Experimental and Numerical Study of Internal Charging on Spacecraft and Risks of Discharge on Floating Metallic Elements

Space system design rules and manufacturing processes may sometimes lead to the use of floating conductors in internal subsystems. This configuration promotes charge accumulation and increases the risk of electrostatic discharges. This paper presents an experimental and numerical study on this issue. We have selected and tested a Sub-D connector that is susceptible to internal charging because it may contain ungrounded conductors. We assessed its charging behavior and the risk of discharges induced by floating pins. For this purpose, the connector is tested in different configurations. It is irradiated using mono-energetic electron beams, carried out in the GEODUR irradiation facility installed at ONERA (Toulouse, France). Electric currents and potentials induced within the irradiated connector have been measured and correlated with simulation performed with SPIS-IC code. Experiments revealed that the connector's charging behavior is directly influenced by energy of the involved particles. The sample could present fast charging kinetics after exposure for a few hours at relatively low electron fluxes. Electrostatic discharges, intense enough to damage sensitive electronic components, have also been observed. We have shown that the discharge risk is mainly related to the connector wiring.