Charging of composites in the space environment

The space environment includes high-energy charged particles, which deposit in the composite materials of satellites. The deposited particles create an electric field, which may grow until an electrostatic discharge occurs. A one-dimensional finite difference model has been developed, which calculates the electric field in space and time as a function of the environment, material properties, and boundary conditions. Using the electron and proton flux for a 7000-km-altitude orbit and the material data for a typical organic polymer, the calculated steady-state electric field is approximately 4400 V/m with a steady-state development time of 1.3 s. This is several orders of magnitude lower than the dielectric strength of the material, 15 MV/m. Based on sensitivity studies done by varying particle fluxes and material properties several orders of magnitude around typical values, it was concluded that typical Bur levels do not cause significant deep dielectric charging in typical composite materials. However, discharges can occur during substorms when particle flux levels can rise by several orders of magnitude.