A report proposes a high-temperature- resistant solar sail with an areal mass density less than 1 g/m2, for a spacecraft that would approach the Sun to within a distance of 0.2 astronomical unit (≈3 × 107 km). The sail would be made in multiple segments of a carbon microtruss fabric held in a network of tensioned lines. The segments and network would be designed to minimize tension in the fabric. The porosity of the fabric would be tailored so that to photons, the fabric would behave as though it were solid. Reflective metal surface films could be attached to the fabric. In advanced versions, the fabric could be directly coated with metal, or, alternatively, the fabric surface would be the sail surface and there would be no metal layer. The sail fabric would be wrapped around a sail cylinder and deployed by use of centrifugal force. A separate structure next to the sail cylinder would contain most of the deployment hardware and would be ejected after deployment of the sail to reduce the mass staying with the sail.
This work was done by Charles Garner, Stephanie Leifer, Timothy Knowles, and William Layman of Caltech for NASA’s Jet Propulsion Laboratory.
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Lightweight Solar Sail for a Spacecraft Flying Near the Sun
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Overview
The document presents a technical report on a lightweight solar sail designed for spacecraft operating near the Sun, developed by researchers at NASA's Jet Propulsion Laboratory (JPL). The primary goal of this project is to create a solar sail with an areal mass density of less than 1 gram per square meter, enabling spacecraft to approach the Sun to within 0.2 astronomical units (approximately 30 million kilometers).
The sail is constructed from a carbon microtruss fabric, which is notable for its controlled porosity. This porosity allows the fabric to behave as a solid to photons, enhancing its effectiveness as a reflective surface. The design incorporates reflective metal films, which can either be directly deposited onto the fabric or omitted entirely, allowing the carbon fabric itself to serve as the sail surface. This innovative approach enables the sail to withstand high temperatures, facilitating closer proximity to the Sun without overheating.
The deployment mechanism of the sail is engineered to minimize the mass that remains attached to the sail after deployment. The fabric is wrapped around a sail cylinder and deployed using centrifugal force. Most of the deployment hardware is housed in a separate structure that is ejected after the sail is deployed, ensuring that the sail remains as lightweight as possible.
The report outlines several key innovations that distinguish this solar sail design from previous technologies. These include the use of carbon microtruss fabric, the metallization of the fabric, the tailored porosity, and the segmented configuration that reduces tension loads during deployment. The design also emphasizes the importance of minimizing external tension on the sail, which is crucial for maintaining its structural integrity during operation.
Overall, this solar sail technology represents a significant advancement in the field of space exploration, particularly for missions aimed at studying the Sun and traveling to distant destinations within our solar system. The work was conducted by a team of researchers, including Charles Garner, Stephanie Leifer, Timothy Knowles, and William Layman, and is part of ongoing efforts to enhance the capabilities of solar sails for future space missions.
