Dimensionally Stable Structural Space Cable

Jet Propulsion Laboratory (JPL) is involved in an ongoing effort to design and demonstrate a full-scale (30-32m diameter) Starshade engineering demonstrator that meets the aggressive deployment dimensional repeatability and stability requirements for exoplanet detection. A key component of the Starshade structural system is a series of dimensionally stable composite cables (or spokes) that connect the center structural hub to the perimeter truss and largely determine the deployed shape and stiffness of the system much like a bicycle wheel. There are many challenges in developing the Starshade spoke. Perhaps most notable is that meeting the CTE requirement necessitates accurate control of fiber volume fraction (resin content) to less than 1%. Also challenging is that meeting the stiffness precision goal of less than 0.5% variation between cables demands that minimal fiber fraying and damage be allowed during the tow spreading and alignment process and that the net cross section be made in one step with no required post-processing. Furthermore, meeting the length precision goal requires uncommon assembly and end fitting bonding methodologies. Finally, there are challenges associated with integrating such high-performance cables into the Starshade while ensuring snag-free deployment and proper on-orbit operation. The DS3 Cable technology addresses all of these challenges with a highly tailorable thermoplastic-tape design that uses Dual Resin Bonding technology for strength and dimensional stability at the end fittings.