Effects of Voltage Ramp Rates on Electrostatic Field Strength in Highly Disordered Insulating
Spacecraft charging is the accumulation and dissipation of charge in materials resulting from their interaction with the space environment. At high enough electrostatic fields or after long times, insulators can breakdown, causing large current flow through the material: this breakdown is called electrostatic discharge (ESD). ESD is a permanent, catastrophic failure of a dielectric material because what was an insulator is now essentially a conductor. ESD breakdown is the main cause of failures and anomalies attributed to the spacecraft charging interactions with the space environment. Previous tests done by the USU Materials Physics Group (MPG) using our ESD custom vacuum chamber have found that, for the polymeric materials biaxially oriented polypropylene (BOPP), polyimide, and low density polyethylene (LDPE), the electrostatic field strength at breakdown depends on the voltage ramp rate applied across some materials, but possibly not others. At ramp rates an order of magnitude lower than the maximum recommended rate of 500 V/s, the breakdown electrostatic field strength was found to vary depending on the material being tested. We present more extensive ramp rate testing data on polypropylene, polyimide, and LDPE. The voltage was incrementally increased at a constant rate across the samples until breakdown occurred. Breakdown is marked by the current increasing significantly and continuing to rise linearly according to Ohm’s law. Different ramp rates were used in order to compare the dependence of electrostatic field strength on ramp rate for each polymeric material to the theory applied to past experiments. Understanding these relationships between electrostatic field strength and voltage ramp rates will aid in the understanding and mitigation of ESD related anomalies and failures due to spacecraft interactions with the plasma space environment.
This work was supported by a USU Undergraduate Research and Creative Opportunities Grant