Patent Publication Number: US-10774518-B1

Title: Systems and methods for joining space frame structures

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/571,712, entitled “SYSTEMS AND METHODS FOR JOINING SPACE FRAME STRUCTURES,” filed Oct. 12, 2017, the entirety of each of which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     TECHNICAL FIELD 
     The present description relates in general to space frame structures, and more particularly to, for example, without limitation, systems and methods for joining space frame structures. 
     BACKGROUND OF THE DISCLOSURE 
     Space frame structures are one of the efficient and commonly used structures used on Earth and in space. Space frame structures are typically truss-like and are used for constructing: buildings, bridges, aircraft, automobiles, spacecraft, and tensegrity structures. Design of modern space frame structures has not changed much since the advent of mechanical fasteners and fusion welding processes back in the industrial revolution era. Hence many large space frame structures involve intricate assembly steps that require significant human interaction and skill. The majority of space frame structures require highly skilled fusion welders to make difficult pipe welds that are the most complicated and defect-ridden joints because of the difficult fit up, accessibility, and positioning required to make full circumferential welds. Thus far, space frame designs and methods suitable for robotic (semi-autonomous and/or fully autonomous) or telerobotic assembly/joining has not yet emerged as a viable solution to replace “handmade” truss structures. 
     The description provided in the background section should not be assumed to be prior art merely because it is mentioned in or associated with the background section. The background section may include information that describes one or more aspects of the subject technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a view of an example of a tetrahedral truss structure with tubular strut-and-node joints. 
         FIG. 1B  illustrates a view of an example of a welded truss structure where smaller strut members are precisely fit up and welded to larger strut members. 
         FIG. 2  illustrates a perspective view of an example of a first order (1-ring) truss structure with a hexagonal node design. 
         FIG. 3A  illustrates a perspective view of an example of a hexagonal node design where the 2-D weld plane is shown as elliptical faces machined out of a solid node member. 
         FIG. 3B  illustrates a perspective view of the node design of  FIG. 3A  shown with transparencies showing the angled-cut strut ends fitting into annular slots/grooves to a position that is ideal for welding from a fixed swiveling position. 
         FIG. 3C  illustrates a sectional view of the hexagonal node shown in  FIGS. 3A and 3B  where the strut ends are fit into annular grooves on the sides. 
         FIG. 3D  illustrates an enlarged sectional view of a portion of  FIG. 3C . 
         FIG. 3E  illustrates an enlarged sectional view of a portion of  FIG. 3C . 
         FIG. 4  illustrates a perspective view of an example of a first order (1-ring) truss structure with hexagonal node design. 
         FIG. 5  illustrates a perspective view of an example of a first order (3-ring) truss structure with hexagonal node design. 
         FIG. 6A  illustrates a perspective view of an example of a tetrahedral node design where the 2-D weld plane is shown as elliptical faces machined out of a solid node member. 
         FIG. 6B  illustrates a perspective view of the node design of  FIG. 6A  shown with transparencies showing the angled-cut strut ends fitting into annular slots/grooves to a position that is ideal for welding from a fixed swiveling position. 
         FIG. 7  illustrates a perspective view of an example of a rim truss structure that can be robotically assembled and welded in space. 
         FIG. 8  illustrates a perspective view of an example of cylindrical truss nodes for vertical and horizontal strut struts. 
         FIG. 9  illustrates a perspective view of another example of cylindrical truss nodes for vertical and horizontal strut struts as well as diagonals. 
         FIG. 10A  illustrates a perspective view of an example of a node member with a parallel machined channel. 
         FIG. 10B  illustrates a sectional view of the node member of  FIG. 10A . 
         FIG. 10C  illustrates a sectional view of an example of an extended tapered anvil attached with a fastener to the node at the backside of the elliptical welding face. 
         FIG. 10D  illustrates another sectional view of an example of an extended tapered anvil attached with a fastener to the node at the backside of the elliptical welding face. 
         FIG. 11A  illustrates a perspective view of an example of a double spring-loaded tapered pin that engages through a strut hole. 
         FIG. 11B  illustrates a sectional view of the double spring-loaded tapered pin of  FIG. 11A . 
         FIG. 12  illustrates a perspective view of an example of a node alignment mechanism (e.g., tapered toggle pin) that holds the node in position against an assembly platform and prevents it from rotating out of position during fit up and welding. 
         FIGS. 13A and 13B  illustrate perspective views of an example of rim truss structure integrated with tensegrity reflector assembly to enable large aperture RF antenna in a collapsed configuration ( FIG. 13A ) and an expanded configuration ( FIG. 13B ). 
         FIG. 14  illustrates a perspective view of an example of strut/tubes shown stowed inside one of another for maximum packing efficiency. 
         FIG. 15A  illustrates a perspective view of an example of a ring truss node with diagonal fitting for a tensegrity strut end demonstrating that all strut ends can still be fit up and welded (2-dimensional) from the exterior position. 
         FIG. 15B  illustrates another perspective view of the ring truss node of  FIG. 15A . 
         FIG. 16A  illustrates a perspective view of an example of a parabolic antenna truss structure design showing various strut and node connections designed for 2-dimensional welding from the exterior position. 
         FIG. 16B  illustrates another perspective view of the parabolic antenna truss structure design of  FIG. 16A . 
         FIG. 17  illustrates a perspective view of an example of parabolic antenna truss nodes with hole features for both positioning the node for precision fit up and joining with struts. 
         FIG. 18  illustrates a perspective view of an example of parabolic antenna truss nodes showing a central hub node member. 
         FIGS. 19 and 20  illustrate perspective views of an example of an intermediate node enabling a larger strut diameter to connect to a smaller strut diameter going towards the dish perimeter. 
         FIG. 21  illustrates a perspective view of an example of a geodesic space frame truss structure with node and strut design. 
         FIG. 22  illustrates a perspective view of an example of a geodesic space frame truss structure with cover panels seal-welded and joined to the nodes to create a hermetically sealed habitat or vessel. 
         FIG. 23  illustrates a perspective view of an example of a recurring pentagonal node with panels fit up on top of a connecting bar that is supported by strut underneath, allowing the panel to be welded to the bars and nodes in the same 2-D path. 
         FIG. 24A  illustrates a perspective view of an example of a central pentagonal node with recessed edges that allow for the panel to be butt-lap welded. 
         FIG. 24B  illustrates a sectional perspective view of the node of  FIG. 24A  with the connector bar installed on top of the strut as well as the panel fit up with the recess of the connector bar. 
         FIG. 25A  illustrates a perspective view of an example of a hexagonal node with machined recess for 2-D butt-lap weld and through holes for conveying fluid. 
         FIG. 25B  illustrates a perspective view of an example of a cap member installed flush with a node such that it can be welded around the perimeter. 
         FIG. 26  illustrates a perspective view of an example of a cap member with gusset features to increase stiffness at top of node. 
         FIG. 27  illustrates a perspective view of an example of a cap member with a fitting for flowing fluid or pressurizing the network of sealed nodes and struts. 
         FIG. 28  illustrates a perspective view of an example of a prismatic truss structure segment showing 3 different strut lengths and diameters, but all utilizing the same node in 6 locations. 
         FIG. 29  illustrates a perspective view of an example of a prismatic truss structure node with branches to accept strut ends at each location with a precise annular groove and 2-D welding face that is accessible from the exterior position. 
         FIG. 30A  illustrates a perspective view of an example of an elliptical strut end when cut at a 45-degree angle, which provides a circular face when facing normal to the newly cut face. 
         FIG. 30B  illustrates a side view of an example of the strut of  FIG. 30A . 
         FIG. 30C  illustrates another side view of an example of the strut of  FIG. 30A . 
         FIG. 31A  illustrates a perspective view of a robotic arm installing an unfurled tensegrity structure into the cylindrical rim truss structure to complete an antenna reflector. 
         FIG. 31B  illustrates a perspective view of an in-space manufactured prismatic truss with subreflector and satlets positioned above the reflector. 
     
    
    
     In one or more implementations, not all of the depicted components in each figure may be required, and one or more implementations may include additional components not shown in a figure. Variations in the arrangement and type of the components may be made without departing from the scope of the subject disclosure. Additional components, different components, or fewer components may be utilized within the scope of the subject disclosure. 
     DETAILED DESCRIPTION 
     The detailed description set forth below is intended as a description of various implementations and is not intended to represent the only implementations in which the subject technology may be practiced. As those skilled in the art would realize, the described implementations may be modified in various different ways, all without departing from the scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. 
     The present disclosure provides a new design and method for building space frame structures with minimal human interaction. Using robotic assembly and joining methods to build large space frame structures on Earth will have a significant technology roadmap before it is deemed safe for humans to safely work and live on (and under) structures built by robots. Therefore, the most realistic near-term use for robotically manufactured space frame structures is where space frame construction is the most expensive and most difficult for humans to build by hand: outer space. 
     It can be desirable to build structures in space more efficiently to enable capability growth and capability preservation of various space-based functions such as human exploration, scientific discovery, and satellite operations. A significant limitation to growing and preserving these functions are the high cost and long lead time of transporting payloads into space. The payloads must be designed to withstand up to 10 G launch loads, but will ultimately operate in an environment with 0 G or minimal G-force loads. Therefore, a tremendous amount of design and configuration testing could be eliminated if the payload could be launched into orbit as raw materials and manufactured/assembled in space. Furthermore, the launching of raw materials instead of deployable/unfurlable payloads will create a transformational change in the volumetric packing efficiency within a given launch vehicle&#39;s payload fairing. Manufacturing and assembly of raw materials in space is complicated. 
     Modern space frame structures are expensive to manufacture and are almost always reliant on complex assembly procedures requiring human labor and skills. This is especially true for space transportation solutions because large payloads are required to deploy and unfurl since a suitable design and joining method for robotic assembly has not been developed yet. 
     One aspect of the present disclosure provides a strut-and-node truss design that is applicable to all space frame structure designs with using innovative robotic (semi-autonomous and/or fully autonomous) or telerobotic assembly/joining. Embodiments of the present disclosure are intended to create transformational change to the space transportation and exploration as well as eventual adoption into terrestrial construction industry. 
     It can be beneficial to introduce a specific joint that can be joined by robots instead of humans. Common truss structures in use today take advantage of the strut-and-node design to maximize structural stiffness with minimal weight.  FIG. 1A  illustrates an examples of a tetrahedral truss structure with tubular strut-and-node joints.  FIG. 1B  illustrates an example of a welded truss structure where smaller strut members are precisely fit up and welded to larger strut members. In these and other examples, the nodes can be brackets with connecting holes, larger strut members, or metallic spheres that are either solid or have threaded inserts. The bracket nodes connect to angular struts with fasteners and the threaded node spheres connect to tubular struts with end fittings that have the matching thread. These struts are screwed into the nodes by hand (and it is worth noting that screw alignment of complex threaded joints is currently not a task done well by robots). The welded truss structures require smaller struts to have precision mitering to ensure proper fit up with the larger strut member (or solid node) and are welded circumferentially in a small volume with limited accessibility, as shown in  FIGS. 1A and 1B . 
     Some embodiments of the present disclosure provide a design that enables a 2-dimensional weld path for the nodes in an effort to reduce the complexity of having to weld in 3-dimensions. Furthermore, each strut to node connection can be concentrated in a small area where each weld can be performed robotically from a fixed position that only requires the robotic weld head to swivel in a small operating window to reach each joint. To access all the strut end joints in this manner, the strut ends can be simply cut at an angle and inserted into an annular slot or groove to position the strut for welding to the node. 
       FIG. 2  illustrates a perspective view of an example of a first order (1-ring) truss structure with a hexagonal node design. As shown in  FIG. 2 , when full assembled with node members  110  connecting struts  190  in a hexagonal arrangement, a first order (1-ring) truss  100  can be produced. Robotic assembly and welding is enabled by the joint design in which all the weld joints on a side of the truss structure  100  can be welded on a common side of each corresponding node member  110  (e.g., from just the top or bottom of the truss structure  100 ). For example, the node members  110  on a first side  102  can provide welding areas all facing in a common first direction, and the node members  110  on a second side  104  can provide welding areas all facing in a common second direction. Hence, the robot(s) do not need to work their way in between the top and bottom plane to access the weld joints. Accessibility between the top and bottom planes can become restrictive as the structure gets larger and more complicated, so the robot can assemble and weld a multitude of these truss structure types without needing to be customized to fit within different size truss members and corresponding clearances. 
       FIG. 3A  illustrates a perspective view of an example of a hexagonal node design where the 2-D weld plane is shown as elliptical faces machined out of a solid node member. As shown in  FIG. 3A , a node member  110  for a truss structure can include a main body  112 . The main body  112  can be machined or otherwise formed with features of the node member  110 . Additionally or alternatively, features of the node member  110  can be connected to the main body  112 . Struts  190  can be inserted into annular grooves  150  of the node member  110 . Each annular groove  150  can extend from a periphery of the main body  112  inwardly toward an interior region  116  of the main body  112 . 
     At the interior region  116 , weld surfaces  130  are provided facing inwardly. Each weld surface  130  can cover an interior end of a corresponding one of the annular grooves  150 . The weld surfaces  130  face in directions that converge at a work point  198 . For example, each weld surface  130  can be planar, and a direction orthogonal to the planar weld surface  130  extends toward the work point  198 . The directions of each can converge at the single work point  198 , so that a weld tool positioned at the work point  198  is aligned with each of the weld surfaces  130 . From the work point  198 , the weld tool can face one of the weld surfaces  130  in a direction that is orthogonal to the weld surface. As such, the entirety of the weld surface  130  is exposed to the weld tool and arranged in a known position and orientation relative to the weld tool. 
       FIG. 3B  illustrates a perspective view of the node design of  FIG. 3A  shown with transparencies showing the angled-cut strut ends fitting into annular slots/grooves to a position that is ideal for welding from a fixed swiveling position. As shown, terminal ends  192  of each of the struts  190  are positioned within the annular grooves  150  and against the main body  112  of the node member  110 . 
     The struts  190  are illustrated as tubular members, but could also be solid (e.g., filled) members. Since tubular members are more common from a specific stiffness and specific strength point of view, the remaining configurations and design features are optimized for strut ends instead of solid ends; however, all embodiments disclosed herein can incorporate tubular and/or solid members. 
       FIG. 3C  illustrates a sectional view of the hexagonal node shown in  FIGS. 3A and 3B  where the strut ends are fit into annular grooves on the sides. The annular grooves  150  can be formed at least in part by anvils  120  that define inner diameters of the annular grooves  150 . The struts  190  can receive the anvils  120  as the struts  190  are received into the annular grooves  150 . The anvils  120  can be attached to or integrally or monolithically formed with the remainder of the main body  112  of the node member  110 . 
     With the node members  110  and struts  190  described herein, the anvils  120  precisely align the terminal ends  192  with the node member  110  to maintain ideal fit-up tolerances. The anvils  120  also stiffen the strut end by increasing its bending resistance. The anvils  120  also serve as a heat sink for the welding process and prevents blowing through with fusion welds. It should be noted that the hexagonal node shown can be sculpted/machined further to achieve higher stiffness around each joint. The anvils  120  can be cylindrical or another shape. In some embodiments, the anvil  120  can be provided with a tapered end to enable easier insertion while helping with precision alignment. 
     As shown in  FIG. 3C , each of the struts extends along a longitudinal axis  196 . The weld surface  130  faces in a direction along a weld axis  136 . As discussed previously, the weld axes  136  can converge at the work point. The longitudinal axes  196  need not converge at a single point. As shown in  FIG. 3C , the weld surface can face in a direction that is not parallel to the longitudinal axis  196  of the corresponding strut  190 , as discussed below with respect to  FIG. 3D . Nonetheless, one or more of the struts  190  can be aligned with the weld surface  130  so that the longitudinal axis  196  is coextensive with and/or parallel to the weld axis  136 , as discussed below with respect to  FIG. 3E . 
       FIG. 3D  illustrates an enlarged sectional view of a portion of  FIG. 3C . As shown in  FIG. 3D , the terminal ends  192  each fit into a matching annular groove  150  on the perimeter of the node member  110 . Each terminal end  192  fits up against a small ligament of the main body  112 , separating the interior end  152  of the annular groove  150  and the terminal end  192  of the strut  190  from the weld surface on the opposite side. Welding can be performed along the weld surface  130  to form a weld nugget  180  that extends from the weld surface  130  at least to the interior end  152  of the annular groove  150  and the terminal end  192  of the strut  190 . Accordingly, the strut  190  can be welded to the main body  112  of the node member  110 . The weld nugget  180  can include added materials or a welding of existing materials without any added materials. 
     As shown in  FIG. 3D , the interior end  152  of the annular groove  150  and the terminal end  192  of the strut  190  can form an angle that provides surfaces parallel to the weld surface  130 . Such an angle may formed by cutting or otherwise forming the struts  190  with ends that form surfaces that are not orthogonal to the longitudinal axis of the strut  190 . 
       FIG. 3E  illustrates an enlarged sectional view of a portion of  FIG. 3C . As shown in  FIG. 3E , and similar to the configuration illustrated in  FIG. 3D , the terminal ends  192  each fit into a matching annular groove  150  on the perimeter of the node member  110 . Welding can be performed along the weld surface  130  to form a weld nugget  180  that extends from the weld surface  130  at least to the interior end  152  of the annular groove  150  and the terminal end  192  of the strut  190 . The interior end  152  of the annular groove  150  and the terminal end  192  of the strut  190  can form an angle that provides surfaces parallel to the weld surface  130 . In contrast to the configuration illustrated in  FIG. 3D , such an angle may formed by cutting or otherwise forming the struts  190  with ends that form surfaces that are orthogonal to the longitudinal axis of the strut  190 . 
     It will be understood that a variety of truss structures can be assembled using the nodes  110  and struts  190  described herein. The illustrated embodiments provide non-limiting examples. It will be understood that arrangements other than those illustrated can be provided. 
     Referring now to  FIGS. 4 and 5 , a more complex version of the node member described herein is a tetrahedral node member that enables some of the most efficient space frame structures. Such a truss structure  100  uses similar hexagonal strut-to-node connections, but has three struts  190  coming off the bottom instead of just one. A 1-ring tetrahedral and 3-ring tetrahedral truss structure are shown in  FIGS. 4 and 5 . The additional strut connections requires a thicker node member  110 , but all the strut ends of the struts  190  can still be welded from a fixed, swiveling position on the top plane. 
     While the tetrahedral structure shown in  FIGS. 4 and 5  are illustrated with substantially flat top and bottom faces, it will be understood that these structures can have a parabolic curvature to one or both of the top and bottom faces. A substantially parabolic curvature enables placement of mirrors at the nodes for telescope applications. Such structures can also be used for aerobrake applications. 
     The truss structures of  FIGS. 4 and 5  can be assembled with node and strut configurations illustrated in  FIGS. 6A and 6B .  FIG. 6A  illustrates a perspective view of an example of a tetrahedral node design where the 2-D weld plane is shown as elliptical faces machined out of a solid node member. 
     As shown in  FIG. 6A , a node member  110  for a truss structure can include a main body  112 . Struts  190  can be inserted into annular grooves  150  of the node member  110 . Each annular groove  150  can extend from a periphery of the main body  112  inwardly toward an interior region of the main body  112 . While a greater number of struts  190  and weld surfaces are provided than in the configuration of  FIGS. 3A and 3B , the provided weld surfaces  130  can still be provided facing inwardly and in directions that converge at a work point.  FIG. 6B  illustrates a perspective view of the node design of  FIG. 6A  shown with transparencies showing the angled-cut strut ends fitting into annular slots/grooves to a position that is ideal for welding from a fixed swiveling position. As shown, terminal ends  192  of each of the struts  190  are positioned within the annular grooves  150  and against the main body  112  of the node member  110 . 
     The hexagonal and tetrahedral truss configuration shown in  FIGS. 4-6B  have significant applicability to roof structures, flooring structures, structural building supports, bridge structures, and telescopes (both Earth-based and space-based). Another application includes using the tetrahedral truss structure as an effective aerobrake for slowing the entry of spacecraft (either human-rated or non-human-rated) as it enters a celestial body with a thin atmosphere. For all of these scenarios, the nodes shown above can easily be adapted with fastener holes with precision adjustment capability to attach mirrors (in the case of telescopes), heat shield panels (in the case of aerobrakes), and other structural panels for construction or debris shielding/collection. 
     Referring now to  FIG. 7 , another application of a node-and-strut design includes assembly of truss structures  100  that serve as structural support for antennas. As shown in  FIG. 7 , one example of an antenna configuration is a cylindrical truss rim that is the structural stiffening element for a mesh reflector element that is tensioned to the truss rim. The cylindrical rim can be assembled in space from raw materials: struts  190  and node members  110   a  and  110   b . The struts  190  can be graphite epoxy and bonded aluminum ends and the nodes can be aluminum (titanium is also an acceptable substitute). The robotic assembly would require the struts to be fit up with the nodes with a mechanical connection such as a spring-loaded taper pin or an electrically actuated taper pin. This will position the strut in place while other struts  190  are attached to the node. The concept of operations is that the robot would assemble the entire structure with mechanical connections first to ensure that everything can fit into the proper locations first. This leverages the phenomenon of freeplay in mechanical joints that provides the ability to bend struts slightly to make them fit because the mechanical joints do not completely immobilize the strut  190 . Once the structure has been fully assembled with mechanical joints, the robotic welding head can weld each joint using robotic arms to move each section into position under the weld head until all the joints are welded. This allows the rim structure to retain fine assembly tolerances with minimal distortion. 
     The truss structure of  FIG. 7  can be assembled with node members illustrated in  FIGS. 8 and 9 . 
       FIG. 8  illustrates a perspective view of an example of cylindrical truss nodes for vertical and horizontal struts. As shown in  FIG. 8 , a node member  110   a  for a truss structure can include a main body  112 . Struts can be inserted into annular grooves  150  of the node member  110   a . Each annular groove  150  can extend from a periphery of the main body  112  inwardly toward an interior region of the main body  112 . The weld surfaces  130  are provided facing inwardly and in directions that converge at a work point  198 . The struts can be arranged to form the vertical and horizontal supports of the truss structure. 
       FIG. 9  illustrates a perspective view of another example of cylindrical truss nodes for vertical and horizontal strut struts as well as diagonals. As shown in  FIG. 9 , a node member  110   b  for a truss structure can include a main body  112 . Struts can be inserted into annular grooves  150  of the node member  110   b . Each annular groove  150  can extend from a periphery of the main body  112  inwardly toward an interior region of the main body  112 . While a greater number of annular grooves  150  are provided than in the node member  110   a , the weld surfaces  130  are still provided facing inwardly and in directions that converge at a work point. The struts can be arranged to form the vertical, horizontal, and diagonal supports of the truss structure. 
     Referring now to  FIGS. 10A-10D , a node member can include various features that facilitate a more cost effective machining approach as well as a more efficient assembly approach.  FIG. 10A  illustrates a perspective view of an example of a node member with a parallel machined channel. As shown in  FIG. 10A , the node member  110  can have a channel  160  that is cut and/or machined to be parallel or nearly parallel to the elliptical welding face  130 . The channel  160  can simplify machining of the small annular groove  150  where the strut is inserted. Because the struts may be thin-walled, the precision of the groove  150  is difficult to machine with standard mill bits. Hence, a mill bit with a diameter of 0.050″ might only be available in a length of 1″ because the depth-to-diameter ratio is not ideal for making precise features with good tolerances. Therefore, the parallel machined channel  160  makes it easier for the small diameter mill bits to machine the annular groove  150  with good tolerances and reasonable feed rate. 
       FIG. 10B  illustrates a sectional view of the node member of  FIG. 10A . As shown in  FIG. 10B , the node member  110  can provide a hole  162  for fastening an anvil  120  onto the main body  112  of the node member. The hole  162  can be opposite the weld surface  130 . The hole  162  can be threaded or otherwise facilitate coupling. 
       FIG. 10C  illustrates another sectional view of the node member of  FIG. 10A , with an extended tapered anvil attached with a fastener at the backside of the elliptical welding face. The hole  162  can receive the fastener  172  that couples the anvil  120  to the main body  112 . The fastener can be a threaded bolt, a PEM insert, a rivet, or another structure that couples the anvil  120  to the main body  112 . 
       FIG. 10D  illustrates another sectional view of an example of an extended tapered anvil attached with a fastener to the node at the backside of the elliptical welding face. As shown in  FIG. 10D , the strut  190  can be inserted about the anvil  120  and into the groove  150 . Welding can be performed along the weld surface  130  to form a weld nugget  180  that extends from the weld surface  130  at least to the annular groove  150  and the strut  190 . The anvil  120  can improve bending stiffness for the strut  190 , promote precision alignment, and enable an effective heat sink for welding. 
     To assist with the positioning of the strut in the annular groove, a positioning mechanism can be provided.  FIG. 11A  illustrates a perspective view of an example of a double spring-loaded tapered pin that engages a strut.  FIG. 11B  illustrates a sectional view of the double spring-loaded tapered pin of  FIG. 11A . As shown in  FIGS. 11A and 11B , a spring-loaded tapered pin  170  can extend at least partially into the groove  150 . The pin is biased to extend inwardly. When a strut is inserted into the groove  150 , the pin is allowed to retract until it engages the strut (e.g., by being inserted into a hole in the strut). The bias of the spring allows the pin to remain engaged with the strut to retain the strut within the groove  150  until the pin is otherwise disengaged. Other mechanisms are contemplated. For example, the pin can be electrically, magnetically, chemically, or otherwise actuated and unactuated. The spring-loaded tapered pin  170  can be singular or double and positioned on one or both sides of the strut to promote redundancy. The pin  170  can extend into a tapered hole on the extended tapered anvil  120 . The pin  170  can also be engaged using a light sensor and an electrically-actuated pin pusher/puller. 
     Node members can be positioned before the struts are connected.  FIG. 12  illustrates a perspective view of an example of a node alignment mechanism (e.g., tapered toggle pin) that holds the node in position against an assembly platform and prevents it from rotating out of position during fit up and welding. As shown in  FIG. 12 , the node members  110  can have a hole  188  (e.g., blind hole or through hole) for positioning onto a tapered guide on a fixed assembly platform  200 . The node member  110  can have more than one of the holes  188  for redundancy. In one embodiment, the node has a through hole and a square channel to accept a tapered toggle pin  214  with a swiveling latch  216 . The latch  216  can be tensioned or electrically-drive to remain in an upright position until the node member  110  has been slid over the pin  214  and comes into contact with the assembly platform  200 . The swivel latch  216  can then be pushed or actuated to a 90 degree position to hold node down and prevent it from swiveling. 
     In completion of a cylindrical antenna, the rim truss structure can be integrated with a mesh or mirrored reflecting element to communicate (e.g., with RF signals from Earth).  FIGS. 13A and 13B  illustrate perspective views of an example of rim truss structure integrated with tensegrity reflector assembly to enable large aperture RF antenna in a collapsed configuration ( FIG. 13A ) and an expanded configuration ( FIG. 13B ). As shown in  FIGS. 13A and 13B , a reflector element  186  (e.g., mesh) can utilize a tensegrity design that uses struts  190  (e.g., telescoping struts) and tension wires  218  to maintain a large aperture shape with moderate precision. At large diameters, the tensegrity elements interface with the cylindrical rim truss structure via mechanical and/or welded joints at the same nodes  110  used for making the rim truss structure  100 . The tension wires  218  can be adjusted using robotic arms and mechanisms after it has been joined to the rim truss structure  100 . 
     Such a design for satellite antennas allows the struts to be stowed inside one another.  FIG. 14  illustrates a perspective view of an example of strut/tubes shown stowed inside one of another for maximum packing efficiency. Longitudinal, batten, and diagonal struts of the truss structure  100  need not have the same diameter. The diameter can step down accordingly such that the strut portions  190   a ,  190   b , and  190   c  can be stowed for launch with minimal volume allocation, as shown in  FIG. 14 . 
     Traditional truss structures have plugged ends that provide threading for attachment and/or a solid plugged end for making mechanical connections or welds. Such a plugged end piece of one of these strut/tubes provides a heat sink for welding to a solid node and avoids the risk of “blowing through” the thin tube wall during welding. For example, a welding machine may apply too much energy and the energy source such as an electric arc, laser beam, or electron beam may melt through the weld interface into an open space and destroys weld continuity as well as the part. 
     In contrast, the struts  190  described herein can have open ends. The struts can define thin walls and still be welded to the node without risk of blowing through the wall. The node&#39;s internal anvil feature stiffens the inside diameter of the tube and avoids any gaps at the weld interface where the weld could blow through. 
     The struts of a tensegrity structure with a reflector element can be designed such that they do not have interference with tension cables and can be inserted into the annual groove of one of the existing nodes used for the ring truss structure.  FIG. 15A  illustrates a perspective view of an example of a ring truss node with diagonal fitting for a tensegrity strut end demonstrating that all strut ends can still be fit up and welded (2-dimensional) from the exterior position.  FIG. 15B  illustrates another perspective view of the ring truss node of  FIG. 15A . As shown in  FIGS. 15A and 15B , the node member  110  and the struts  190  can be assembled and welded in a manner that maintains high stiffness while the tensegrity structure still has freeplay/flexibility at its extents. The ends of the struts  190  can be inserted into the grooves  150  of the node members  110  at the diagonal location. All the tensegrity tube ends can be mechanically locked into the node using the techniques discussed herein. After all the node members  110  are assembled, the joints can be welded at the weld surfaces  130  to lock in the structural positioning and increase stiffness. 
     A parabolic antenna truss structure designs can also be provided with the node design described herein.  FIG. 16A  illustrates a perspective view of an example of a parabolic antenna truss structure design showing various strut and node connections designed for 2-dimensional welding from the exterior position.  FIG. 16B  illustrates another perspective view of the parabolic antenna truss structure design of  FIG. 16A . 
     As shown in  FIGS. 16A and 16B , node members  110   a  and  110   b  and struts  190  can be assembled to form a parabolic antenna truss structure  100 . Using a node-and-strut design to make the stiffened structure, the node and strut connections are mechanically assembled (e.g., using the robotic arms attached to a powered satellite). The struts  190  start connecting at a central hub node member  110   a  in the center of the parabolic dish and the additional rings or webs are connected all the way out to the desired perimeter of the dish with cross-member node members  110   b . The reflector element  186  can be a metallic mesh that has integrated stiffeners and/or attach points that will connect to holes/attach points on the nodes members  110   a  and  110   b . The parabolic dish shown can also be a mirror or segments of mirrors that attach at the nodes members  110   a  and  110   b  ( FIG. 16A ). 
       FIG. 17  illustrates a perspective view of an example of parabolic antenna truss nodes with hole features for both positioning the node for precision fit up and joining with struts. The nodes members  110   a  and  110   b  enable connecting of a larger diameter struts  190  closer to the central hub  110   a  to smaller diameters struts  190  moving towards the perimeter of the dish. The intermediate nodes  110   b  in the first ring can transition the largest radial strut to the next size smaller radial strut and so on until the full parabolic aperture diameter has been reached. This enables packs of struts to be stowed inside of one another for ideal packing efficiency, especially for spacecraft. Furthermore, the parabolic reflective element can be additively manufactured from node to node using a robot that travels along the “spider web” truss structure and spirals outwards to fabricate the entire dish. 
       FIG. 18  illustrates a perspective view of an example of parabolic antenna truss nodes showing a central hub node member. The hub node member  110   a  accepts the largest diameter strut/tube and will likely be the same dimension for each radial spoke. As shown in  FIG. 17 , struts can be inserted into annular grooves of the hub node member  110   a . The weld surfaces  130  are provided facing inwardly and in directions that converge at a work point. The hub node member  110   a  can include an attachment mechanism  220   a  for connecting the reflector element  186  (e.g., mesh) to the hub node member  110   a . The attachment mechanism  220   a  can include a hole for receiving a fastener or a fastener for engaging the reflector element  186  directly or indirectly. 
       FIGS. 19 and 20  illustrate perspective views of an example of an intermediate node enabling a larger strut diameter to connect to a smaller strut diameter going towards the dish perimeter. The intermediate node member  110   b  accepts the largest diameter strut/tube and will likely be the same dimension for each radial spoke. As shown in  FIG. 20 , struts  190  can be inserted into annular grooves of the node member  110   a . The weld surfaces  130  are provided facing inwardly and in directions that converge at a work point. The intermediate node member  110   b  can include an attachment mechanism  220   b  for connecting the reflector element  186  (e.g., mesh) to the intermediate node member  110   b . The attachment mechanism  220   b  can include a hole for receiving a fastener or a fastener for engaging the reflector element  186  directly or indirectly. 
     Even further concepts for truss structures can lead to sealed vessels that can be used as air-tight habitats or containment of pressured fuels/gases for fuel depots.  FIG. 21  illustrates a perspective view of an example of a geodesic space frame truss structure with node and strut design.  FIG. 22  illustrates a perspective view of an example of a geodesic space frame truss structure with cover panels seal-welded and joined to the nodes to create a hermetically sealed habitat or vessel. As shown in  FIG. 21 , the backbone for this type of structure can use node members  110  and struts  190 . As shown in  FIG. 22 , panels  184  can be attached to the supporting truss structure  100  such that all panels complete a hermetic seal. The approach can utilize familiar geodesic dome or sphere structures. 
       FIG. 23  illustrates a perspective view of an example of a recurring pentagonal node with panels fit up on top of a connecting bar that is supported by strut underneath, allowing the panel to be welded to the bars and nodes in the same 2-D path. As shown in  FIG. 23 , the geodesic vessel is comprised of hexagonal and pentagonal nodes where panels  184  are fit up with struts  190 , a machined connector bar, and node members  110  such that each individual panel  184  can be butt-lap welded in 2-dimensions along its perimeter. 
       FIG. 24A  illustrates a perspective view of an example of a central pentagonal node with recessed edges that allow for the panel to be butt-lap welded.  FIG. 24B  illustrates a sectional perspective view of the node of  FIG. 24A  with the connector bar installed on top of the strut as well as the panel fit up with the recess of the connector bar. As shown in  FIG. 24B , connector bars  230  are supported upon struts  190  and connect the struts  190  to the reflector element  186 . The connector bar  230  can be secured to the strut  190  and/or the node member  110  with a mechanical fastener, spring-loaded press-fit mechanism, etc. The panels  184  (e.g., triangular panels) can also have a small projecting feature at each of the tips that can be mechanically assembled with the node member  110  with a mechanical fastener, spring-loaded press-fit mechanism, etc. A robotic welding head will have sufficient 2-dimensional travel such that it can weld the perimeter of a single panel  184 . The robotic arms will continuously reposition the structure to add the required pieces and move the next panel  184  into position to be welded. For example, the connector bars  230 , the panels  184 , and the node members  110  can be welded together. Each portion of the corresponding weld can be in a two-dimensional plane, thereby avoiding complications of welding in three dimensions. Thus, the welding robot only requires a minimal operation window because it is welding a small quadrant at a time to make a very large structure. 
     In one or more of the designed illustrated herein, fluid cooling can be provided by a network of interconnected struts and node members.  FIG. 25A  illustrates a perspective view of an example of a hexagonal node with machined recess for 2-D butt-lap weld and through holes for conveying fluid. As shown in  FIG. 25A , the main body  112  of the node member can define openings  240  extending through the weld surfaces  130 . The struts  190  can also define lumens  194 . The lumens  194  of different struts can be in fluid communication with each other through the openings  240  of the main body  112 . 
     The network of sealed node members  110  and hollow struts  190  allow the structure to be actively or passively cooled using a variety of cooling fluids and techniques. The cooling feature is especially helpful for space structures since one such structure could provide a dual-purpose for enhanced in-space utility. Hence, the same truss structure used for an antenna or telescope could also be used to cool the structure down to prevent thermal distortion from the heat of the sun. Likewise, truss structures used to construct in-space habitats, fuel depots, or life-support systems could utilize the network of nodes and tubes for cooling and/or heating purposes. 
     The weld surfaces  130  (e.g., elliptical faces) of the node members can be provided with such lumens while still providing an area sufficient to perform a 2-D weld path and effectively join the struts  190  to the node member  110 . 
     In one or more of the designed illustrated herein, a cap member can be provided to an exterior face of a mode member.  FIG. 25B  illustrates a perspective view of an example of cap member installed flush with a node such that it can be welded around the perimeter. As shown in  FIG. 25B , a cap member  202  is provided over a portion of the node member  110 . In particular, the cap member  202  can enclose the interior region  116  shown in  FIG. 25A . As such, the fluid communication provided through the interior region  116  can be sealed so that fluid traveling therein is retained. The interior region  116  is thereby sealed from an external environment. 
     The cap member  202  can also provide more stiffness to the node member  110 . As the main body  112  defined the interior region  116  having an open space, less structural support is provided in this region. The cap member  202  stiffens the top end of the node member, which has more material removed than the bottom face. This increases stiffness while also creating a hermetically sealed network of nodes and tubes that is adequate for passing fluids through. 
       FIG. 26  illustrates a perspective view of an example of a cap member with gusset  204  features to increase stiffness at top of node. The gusset  204  can fit within the interior region of the main body of the node member. 
       FIG. 27  illustrates a perspective view of an example of a cap member with a fitting  206 . The fitting can engage and/or be engaged by the main body  112  of the node member  110 . Secure engagement and sealing can be accomplished by the interaction of the fitting  206  and the node member  110 . 
     Referring now to  FIGS. 28 and 29 , a prismatic truss structure can be formed by the assembly of node members and struts.  FIG. 28  illustrates a perspective view of an example of a prismatic truss structure segment showing three different strut lengths and diameters, but all utilizing the same node in six locations. As shown in  FIG. 28 , the prismatic truss structure  100  is formed with a single prism segment that can be repeated and reconfigured in a variety of different structural shapes. This structure can utilize struts  190  of different diameter and lengths, but still connect to the same node member  110  on each corner of the prism. This is ideal for spacecraft payload scenario because the tubes can still be stowed within each other in small packing volume while the nodes can also pack efficiently where only a single node design is needed to make the repeated truss segments. 
     The prismatic truss structure  100  of  FIG. 28  can be assembled with the node configuration illustrated in  FIG. 29 .  FIG. 29  illustrates a perspective view of an example of a prismatic truss structure node with branches to accept strut ends at each location with a precise annular groove and 2-D welding face that is accessible from the exterior position. As shown in  FIG. 29 , a node member  110  for a truss structure can include a main body  112 . Struts can be inserted into annular grooves  150  of the node member  110 . Each annular groove  150  can extend from a periphery of the main body  112  inwardly toward an interior region of the main body  112 . At least some of the weld surfaces  130  are provided facing inwardly and in directions that converge at a work point. Other weld surfaces  130  can be provided facing in directions that converge at a second work point. Nonetheless, the work points can still facilitate alignment for a weld tool operating on corresponding weld surfaces  130 . 
     Referring now to  FIGS. 30A-30C , one or more of the embodiments described herein can employ struts  190  that extend along a longitudinal axis and have a terminal end  192 . Along the length, the struts  190  can be cylindrical with a circular cross-section. At the terminal ends  192 , the struts  190  can provide a surface at an angle such that the end face is elliptical. The angle can be with respect to the longitudinal axis of the strut  190 . The angle can be between 30 and 60 degrees, for example 45 degrees. The elliptical face is inserted into the annular groove of the node member and mates up with an elliptical face at the interior end thereof. Opposite this end is the weld surface. In some embodiments, it might beneficial to use an elliptical tube where the angled cut end face becomes circular. The tube ends can be inserted into an elliptical internal anvil of the node and mate up with a circular face. Thus, the face of node at the interface of the tube will be circular and the weld path can also be circular. This allows more area on the node for fitting in circular cutouts instead of elliptical and an array of elliptical tubes has better packing efficiency than circular tubes. This could make the weld path and programming easier and enables other welding processes to be used such as resistance stud welding, friction stud welding, friction push plug welding, or deformation resistance welding. 
     The struts described herein can be a single material or multi-material as long as the material on the end of the tubes can be joined via welding. The multi-material struts/tubes have the advantage of having neutral Coefficient of Thermal Expansion (CTE) that is highly desirable for precision space structures because of the large variation in temperature in space. 
     Referring now to  FIGS. 31A and 31B , the structures described herein can be assembled by an automated process. The features of the disclosed structures and methods can benefit from an in-space assembled and welded cylindrical rim truss and a tensegrity deployable element to manufacture a functional antenna in space where all the materials required can fit into a minimal payload volume. 
     The components required for assembly can be stored and transported within a mobile unit  208  having thrust capabilities and assembly mechanisms. As shown in  FIG. 31A , the mobile unit  208  can assemble a truss structure  100  that serves as structural support for an antenna. The truss structure  100  can include node members  110  and struts  190  that are deployed and welded together as described herein by a welding tool  300  of the mobile unit  208 . A reflector element  186  can be provided and supported by the truss structure  100 . 
     As shown in  FIG. 31B , other structures can be assembled, such as a prismatic truss structure. These additional structures can be assembled by the same methods and by the same mobile unit. Thus, the versatility of this design allows another form of the structure (e.g., prismatic truss structure) to be utilized on the base structure (e.g., antenna support) to complete the functional antenna by integrating a prismatic truss structure to position the subreflector element  186 . The additional components  212  shown on the prismatic truss structure are microsatellites or cubesats that fly as ride shares on the secondary payload adapter. 
     Accordingly, the designs disclosed herein provide an ability to build structures in space more efficiently to enable capability growth and capability preservation of various space-based functions such as human exploration, scientific discovery, and satellite operations. The structures can be stored in a compact payload and assembled in space. Alignment mechanisms to facilitate automated assembly are provided to produce strong and durable truss structures that can be assembled in space. 
     A reference to an element in the singular is not intended to mean one and only one unless specifically so stated, but rather one or more. For example, “a” module may refer to one or more modules. An element proceeded by “a,” “an,” “the,” or “said” does not, without further constraints, preclude the existence of additional same elements. 
     Headings and subheadings, if any, are used for convenience only and do not limit the invention. The word exemplary is used to mean serving as an example or illustration. To the extent that the term include, have, or the like is used, such term is intended to be inclusive in a manner similar to the term comprise as comprise is interpreted when employed as a transitional word in a claim. Relational terms such as first and second and the like may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. 
     Phrases such as an aspect, the aspect, another aspect, some aspects, one or more aspects, an implementation, the implementation, another implementation, some implementations, one or more implementations, an embodiment, the embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, the configuration, another configuration, some configurations, one or more configurations, the subject technology, the disclosure, the present disclosure, other variations thereof and alike are for convenience and do not imply that a disclosure relating to such phrase(s) is essential to the subject technology or that such disclosure applies to all configurations of the subject technology. A disclosure relating to such phrase(s) may apply to all configurations, or one or more configurations. A disclosure relating to such phrase(s) may provide one or more examples. A phrase such as an aspect or some aspects may refer to one or more aspects and vice versa, and this applies similarly to other foregoing phrases. 
     A phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list. The phrase “at least one of” does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, each of the phrases “at least one of A, B, and C” or “at least one of A, B, or C” refers to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C. 
     It is understood that the specific order or hierarchy of steps, operations, or processes disclosed is an illustration of exemplary approaches. Unless explicitly stated otherwise, it is understood that the specific order or hierarchy of steps, operations, or processes may be performed in different order. Some of the steps, operations, or processes may be performed simultaneously. The accompanying method claims, if any, present elements of the various steps, operations or processes in a sample order, and are not meant to be limited to the specific order or hierarchy presented. These may be performed in serial, linearly, in parallel or in different order. It should be understood that the described instructions, operations, and systems can generally be integrated together in a single software/hardware product or packaged into multiple software/hardware products. 
     In one aspect, a term coupled or the like may refer to being directly coupled. In another aspect, a term coupled or the like may refer to being indirectly coupled. 
     Terms such as top, bottom, front, rear, side, horizontal, vertical, and the like refer to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference. Thus, such a term may extend upwardly, downwardly, diagonally, or horizontally in a gravitational frame of reference. 
     The disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject technology. The disclosure provides various examples of the subject technology, and the subject technology is not limited to these examples. Various modifications to these aspects will be readily apparent to those skilled in the art, and the principles described herein may be applied to other aspects. 
     All structural and functional equivalents to the elements of the various aspects described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for”. 
     The title, background, brief description of the drawings, abstract, and drawings are hereby incorporated into the disclosure and are provided as illustrative examples of the disclosure, not as restrictive descriptions. It is submitted with the understanding that they will not be used to limit the scope or meaning of the claims. In addition, in the detailed description, it can be seen that the description provides illustrative examples and the various features are grouped together in various implementations for the purpose of streamlining the disclosure. The method of disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, as the claims reflect, inventive subject matter lies in less than all features of a single disclosed configuration or operation. The claims are hereby incorporated into the detailed description, with each claim standing on its own as a separately claimed subject matter.