Colloid Thruster Porous Reservoir Leakage Prevention
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Solution Overview
Problem
Ion electrospray thrusters face failures due to ionic liquid leakage or bridging between the emitter and electrode, and partial filling of the reservoir can lead to gaps, causing operational issues, especially in space applications where propellant pressurization systems are not feasible.
Innovation Solution
A porous compliant interface is used between the reservoir and emitter, with a fluid injection section that fills the emitter first and then partially fills the reservoir, maintaining equilibrium capillary forces to prevent leakage and bridging, utilizing a porous reservoir and emitter with distinct capillary pressures and pore sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reservoir is fully filled with ionic liquid, then the emitter can be consistently filled with liquid, but liquid leaks out of the emitter tip and forms a bridge between the emitter and electrode resulting in thruster failure
Solution Approach 1:
The reservoir is designed with spatially varying porosity - the proximal portion (near the emitter) has lower porosity to provide stronger capillary forces for suppressing liquid leakage, while the distal portion has higher porosity to accommodate bulk liquid storage. This local differentiation of porosity creates the desired capillary pressure gradient that prevents overfilling and bridging while maintaining reliable emitter filling.
2Object-affected harmful factors
If the reservoir is partially filled with ionic liquid, then liquid leakage is prevented, but a void or gap of ionic liquid between the reservoir and the emitter occurs resulting in thruster failure
Solution Approach 1:
The proximal portion of the reservoir adjacent to the emitter is designed with lower porosity to generate stronger capillary forces that actively pull liquid toward the emitter, ensuring continuous filling of the emitter and preventing void formation. This localized capillary enhancement guarantees a reliable liquid path from the reservoir to the emitter even when the bulk reservoir is only partially filled.
3Object-affected harmful factors
If a porous reservoir with appropriate capillary forces is used, then liquid leakage is suppressed, but the tank mass is relatively large due to high density material requirements
Solution Approach 1:
Only the proximal portion of the reservoir near the emitter uses low-porosity, high-density material to provide the necessary capillary suppression of leakage. The distal portion uses high-porosity, low-density material for bulk storage, significantly reducing overall reservoir mass while maintaining leakage suppression at the critical emitter interface.
Solution Approach 2:
The reservoir is constructed as a composite structure combining materials with different porosity and density characteristics - a low-porosity, higher-density material in the proximal region for capillary control, and a high-porosity, lower-density material in the distal region for lightweight storage. This composite approach achieves both leakage suppression and mass reduction.
4Reliability
If an engineered gradient in the reservoir porosity is implemented, then gaps in the bulk liquid to the emitter flow path are suppressed, but the fabrication cost and complexity increase significantly
Solution Approach 1:
The reservoir is divided into two discrete segments - a proximal portion with lower porosity and a distal portion with higher porosity. This segmentation achieves the desired porosity gradient effect while simplifying fabrication compared to continuous gradients, as each segment can be manufactured separately using standard porous materials and then assembled.
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 consistently fills the emitter with propellant, suppresses liquid leaks, and maintains a stable liquid bridge, ensuring thruster operation while minimizing mass and cost, particularly suitable for space applications.
Implementation Method 1
a porous propellant reservoir and a porous emitter may be used with propellant transferred from the reservoir to the emitter by capillary action
Implementation Method 2
The interface has a characteristic capillary pressure stronger than the characteristic capillary pressure of the porous reservoir in order to fill the porous emitter first with fluid
Data Source
AI summary
An ion electrospray device with a porous reservoir and at least one porous emitter includes a porous compliant interface sandwiched between the porous reservoir and the porous emitter for transferring fluid from the porous reservoir to the porous emitter. The interface has a characteristic capillary pressure stronger than the characteristic capillary pressure of the porous reservoir to fill the porous emitter with fluid via a fluid injection section of the interface and before the porous reservoir is then partially filled with fluid. Emitter leakage and propellant bridging problems are addressed.