Document Type

Conference Paper

Journal/Book Title/Conference

14th Spacecraft Charging Technology Conference

Publication Date

Spring 4-2016

Abstract

This work investigated the dependence of electrostatic field strength for spacecraft materials on voltage ramp rate, by applying an increasing electrostatic field until electrostatic breakdown (a permanent, catastrophic failure of a dielectric material) occurs. Enhanced understanding of prolonged exposure to high static electric fields (DC aging) of insulating materials based on expanded experimental studies is of critical to understand the physics of highly disordered insulating materials, as well as for applications in spacecraft charging, high voltage DC power transmission cables and switching, thin film dielectrics, and semiconductor devices and sensors. Electrostatic discharge (ESD) and the associated material breakdown at the electrostatic field strength (FESD) is the primary cause for spacecraft damage due to space environmental interactions. For many real spacecraft charging situations, standard tests with rapidly increasing applied fields do not provide an appropriate measure of the likelihood of failures or an accurate determination of FESD under space-like conditions.

For the ramp rate tests done in a custom ESD vacuum test chamber (<10-3 Pa base pressure), voltage applied across the materials was incrementally increased at a constant rate until breakdown occurred. Tests found that at ramp rates two or three orders of magnitude lower than the maximum recommended rate of 500 V/s, FESD was lower than at rapid rates by a factor or two or more. This suggests that tabulated values of FESD which have been used by the spacecraft charging community can substantially overestimate FESD in common slowly evolving spacecraft situations.

The data from these tests for the polymeric materials polyimide (PI), low density polyethylene (LDPE), and biaxially oriented polypropylene (BOPP) are compared to a microscopic mean field theory for dielectric breakdown in highly disordered insulating materials. The broader range of measured ramp rates (~0.1 V/s to ~500 V/s) provides a stringent test of the signature curves predicted by approximate and more complete theoretical models.

*Supported through funding from NASA Goddard Space Flight Center, a USU URCO Fellowship, and a NASA Space Technology Research Fellowship.

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