A report discusses a proposed nesting-hoop solar sail that would be used to propel a spacecraft on a deep-space mission. The nesting-hoop design concept was chosen as one that would afford a desired combination of small mass and compact stowage during launch. The sail would include multiple disks, each comprising a thin fabric stretched over a hoop of wire or thin tubing (e.g., hypodermic-needle tubing). The adjacent hoops would be bonded together by springy extensions that would be fabricated in their sail-deployed positions. The sail would be stowed by folding at the springy extensions. Successive hoops would be progressively slightly smaller so that when stowed, the hoops would nest and therefore the thickness of the stowed sail would be approximately proportional to the thickness of the fabric (instead of the much greater thickness of the hoops). The fabric would not be folded for stowage; consequently, the spring tension (and thus the required thickness of the hoops) needed to keep the fabric from wrinkling could be kept to a minimum. The sail would be deployed by allowing it to unfold under its own springiness.

This work was done by Brian Wilcox of Caltech for NASA's Jet Propulsion Laboratory . To obtain a copy of the report, "Nesting-Hoop Solar Sail," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Materials category. NPO-20879