Hollow Cathode Orifice Plate Segmentation for Conductance Decoupling
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Solution Overview
Problem
Existing hollow cathodes for spacecraft propulsion systems face challenges in reducing the required gas flow for ignition and sustaining operation while minimizing resistive losses, as the size of the orifice affects both gas and electrical conductance, leading to inefficiencies.
Innovation Solution
The design incorporates a keeper orifice with a plurality of openings that decouple gas conductance and electrical conductance, with diameters ranging from 20%-60% of a single circular opening, allowing for efficient electron emission and reduced gas flow requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a smaller keeper orifice is used, then the gas flow required for ignition is reduced, but the resistive losses increase due to higher electrical resistance
Solution Approach 1:
The single orifice is segmented into multiple smaller openings (e.g., 2-10 openings arranged in a circular pattern). This segmentation allows the total open area to be distributed across multiple openings, reducing the gas flow requirement for ignition while maintaining adequate electrical conductance through the combined aperture area, thus balancing both gas conductance and electrical conductance requirements
2Loss of energy
If a larger keeper orifice is used, then the resistive losses are reduced, but the gas flow required for ignition and stable operation increases
Solution Approach 1:
By dividing the orifice into multiple openings, the design achieves a configuration where the total area provides low electrical resistance while the distributed geometry reduces the gas flow needed for ignition. The multiple openings create favorable pressure distribution and plasma confinement that reduce ignition requirements compared to a single large opening of equivalent total area
3Quantity of substance
If the orifice area is reduced, then gas conductance is improved, but electrical conductance deteriorates due to higher resistance
Solution Approach 1:
The orifice plate features multiple openings (e.g., 2-10 openings) distributed across the plate. This segmentation allows the total open area to be optimized for gas conductance while the distributed arrangement maintains electrical conductance pathways. The multiple openings provide redundant electrical pathways that maintain reliability even with reduced total area compared to a single large orifice
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 reduces the gas flow needed for ignition and sustains the discharge with lower keeper voltage, resulting in lower resistive losses and improved power efficiency, as evidenced by plots showing reduced voltage and power consumption compared to single orifice configurations.
Implementation Method 1
an electron source capable of supplying sufficient electron current to sustain the electron discharge is also required
Implementation Method 2
The plurality of openings decouple gas conductance and electrical conductance across the orifice plate
Implementation Method 3
a gas supply source configured to supply gas to the plasma holding region
Implementation Method 4
The cathode includes a plasma holding region configured to hold a plasma
Implementation Method 5
A smaller keeper orifice reduces the gas flow required to sustain the minimum pressure for ignition in either the heated or heaterless case, but also increases the resistive losses during operation by forcing the electron current to exit through a smaller diameter opening with correspondingly higher resistance
Data Source
AI summary
Methods and apparatuses for emitting electrons from a hollow cathode are provided. The cathode includes a plasma holding region configured to hold a plasma, a gas supply source configured to supply gas to the plasma holding region, and an orifice plate disposed on a periphery of the plasma holding region. The orifice plate comprises a plurality of openings constructed to receive electrons from the plasma. The plurality of openings decouple gas conductance and electrical conductance across the orifice plate. The diameters of the plurality of openings are within a range of 20%-60%, inclusive, of a diameter of a circular opening with an area equal to a sum of the areas of the plurality of openings.