is in a folded position.

FIG.3Bdepicts a pictorial diagram of the subpanels302,304comprising the subpanel pair300in a partially unfolded position. The SMA springs308and tethers310are more visible in this view.

FIG.3Cdepicts a pictorial diagram of the two subpanels302,304comprising the subpanel pair300in an unfolded position. In this position, SMA hinge306is in an extended state. This unfolded position is trained into the SMA hinge306to ensure precise kinematic mating between the first and second subpanels302,304when pulled together (seeFIG.3E).

FIG.3Ddepicts a pictorial diagram of the two subpanels302,304comprising the subpanel pair300partially pulled together in the unfolded position. In response to electric current, the SMA springs308shorten and pull subpanels302and304together via tethers310.

FIG.3Edepicts a pictorial diagram of the two subpanels302,304comprising the subpanel pair300pulled together in a closed, coplanar position.

FIGS.4A-4Ddepict a sequence of pictorial diagrams illustrating the deployment of a panel array in accordance with an illustrative embodiment. In the present example, the deployable panel400comprises an array of nine subpanels as shown inFIG.2and is shown mounted to an ESPA (Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter) ring402.

FIG.4Adepicts the deployable panel array400in a folded state.

FIG.4Bdepicts the deployable panel array400in a partially unfolded state along the axis of the center subpanels of each row. InFIG.4B, the center subpanels are unfolding from each other, but the lateral subpanels are still folded over the center subpanel of each row.

FIG.4Cdepicts the lateral subpanels of each row of the deployable panel array400in a partially unfolded state. At this stage, the center subpanels have unfolded from each other and are in a coplanar position as the lateral subpanels in each row begin to unfold from the center subpanel.

FIG.4Ddepicts the deployable panel array400in an open, unfolded state. In this state, the lateral subpanels in each row have fully deployed, and all of the subpanels are coplanar with each other, but the separate rows have not yet been pulled together.

FIG.4Edepicts the deployable panel array400in a closed, unfolded state after the rows have been pulled together, resulting in a seamless, featureless surface of the deployable panel array400.

FIG.4Fdepicts the deployable panel array400folded over the ESPA ring402. In this position, the panel array400is its final operational position.

In applications such as deployment in space (e.g., on a satellite), solar radiation might provide the energy source to heat the SMA hinges to unfold and deploy the panel. Solar heating might be used as a passive nonelectrical method of deployment or as a backup in the event of electrical failure.

FIG.5depicts an SMA spring-driven hinge in accordance with an alternate illustrative embodiment. In this embodiment, an SMA spring502runs along the rotational axis of the hinge504comprising the hinge. The SMA spring502is configured to maintain a preload on the hinge and remains in the load path.

In this embodiment, the martensitic SMA spring502is deformed to a spring with more coils and more rotation at its ends when the hinge504is folded. When a current is applied, the SMA spring502returns to a remembered shape that has fewer coils and a smaller angle between ends, thereby rotating the hinge504open and maintaining load against the hinge.

FIGS.6A-6Cdepict a sequence of pictorial diagrams illustrating the operation of the SMA spring-driven hinge504shown inFIG.5opening adjacent panels.

FIG.6Adepicts three SMA spring-driven hinges504connecting two panels602,604in a folded position.

FIG.6Bdepicts the panels602,604in a partially opened position resulting from the heating and unwinding of the SMA springs inside the hinges504in response to electric current or an external thermal source.

FIG.6Cdepicts the panels602,604in a fully opened position. In this position, the warmed SMA springs have returned to the remembered shape and maintain preload against the hinges504to keep the panels602,604in the deployed state. A hinge stop606attached to panel602provides a rotation constraint to ensure the panels602,604remain coplanar and prevents the hinges504from overextending.

FIGS.7A and7Bdepict perspective and side view pictorial diagrams, respectively, of a deployable subpanel in accordance with another alternate embodiment.

This embodiment is suitable for deployments that require a seamless, extremely precise, deployed panel with no apparent hinges on the front or back side and the subpanels form one continuous, smooth surface without apparent seams or surface features. The precision of shape in the deployed panel is a product of the kinematic interface between panels. The kinematic interface is preloaded into the SMA's initial shape, which is “remembered” upon application of an electric current or external thermal source. Magnets can also be used to establish the precision of position of the deployed subpanels.

In this embodiment, SMA springs710act as both a hinge and tensile element. The SMA springs710can be mounted to contact points706inside the subpanel700and fed through hole in cones702or cone holes708and similarly connect with another subpanel at the other end. In the martinsitic, stowed state, the SMA hinges are both folded and lengthened.

FIGS.8A-8Cdepict a sequence of pictorial diagrams illustrating the deployment of an array of subpanels using the spring hinge subpanel embodiment shown inFIGS.7A and7B. The example shown inFIGS.8A-8Dcomprises a nine-subpanel array analogous to deployable panel200inFIG.2.

When an electric current is applied, the SMA springs710remember a straighter, shorter spring position and thereby both unfold the subpanels700and then apply tensile force to pull the gaps between subpanels shut. As with the embodiments described above, the unfolded position is trained into the SMA springs710to ensure precise kinematic mating between the subpanels when they are unfolded and pulled together as a unitary panel. Magnets704can be used in combination with the SMA preload to form one, seamless panel in the deployed position. The sequence shown inFIGS.8A-8Dillustrates the ability of the SMA to act as both a hinge and a motor without requiring a rotation constraint. In addition, an SMA such as nitinol acts as a conductor path (between the spring coils) for wiring/electrical interface between subpanels. The inner diameters of SMA hinges can act as conduits between subpanels (e.g., for wiring, electrical connections, fluid lines, etc.).

As used herein, the phrase “at least one of,” when used with a list of items, means different combinations of one or more of the listed items can be used, and only one of each item in the list may be needed. In other words, “at least one of” means any combination of items and number of items may be used from the list, but not all of the items in the list are required. The item can be a particular object, a thing, or a category.

For example, without limitation, “at least one of item A, item B, or item C” may include item A, item A and item B, or item B. This example also may include item A, item B, and item C or item B and item C. Of course, any combinations of these items can be present. In some illustrative examples, “at least one of” can be, for example, without limitation, two of item A; one of item B; and ten of item C; four of item B and seven of item C; or other suitable combinations.

As used herein, “a number of” when used with reference to items, means one or more items. For example, “a number of different types of networks” is one or more different types of networks. In illustrative example, a “set of” as used with reference items means one or more items. For example, a set of metrics is one or more of the metrics.

The description of the different illustrative embodiments has been presented for purposes of illustration and description and is not intended to be exhaustive or limited to the embodiments in the form disclosed. The different illustrative examples describe components that perform actions or operations. In an illustrative embodiment, a component can be configured to perform the action or operation described. For example, the component can have a configuration or design for a structure that provides the component an ability to perform the action or operation that is described in the illustrative examples as being performed by the component. Further, to the extent that terms “includes”, “including”, “has”, “contains”, and variants thereof are used herein, such terms are intended to be inclusive in a manner similar to the term “comprises” as an open transition word without precluding any additional or other elements.

Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different features as compared to other desirable embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.