Inverted Electrospray Thruster Grid Geometry

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Solution Overview

Problem

Current electrospray thrusters have short lifetimes due to ion impingement on the extractor grid, leading to material deposition and thruster failure, as the grid impingement reduces performance and creates a conductive path between emitters and the extractor grid, preventing the maintenance of a potential difference.

Innovation Solution

A unique geometry is adopted where the extractor grid is positioned beneath the emitter tips, eliminating ion interception and allowing higher electric fields at the emitter tip for lower operational voltages, thereby increasing thruster lifetime and thrust production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the extractor grid is positioned above the emitter tips to enforce sufficient electric field, then ion emission can be induced, but ion impingement on the grid occurs leading to material deposition and thruster failure

Engineering Contradiction:

Improvethruster lifetimeVSAvoidion impingement on extractor grid

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the traditional geometry by positioning the extractor grid beneath the emitter tips instead of above them. This inversion eliminates ion impingement on the grid while maintaining sufficient electric field strength through optimized emitter-tip-to-grid-distance, thereby resolving the contradiction between inducing ion emission and preventing grid damage

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the spatial dimension of the extractor grid position from above to below the emitter tips. This dimensional change repositions the grid out of the ion emission path while maintaining electrical field effectiveness through controlled distance, thus preventing harmful impingement while preserving thrust generation

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If the extractor grid is positioned above the emitter tips, then electric field can be enforced for ion emission, but material deposition forms conductive path causing thruster failure

Engineering Contradiction:

Improvethruster operational lifetimeVSAvoidmaterial deposition on extractor grid

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

By inverting the geometry to place the extractor grid beneath the emitter tips, the patent eliminates the path for material deposition on the grid. This prevents the formation of conductive paths that would cause thruster failure, thereby extending operational lifetime while maintaining ion emission capability

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If traditional geometry is used with extractor grid above emitter tips, then ion emission can occur, but thrust production is reduced due to grid impingement

Engineering Contradiction:

Improvethrust productionVSAvoidion interception by grid

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The inverted geometry positions the extractor grid beneath the emitter tips, completely removing it from the ion emission path. This eliminates ion interception by the grid, allowing all emitted ions to contribute to thrust production, thereby maximizing productivity while maintaining reliable operation

Inventive Principle:

Principle #13The other way round (Inversion)

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 significantly extends the operational lifetime of electrospray thrusters and enhances thrust production by preventing grid impingement, allowing for lower operational voltages and increased electric fields at the emitter tip.

Implementation Method 1

a unique geometry for the emitters and extractor grid in which the grid was removed from the path of the emitted ions... allows for higher electric fields at the emitter tip for a given applied voltage

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

electric fields to accelerate liquid propellant to high velocities, thus providing thrust to the attached spacecraft

Methodology Applied

Scientific EffectIon emission: Ionisation

Data Source

PatentUS11359613B1Electrospray thruster with inverted geometry

Publication Date: 2022.06.14 THE GOVERNMENT OF THE UNITED STATES AS REPRESENTED BY THE SECRETARY OF THE AIR FORCE

AI summary

The present invention relates to electrospray thrusters, processes of making electrospray thrusters, and methods of using such electrospray thrusters. Applicant's thruster incorporates a unique geometry for the emitters and extractor grid that effectively eliminates ion interception on the grid, which is the primary failure mechanism of current devices, yet maintains the electric field conditions necessary for ion emission to occur. Without grid impingement, the thrust produced by the thruster is increased and thruster operational lifetime is increased substantially. Additionally, this non-traditional geometry also allows for higher electric fields at the emitter tip for a given applied voltage, thus enabling lower operational voltage of the thruster as compared to conventional designs.