Electrowetting Valve for Electrospray Thruster Flow Isolation
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Solution Overview
Problem
Existing electrospray thrusters face issues with premature propellant wetting of emitter tips during storage and launch, leading to potential thruster damage and uncontrolled propellant flow due to capillary forces, and existing electrowetting valves lack the ability to regulate propellant flow rates effectively.
Innovation Solution
An electrically-actuated valve with through holes and channels is designed to inhibit propellant flow until activated by a voltage potential, allowing controlled flow to electrospray thrusters, utilizing electrowetting principles to modulate the flow rate by adjusting the voltage applied, thus preventing premature wetting and flooding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If capillary forces are used to passively feed propellant to electrospray emitters, then propellant delivery is simplified, but premature propellant wetting and uncontrolled flow occur during storage and launch
Solution Approach 1:
An electrowetting valve is introduced as an intermediary component between the propellant reservoir and the electrospray emitters. This valve uses electrowetting-on-dielectric (EWOD) effect to control propellant flow, acting as a mediator that prevents direct uncontrolled flow while maintaining the passive capillary feed system. The valve selectively allows or blocks propellant passage based on applied voltage, thus protecting the emitters during storage and enabling controlled operation during thrust.
Solution Approach 2:
The electrowetting valve changes the wetting parameters of the propellant channel surfaces by applying voltage. At zero or low voltage, the surfaces remain non-wetting to prevent propellant flow during storage. When voltage is applied, the surfaces transition to a wetting state, allowing controlled propellant flow to the emitters. This dynamic parameter change enables the system to adapt between storage and operation modes.
2Reliability
If electrowetting valves are used to control propellant flow, then premature wetting is prevented, but flow rate regulation capability is limited
Solution Approach 1:
The electrowetting valve provides dynamic control of propellant flow by adjusting the applied voltage. By varying the voltage level, the degree of wetting can be modulated, which in turn regulates the propellant flow rate to the emitters. This dynamic adjustment capability allows the system to optimize flow rates for different operational requirements while maintaining reliable flow control.
3Volume of moving object
If through holes are used in the valve substrate, then compact design is achieved, but electrical isolation and non-wetting surface maintenance become more difficult
Solution Approach 1:
The valve employs thin film layers deposited on the substrate to provide electrical isolation and control wetting properties. These thin films are deposited conformally on the substrate including the through holes, creating a continuous dielectric layer that electrically isolates the conductive layers while maintaining the compact through-hole structure. This approach enables compact valve design without compromising manufacturing feasibility.
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 electrically-actuated valve effectively isolates propellants from emitter tips during non-operation and regulates flow rates, enhancing thruster reliability and performance by preventing premature wetting and flooding, while maintaining compactness and compatibility with launch environments.
Implementation Method 1
the at least one valve is configured to inhibit propellant flow from the reservoir to the thruster, and the first power source is configured to apply a voltage potential to the at least one valve relative to the propellant to facilitate flow of the propellant from the reservoir to the thruster
Data Source
AI summary
Electrical propulsion systems and related methods are generally described. In some embodiments, an electrical propulsion system may include an electrically-actuated valve to selectively permit flow of propellant from a reservoir tank to a thruster. The valve may physically isolate the propellant from the thruster when inactivated, exhibiting a non-wetting surface which may inhibit propellant from passing through the valve towards the thrusters. In some embodiments, a valve may be activated through application of a voltage potential to the valve relative to the propellant, which may change the wettability of the valve, permitting propellant to wet and subsequently pass through the valve. The voltage potential may be adjusted to vary the wettability of the valve, resulting in the valve effectively regulating propellant flow rate. The valve may include a conductive layer, a dielectric or insulating layer, and a non-wetting layer to enhance the non-wetting behavior of the valve.