Satellite Formation Control Using Drag Flaps Without Propellant
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Solution Overview
Problem
Existing methods for maintaining satellite formations in co-planar orbits rely on expendable-mass propulsion systems, which are costly and complex, especially for micro- and nano-satellites with space and mass constraints, and are not suitable for satellites with asymmetric antenna patterns.
Innovation Solution
The use of standard drag flaps to increase the cross-sectional area of satellites in the direction of motion, allowing for the maintenance of a single orientation and enabling the use of asymmetric antenna patterns, with control methods that do not rely on linearized equations of motion, enabling formation establishment and maintenance without propellant-fueled thrusters or expendable mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expendable-mass propulsion systems are used to maintain satellite formations, then formation maintenance capability is achieved, but spacecraft mass, cost, and complexity increase
Solution Approach 1:
The patent extracts and eliminates the expendable mass propulsion system from the spacecraft, replacing it with a passive differential drag mechanism that uses the spacecraft's own cross-sectional area variations to achieve formation maintenance without carrying propellant
Solution Approach 2:
The formation maintenance system serves itself by utilizing the spacecraft's inherent geometric properties (cross-sectional area) and the natural atmospheric drag force to achieve relative positioning control, eliminating the need for external propulsion systems
2Reliability
If expendable-mass propulsion systems are used to maintain satellite formations, then formation maintenance capability is achieved, but device complexity increases
Solution Approach 1:
The patent removes the complex propulsion system (engines, tanks, control mechanisms) and replaces it with a simple geometric control mechanism involving drag flaps or solar panel orientation adjustments
Solution Approach 2:
The patent replaces the mechanical propulsion system with a control mechanism that adjusts the spacecraft's geometric properties (cross-sectional area) to interact with atmospheric drag forces, eliminating the need for chemical or electrical propulsion hardware
3Reliability
If attitude control is used to increase cross-sectional area for differential drag, then formation maintenance is enabled, but directional fixation is lost
Solution Approach 1:
The patent segments the spacecraft's surface area control into independent adjustable elements (drag flaps, solar panel orientations) that can be modified without affecting the spacecraft's overall attitude or directional fixation
Solution Approach 2:
The patent applies local modifications to the spacecraft's geometry (adjusting specific drag flaps or solar panel orientations) to change the cross-sectional area in the direction of motion while maintaining the spacecraft's overall directional stability and antenna orientation
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
This approach allows for the establishment and maintenance of global satellite formations using naturally occurring forces, reducing costs and complexity, and is applicable for large separation distances and non-circular orbits, including scenarios with satellite failures.
Implementation Method 1
Atmospheric drag is typically a dominant perturbing force for spacecraft in Low Earth Orbit ('LEO'). The acceleration due to atmospheric drag is given by the following equation: a = -(p*V*A*CD)/(2*M)
Data Source
AI summary
A method of establishing a formation of a plurality of directionally fixed satellites, such as primary formation of the satellites with in-track velocity disparity. The plurality of satellites includes an anchor satellite and at least one non-anchor satellite, each satellite of the plurality of satellites including at least one drag flap, each satellite of the plurality of satellites being free of one of a propulsion system and an expendable mass propellant. Control is applied to deploy the at least one drag flap of the at least one non-anchor satellite based on the current spacing and the current separation rate of the each non-anchor satellite, and the predicted final spacing of the plurality of satellites. The final spacing predicting and the drag flap control applying is repeated until the current separation rate has been nulled to within a threshold value.