Space radiation electrostatic shielding scaling laws: Beam-like and isotropic angular distributions

Abstract

Passive radiation shielding alone cannot provide adequate protection for astronauts on long-term, deep-space missions. High atomic number and energy (HZE) ions, and/or their secondaries, can penetrate any realistic mass shielding for long-term deep-space missions and cause damage to cells via direct energy deposition and/or through the production of secondary particles and fragmented nuclei. Active shielding, or the use of electromagnetic fields to deflect or stop incoming ions before reaching the spacecraft, has gained substantial attention over the last decade as a way to augment passive shielding. Recently, a mathematical relationship between a dimensionless scaling parameter characterizing the active shield and the incoming ion and a protected area formed on a downstream detector due to the deflection of HZE ions by the applied field was validated in Earth-based laboratory conditions. In the present work, the mathematical formulation is extended to relate electrostatic shielding efficacy with the ability to deflect positively charged ions with parameters relevant to space applications. Additionally, a modified scaling parameter is formulated to characterize the shielding efficacy of a “family” of electrostatic active shielding configurations for reducing flux density for a space-relevant isotropic source of energetic protons. The results of this study demonstrate a strong correlation among dimensionless scaling parameters and shielding efficacy metrics for space radiation-relevant HZE ions in beam and isotropic angular distributions. Furthermore, it establishes a framework for optimizing design of three-dimensional electrostatic shielding configurations to improve space radiation protection for astronauts on exploration-class missions.