Spacecraft Spin Stabilization via Gimbaled Electric Thrusters
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Solution Overview
Problem
Geosynchronous satellite transfer orbits pose challenges in maintaining attitude control due to high disturbance torques, especially when passing through low perigees, making it difficult to efficiently raise a satellite to a higher orbit using traditional thruster systems.
Innovation Solution
A spacecraft system with a momentum subsystem and a propulsion subsystem featuring electric thrusters installed on a two-axis gimbal assembly, allowing the thrusters to burn at angles that align thrust forces parallel to a target spin axis, minimizing cosine loss and efficiently producing a change in velocity (ΔV) while compensating for thruster torque through angular momentum offsetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional thruster systems are used for orbit raising maneuvers, then the satellite can be raised to higher orbit, but attitude control becomes difficult due to high disturbance torques and thruster alignment losses
Solution Approach 1:
The thruster system is made dynamically adjustable through two-axis gimbaling mechanisms, allowing real-time repositioning of thrusters to maintain optimal alignment with the velocity vector while compensating for attitude disturbances during orbit raising maneuvers
Solution Approach 2:
A control system acts as an intermediary between the thruster system and the satellite bus, processing attitude data and commanding gimbal adjustments to maintain thruster alignment while compensating for disturbance torques, thereby decoupling the complexity of attitude control from the orbit raising function
2Loss of energy
If thrusters are positioned to align with velocity vector for efficient delta-V production, then cosine loss is minimized, but thruster torque disturbs the spin axis alignment
Solution Approach 1:
The system employs feedback control where attitude sensors continuously monitor spin axis alignment and velocity vector orientation, and the control system adjusts gimbal angles in real-time to maintain optimal thruster alignment while compensating for any spin axis disturbances caused by thruster firing
Solution Approach 2:
The thruster orientation parameters (gimbal angles) are dynamically changed during operation to optimize the alignment between thrust vector and velocity vector, thereby minimizing cosine loss while maintaining spin axis stability through active compensation
3Use of energy by moving object
If electric thrusters are used instead of chemical thrusters, then fuel efficiency is improved, but thrust magnitude is reduced requiring longer maneuver durations
Solution Approach 1:
The electric thruster system operates in continuous mode rather than intermittent pulses, maintaining steady thrust application throughout the orbit raising maneuver to maximize the efficiency advantage of electric propulsion while managing the extended duration through optimized continuous firing
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 configuration stabilizes the spacecraft in transfer orbits, increases thruster efficiency, and maintains the spin axis aligned with the desired ΔV direction, reducing the duration of the transfer orbit and conserving fuel.
Implementation Method 1
a propulsion subsystem that includes only electric thrusters, the electric thrusters comprising a plurality of electric thrusters installed on the zenith side of the bus to produce a change in velocity (delta-V) on the spacecraft
Implementation Method 2
a momentum subsystem configured to store angular momentum relative to a center of mass of the spacecraft; the momentum subsystem is configured to compensate for a thruster torque produced by the burn of at least one electric thruster
Implementation Method 3
each of the electric thrusters is coupled to the bus by a two-axis gimbal assembly, wherein each of the electric thrusters is configured to burn at gimbal angles for the each of the electric thrusters
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Apparatus and methods for controlling a spacecraft (100) for a transfer orbit (214). The spacecraft (100) includes a momentum subsystem (502) that stores angular momentum relative to a center of mass (440) of the spacecraft (100), and a propulsion subsystem (310) that includes electric thrusters (314-317). A controller (522) identifies a target spin axis (720) for the spacecraft (100), determines gimbal angles for electric thruster(s) (314-317) that so that thrust forces from the electric thrusters (314-317) are parallel to the target spin axis (720), and initiates a burn of the electric thruster(s) at the gimbal angles. The controller (522) controls the momentum subsystem (502) to compensate for a thruster torque (950) produced by the burn of the electric thrusters (314-317). The momentum subsystem (502) is able to produce a target angular momentum about the center of mass (440), where a coupling between the target angular momentum and an angular velocity of the spacecraft (100) creates an offset torque to counteract the thruster torque (950).