Satellite Attitude Control Using Off-Center Electric Thrusters
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Solution Overview
Problem
Satellites in high altitude orbits face challenges in controlling attitude due to solar pressure, requiring frequent desaturation of angular momentum storage devices, which often necessitates chemical propellant thrusters, leading to excessive consumption and limited availability.
Innovation Solution
A method utilizing controllable solar panels and electric thrusters to create desaturation torques along three axes without chemical propellants, where electric thrusters are aligned off-center to generate torques along the Y-axis, and solar panels create torques in orthogonal planes to manage angular momentum, reducing the need for propellant thrusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical propellant thrusters are used to de-saturate the angular momentum storage device, then the wheels can be de-saturated along all three axes, but the consumption of chemical propellants increases excessively
Solution Approach 1:
The patent combines the functions of orbit control and angular momentum de-saturation into a single electric thruster system. The electric thrusters are positioned and controlled to simultaneously perform North-South orbit control and de-saturation of the reaction wheels, eliminating the need for separate chemical propellant thrusters and thereby reducing propellant consumption while maintaining de-saturation capability along all three axes
Solution Approach 2:
The electric thrusters are designed to perform multiple functions: orbit control (North-South positioning) and angular momentum de-saturation. By making the thruster system universal, the patent eliminates the need for dedicated chemical propellant thrusters, thus reducing propellant consumption while maintaining the ability to de-saturate the reaction wheels along all three axes
2Reliability
If solar panels are depointed with respect to the Sun to create de-saturation torques, then the wheels can be de-saturated, but the electrical energy generated by the solar panels drops significantly
Solution Approach 1:
The patent replaces the mechanical approach of using solar pressure (which requires depointing solar panels) with an electromagnetic approach using electric thrusters. The electric thrusters generate the necessary de-saturation torques through electromagnetic propulsion, allowing the solar panels to remain properly oriented toward the Sun for maximum energy generation while still achieving de-saturation along all three axes
3Loss of energy
If solar panels with lateral fins are used to create de-saturation torques, then the need for offsetting solar panels is limited, but significant torques around the axis of rotation of the solar panels cannot be created
Solution Approach 1:
The patent segments the de-saturation function across multiple electric thrusters positioned at different locations and orientations on the satellite. This segmentation allows the system to generate de-saturation torques along all three axes, including the axis of solar panel rotation, without requiring solar panel offsetting, thereby maintaining both energy efficiency and complete de-saturation capability
Solution Approach 2:
The patent uses the spatial dimension by strategically positioning electric thrusters at different locations on the satellite body. This spatial arrangement enables the generation of torques along all three axes through coordinated thruster firing, overcoming the limitation of solar panel-based systems that cannot generate significant torques around the panel rotation axis
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 efficient desaturation of angular momentum storage devices along all axes using only electrical means, reducing propellant consumption and extending satellite operation by eliminating the reliance on chemical thrusters.
Implementation Method 1
at least one electric thruster (14a, 14b) also implemented as means for controlling the orbit of said satellite (10) to create, by exploiting the solar pressure, de-saturation torques of the device (16) for storing angular momentum along the Y axis
Implementation Method 2
controllable surfaces of the satellite adapted to create de-saturation torques of the storage device by exploiting the solar pressure
Data Source
AI summary
The present invention concerns a method of controlling the attitude of a satellite in orbit around a celestial body, the attitude of the satellite being controlled by means of a momentum storage device and by means of controllable surfaces of the satellite capable of creating desaturation torques in the storage device by using solar pressure, said controllable surfaces being arranged on solar panels mobile in rotation around an axis Y. The attitude of the satellite is also controlled by means of at least one electric thruster also implemented to control the orbit of the satellite, the orientation of the at least one electric thruster being controlled in such a way as to activate said at least one electric thruster with a thrust direction deliberately not aligned with a centre of mass of the satellite in order to create desaturation torques in the storage device along axis Y, the controllable surfaces being controlled to create desaturation torques of said storage device in a plane orthogonal to the Y axis. The present invention also concerns an attitude-controlled satellite (10).