Ion Source Baffles for Reliable Propellant Flow
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Solution Overview
Problem
Existing ion sources face reliability issues due to propellant retraction during solidification, leading to operational failures, particularly in spacecraft applications, as passive forces are insufficient to restart propellant supply after pauses, and external mechanisms like pressurized reservoirs or mechanical pumps are undesirable for safety and complexity reasons.
Innovation Solution
Incorporation of baffles upstream of the emitter to limit the propellant stream's cross-sectional area and deflect cohesive forces, reducing retraction risks by introducing mechanical obstructions that maintain propellant flow without significantly impeding the supply, ensuring reliable operation and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive forces (capillary effects, adhesion effects) are used to transport propellant from the reservoir to the emitter, then the device complexity is reduced and safety is improved, but the reliability deteriorates when propellant retracts into the reservoir during solidification
Solution Approach 1:
A wick is introduced as an intermediary element between the reservoir and emitter. The wick actively draws propellant toward the emitter using capillary forces, counteracting the retraction caused by reservoir solidification. This mediator ensures continuous propellant supply to the emitter even when the reservoir propellant contracts, thereby maintaining reliability without adding complex external systems.
Solution Approach 2:
The system changes the physical state parameters of the propellant by controlled heating. The propellant is heated to melt and liquefy it, enabling it to flow through the wick to the emitter. By controlling the thermal state, the system ensures the propellant remains in a liquid state at the emitter while allowing solidification in the reservoir, thus preventing retraction issues.
2Reliability
If external forces (pressurizing the reservoir, mechanical pumps, or pistons) are applied to prevent propellant retraction, then the reliability is improved, but the device complexity increases and safety deteriorates
Solution Approach 1:
The wick serves as a passive intermediary that uses inherent capillary forces to draw propellant to the emitter, eliminating the need for active pumping or pressurization systems. This approach maintains reliability by ensuring continuous propellant supply while avoiding the complexity and safety issues associated with mechanical pumps, pistons, or pressurization systems.
Solution Approach 2:
The wick system is self-service in that it automatically draws propellant toward the emitter using capillary forces without requiring external control systems, power sources, or mechanical actuation. The system self-regulates the propellant flow based on the liquid level and capillary pressure, eliminating the need for complex external forcing mechanisms.
3Duration of action of moving object
If the propellant volume in the reservoir is large, then the operation duration is extended, but the cohesive forces increase causing stronger retraction during solidification
Solution Approach 1:
The wick acts as an intermediary that decouples the large reservoir volume from the emitter. It creates a localized liquid propellant zone at the emitter end, ensuring continuous supply while isolating the emitter from the cohesive retraction forces generated by the large volume of solidifying propellant in the reservoir. This allows extended operation duration without proportionally increasing retraction forces at the emitter.
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 baffle system ensures reliable ion source operation by preventing propellant retraction during solidification, allowing safe shutdown and efficient restart, enhancing safety and reliability compared to pressurized reservoirs and mechanical pumps.
Implementation Method 1
the propellant can be heated to liquefy into its liquid state in the reservoir by the heater
Implementation Method 2
passive forces, like capillary effects produced by capillary ducts penetrating the emitter
Implementation Method 3
an extractor facing the emitter for extracting ions of the liquefied propellant from the emitter and accelerating the extracted ions away from the emitter
Data Source
AI summary
An ion source, in particular an ion thruster for propelling a spacecraft, comprises a reservoir for a propellant that has a solid state and can be liquefied into a liquid state, a heater for liquefying the propellant in the reservoir, an emitter in fluid communication with the reservoir for receiving a stream of liquefied propellant from the reservoir, an extractor facing the emitter for extracting ions of the liquefied propellant from the emitter and accelerating the extracted ions away from the emitter, wherein at least one baffle is arranged upstream of the emitter in the stream of the propellant to the emitter.