SPIS Multitimescale and Multiphysics Capabilities: Development and Application to GEO Charging and Flashover Modeling

While it demonstrated its capability to simulate many common situations, Spacecraft Plasma Interaction Software (SPIS) open source code lacked the possibility to model more challenging situations. The major cases of interest were identified as related to either multitimescale or multiphysical situations. Two major improvements were brought to SPIS code to answer these needs. The first one was an implicit circuit solver with an automatic determination of time steps. The implemented Newton-type algorithm makes use of a predictor for the plasma current variations when surface potentials change. The second major development was a multiphysical model for electrons. The approach consisted in using equilibrium or dynamical electron models in two different zones and connecting these zones at their boundary through a Child-Langmuir (CL)-type condition. Fulfilling this condition dynamically determines the location of the boundary and the electron current to be injected from the dense thermal zone to the space-charge zone. These new features were then used to simulate validation and application cases. The first one consisted in modeling a charging situation in GEO, which had been modeled with NASA charging analyzer (NASCAP) codes and published. Concerning the multiphysical model of electrons, the loop controlling the CL condition was first tested on elementary cases, exhibiting a good qualitative and quantitative behavior. It was then applied to the modeling of a ground experiment performed in JONAS plasma tank at the Office National d'Etudes et Recherches Aérospatiales, i.e., the expansion of the flashover generated by an electrostatic discharge over a precharged solar array coupon, leading to its neutralization.