Hall-Effect Thruster Magnetic Circuit Erosion Shielding
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Solution Overview
Problem
Hall-effect thrusters (HETs) face challenges with discharge chamber erosion, increased manufacturing costs due to tight magnetic shielding gaps, and complex assembly processes that hinder efficient testing and production, particularly in achieving a balance between propellant throughput and thruster performance while minimizing volume and cost.
Innovation Solution
The design incorporates an improved magnetic circuit with partial magnetic shielding, low-profile sacrificial pole covers, a unique discharge chamber subassembly, and a mechanically crimped cathode emitter retainer to enhance efficiency and simplify assembly, featuring a center-mounted hollow cathode and optimized magnetic field topology to reduce erosion and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full magnetic shielding is implemented to protect discharge chamber walls from ion erosion, then discharge chamber wall erosion is minimized, but manufacturing complexity and cost increase due to tight gap requirements
Solution Approach 1:
The patent implements partial magnetic shielding where the magnetic field is optimized to provide adequate protection against ion erosion to the discharge chamber walls, rather than attempting complete shielding. This partial approach achieves sufficient erosion resistance while avoiding the prohibitively tight gap requirements and manufacturing complexity associated with full magnetic shielding configurations.
2Reliability
If discharge chamber walls are fully protected from ion contact, then erosion rates decrease, but propellant throughput capability is reduced
Solution Approach 1:
The patent applies local quality by creating zones of different magnetic field strength and ion exposure within the discharge chamber. The magnetic field topology is designed to provide enhanced protection in regions most susceptible to erosion while maintaining open plasma flow paths in regions critical for propellant throughput, achieving a balance between erosion resistance and productivity.
3Reliability
If complex magnetic shielding configurations are used to minimize erosion, then discharge chamber protection improves, but assembly and testing complexity increases
Solution Approach 1:
The patent segments the magnetic shielding function into modular components including discrete magnetic poles, pole covers, and field-shaping elements that can be independently manufactured, assembled, and tested. This segmentation allows for simplified fabrication and assembly procedures while maintaining effective discharge chamber protection, avoiding the need for complex integrated magnetic circuits.
4Productivity
If tight magnetic shielding gaps are maintained to optimize plasma confinement, then thruster performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by optimizing the magnetic field strength, pole geometry, and gap dimensions to achieve effective plasma confinement and thruster performance with relaxed manufacturing tolerances. The magnetic circuit design incorporates features such as adjustable pole positions and compensating geometries that maintain performance across a broader range of gap dimensions, reducing the stringency of manufacturing precision requirements.
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 extends thruster operational life, reduces erosion rates, minimizes contamination, and simplifies assembly and testing, achieving high propellant throughput while balancing performance and reducing manufacturing costs, suitable for small spacecraft missions.
Implementation Method 1
an improved magnetic circuit that mostly shields the discharge chamber walls from high-energy ionized propellant
Implementation Method 2
The cathode feeds electrons to the HET plasma and neutralizes the plasma plume ejected from the thruster
Implementation Method 3
The {right arrow over (E)}×{right arrow over (B)} force greatly slows the mean axial velocity of electrons and results in an azimuthal electron current many times greater than the beam current. These ions are then electrostatically accelerated
Implementation Method 4
The Hall-effect thruster (HET) is the most successful in-space electric propulsion technology
Data Source
AI summary
High propellant throughput Hall-effect thrusters (HETs) and components thereof are disclosed. A compact and high propellant throughput HET has an improved magnetic circuit that mostly shields the discharge chamber walls from high-energy ionized propellant, low-profile sacrificial pole covers to delay magnetic pole erosion, a unique discharge chamber subassembly, a mechanically crimped cathode emitter retainer to increase efficiency, a center-mounted hollow cathode, or a combination thereof. Such feature(s) may balance propellant throughput and thruster performance, minimize the volume of the thruster envelope, and/or simplify the thruster assembly.