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.
This work was done by Wousik Kim and Insoo Jun of Caltech, and Gilbert Ghang for NASA’s Jet Propulsion Laboratory. This software is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
NUMIT2.0
(reference NPO49296) is currently available for download from the TSP library.
Don't have an account?
Overview
The document is a Technical Support Package for NUMIT 2.0, developed by NASA's Jet Propulsion Laboratory (JPL). It addresses the critical issue of internal electrostatic discharge (IESD) in spacecraft, particularly in high-radiation environments such as those encountered by missions like ESA's Jupiter Icy Moons Explorer (JUICE) and NASA's Europa mission concepts. IESD occurs when high-energy electrons accumulate in dielectric materials, potentially leading to damaging discharges that can affect sensitive electronics onboard spacecraft.
The document outlines the importance of assessing IESD risks through various analysis codes, including NUMIT, DICTAT, CB_IESD, and Aerospace 3-D model. These codes utilize fundamental physical principles such as Ohm’s law, continuity equation, and Gauss’s law to evaluate charge and energy deposition profiles. The primary distinction among these codes lies in their methods for calculating these profiles.
NUMIT 2.0 introduces significant improvements over previous versions. One notable enhancement is the ability to input either a mono-energetic electron beam with constant current density or a time-varying electron spectrum, allowing for more accurate modeling of real-world conditions. Additionally, NUMIT 2.0 adopts Tabata’s 1974 algorithm for energy deposition profiles, which improves the accuracy of dose rate calculations.
The document also highlights the time-delay nature of Radiation Induced Conductivity (RIC), which does not dissipate immediately after radiation exposure. Future modifications to NUMIT will address this characteristic to enhance its predictive capabilities.
Overall, the Technical Support Package serves as a resource for understanding the advancements in NUMIT 2.0 and its application in assessing IESD risks in spacecraft design. It emphasizes the importance of these analyses for ensuring the reliability and safety of missions operating in challenging space environments. The document is intended for use by aerospace professionals and researchers, providing insights into the technological developments that can have broader applications in the field. For further inquiries, contact information for JPL's Innovative Technology Assets Management is provided.
