Phased Spacecraft Control During Low-Thrust Orbit Transfer
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Solution Overview
Problem
Existing spacecraft control systems face challenges in maintaining precise phasing and positioning of multiple spacecraft during low-thrust transfer maneuvers from an initial insertion orbit to a target orbit, particularly due to variations in thrust and mass, which can lead to potential collisions and inefficiencies in Electric Orbit Raising (EOR) durations.
Innovation Solution
A method utilizing a modified compound steering law with weight factors, specifically manipulating the β weight factor, to control the in-plane and out-of-plane change in velocity components of spacecraft, ensuring a constant phase offset is maintained between lead and follower spacecraft by adjusting their semi-major axes, thereby controlling their mean motion and preventing collisions during the transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If low-thrust propulsion systems are used for sustained propulsion over extended-duration missions, then propellant mass is significantly reduced, but precise phasing control between multiple spacecraft becomes difficult to maintain
Solution Approach 1:
The patent applies dynamic control by continuously adjusting the compound steering law parameters during the transfer maneuver. The control system dynamically modifies the in-plane and out-of-plane Δv components based on real-time phase offset measurements, allowing the system to adapt to thrust variations and maintain precise phasing throughout the extended transfer duration.
Solution Approach 2:
The patent changes control parameters by manipulating the weight factors (α and β) in the compound steering law. By varying these parameters, the system can adjust the distribution of Δv between in-plane and out-of-plane components, enabling precise control of mean motion and phase offset while using low-thrust propulsion.
2Productivity
If compound steering law is used to accomplish orbital objectives with continuous thruster firing, then orbital eccentricity and semi-major axis targets are achieved, but maintaining constant phase offset between multiple spacecraft becomes challenging
Solution Approach 1:
The patent segments the control of multiple spacecraft by treating each spacecraft individually with its own phase offset control. The compound steering law is applied separately to each spacecraft, allowing independent adjustment of their trajectories while maintaining coordinated phasing across the entire constellation.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the phase offset between spacecraft and adjusting the compound steering law parameters accordingly. The control system uses the measured phase offset to determine necessary corrections in the in-plane and out-of-plane Δv components, ensuring constant phase maintenance throughout the transfer.
3Adaptability or versatility
If thrust and mass variations occur during transfer maneuver, then propulsion system flexibility is improved, but collision probability between spacecraft increases
Solution Approach 1:
The patent applies preliminary action by establishing desired trajectories and phase offset targets before the transfer maneuver begins. The control system pre-calculates the necessary Δv components and weight factor adjustments to maintain safe spacing, allowing the system to proactively compensate for anticipated thrust and mass variations rather than reacting to collisions after they occur.
Data Source
AI summary
A method for controlling phased transfer of multiple spacecraft from a separation orbit to a target orbit includes, while maintaining an in-phase relationship of the spacecraft relative to each other within the separation orbit, computing, via a control system, respective desired trajectories for a lead spacecraft and two or more follower spacecraft to reach the target orbit. The method includes establishing a constant phase offset between the spacecraft in mean anomaly of the separation orbit. During a series of transfer orbits of the spacecraft from the separation orbit to the target orbit, the method includes applying the desired trajectories via the control system such that the constant phase offset is maintained and the follower spacecraft are simultaneously transferred to the target orbit in-phase with the lead spacecraft. The control system includes a processor and computer-readable storage medium programmed with instructions for performing the method.