Development of Compact Mechanically Driven Systems for High Strain Composite Slit-Tubes

摘要

Since the pioneering days of space exploration, large deployable structures have played an important rolernin expanding satellite capability and performance. Perhaps one of the more prominent and simplisticrnbuilding blocks of deployable structures is the rollable slit-tube boom, or a “Storable Tubular ExtendiblernMember” [1,2]. This device functions in a mechanically similar fashion to a tape measure where a longrnmetallic cross-section is rolled into a coil, providing a high packaging efficiency and the ability to deploy tornvarious lengths. This technology has been commonly employed in space for 50+ years due to the simplernnature of the design and the limited number of mechanical components required to deploy in orbit.rnMoreover, the industry has long known and applied a wealth of lessons learned from early flights of thesernsimple devices [2]. Examples include using the slit-tube as a standalone structure to offset sensors orrncameras from a spacecraft body to more fully integrated systems such as the primary drive mechanismsrnfor telescoping booms used to deploy the sunshade on the James Webb Space Telescope. Despite thernextensive use, this technology is limited when the deployable structure requires high precision or isrnsubjected to large structural loads. For these cases a complex set of mechanisms consisting of rollers,rnguides, and bearings to unravel the metallic slit-tube becomes necessary in order to contain its considerablernstored strain energy in the coil and properly manage its deployment. Conversely, the use of High StrainrnComposite (HSC) slit-tubes [3,4,5] can allow greatly increased boom strength and stability.rnRoccor LLC, based in Louisville, Colorado is currently developing a series of HSC slit-tube deployers thatrntake advantage of the non-isotropic material properties HSC materials to reduce their stored energy.rnSpecifically, Roccor is developing HSC slit-tube laminates composed of traditional space-qualifiedrnmaterials, which are highly structural in the extended configuration but also have a relatively low storedrnstrain energy in the stowed configuration. As a result, the need for a complex set of rollers and constraintsrnon the coil are eliminated and the deployment device volume is reduced. In addition, these laminatesrnprovide near zero coefficient of thermal expansion (CTE) and/or the opportunity to embed internalrnconductors, which can act as an RF element or to transfer power/data without a standalone harness. ThernRoccor team has developed a series of integrated HSC slit-tube boom deployer systems that vary in size,rnperformance and application. In this paper, a design review of four selected systems is outlined with a focusrnon the mechanical components enabling deployment/retraction while also ensuring structural rigidity. Inrnaddition, the best practices for ensuring adequate boundary conditions are also identified.