Multiple-Emitter FEEP Thruster Current Control
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Solution Overview
Problem
Current satellite and spacecraft thrusters require significant fuel mass, which increases launch costs and reduces efficiency due to low specific impulse values, particularly in field emission electric propulsion (FEEP) thrusters with single emitter needles, which produce low thrust levels.
Innovation Solution
A multiple-emitter FEEP thruster design with a plurality of emitters connected to a common electrical conductor, where the liquid metal is extracted and ionized, and a power supply operating in a regulated current mode to control the extractor voltage and ion current, ensuring even distribution among emitters for improved thrust and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single emitter needle is used in FEEP thruster, then the device complexity is reduced, but the thrust level becomes very low
Solution Approach 1:
The single emitter needle is segmented into a plurality of emitter needles arranged in an array. Each needle acts as an independent emission source, and their combined effect produces higher thrust levels while maintaining the simplicity of individual needle structures.
2Force
If a large plurality of emitter needles is used to produce higher thrust levels, then the thrust level is improved, but the manufacturing precision requirements increase due to variations in emission characteristics
Solution Approach 1:
The system changes the operational parameter from fixed voltage to regulated current mode. By controlling the total ion current and dynamically adjusting the extractor voltage, the system compensates for manufacturing variations in emitter characteristics, allowing less precise manufacturing while maintaining consistent thrust output.
Solution Approach 2:
The feedback control system automatically adjusts the extractor voltage to maintain the desired ion current level, allowing the system to self-correct for variations in emitter properties without requiring manual calibration or highly precise manufacturing.
3Ease of operation
If fixed voltage mode is used to operate FEEP thruster, then the operation is simple, but the ion current distribution among emitters is uneven due to manufacturing variations
Solution Approach 1:
The system implements feedback control by monitoring the total ion current and using this information to dynamically adjust the extractor voltage. This ensures that the ion current is evenly distributed among all emitter needles, improving reliability and preventing any single emitter from being overloaded.
4Reliability
If regulated current mode is used to control ion current, then the thrust control is improved and emitter current distribution is even, but the device complexity increases
Solution Approach 1:
The feedback control circuit monitors the ion current and automatically adjusts the extractor voltage to maintain the desired current level. This relatively simple feedback mechanism enables precise thrust control and even current distribution without requiring complex mechanical or structural modifications.
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 enhances thrust control, reduces manufacturing variations, and increases thruster reliability by evenly distributing ion current among emitters, leading to more efficient and cost-effective satellite propulsion.
Implementation Method 1
the tip of a microscopic emitter needle which is coated with the liquid metal by surface tension or other mechanism
Implementation Method 2
accelerated by a high electric field
Implementation Method 3
the expelled mass is droplets or ions of a metal which are extracted from a reservoir of liquid metal
Data Source
AI summary
There is disclosed a field emission electric propulsion (FEEP) system including a FEEP thruster having at least one emitter and an extractor electrode, and a power supply. The power supply may provide an extractor voltage applied between the emitter and the extractor electrode. The power supply may be operable in a constant current mode in which the extractor voltage is controlled to set an ion current flowing from the emitter at a target current level.