Ion Thruster Extractor Capillary Absorption for Clogging Prevention
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Solution Overview
Problem
Ion sources with liquid metal ion sources (LMIS) face catastrophic failure due to clogging caused by the accumulation and deposition of liquid metal on the extractor, which leads to contact with the emitter, especially in ion thrusters for spacecraft where this is permanent.
Innovation Solution
The extractor is designed with a structure that absorbs liquid metal using capillary forces, such as fins, pores, or grooves, to diffuse and prevent accumulation, and a cleaning mode is implemented to heat and remove deposited metal, ensuring efficient operation and extended lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the extractor faces the emitter to accelerate ions, then ion acceleration efficiency is improved, but liquid metal deposits on the extractor causing clogging
Solution Approach 1:
The extractor is designed with a porous structure that allows liquid metal to be absorbed through capillary forces. The pores enable the extractor to take up deposited liquid metal, preventing accumulation and clogging while maintaining the extractor's ion acceleration function. This resolves the contradiction by allowing the extractor to face the emitter (maintaining productivity) while the porous structure prevents harmful deposition (maintaining reliability).
Solution Approach 2:
The harmful liquid metal deposition on the extractor is converted into a beneficial effect by designing the extractor with capillary-absorbing properties. The deposited liquid metal, instead of causing clogging, is automatically absorbed by the extractor through capillary forces in the pores. This transforms the harmful accumulation into a self-cleaning mechanism, resolving the reliability issue while maintaining ion acceleration efficiency.
2Device complexity
If passive forces are used to transport liquid metal to the emitter, then device complexity is reduced, but liquid metal accumulates on the extractor
Solution Approach 1:
The extractor's porous structure serves dual functions: it maintains the simple passive transport system (no additional complexity) while simultaneously providing capillary absorption to prevent liquid metal accumulation. The pores in the extractor material enable automatic absorption of deposited metal through capillary forces, resolving the reliability issue without adding complex active transport mechanisms.
Solution Approach 2:
The extractor performs self-service by using its own porous structure to absorb and remove liquid metal deposits through capillary forces. This self-cleaning mechanism eliminates the need for additional active transport systems or complex control mechanisms, maintaining device simplicity while preventing clogging and improving reliability.
3Ease of manufacture
If the extractor has a smooth surface, then manufacturing is simplified, but liquid metal deposits and causes clogging
Solution Approach 1:
The extractor is manufactured with a porous structure that can be achieved through standard manufacturing techniques such as sintering, foaming, or additive manufacturing. While the surface is not perfectly smooth, the porous structure can be created with relatively simple processes. The pores enable capillary absorption of liquid metal, preventing clogging and improving reliability, while maintaining reasonable manufacturing simplicity.
Solution Approach 2:
The surface parameters of the extractor are changed from a smooth surface to a porous surface structure. This parameter change enables the extractor to absorb liquid metal through capillary forces in the pores, preventing deposition and clogging. The porous structure can be achieved through various manufacturing methods, balancing the ease of manufacture with the improved reliability.
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 design significantly delays or prevents clogging, maintaining the reliability and efficiency of the ion source by effectively absorbing and removing liquid metal deposits, thereby avoiding catastrophic failures.
Implementation Method 1
the extractor, on a side facing the emitter, has a structure configured to absorb liquid metal by means of capillary forces
Implementation Method 2
an annular extractor coaxial to and facing the emitter for accelerating the ions away from the emitter
Implementation Method 3
Applying the electric field to such a sharp tip or edge causes the formation of a so-called Taylor cone on top of the tip or edge of the emitter's projection; neutral atoms of liquid metal at the apex of the Taylor cone evaporate from the surface, due to field emission negative electrons tunnel back to the surface changing the formerly neutral atoms to positively charged ions
Implementation Method 4
the liquid metal (usually either caesium, indium, gallium, mercury or bismuth) is heated to its liquid state in the reservoir
Data Source
Figure 1a~1b
Figure 2~7
Figure 3~4
AI summary
What is disclosed is an ion source, in particular an ion thruster for propelling a spacecraft, comprising a reservoir (2) for a liquid metal (3), an emitter (4) with a central axis (C) and in fluid communication with the reservoir (2) for emitting ions (5) of liquid metal (3) drawn from the reservoir (2), an annular extractor (6) coaxial to and facing the emitter (4) for accelerating the ions (5) away, a voltage source (7) for effecting said emitting and accelerating, and a chassis (10) mounting the reservoir (2), the emitter (4) and the extractor (6), wherein the extractor (6), on a side (15) facing the emitter (4), has a structure (14) configured to absorb liquid metal (3) by capillary forces. Also disclosed is a method (21) for operating the ion source (1).