Internal electrostatic discharge (IESD) can cause spacecraft failure and anomalies related to the space environment, but it is very hard to predict when IESD might happen. Therefore, assessment of the IESD at a given space environment and a given dielectric geometry is important for spacecraft reliability.
Several IESD analysis codes have been developed, and all share the similar physics and physical equations — namely, Ohm’s law, continuity equation, and Gauss’s law. In NUMIT, the energy deposition profile is calculated by Tabata’s algorithm, and the charge deposition profile is calculated by an algorithm developed by Frederickson. Unfortunately, NUMIT was not configuration-controlled, so several versions of NUMIT are being used in the community.
NUMIT2.0 solves for the electric fields, charge densities, and current densities internal to the dielectric layers and current through the backside grounded electrode due to the deposition of high-energy electrons. It calculates the charge deposition and dose rate profiles without running a Monte Carlo simulation, and solves continuity, Ohm’s law, and Poisson’s equations internal to the dielectric materials to simulate the internal electric field, which is almost impossible to measure experimentally, but is essential to predict if an IESD happens.
NUMIT2.0 combines all versions and corrects most flaws in the previous versions. Several additional improvements were made: (1) the lower limit of the electron energy is extended from 100 keV to 10 keV using new charge and energy deposition algorithms developed by the authors; (2) the erroneous cusp in the previous energy deposition profile is removed; and (3) the code accepts not only the mono-energetic constant flux electrons as the previous code, but also takes electrons with a time-varying spectra.