Speaker
Mr
Pierre Sarrailh
(ONERA - The French Aerospace Lab)
Description
Despite the shielding of the spacecraft payloads, the internal charging events are resulting from the high energy electrons accumulation inside thick dielectrics. On long time scales, this can create IESD (internal electrostatic discharges). This internal charging phenomenon, potentially leading to part or system failure, is well known to spacecraft designers and requires efficient shielding to protect vulnerable components of the payload. In order to assist the designer during the shielding design, ESA has initiated the development of radiation analysis software in the frame of the ELSHIELD project (Energetic Electron Shielding, Charging and Radiation Effects and Margins). This software is based on the GEANT4 library for high energy electron transport in the spacecraft and on SPIS [1]–[3] for the deposited charge transport in the payload components. Among other radiation tools, Geant4 has the capabilities to compute local three-dimensional maps of total ionizing dose and deposited charge. Whereas the common use of Geant4 is to evaluate consequences of radiation on electronics, these two specific capabilities allow addressing the issue of internal charging. This charging effect can be mitigated by material conductivity, which is enhanced by dose deposition (i.e. radiation induce conductivity). Since Geant4 can supply three-dimensional maps of charge deposit and dose, it offers a very good opportunity to use these data to perform three-dimensional computations of internal charging. A specific version of SPIS called SPIS-IC (IC for Internal Charging) uses the Geant4 results as input in order to compute the material conductivity and the charge deposit transport.
In this workshop, we propose to present some simulations of the effect of the radiation belt electrons at a Galileo like orbit on a thick dielectric component inside the payload. As a component, we select a high flow rate communication cable from a SpaceWire standard platform. A natural electron environment coming from the radiation belts has been defined at the Galileo orbit (from a CNES/Onera R&T study). The simulations have been performed for three different shielding (i.e. two isotropic and one anisotropic) and for two different worst environments spectrum (i.e. worst one hour and worst six hours). The results of the simulation are analyzed in term of charging level (as a function of the time and the location inside the component) and IESD risk. We also analyze the uncertainty and the numerical error created at each stage of the simulation (GDML geometry, scoring mesh geometry, transport and scoring calculation using Geant4/GRAS, conductivity calculation in SPIS, transport equation in SPIS, …). We finally conclude on the necessity to perform time dependent and 3D calculations to have an accurate assessment of internal charging.
[1] P. Sarrailh, T. Paulmier, B. Dirassen, D. Rodgers, G. Santin, and F. Cipriani, “3D time dependent model of internal charging, comparison with experiments,” presented at the 2015 IEEE Nuclear & Space Radiation Effects Conference (NSREC 2015), Boston, MA, USA, 2015.
[2] P. Sarrailh et al., “Three-Dimensional Model of Internal Charging using SPIS,” in Proceedings of 12th Spacecraft Charging Technology Conference, Kitakyushu, Japan, 2012.
[3] “Spis website: http://dev.spis.org/.”
Summary
Internal charging simulations results of the effect of the radiation belt electrons at a Galileo like orbit on a thick dielectric component inside the payload are presented. As a component, a high flow rate communication cable from a SpaceWire standard platform has been selected. A natural electron environment coming from the radiation belts has been defined at the Galileo orbit. The results conclude on the necessity to perform time dependent and 3D calculations to have an accurate assessment of internal charging.
Primary author
Mr
Pierre Sarrailh
(ONERA - The French Aerospace Lab)
