Drift-Based Spacecraft Rendezvous Control for Fuel-Saving Coasting
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Solution Overview
Problem
Current chaser spacecraft rendezvous methods are inefficient and unsafe, particularly in scenarios where thruster control is lost, due to reliance on open-loop trajectory design and suboptimal closed-loop tracking, which can lead to collisions and high fuel consumption.
Innovation Solution
A drift-based rendezvous control system that utilizes natural orbital motions and perturbations to minimize thruster usage by selecting drift regions where thrusters can be turned off, employing model predictive control and backwards reachable sets to ensure safe and collision-free trajectories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If open-loop trajectory design and suboptimal closed-loop tracking are used, then the rendezvous can be completed, but the fuel consumption is excessive and the thruster operation time is prolonged
Solution Approach 1:
The system dynamically adjusts the trajectory by computing drift regions in real-time based on current spacecraft state and predicted target position, allowing the chaser to exploit natural orbital mechanics rather than following a fixed open-loop trajectory. This dynamic adaptation enables fuel-efficient coasting phases while maintaining rendezvous completion.
Solution Approach 2:
The invention changes the control parameters from continuous thruster firing to discrete drift region transitions. By identifying specific drift regions where natural orbital motion achieves the desired relative position, the system minimizes thruster operation time and fuel consumption while completing the rendezvous mission.
2Reliability
If conventional closed-loop trajectory tracking is employed, then the chaser can follow the target, but the ability to avoid collision in case of thruster failure is insufficient
Solution Approach 1:
The system pre-computes drift regions that guarantee safe coasting trajectories to the target. By planning these safe regions in advance and constraining the trajectory to pass through them, the system ensures collision avoidance capability is built into the trajectory design rather than relying solely on reactive control during thruster failure.
Solution Approach 2:
The system continuously updates the drift region computation based on current spacecraft state and predicted target position, creating a feedback mechanism that adapts to changing conditions while maintaining safety guarantees. This feedback loop ensures the chaser remains on a safe trajectory even when thruster control is lost.
3Manufacturing precision
If the chaser spacecraft uses continuous thruster operation to maintain precise trajectory, then the rendezvous accuracy is improved, but the thruster wear and mission lifetime are reduced
Solution Approach 1:
Instead of continuous thruster operation, the system uses periodic impulsive maneuvers to transition between drift regions. The thrusters are fired only when needed to enter or exit drift regions, allowing long coasting phases where natural orbital motion maintains sufficient accuracy, thereby reducing cumulative thruster wear while completing the rendezvous.
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
The system reduces thruster operation time and fuel consumption, ensuring safe rendezvous even in cases of partial or full thruster failure by leveraging natural orbital forces and perturbations, thereby increasing mission lifetime and reducing launch costs.
Implementation Method 1
The drift-based rendezvous control system that utilizes natural orbital motions and perturbations to minimize thruster usage
Data Source
AI summary
Drift-based rendezvous control system for controlling an operation of a spacecraft to rendezvous the spacecraft to a goal region over a finite time (FT) horizon. The system including accepting data including values of spacecraft states at a specified time period within the FT horizon. A processor at the specified time period selects a set of drift regions corresponding to a desired goal region at a location on an orbit where the target is located at the specified time period. Update a controller having a model of dynamics of the spacecraft with the accepted data. Formulate the set of drift regions as a penalty in a cost function of the updated controller. Generate control commands resulting in a real-time drift-based control policy where upon entering the drift region, the thrusters are turned off in order to minimize an amount of operation of the thrusters while rendezvousing with the desired goal region.