Controllable liquid crystal diffractive sail and its potential applications

This paper introduces a new type of diffractive solar sail composed of liquid crystal optical phased arrays, which control the thrust through electric modulation. The main feature of the proposed liquid crystal diffractive sail is its capability of generating a continuously variable and actively controllable tangential radiation pressure at the sun-facing attitude. The principles governing the generation of radiation pressure by electric modulation of the liquid crystal optical phased array under a broad spectrum of solar radiation are derived by considering a periodical voltage distribution analogous to a reflection step-shaped binary phase grating. Then the reliability of the theoretical model of radiation pressure is verified through comparison with finite-difference time-domain (FDTD) simulation results. A sun-facing liquid crystal diffractive sail may be utilized to replace the reflective sail in space missions by taking the advantage that no active attitude control of the sail surface towards sunlight is required. We also study the attitude control strategy of the proposed diffractive sail along its normal axis, allowing for the direction of tangential radiation pressure to be varied without changing its sun-facing attitude.