Gradient-index Solar Sail and its Optimal Orbital Control

TL;DR

This paper introduces a gradient-index solar sail designed using transformation optics and metamaterials, achieving high efficiency in generating tangential radiation pressure for improved orbital control of sailcraft.

Contribution

It presents the concept, design, and performance evaluation of a novel gradient-index solar sail utilizing metamaterials and transformation optics for enhanced orbital maneuverability.

Findings

Achieved 90.5% efficiency in tangential radiation pressure generation.

Demonstrated full orbital control by adjusting sail attitude around the sun-sail axis.

Validated the design through ray tracing simulations across the solar spectrum.

Abstract

Solar sails with the capability of generating a tangential radiation pressure at the sun-pointing attitude, such as refractive sails can provide more efficient methods for attitude and orbital control of sailcraft. This paper presents the concept of gradient-index sail as an advanced class of refractive sail, which operates by guiding the solar radiation through a structure made of graded refractive index material. The design of the sail's refractive index distribution is performed by transformation optics, and the resultant index realized by the effective refractive index of non-resonant bulk metamaterials made of silica. The performance of the sail was evaluated by using ray tracing for a broad spectrum of solar radiation under the normal incidence angle, which showed an efficiency of 90.5% for generation of a tangential radiation pressure. We also studied the orbital control of the tangential-radiation-pressure-generating sails, and showed that the full orbital control, including the modification of orbital axes, eccentricity, and inclination can be applied by changing the attitude of the sail merely around the sun-sail axis, while the sail keeps the sun-pointing attitude at every point of the orbit.