A sister to SHEARLESS booms, the Bistable Collapsible Tubular Mast (Bi-CTM) boom offers compact storage on a cylindrical drum that deploys a composite material boom with a closed tubular cross-section that has unmatched bending and torsional stiffness for the mass of the thin-shell structure. The Bi-CTM is also scalable for long booms, given the load-carrying capacity.

A cylindrical drum deploys a composite material boom with a closed tubular cross-section. (Image: NASA)

The Bi-CTM’s two omega-shaped composite thin shells form a bonded closed section that can spool onto a relatively compact drum for compact launch packaging and provide unparalleled stiffness-to-mass ratio when deployed. When using the booms as beam-column structures with a primarily compressive load component, this ratio determines the structural mass efficiency of the components, making the Bi-CTM exceptional for lightweight deployable structural rigging with higher load demands. The improved dimensional and thermal stability offered by the closed-section shape and low coefficient of thermal expansion materials of the Bi-CTM enables the use of the boom technology in precision applications that require high stability in harsh environments.

Just like a kid’s “slap bracelet,” the Bi-CTM design includes a secondary, stable, low-energy state aside from the rigid deployed state. The result is that the Bi-CTM is not under high-spring stress when coiled up, which simplifies the stowage process as well as enabling a more controllable extension of the boom. The simplified stowage process enables reduced size, mass, and complexity of the storage and deployment mechanism system.

Compared to the majority of deployable thin-shell booms — which have at best a semi-open cross-section — this true closed cross-section boom is stronger while keeping the compact nature of rollable booms and is able to overcome both bend and twist buckling-related limitations. Using omega-shaped cross-sections with optionally circular, parabolic, or ellipsoidal segments — where each half of these thin-shell composite booms can use equal (symmetric boom) or different (asymmetric boom) cross-section geometry and/or composite laminates — offers a great deal of boom customization in terms of stable coiled diameter and structural properties.

NASA is actively seeking licensees to commercialize this technology. Please contact NASA’s Licensing Concierge at This email address is being protected from spambots. You need JavaScript enabled to view it. or call us at 202-358-7432 to initiate licensing discussions. Follow this link here  for more information.