Systematic modeling of electrostatic radiation shields for deep space flight

Abstract

Astronauts are exposed to a unique radiation environment during space missions. This environment is dominated by high charge and energy (HZE) ions with sources that include solar energetic particles (SEPs), galactic cosmic rays (GCRs), and trapped electrons and protons around planetary bodies with substantial magnetic fields. Traditional shielding strategies aim to reduce astronaut radiation exposure by increasing vehicle mass, but this is ineffective for the extremely penetrating GCRs. Use of electromagnetic fields has been investigated previously, but these studies have been limited to single point designs. The NASA Active Shielding project has instead developed a workflow that includes a fast and accurate particle propagation code (Active Shielding Particle Pusher), which can be used to rapidly evaluate the shielding efficacy of many different permutations of electromagnetic shielding designs. While some validation of the code has been previously done, additional validation is needed to increase user confidence in simulation results involving more complicated electrostatic conductor configurations. In the present study, we evaluated shielding properties of spherical electrode arrays and planar grid structures against 2 MeV or 6 MeV H+ and 22.5 MeV Fe6+ ions using ASPP, SIMION, and COMSOL, and compared these results to laboratory-based measurements. Many numerical experiments were conducted to reproduce experimental ion beam tests that measure the consequential particle reduction rate in a safe zone compared to the initial number of ions. The experimental visualizations were also compared with the present numerical results and found to be in close agreement with each other for all considered voltage combinations applied to electrode structures. This comparison allows us to use numerical models to predict the behavior of complex shielding structures at much larger scales not feasible in a laboratory environment.