Field-Emission Array for Spacecraft Charging Mitigation
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Solution Overview
Problem
Spacecraft charging leads to significant potential differences between sunlit and shadowed surfaces, causing electrostatic discharging and damage to solar arrays due to inverted electric-field gradients, which existing technologies fail to effectively mitigate.
Innovation Solution
A micro-fabricated field-emission array device is integrated into the spacecraft, with an electrically conductive surface on the sunlit side and emitters on the shadowed side, emitting electrons when a voltage threshold is exceeded to reduce potential differences and prevent electrostatic discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spacecraft surfaces are exposed to UV photons and plasma in space environment, then photoelectron emission occurs and surfaces charge positively, but potential differences develop between sunlit and shadowed surfaces causing electrostatic discharging
Solution Approach 1:
The invention utilizes the naturally occurring photoelectron emission from sunlit surfaces, which normally creates harmful potential differences, as the driving force for a beneficial effect. The field-emission array is triggered by these potential differences to emit electrons that neutralize the charge separation, converting the harmful charging phenomenon into the activation signal for protection.
Solution Approach 2:
The field-emission array acts as an intermediary device between the sunlit and shadowed surfaces. It provides a controlled electron emission path that mediates the charge imbalance, allowing electrons to flow from the shadowed side to neutralize the positively charged sunlit surfaces, thereby preventing direct electrostatic discharge through the solar arrays.
2Reliability
If field-emission array emits electrons to neutralize charge differences, then potential differences are reduced and electrostatic discharge is prevented, but device complexity increases
Solution Approach 1:
The field-emission array is designed to operate autonomously without external control systems. The potential differences created by natural spacecraft charging directly trigger the electron emission, and the emission continues automatically until the charge imbalance is neutralized. This self-regulating mechanism eliminates the need for complex control electronics, sensors, or power management systems.
Solution Approach 2:
The invention changes the operational parameters of the field-emission array to match the natural charging characteristics of the spacecraft. The array is designed to activate at potential differences typically encountered in space (hundreds to thousands of volts) and to emit electron currents that match the photoelectron emission rates, allowing it to operate passively within the natural electrical environment of the spacecraft.
3Reliability
If conventional charging mitigation methods are used, then some protection is provided, but they fail to effectively mitigate inverted electric-field gradients causing catastrophic failures
Solution Approach 1:
Conventional methods attempt to prevent surface charging or equalize potentials through conductive paths. This invention inverts the approach by allowing the sunlit surfaces to charge positively as they naturally would, then using this charge as the trigger to emit electrons from the shadowed surfaces to neutralize the imbalance. This reverse approach of permitting natural charging then correcting it proves more effective than attempting to prevent charging in the first place.
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 solution effectively limits the potential difference between sunlit and shadowed surfaces, preventing primary arcs and reducing the risk of catastrophic solar array failures by continuously emitting electrons, thus ensuring the reliability of spacecraft operations.
Implementation Method 1
A micro-fabricated field-emission array device is integrated into the spacecraft, with an electrically conductive surface on the sunlit side and emitters on the shadowed side, emitting electrons when a voltage threshold is exceeded
Implementation Method 2
one side of the chassis is impinged upon by ultraviolet (UV) photons... The array of emitters discharges electrons from the surface on the shielded side of the chassis when a voltage difference in excess of a threshold voltage develops
Data Source
AI summary
The chassis of a spacecraft has one side exposed to ultraviolet photons and another side shielded from the ultraviolet photons. An electrically conductive surface is disposed on the exposed side of the chassis and is electrically isolated from the chassis. A field-emission array device has a gate, an emitter array, a first terminal electrically connected to the gate, and a second terminal electrically connected to the emitter array. The first terminal electrically couples the gate to the electrically conductive surface on the exposed side of the chassis, and the second terminal electrically couples the emitter array to a surface on the shielded side of the chassis. The emitter array discharges electrons from the surface on the shielded side when a voltage difference in excess of a threshold voltage develops between the gate and the emitter array because of differential charging of the exposed and shielded sides of the chassis.