Tungsten Electron Emitter for Halogen Ion Engine Neutralizer

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Solution Overview

Problem

Ion engines using alternative propellants like iodine or other halogens are incompatible with traditional neutralizers, as these propellants contaminate dispenser cathodes, impairing their functionality due to high temperature operation.

Innovation Solution

A neutralizer design featuring a halogen gas source and an electrode tube with a tungsten-based electron emitter that forms tungsten halides to counteract erosion, allowing operation with iodine or other halogens, and optionally using a keeper electrode or potential difference to ignite gas discharge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a dispenser cathode is used in a neutralizer, then electron emission is achieved, but the cathode is contaminated by halogen propellants at high temperatures, impairing its functionality

Engineering Contradiction:

Improveneutralizer functionalityVSAvoidcathode contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the electron emitter material (tungsten) from the halogen-prone dispenser cathode environment by using a getter material that preferentially binds halogens, separating the electron emission function from the halogen contamination issue

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a getter material as an intermediary between the electron emitter and halogen propellant. This getter material acts as a mediator that binds halogens through chemisorption, protecting the electron emitter from direct contamination while maintaining electron emission functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the electron emitter operates at high temperatures to emit electrons, then electron emission is achieved, but the emitter material evaporates causing erosion and shortening lifetime

Engineering Contradiction:

Improveelectron emission capabilityVSAvoidelectron emitter lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent converts the harmful effect of tungsten evaporation into a beneficial self-healing mechanism. The evaporated tungsten reacts with halogen to form tungsten halide, which then redeposits on the electron emitter surface, transforming material loss into a protective coating that extends emitter lifetime

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a material recovery cycle where evaporated tungsten is not lost but recovered through chemical reaction to form tungsten halide, which then redeposits on the electron emitter, creating a closed-loop material utilization system that extends component life

Inventive Principle:

Principle #34Discarding and recovering

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 neutralizer effectively neutralizes ion beams in ion engines using iodine or halogen propellants by mitigating electron emitter erosion through tungsten halide decomposition, extending its lifespan and maintaining performance.

Implementation Method 1

the halogen gas is ionized by electrons which collide with initially neutral gas atoms in the discharge space of the electrode tube and thus ionize them

Methodology Applied

Scientific EffectIonization: Ionisation

Implementation Method 2

the electron emitter reaches very high operating temperatures of up to 3000° C. This causes the material of the electron emitter to evaporate

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

the tungsten vaporized by the electron emitter reacts with the halogen present in the discharge space of the electrode tube to form a tungsten halide

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 4

The tungsten halide is stochastically transported back to the electron emitter, where it decomposes back into its constituents due to the high temperatures prevailing on the surface of the electron emitter

Methodology Applied

Scientific EffectDecomposition: Decomposition (biological)

Implementation Method 5

The tungsten released during this decay reaction is deposited on the surface of the electron emitter

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS11649809B2Neutralizer for an ion engine, method of operating a neutralizer and ion engine

Publication Date: 2023.05.16 AIRBUS DEFENCE & SPACE GMBH

AI summary

A neutralizer suitable for use in an ion engine comprises a halogen gas source and an electrode tube comprising an inlet opening connected to the halogen gas source for supplying a halogen gas provided by the halogen gas source into the electrode tube, a discharge space for generating a plasma from the halogen gas supplied into the electrode tube, and an outlet opening for discharging the plasma generated in the discharge space and free electrons from the electrode tube. An electron emitter is arranged in the discharge space of the electrode tube, which is at least partially made of tungsten, a tungsten alloy or a tungsten composite material containing at least one of iridium, rhenium, ruthenium, rhodium and osmium.