Liquid Crystal Optical Device for Spacecraft Attitude Control
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Solution Overview
Problem
Solar sails with optical devices struggle to perform attitude control that requires radiation pressure components along the light-receiving surface, such as rotation about an axis orthogonal to the sail, due to the lack of directional pressure from sunlight, and adding structures like reflecting mirrors increases weight and power consumption.
Innovation Solution
A sheet-like optical device with a liquid crystal layer and prism surfaces that can selectively change the orientation of light's optical path, allowing for adjustable radiation pressure components in both reflective and transmissive configurations, enabling precise attitude control without increasing weight or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a three-dimensional structure such as a reflecting mirror capable of adjusting an angle is provided, then it is possible to receive, from the sunlight, a radiation pressure having a component of a direction along the light-receiving surface of the sail, but the weight increases, and thus the consumption of fuel or electric power increases
Solution Approach 1:
The patent replaces mechanical three-dimensional reflecting mirror structures with a two-dimensional sheet-like optical device comprising a liquid crystal layer and patterned reflective regions. The liquid crystal layer, when subjected to electric fields, changes its optical properties to redirect sunlight and generate radiation pressure components along the light-receiving surface without requiring bulky mechanical adjustment mechanisms or heavy mirror structures.
Solution Approach 2:
The patent utilizes the ability of liquid crystal materials to change their optical parameters (refractive index, orientation) in response to applied electric fields. By controlling the orientation of liquid crystal molecules through electric fields, the device can dynamically adjust the direction of reflected sunlight and the resulting radiation pressure components, enabling attitude control without mechanical movement or structural changes.
2Force
If a three-dimensional structure such as a reflecting mirror capable of adjusting an angle is provided, then it is possible to receive, from the sunlight, a radiation pressure having a component of a direction along the light-receiving surface of the sail, but the consumption of fuel or electric power increases
Solution Approach 1:
The patent replaces mechanical three-dimensional reflecting mirror structures with a two-dimensional sheet-like optical device comprising a liquid crystal layer and patterned reflective regions. The liquid crystal layer, when subjected to electric fields, changes its optical properties to redirect sunlight and generate radiation pressure components along the light-receiving surface without requiring bulky mechanical adjustment mechanisms or heavy mirror structures.
Solution Approach 2:
The patent utilizes the ability of liquid crystal materials to change their optical parameters (refractive index, orientation) in response to applied electric fields. By controlling the orientation of liquid crystal molecules through electric fields, the device can dynamically adjust the direction of reflected sunlight and the resulting radiation pressure components, enabling attitude control without mechanical movement or structural changes.
3Ease of operation
If optical devices are arranged along the outer edge of a light-receiving surface to perform attitude control, then the orientation of the sail can be optionally changed, but the radiation pressure received from sunlight does not include a component of a direction along the light-receiving surface of the sail
Solution Approach 1:
The patent divides the light-receiving surface into multiple independent control regions, each containing patterned reflective regions and liquid crystal layers. By independently controlling the liquid crystal orientation in each segment, the device can generate differential radiation pressure components across different areas of the sail, enabling precise attitude control with rotational moments about axes parallel to the light-receiving surface.
Solution Approach 2:
The patent transitions from edge-based optical devices to a two-dimensional distributed array of reflective regions across the sail surface. This dimensional expansion allows radiation pressure components to be generated not only at the edges but throughout the entire light-receiving surface, creating force couples and moments that enable rotation about axes parallel to the sail surface.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and fuel-free attitude control of spacecraft by selectively altering the radiation pressure components received from sunlight, allowing for rotation about optional axes without the need for additional structural weight or increased power consumption.
Implementation Method 1
a liquid crystal layer (50) disposed between the first sheet and the second sheet
Implementation Method 2
at least one of the first base material (10) and the second base material (20) is a second sheet including a prism surface (60) formed along an XY-plane
Implementation Method 3
a prism surface (60) formed along the XY-plane; reflecting or refracting light incident on the optical device (1) in the Z-axis direction
Implementation Method 4
the radiation pressure received from sunlight; Each optical device can electrically change the magnitude of the radiation pressure received from the sunlight
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
[Object] To provide a sheet-like optical device capable of selectively emitting light whose optical path has a changed orientation. [Solving Means] An optical device includes a first sheet and a second sheet. The first sheet is configured to be electrically switchable between a first state in which the first sheet extends along an in-plane direction orthogonal to a thickness direction and has transparency in the thickness direction, and a second state in which the first sheet has lower transparency in the thickness direction than the transparency in the first state. The second sheet has a prism surface on which an inclined surface inclined with respect to the in-plane direction is arranged along the in-plane direction, the second sheet facing the first sheet in the thickness direction.