Dayside-Only Roll Steering for Spacecraft Attitude Control
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Solution Overview
Problem
Existing spacecraft yaw steering techniques preclude efficient thruster use for orbit modifications due to thruster rotation away from the velocity vector, limiting maneuvers like air drag compensation and formation flying, especially in low Earth orbit.
Innovation Solution
Implementing dayside-only roll steering, where the spacecraft rotates about its orbital motion axis to align solar arrays with the sun only when not in eclipse, allowing thruster use during eclipses and reducing solar array power inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If yaw steering is used to position solar arrays toward the sun, then solar array power efficiency is improved, but thruster use for orbit modifications is precluded
Solution Approach 1:
The patent segments the steering operation into two distinct modes: yaw steering for solar array positioning and roll steering for orbit modification. By separating these functions into different rotational modes, the system can selectively apply yaw steering only when solar array positioning is needed, while using roll steering for thruster-based maneuvers, thus resolving the conflict between power efficiency and maneuver capability
Solution Approach 2:
The patent implements dynamic switching between yaw and roll steering modes based on operational requirements. The control system dynamically selects the appropriate steering mode: yaw steering when solar array positioning is prioritized, and roll steering when thruster maneuvers are needed, allowing the system to adapt its behavior to current mission needs
2Use of energy by moving object
If continuous roll steering is applied to align solar arrays with the sun, then power efficiency is improved, but momentum storage requirements and attitude control hardware complexity increase
Solution Approach 1:
The patent applies roll steering selectively only during the dayside portion of the orbit when solar array alignment provides benefit, rather than continuously throughout the entire orbit. This localized application of roll steering reduces the cumulative rotational demand on momentum storage devices and simplifies attitude control hardware while maintaining power efficiency during the periods when it is most valuable
3Adaptability or versatility
If roll steering is used to enable thruster maneuvers, then maneuver versatility is improved, but solar array alignment precision during eclipse transitions may deteriorate
Solution Approach 1:
The patent implements periodic switching between yaw and roll steering modes based on the spacecraft's orbital position and eclipse state. Yaw steering is applied during periods when solar array alignment is critical, while roll steering is applied during eclipse transitions when alignment precision is less critical but maneuver capability is needed, creating a rhythmic pattern of mode switching that balances both requirements
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
Enhances power efficiency, enables thruster use for maneuvers like air drag compensation and formation flying, minimizes spacecraft rotation and momentum storage requirements, and simplifies attitude control hardware.
Implementation Method 1
Spacecraft use solar arrays to harness the power of the sun to sustain operability for long periods of time in space
Implementation Method 2
a reflected component of the solar radiation pressure to selectively apply a force to the spacecraft that translates or alters the position of the spacecraft in orbit
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A method of roll steering of a spacecraft to align an aspect of the spacecraft, such as the surface of solar arrays carried by the spacecraft, to the sun, is described. The roll steering occurs only when the sun is at an angle relative to the orbital plane of the spacecraft and when the spacecraft is not eclipsed by a body it is orbiting. A spacecraft may include a controller which causes an attitude control subsystem to steer the spacecraft about a roll axis to position the surface of the solar array such that an axis normal to the surface of the solar array is aligned with the direction to a sun when the sun is visible to the spacecraft, and maintain a fixed orientation of the spacecraft about the roll axis when the sun is not visible to the spacecraft.