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
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Nesting-Hoop Solar Sail
(reference NPO-20879) is currently available for download from the TSP library.
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Overview
The document discusses the innovative concept of the Nesting-Hoop Solar Sail, developed by Brian H. Wilcox at NASA's Jet Propulsion Laboratory (JPL). This design addresses historical challenges associated with solar sails used for deep-space propulsion, particularly the need for lightweight structures and efficient deployment mechanisms.
The Nesting-Hoop Solar Sail consists of a large array of hoops made from fine wires or tubes, over which a light sail material is bonded. The key innovation lies in the nesting design of the hoops, which allows them to fit inside one another, significantly reducing the overall thickness of the sail when packed for launch. For instance, a sail with a diameter of 25 meters could contain approximately 4000 hoops, stacking to only about 5 centimeters thick. This nesting approach eliminates the need for heavy compressive frames that have traditionally been required to maintain tension and prevent wrinkling in the sail material.
The document highlights the advantages of this design, particularly in terms of deployment. Each hoop is pre-deployed, meaning that the tension required to keep the sail flat is much less than that needed to pull it flat from a folded state. This results in a lighter system mass, which enhances the overall performance of the solar sail. The deployment mechanism is designed to allow the sail to unfold smoothly, either in a "jellyroll" or "accordion" fashion, ensuring that the sail remains taut and wrinkle-free.
The document also mentions the potential application of a 64x64 array of 4096 hoops, which would be suitable for a nanorover-based solar sail mission. This configuration would allow for efficient packing and deployment, with fronds of hoops deployed at right angles to a central spine.
In summary, the Nesting-Hoop Solar Sail represents a significant advancement in solar sail technology, offering a lightweight, compact, and efficient solution for deep-space propulsion. The design's innovative nesting mechanism and deployment strategy address previous challenges, paving the way for future exploration missions. The work is part of ongoing research at JPL under NASA's auspices, aiming to enhance the capabilities of solar sails in interplanetary travel.
