Deployable Composite Boom

The SHEARLESS composite boom has a rollable structure with a large moment of inertia per unit of stored height that does not suffer from shear-derived problems. The boom is fabricated from joining two independent tape-springs front-to-front with the use of a durable seamless polymer sleeve. This sleeve allows the two parts to slide past each other during the coiling/deployment process so as to minimize shear and its derived problems. The innovation enables a lightweight structure that can be stowed on a reel without appreciable shear stresses developing in its constitutive composite parts, allowing for unprecedentedly small coiling diameters for the total thickness of the structure. As demonstrated, through specific laminate design of the two inner composite parts, the SHEARLESS composite boom can also be fabricated with a special inherent feature, bi-stability, which enables designs with minimal mechanisms and aids in deployment controllability and reliability.

Deployable composite booms are particularly attractive in space constrained applications. Their high packaging volume efficiency enables relatively large spacecraft systems required for power generation, communications, or propulsion to be housed within small volumes. COROTUB is a monolithic closed-section tubular thin-shelled structure thats been shown to scale efficiently up to 50m yet maintain its strength. COROTUBs two corrugated thin shells form a closed section, which yields high bending and torsional stiffness, allowing for high dimensional stability. Computational analysis and early tests show that the corrugation provides increased strength against buckling, enabling longer booms and targeting more demanding structural applications than non-corrugated designs. The corrugation geometry that dictates the boom cross-section shape was informed by parametric studies to optimize the parameters that most influence the cross-sections area moment of inertia and torsional constant. The corrugated designs were found to improve the boom bending and axial strength and to shorten the length of the boom transition from flat/rolled to deployed.

The Multi-Link Spherical Joint developed at NASA Johnson Space Center provides a substantial improvement over typical joints in which only two linearly actuated links move independently from one another. It was determined that the rotation point of a trussed link needed to be collocated at a shared point in space for maximum articulation. If not allowed separate rotation, the line of action through a universal joint and hinge acts effectively as another linkage. This leads to a much more complex and uncontrollable structure, especially when considering multiple dimensions. Comprising the Multi-Link Spherical Joint, a spherical shell encases the cupped ends of each six possible attachments and allows each of those attachments to be independently controlled and rotated without inhibiting the motion of the others. To do this, each link is precisely limited to 15 degrees of rotation off the link centerline, thus allowing a total of 30 degrees of rotation for each link. The shell-and-cup structure can handle the loads of linear actuators that may be used to control and vary the geometry of a truss system utilizing the new joint technology. The calculated operating load that the truss system must handle can be used to scale the size of the joint, further allowing customization of any potential truss system. Additionally, the incorporated linear actuators can be controlled and powered by wiring routed through the joint without putting undo stress on the wires during operation. Accordingly, this innovative joint technology enables more efficient deployment and precise operation of articulating structures. The Multi-Link Spherical Joint is at technology readiness level (TRL) 4 (component and/or breadboard validation in laboratory environment) and is available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.

This technology is a joint connector for application between two or more tubular parts, or to connect one or more tubular parts to a fixed structure. This attachment technology is more structurally efficient and reduces failure characteristics due to the uniformity of composite material across the joint. In comparison to a typical joint, this technology reduces weight while minimizing stress variations that lead to structural failure. Moreover, typical joints must be bonded or screwed together, which further reduces efficiency. The invented technology, however, is designed so that it is both bonded and mechanically locked by design rather than relying on separate mechanical fasteners. The result is a design that mitigates failure of a structural joint.

Formation of the inventive polymer composite matrix begins by growing carbon nanotubes directly on a veil substrate. The carbon nanotubes are grown from both sides of a non woven carbon fiber mat. The carbon nanotubes can be single or multi walled and can be grown to predetermined lengths. The veiled substrate is positioned between carbon fiber/ polymer prepreg layers such that the carbon nanotubes protrude into the reinforcement layers. The polymer composite matrix formed following curing of the resin exhibits improved interlaminar strength, fracture toughness and impact resistance. Because of the thinness of the veil layer, electricity can pass from conductive carbon nanotubes on one side of the veil to conductive carbon nanotubes on the other side of the veil. Electricity can also pass between two veils intercalated into the same reinforcement layer when the length of the nanotubes is sufficiently long enough to provide overlap within the reinforcement layers.